Cancer Cell Biology and Mutations
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Questions and Answers

What happens to cells when they undergo senescence?

  • They rapidly grow and divide
  • They enter a permanent state of cell cycle arrest (correct)
  • They undergo rapid apoptosis
  • They repair DNA damage successfully

    • What is the purpose of injecting F-luorodeoxyglucose into patients?

  • To repair DNA damage in tumors
  • To visualize tumors through positron emission tomography (PET) scanning (correct)
  • To induce DNA damage in tumors
  • To promote cell division in normal tissues

    • What is the result of inducing DNA damage in cells with active p53?

  • DNA repair and cellular recovery
  • Rapid cell division and growth
  • Apoptosis and cell death
  • Cellular senescence and permanent cell cycle arrest (correct)

    • What kind of tumors are typically PET-positive?

    <p>Malignant tumors</p> Signup and view all the answers

    What is the effect of DNA damage on cells without active p53?

    <p>Rapid cell division and growth</p> Signup and view all the answers

    What happens to DNA when cells undergo senescence?

    <p>DNA damage is irreparable</p> Signup and view all the answers

    What is the purpose of PET scanning in tumor detection?

    <p>To visualize tumors and track their growth</p> Signup and view all the answers

    What is the result of successful DNA repair in cells?

    <p>Cellular recovery and continued cell division</p> Signup and view all the answers

    Which of the following best describes the role of NF1 in the regulation of cell growth?

    <p>NF1 acts as a GTPase-activating protein (GAP) that promotes the hydrolysis of GTP bound to RAS, leading to inactivation of RAS and suppression of cell growth.</p> Signup and view all the answers

    How does the inactivation of RAS by NF1 contribute to the regulation of cell growth?

    <p>Inactivation of RAS prevents the activation of downstream signaling pathways involved in cell growth, such as the MAPK pathway.</p> Signup and view all the answers

    Which of the following statements accurately describes the relationship between RAS and MYC in the context of cell growth?

    <p>RAS indirectly activates MYC by stimulating the expression of a transcription factor that binds to the MYC promoter.</p> Signup and view all the answers

    What is the primary function of cyclin D in the context of cell growth?

    <p>Cyclin D forms a complex with CDK4/6, leading to phosphorylation of the retinoblastoma protein (Rb) and promoting the transition from G1 to S phase.</p> Signup and view all the answers

    What is the significance of the regulation of RAS activity by NF1 in the context of cancer development?

    <p>All of the above.</p> Signup and view all the answers

    How does the activation of MYC contribute to the development of cancer?

    <p>MYC promotes the expression of genes involved in cell growth and proliferation, leading to uncontrolled cell growth and tumor formation.</p> Signup and view all the answers

    Which of the following statements accurately describes the role of RAS in the context of cell growth?

    <p>RAS acts as a molecular switch that can be activated by growth factors and other signals, triggering downstream signaling pathways involved in cell growth and proliferation.</p> Signup and view all the answers

    Which of the following correctly describes the relationship between GTP hydrolysis and the activity of RAS?

    <p>GTP hydrolysis inactivates RAS, leading to the suppression of downstream signaling pathways involved in cell growth.</p> Signup and view all the answers

    What role does RAS play in cellular signaling?

    <p>Activates downstream signaling pathways.</p> Signup and view all the answers

    How does RAS become activated?

    <p>Via farnesyl membrane anchoring.</p> Signup and view all the answers

    What can disrupt the signaling function of RAS?

    <p>Severe mutations that affect membrane anchoring.</p> Signup and view all the answers

    What is formed when RAS is in its active state?

    <p>A GTP-bound signaling complex.</p> Signup and view all the answers

    What is NOT a consequence of activated RAS?

    <p>Inhibition of cell proliferation.</p> Signup and view all the answers

    Which factor is essential for RAS's membrane attachment?

    <p>Farnesylation</p> Signup and view all the answers

    What type of mutations can interfere with RAS signaling?

    <p>Mutations that cause amino acid substitutions</p> Signup and view all the answers

    Which of the following is a downstream effect of active RAS?

    <p>Recruitment of signaling and transcription factors.</p> Signup and view all the answers

    What is the primary role of p53 in maintaining genome integrity?

    <p>Promoting DNA repair and cell cycle arrest</p> Signup and view all the answers

    Which of the following is NOT a consequence of p53 activation by DNA damage?

    <p>Increased mitochondrial oxidative phosphorylation</p> Signup and view all the answers

    What is the consequence of TP53 gene mutations in cells?

    <p>Uncontrolled cell proliferation and potential for malignancy</p> Signup and view all the answers

    How does p53 promote DNA repair?

    <p>Upregulating genes involved in DNA repair pathways</p> Signup and view all the answers

    Which of the following is NOT a mechanism by which p53 promotes cell cycle arrest?

    <p>Promotion of mitochondrial apoptosis</p> Signup and view all the answers

    What is the significance of p53's role in preventing the proliferation of genetically damaged cells?

    <p>It prevents the accumulation of mutations that can lead to cancer</p> Signup and view all the answers

    What is the relationship between p53 and senescence?

    <p>p53 triggers senescence as a backup mechanism if DNA repair fails</p> Signup and view all the answers

    Which of the following statements accurately describes the role of p53 in preventing cancer?

    <p>p53 prevents the accumulation of mutations that can lead to cancer</p> Signup and view all the answers

    What is the likelihood of patients developing a wide spectrum of malignant tumors by age 50?

    <p>25% greater chance compared to the general population</p> Signup and view all the answers

    Which of the following types of cancers are most commonly seen in patients with this syndrome?

    <p>Sarcomas and carcinomas</p> Signup and view all the answers

    At what age do many patients with this syndrome typically develop multiple tumors of different types?

    <p>At a young age</p> Signup and view all the answers

    Which specific types of tumors are frequently occurring in these patients?

    <p>Breast tumors and certain leukemias</p> Signup and view all the answers

    What is the significance of the RB gene mentioned in the context of the syndrome?

    <p>It is associated with hyperphosphorylation leading to cancer</p> Signup and view all the answers

    What is the risk associated with tumors developing in patients with this syndrome?

    <p>They can occur at multiple sites</p> Signup and view all the answers

    Which statement best describes the tumors seen in patients by age 50?

    <p>They commonly involve sarcomas and carcinomas</p> Signup and view all the answers

    What type of tumors is least likely to occur in patients with this syndrome?

    <p>Adenomas</p> Signup and view all the answers

    The gene ABL converts nonreceptor tyrosine kinase genes into oncogenes through chromosomal translocations.

    <p>True</p> Signup and view all the answers

    RAS functions as a guanosine diphosphate hydrolase, returning GDP to GTP.

    <p>False</p> Signup and view all the answers

    The intrinsic activity of RAS is that of a GTPase, which regulates its active state.

    <p>True</p> Signup and view all the answers

    The GDP-bound form of RAS is considered the active state of the protein.

    <p>False</p> Signup and view all the answers

    Tyrosine kinase genes primarily regulate the biosynthesis of lipids.

    <p>False</p> Signup and view all the answers

    RAS can return to its quiescent state after hydrolyzing GTP to GDP.

    <p>True</p> Signup and view all the answers

    Nonreceptor tyrosine kinases do not participate in cell signaling.

    <p>False</p> Signup and view all the answers

    Chromosomal translocations can alter the function of genes involved in cell growth and regulation.

    <p>True</p> Signup and view all the answers

    Transcription factors activate the expression of proteins that can lead to increased signaling even when growth factor levels are very low.

    <p>True</p> Signup and view all the answers

    The activation of transcription factors only occurs when surface receptors are stimulated.

    <p>False</p> Signup and view all the answers

    Oncogenic mutations can lead to the overexpression of structural normal receptors, allowing for continued signaling.

    <p>True</p> Signup and view all the answers

    Transient activation of the growth factor receptor does not affect signaling pathways.

    <p>False</p> Signup and view all the answers

    Second messengers are crucial for the transmission of signals from the cytosol to the nucleus.

    <p>True</p> Signup and view all the answers

    Overexpression of kinases does not influence the activation of signaling pathways in cells.

    <p>False</p> Signup and view all the answers

    Surface receptors are the only mechanism of cellular signaling in the context of tyrosine kinase activity.

    <p>False</p> Signup and view all the answers

    The ability of cells to respond to growth factors is solely determined by the presence of those factors.

    <p>False</p> Signup and view all the answers

    RAS proteins are members of a family of proteins that bind to DNA.

    <p>False</p> Signup and view all the answers

    Guanosine triphosphate (GTP) is required for RAS to be in its active state.

    <p>True</p> Signup and view all the answers

    Cyclin D is a major factor in the regulation of RAS activity.

    <p>False</p> Signup and view all the answers

    RAS proteins can bind to either GTP or GDP to be active.

    <p>False</p> Signup and view all the answers

    GTP hydrolysis is required for RAS to be in its inactive state.

    <p>True</p> Signup and view all the answers

    RAS proteins are typically localized to the nucleus.

    <p>False</p> Signup and view all the answers

    The GTP-bound state of RAS is unstable and short-lived.

    <p>True</p> Signup and view all the answers

    RAS proteins can switch between their active and inactive states spontaneously.

    <p>False</p> Signup and view all the answers

    Activation of Ras proteins can be initiated by the binding of growth factors to their receptors.

    <p>True</p> Signup and view all the answers

    Ras proteins are active when bound to GDP.

    <p>False</p> Signup and view all the answers

    Cyclin-dependent kinases (CDKs) are enzymes that regulate the cell cycle by phosphorylating target proteins.

    <p>True</p> Signup and view all the answers

    CDK inhibitors (CDKIs) promote cell cycle progression by activating CDKs.

    <p>False</p> Signup and view all the answers

    The MYC and NMYC genes act as tumor suppressors by promoting apoptosis.

    <p>False</p> Signup and view all the answers

    RB is an oncogene that promotes cell cycle progression.

    <p>False</p> Signup and view all the answers

    The activation of Ras promotes the transition from the G1 phase to the S phase of the cell cycle.

    <p>True</p> Signup and view all the answers

    Amplification of the HER2 gene is commonly associated with breast cancers.

    <p>True</p> Signup and view all the answers

    The Rb protein acts as a tumor suppressor by inhibiting the activity of cyclin D.

    <p>False</p> Signup and view all the answers

    Mutations in the p53 gene can lead to uncontrolled cell growth and tumor formation.

    <p>True</p> Signup and view all the answers

    BRAF mutations are primarily linked to colorectal cancer.

    <p>False</p> Signup and view all the answers

    The p53 protein is activated by DNA damage and promotes the repair of damaged DNA.

    <p>True</p> Signup and view all the answers

    IDH1 and IDH2 mutations produce a new enzyme activity that leads to the production of an oncometabolite.

    <p>True</p> Signup and view all the answers

    Senescence is a state of irreversible cell cycle arrest, characterized by the accumulation of cellular damage.

    <p>True</p> Signup and view all the answers

    Overexpression of PDL1 and PDL2 enhances T cell activation.

    <p>False</p> Signup and view all the answers

    BCL2 is a pro-apoptotic factor that promotes apoptosis in cancer cells.

    <p>False</p> Signup and view all the answers

    The Rb protein is a key regulator of the G1/S checkpoint and promotes cell cycle progression if damaged DNA is detected.

    <p>False</p> Signup and view all the answers

    The RAS gene family is involved in signaling pathways that typically promote growth factor-independent signaling when activated.

    <p>True</p> Signup and view all the answers

    Cyclin D acts as a negative regulator of the cell cycle.

    <p>False</p> Signup and view all the answers

    Loss of function mutations in TP53 are associated with genomic stability and resistance to cellular stress.

    <p>False</p> Signup and view all the answers

    What is the role of mutations in oncogenes concerning cancer cell proliferation?

    <p>Mutations in oncogenes alone are insufficient for the excessive proliferation characteristic of cancer cells.</p> Signup and view all the answers

    How do tumor suppressor genes contribute to the regulation of cellular proliferation?

    <p>Tumor suppressor genes apply 'brakes' to cellular proliferation in normal cells.</p> Signup and view all the answers

    Describe the impact of activating transcription factors in the context of cancer.

    <p>Activating transcription factors can lead to increased protein synthesis associated with pro-growth pathways.</p> Signup and view all the answers

    What is the relationship between PTEN mutations and cellular growth signals?

    <p>PTEN mutations result in insensitivity to growth-inhibitory signals, leading to uncontrolled growth.</p> Signup and view all the answers

    What role does MYC play in the metabolism of cancer cells?

    <p>MYC is involved in increasing metabolic activity and protein synthesis, fueling cancer cell proliferation.</p> Signup and view all the answers

    How does the MAPK pathway relate to cancer development?

    <p>The MAPK pathway promotes pro-growth signals that contribute to cancer cell proliferation.</p> Signup and view all the answers

    Why is the mutation of oncogenes not solely sufficient for cancer progression?

    <p>Cancer progression also requires mutations that inhibit tumor suppressor genes, beyond just oncogene mutation.</p> Signup and view all the answers

    What is the consequence of increased protein synthesis in cancer cells?

    <p>Increased protein synthesis supports the high metabolic demands of rapidly proliferating cancer cells.</p> Signup and view all the answers

    What is the role of RB protein in cancer cells with abnormal signaling pathways?

    <p>RB protein normally inhibits cell cycle progression; in cancer cells, its inactivation leads to uncontrolled cell proliferation.</p> Signup and view all the answers

    How does the dysregulation of the G1-S checkpoint contribute to cancer development?

    <p>Dysregulation of the G1-S checkpoint allows cells to bypass critical control mechanisms, leading to unchecked cell division.</p> Signup and view all the answers

    What is the relationship between p53 and MDM2 in cancer biology?

    <p>MDM2 targets p53 for degradation, inhibiting its function in DNA repair and cell cycle arrest, which is crucial for preventing cancer.</p> Signup and view all the answers

    What impact does increased RAS activity have on cell survival in cancerous environments?

    <p>Increased RAS activity promotes cell survival and proliferation, even under stress conditions, thus contributing to tumorigenesis.</p> Signup and view all the answers

    How does hypoxia influence the behavior of cancer cells?

    <p>Hypoxia leads to the activation of survival pathways in cancer cells, promoting their growth and resistance to therapies.</p> Signup and view all the answers

    In the context of cancer, what is the significance of DNA damage signaling through the p53 pathway?

    <p>The p53 pathway responds to DNA damage by inducing cell cycle arrest or apoptosis, preventing the propagation of damaged cells.</p> Signup and view all the answers

    Describe the mechanism by which cyclin D/CDK4 complexes influence RB function in cancer.

    <p>Cyclin D/CDK4 complexes phosphorylate RB, leading to its inactivation and allowing progression through the cell cycle.</p> Signup and view all the answers

    What are the downstream effects of activated RAS in cellular signaling?

    <p>Activated RAS influences multiple pathways such as MAPK and PI3K, promoting cell growth, survival, and metabolism.</p> Signup and view all the answers

    Describe the role of RB protein in the cell cycle and its interaction with CDK4 and CDK6.

    <p>RB is a tumor suppressor protein that acts as a gatekeeper of the cell cycle. It prevents cells from entering S phase by binding to and inactivating E2F transcription factors, which are necessary for the expression of genes required for DNA replication. CDK4 and CDK6 are cyclin-dependent kinases that phosphorylate RB, leading to its inactivation and release of E2F. This allows cells to progress through the G1 phase and into S phase.</p> Signup and view all the answers

    Explain how the TP53 gene functions as a "guardian of the genome" and its role in response to cellular stress.

    <p>TP53 is a tumor suppressor gene that encodes a transcription factor called p53. p53 is activated in response to cellular stress, such as DNA damage. Once activated, p53 triggers various responses, including cell cycle arrest to allow for DNA repair, apoptosis to eliminate severely damaged cells, and senescence to prevent further proliferation of damaged cells. This multifaceted role of p53 protects the integrity of the genome and prevents the development of cancer.</p> Signup and view all the answers

    What are the consequences of RB inactivation in the context of uncontrolled cell growth and cancer development?

    <p>RB inactivation, either through mutations or by hyperactivation of CDK4/6, removes the brake on cell cycle progression. This allows cells to enter S phase and divide uncontrollably, even in the presence of damaged DNA. Uncontrolled cell proliferation is a hallmark of cancer, and RB inactivation is a common event in many cancers.</p> Signup and view all the answers

    Explain how the p53 pathway can be disrupted by mutations in the TP53 gene and the potential consequences of such mutations.

    <p>Mutations in the TP53 gene can lead to the production of a non-functional p53 protein or a protein that cannot be activated. This disruption of the p53 pathway prevents the normal responses to cellular stress, such as DNA damage. Cells with a mutated TP53 gene are more likely to accumulate mutations and become cancerous. Such mutations are found in a wide range of human cancers, highlighting the critical role of p53 in tumor suppression.</p> Signup and view all the answers

    Discuss the relationship between the RB and TP53 pathways in controlling cell cycle progression and preventing cancer.

    <p>The RB and TP53 pathways work together to maintain genomic integrity and control cell cycle progression. RB regulates entry into S phase, ensuring that cells only divide when appropriate. TP53, when activated by cellular stress, can trigger cell cycle arrest, DNA repair, or apoptosis, depending on the severity of the damage. These pathways are interconnected, with p53 being able to regulate RB activity. Both pathways are critical for preventing the development of cancer.</p> Signup and view all the answers

    Describe the role of E2F transcription factors in cell cycle regulation and their interaction with RB.

    <p>E2F transcription factors are critical for the expression of genes required for DNA replication and entry into S phase. They are normally held inactive by RB, a tumor suppressor protein. Upon phosphorylation of RB by CDK4/6, RB releases E2F, allowing it to activate gene expression necessary for DNA replication and cell cycle progression.</p> Signup and view all the answers

    Compare and contrast the roles of RB and p53 in preventing the development of cancer.

    <p>RB and p53 are both tumor suppressor proteins that play critical roles in preventing cancer. RB functions as a gatekeeper, controlling entry into the cell cycle and preventing uncontrolled proliferation. p53 is a guardian of the genome, responding to cellular stress by activating DNA repair, cell cycle arrest, or apoptosis. While RB prevents uncontrolled cell division, p53 protects the genome from damage. Both proteins are crucial for preventing cancer development, and mutations in their genes are often found in cancer cells.</p> Signup and view all the answers

    Explain how the p53 pathway is involved in maintaining genome stability and preventing the accumulation of mutations.

    <p>The p53 pathway plays a critical role in maintaining genome stability. When DNA damage occurs, p53 is activated. This activation triggers a cascade of events that can result in cell cycle arrest, allowing time for DNA repair. If the damage is too severe, p53 can induce apoptosis, eliminating the damaged cell and preventing it from transmitting mutations to its progeny. By these mechanisms, the p53 pathway prevents the accumulation of mutations that can lead to cancer.</p> Signup and view all the answers

    Explain how the viral oncoprotein E6, encoded by HPV, disrupts the normal function of p53 and its role in cell cycle regulation.

    <p>E6, a viral oncoprotein encoded by HPV, binds to and degrades p53, a tumor suppressor protein. This disruption of p53 function prevents its normal roles in cell cycle arrest, DNA repair, and apoptosis in response to DNA damage. Consequently, cells with damaged DNA can continue to proliferate unchecked, contributing to the development of cervical cancer.</p> Signup and view all the answers

    Considering the role of p53 in cell cycle regulation, why is its inactivation by viral oncoproteins like E6 a significant factor in cancer development?

    <p>p53 acts as a guardian of the genome, halting the cell cycle to allow for DNA repair or triggering apoptosis if damage is irreparable. E6's inactivation of p53 removes this critical checkpoint, enabling cells with damaged DNA to proliferate uncontrollably, ultimately contributing to tumor formation.</p> Signup and view all the answers

    How does the inactivation of p53 by viral oncoproteins like E6 contribute to the development of cervical cancer?

    <p>E6, encoded by HPV, targets and degrades p53, a critical tumor suppressor protein. This inactivation allows cells with DNA damage to bypass the cell cycle checkpoints normally enforced by p53, leading to uncontrolled proliferation. This unchecked growth contributes to the development of cervical cancer.</p> Signup and view all the answers

    Explain the significance of E2F in the context of the viral oncoprotein E6 and its impact on cell cycle regulation.

    <p>E2F is a transcription factor that promotes the expression of genes required for cell cycle progression. E6, encoded by HPV, targets p53 for degradation, removing its inhibitory effect on E2F. This allows E2F to become constitutively active, driving uncontrolled cell proliferation and contributing to cancer development.</p> Signup and view all the answers

    Discuss the significance of the p53 protein in maintaining genomic integrity and preventing the development of cancer.

    <p>p53 is a crucial tumor suppressor protein that safeguards genomic integrity by halting the cell cycle in response to DNA damage, allowing time for repair or initiating apoptosis if the damage is irreparable. Its inactivation by viral oncoproteins like E6 eliminates this protective mechanism, contributing to uncontrolled cell proliferation and tumor development.</p> Signup and view all the answers

    Describe the relationship between E6, p53, and E2F in the context of HPV infection and cervical cancer development.

    <p>E6, a viral oncoprotein encoded by HPV, binds to and degrades p53, a tumor suppressor protein. This inactivation removes the inhibitory effect of p53 on E2F, a transcription factor that promotes cell cycle progression. The resulting constitutive activation of E2F drives uncontrolled cell proliferation, contributing to the development of cervical cancer.</p> Signup and view all the answers

    Explain how the inactivation of p53 by viral oncoproteins like E6 can lead to the development of tumors with specific characteristics, such as those associated with HPV-related cervical cancer.

    <p>The inactivation of p53 by viral oncoproteins like E6 allows cells to bypass checkpoints that normally arrest the cell cycle in response to DNA damage. This unchecked proliferation can lead to the accumulation of mutations, contributing to the development of tumors with specific characteristics. In the case of HPV-related cervical cancer, these characteristics can include uncontrolled cell growth, invasiveness, and the potential for metastasis.</p> Signup and view all the answers

    Why is the inactivation of p53 by viral oncoproteins, such as E6 encoded by HPV, a significant factor in the progression of cervical cancer, despite the presence of other oncogenes and tumor suppressor genes?

    <p>The inactivation of p53 by E6 is particularly significant because p53 acts as a central regulator of cell cycle arrest, DNA repair, and apoptosis in response to DNA damage. Its loss eliminates a critical checkpoint that prevents cells with damaged DNA from proliferating uncontrollably. While other oncogenes and tumor suppressor genes may contribute to the progression of cervical cancer, the inactivation of p53 is a critical event that allows for the accumulation of mutations and the development of aggressive, invasive tumors.</p> Signup and view all the answers

    How does the activity of RB protein influence the G1 to S phase transition in relation to HPV E7 protein?

    <p>The RB protein, when phosphorylated by HPV E7, releases E2F transcription factors, promoting the G1 to S phase transition.</p> Signup and view all the answers

    What is the consequence of RB being in a hypophosphorylated active state during early G1?

    <p>In its hypophosphorylated state, RB binds to E2F and inhibits transcription of genes required for progression into S phase.</p> Signup and view all the answers

    What role does E2F play in the context of HPV infection and cancer progression?

    <p>E2F is crucial for activating genes that drive cell cycle progression; its inhibition by RB prevents excessive cell division, which HPV seeks to bypass.</p> Signup and view all the answers

    How do squamous cell carcinomas relate to HPV's effect on RB and E2F?

    <p>Squamous cell carcinomas often arise when HPV induces mutations that lead to the dysfunction of RB and uncontrolled E2F activation.</p> Signup and view all the answers

    Identify the genes susceptible to HPV infection and their link to RB activity.

    <p>Genes required for S phase progression in cervical and crypt cells are susceptible; RB normally acts to prevent their activation in the presence of HPV.</p> Signup and view all the answers

    What cellular signals typically lead to the activation of growth factor receptors that interact with RB?

    <p>Activated growth factor receptors usually signal growth through downstream pathways that can ultimately influence RB phosphorylation.</p> Signup and view all the answers

    Why is the prevention of mutations critical in the context of RB and E2F signaling?

    <p>Preventing mutations ensures that RB can effectively regulate E2F, thus controlling cell proliferation and reducing cancer risk.</p> Signup and view all the answers

    Explain the importance of maintaining the integrity of the RB pathway in cancer biology.

    <p>Maintaining the integrity of the RB pathway is vital, as its disruption can lead to unregulated cell division and tumorigenesis.</p> Signup and view all the answers

    β-catenin is a ______ activator

    <p>transcriptional</p> Signup and view all the answers

    In colon cancer, a ______ copy of APC can lead to adenomatous polyposis

    <p>defective</p> Signup and view all the answers

    β-catenin is a ______ of the Wnt signaling pathway

    <p>component</p> Signup and view all the answers

    In the absence of Wnt signaling, β-catenin is targeted for ______

    <p>degradation</p> Signup and view all the answers

    Wnt signaling leads to the accumulation of β-catenin in the ______

    <p>nucleus</p> Signup and view all the answers

    β-catenin acts as a ______ factor, regulating gene expression

    <p>transcription</p> Signup and view all the answers

    β-catenin promotes the expression of genes involved in ______ and cell proliferation

    <p>growth</p> Signup and view all the answers

    Mutations in β-catenin can lead to its ______ activation, contributing to cancer development

    <p>constitutive</p> Signup and view all the answers

    Mutations in genes that regulate some or all of these ______ cellular traits result in abnormal behavior.

    <p>cell</p> Signup and view all the answers

    This process is seen in every ______; accordingly, these traits form the basis of the cells’ normality.

    <p>cancer</p> Signup and view all the answers

    During which they promote cell cycle ______ (growth factors, growth factor).

    <p>progression</p> Signup and view all the answers

    We will also discuss a subset of cancer genes which frequent or well- ______ receptors.

    <p>known</p> Signup and view all the answers

    Also, signaling molecules, and cyclin/cyclin-______ kinases defined roles in cancer.

    <p>dependent</p> Signup and view all the answers

    The progression of cancer often entails changes in the expression of ______ which regulate cell division.

    <p>genes</p> Signup and view all the answers

    The cellular behavior leading to cancer is typically a result of imbalances in ______ pathways.

    <p>signaling</p> Signup and view all the answers

    In many cases, alterations will lead to an increase in the rate of ______ among the daughter cells.

    <p>division</p> Signup and view all the answers

    Inactivation by NF1 leads to the upregulation of the expression of genes that support ______.

    <p>cell growth</p> Signup and view all the answers

    The hydrolysis of GTP is required for cell cycle ______.

    <p>progression</p> Signup and view all the answers

    Active RAS is discussed in terms of its role in ______ metabolism.

    <p>anabolic</p> Signup and view all the answers

    Cyclin D is a factor required for cell ______.

    <p>cycle</p> Signup and view all the answers

    MYC is recognized as a transcription factor involved in cell ______.

    <p>growth</p> Signup and view all the answers

    The inactivation of RAS can influence cell ______ and growth.

    <p>regulation</p> Signup and view all the answers

    Discussion of the mechanisms by which ______ influences cell growth is included.

    <p>RAS</p> Signup and view all the answers

    The relationship between RAS and MYC is important for understanding cancer ______.

    <p>development</p> Signup and view all the answers

    More than 70% of human cancers have defects in ______.

    <p>TP53</p> Signup and view all the answers

    Cancers often have defects in genes upstream or downstream of ______.

    <p>TP53</p> Signup and view all the answers

    ______ inhibitors activate the signaling pathways related to cancer.

    <p>CDK</p> Signup and view all the answers

    Defects in ______ and p21 are commonly observed in various cancers.

    <p>p16</p> Signup and view all the answers

    The dysregulation of ______ is implicated in cancer development.

    <p>TP53</p> Signup and view all the answers

    The importance of TP53 dysregulation in cancer is highlighted by its ______ in numerous cases.

    <p>significance</p> Signup and view all the answers

    CDK inhibitors are crucial for the ______ of cancer treatments.

    <p>activation</p> Signup and view all the answers

    Cancers often exhibit faults in ______ pathways that regulate TP53.

    <p>signaling</p> Signup and view all the answers

    The activity of RAS is normally held in check by ______ (GTPase-activating proteins) such as NF1.

    <p>GAPs</p> Signup and view all the answers

    Factors shown in ______ are oncoproteins that are activated by gain-of-function mutations.

    <p>green</p> Signup and view all the answers

    The presence of one defective copy of the ______ gene in the germline of affected individuals increases cancer risk.

    <p>RB</p> Signup and view all the answers

    Factors shown in ______ are tumor suppressors that are often missing due to loss-of-function mutations.

    <p>red</p> Signup and view all the answers

    The activity of PI3 kinase is antagonized by ______.

    <p>PTEN</p> Signup and view all the answers

    Renoblastomas are a familial cancer, which predisposes to the development of ______.

    <p>tumors</p> Signup and view all the answers

    The activity of RAS can lead to various types of cancer, whereas its ______ is regulated by GAPs.

    <p>activity</p> Signup and view all the answers

    The ______ of RAS is crucial for its role in cellular signaling pathways.

    <p>regulation</p> Signup and view all the answers

    Match the following metabolic processes with their primary functions:

    <p>Oxidative phosphorylation = Produces ATP through the breakdown of glucose Glycolysis = Breaks down glucose into pyruvate Autophagy = Degrades cellular components for survival during nutrient deprivation Krebs cycle = Produces electron carriers for oxidative phosphorylation</p> Signup and view all the answers

    Match the following cellular processes with their respective roles in maintaining genomic integrity:

    <p>DNA repair = Corrects damaged DNA to prevent mutations Cell cycle arrest = Halts cell division to allow for DNA repair Apoptosis = Programmed cell death eliminates severely damaged cells Senescence = Irreversible growth arrest prevents proliferation of damaged cells</p> Signup and view all the answers

    Match the following proteins with their functions in the p53 pathway:

    <p>p53 = A tumor suppressor protein that activates DNA repair and cell cycle arrest CDKN1A (p21) = A cyclin-dependent kinase inhibitor that blocks cell cycle progression GADD45 = A gene involved in DNA repair and cell cycle checkpoint control TP53 = The gene encoding the p53 protein</p> Signup and view all the answers

    Match the following scenarios with their consequences in cells with mutated TP53:

    <p>DNA damage = Fails to trigger cell cycle arrest or DNA repair Cell cycle progression = Occurs despite DNA damage, leading to mutations Proliferation = Of genetically damaged cells, increasing the risk of cancer Apoptosis = Is not induced, allowing damaged cells to survive and proliferate</p> Signup and view all the answers

    Match the following cellular states with their respective characteristics:

    <p>Normal cells with active p53 = Respond to DNA damage by repairing or eliminating damaged cells Cells with mutated TP53 = Fail to repair or eliminate damaged DNA, leading to uncontrolled proliferation Senescent cells = Have irreversibly arrested growth, preventing further proliferation Apoptotic cells = Undergo programmed cell death, eliminating severely damaged cells</p> Signup and view all the answers

    Match the following cellular processes with their respective roles in cancer development:

    <p>Mutations in TP53 = Lead to the loss of p53 function, promoting tumor growth Uncontrolled proliferation = Of genetically damaged cells contributes to tumor formation Evasion of apoptosis = Allows damaged cells to survive and proliferate Failure of DNA repair = Accumulates mutations, increasing the risk of cancer</p> Signup and view all the answers

    Match the following molecular events with their respective consequences in the p53 pathway:

    <p>Activation of p53 = Induces DNA repair, cell cycle arrest, and apoptosis Upregulation of CDKN1A (p21) = Inhibits cyclin-dependent kinases, halting cell cycle progression Expression of GADD45 = Promotes DNA repair and cell cycle checkpoint control Successful DNA repair = Allows cells to proceed with the cell cycle</p> Signup and view all the answers

    Match the following terms with their definitions:

    <p>Genome integrity = The state of a complete set of genetic material in an organism DNA damage = Alterations to the structure or sequence of DNA Cell cycle arrest = A temporary halt in cell division Apoptosis = Programmed cell death</p> Signup and view all the answers

    Match the following factors with their roles in cancer development:

    <p>Mutations in tumor suppressor genes = Loss of function that promotes uncontrolled cell growth Activation of oncogenes = Gain of function that drives uncontrolled cell growth Evasion of apoptosis = Allows damaged cells to survive and proliferate Uncontrolled proliferation = Leads to the accumulation of abnormal cells, forming tumors</p> Signup and view all the answers

    Match the following cellular processes with their associated genes:

    <p>Cyclin D = regulation of cell growth p53 = DNA repair and maintenance of genome integrity RAS = cell signaling and proliferation MYC = regulation of cell growth and proliferation</p> Signup and view all the answers

    Match the following genes with their roles in cancer development:

    <p>NF1 = regulation of RAS activity TP53 = promotion of DNA repair and prevention of cancer ABL = conversion of nonreceptor tyrosine kinase genes into oncogenes MYC = promotion of cell growth and proliferation</p> Signup and view all the answers

    Match the following cellular processes with their associated outcomes:

    <p>Induction of DNA damage = activation of p53 and cell cycle arrest RAS activation = promotion of cell growth and proliferation p53 activation = promotion of DNA repair and apoptosis NF1 inactivation = unregulated RAS activity and cell growth</p> Signup and view all the answers

    Match the following genes with their associated functions:

    <p>RB = regulation of cell cycle progression RAS = cell signaling and regulation of cell growth MYC = regulation of cell growth and proliferation NF1 = regulation of RAS activity and cell growth</p> Signup and view all the answers

    Match the following cellular processes with their associated genes:

    <p>Cell signaling = RAS DNA repair = p53 Regulation of cell growth = MYC Regulation of RAS activity = NF1</p> Signup and view all the answers

    Match the following genes with their associated outcomes in cancer development:

    <p>TP53 = increased risk of cancer RAS = unregulated cell growth and proliferation MYC = promotion of cell growth and tumorigenesis NF1 = unregulated RAS activity and cancer development</p> Signup and view all the answers

    Match the following cellular processes with their associated genes:

    <p>Cell cycle regulation = RB DNA repair and genome integrity = p53 Cell growth and proliferation = MYC Cell signaling and RAS regulation = NF1</p> Signup and view all the answers

    Match the following genes with their associated roles in cell growth regulation:

    <p>RAS = promotion of cell growth and proliferation NF1 = regulation of RAS activity MYC = promotion of cell growth and proliferation p53 = regulation of cell growth and prevention of cancer</p> Signup and view all the answers

    Match the following components with their associated functions in cell growth and signaling:

    <p>RAS = Active signaling involved in downstream effects GTP = Substrate hydrolyzed for RAS inactivation MYC = Transcription factor promoting cell proliferation NF1 = Negative regulator of RAS activity</p> Signup and view all the answers

    Match the following terms with their definitions related to cellular processes:

    <p>Inactivation = Process of reducing activity of a signaling molecule Upregulation = Increase in the expression of certain genes Hyperphosphorylation = Addition of phosphate groups to proteins increasing their function Cyclin D = Regulator required for progression through the cell cycle</p> Signup and view all the answers

    Match the following cancer-related genes with their roles in cell growth:

    <p>NF1 = Facilitates GTP hydrolysis in RAS signaling MYC = Encodes a transcription factor essential for growth Cyclin D = Controls the transition from G1 to S phase in the cell cycle RAS = Oncogene with a pivotal role in many cancers</p> Signup and view all the answers

    Match the following processes with their consequences in cell signaling:

    <p>GTP hydrolysis = Leads to RAS inactivation RAS activation = Enhances cell proliferation and growth MYC activation = Promotes transcription of growth-related genes Cyclin D function = Facilitates cell cycle progression</p> Signup and view all the answers

    Match the following proteins with their respective roles in cellular mechanisms:

    <p>NF1 = Inhibitor of cell growth via RAS regulation Cyclin D = Activator of cell cycle transition MYC = Stimulator of gene expression for proliferation Active RAS = Regulator of anabolic metabolism and growth</p> Signup and view all the answers

    Match the following conditions with their potential implications in cancer biology:

    <p>Abnormal NF1 function = Increased RAS signaling leading to tumorigenesis High MYC levels = Enhanced expression of pro-growth genes Deficient GTP hydrolysis = Sustained activation of RAS Overexpression of Cyclin D = Uncontrolled cell cycle progression</p> Signup and view all the answers

    Match the following cellular responses with their triggering events:

    <p>Cell proliferation = Result of active RAS signaling Cell cycle arrest = Potential response to DNA damage Gene expression changes = Triggered by MYC activation Signal transduction = Conducted through active proteins like RAS</p> Signup and view all the answers

    Match the following signaling pathways with their associated roles in cell regulation:

    <p>RAS pathway = Regulates cell growth and metabolism MYC pathway = Induces gene expression for proliferation NF1 pathway = Negatively regulates RAS activity Cyclin D pathway = Promotes cell cycle progression</p> Signup and view all the answers

    Match the following terms related to signal transduction with their corresponding descriptions:

    <p>Tyrosine kinases = Enzymes that add phosphate groups to tyrosine residues on target proteins Transcription factors = Proteins that bind to DNA and regulate gene expression Second messengers = Small intracellular molecules that relay signals from activated receptors Growth factor receptors = Transmembrane proteins that bind to growth factors and initiate signaling cascades</p> Signup and view all the answers

    Match the following types of mutations with their potential consequences in signal transduction:

    <p>Oncogenic mutations = Mutations that lead to constitutive activation of signaling pathways Loss-of-function mutations = Mutations that disrupt the function of signaling proteins, leading to decreased signaling Gain-of-function mutations = Mutations that enhance the activity of signaling proteins, leading to increased signaling Silent mutations = Mutations that do not alter the amino acid sequence of a protein and have no functional effect</p> Signup and view all the answers

    Match the following components of the RAS signaling pathway with their respective roles:

    <p>RAS = A small GTPase that acts as a molecular switch in signal transduction NF1 = A tumor suppressor gene that inactivates RAS by promoting GTP hydrolysis MYC = A transcription factor that promotes cell growth and proliferation Cyclin D = A protein that regulates the cell cycle by promoting entry into S phase</p> Signup and view all the answers

    Match the following cellular processes with their respective descriptions:

    <p>Signal transduction = The process by which cells receive and respond to external stimuli Cell cycle = A series of events that lead to cell growth and division Gene expression = The process by which genetic information is transcribed into RNA and translated into protein Apoptosis = Programmed cell death, a process that eliminates damaged or unwanted cells</p> Signup and view all the answers

    Match the following terms related to cancer development with their corresponding definitions:

    <p>Oncogene = A gene that promotes uncontrolled cell growth and proliferation Tumor suppressor gene = A gene that normally inhibits cell growth and proliferation, but when mutated can contribute to cancer Proto-oncogene = A normal gene that can become an oncogene through mutation or misregulation Carcinogen = An agent that can cause cancer</p> Signup and view all the answers

    Match the following terms related to DNA damage and repair with their corresponding descriptions:

    <p>DNA damage = Alterations to the structure or sequence of DNA, which can lead to mutations DNA repair = Cellular mechanisms that repair DNA damage to maintain genome integrity Checkpoint control = A mechanism that pauses the cell cycle to allow for DNA repair before cell division Apoptosis = Programmed cell death, which can be triggered by unrepaired DNA damage</p> Signup and view all the answers

    Match the following terms related to cell cycle regulation with their corresponding roles:

    <p>Cyclin-dependent kinases (CDKs) = Enzymes that phosphorylate target proteins to regulate cell cycle progression Cyclins = Proteins that bind to and activate CDKs Cell cycle checkpoints = Points in the cell cycle where progress is halted until certain conditions are met Cell cycle arrest = A temporary halt in the cell cycle to allow for DNA repair or other cellular processes</p> Signup and view all the answers

    Match the following terms related to senescence with their corresponding descriptions:

    <p>Cellular senescence = A state of permanent cell cycle arrest, often triggered by DNA damage or telomere shortening Replicative senescence = A type of senescence that occurs after a limited number of cell divisions Oncogene-induced senescence (OIS) = A type of senescence that is triggered by the activation of oncogenes Senescence-associated secretory phenotype (SASP) = A complex set of secreted factors that are released by senescent cells</p> Signup and view all the answers

    Study Notes

    Cancer and RAS Signaling

    • RAS proteins play a crucial role in signal transduction and are frequently involved in cancer pathways, particularly through mutations.
    • Mutations in RAS can lead to amino acid substitutions that disrupt its normal function and promote continuous active signaling via GTP-binding forms.
    • Active RAS facilitates the activation of downstream signaling pathways, influencing factors that regulate cell growth and proliferation.

    RAS Activation and Impact

    • RAS is activated by guanosine triphosphate (GTP) hydrolysis, while its inactivation is mediated by various factors including NF1.
    • Active RAS stimulates the expression of genes involved in cell cycle progression, including those critical for synthesizing cyclin D.
    • Key transcription factors influenced by RAS signaling include MYC, which broadly affects gene expression related to growth.

    Genetic Syndromes and Cancer Risk

    • Patients with certain genetic conditions, such as RAS syndrome, have a significantly increased risk (25-fold) of developing various malignancies by age 50.
    • Common cancers associated with these syndromes include sarcomas and specific carcinomas of the breast, as well as certain leukemias and brain tumors.
    • These cancers often occur at a young age and can manifest as multiple different tumor types in affected individuals.

    Cellular Mechanisms in Cancer

    • The distinction between hypophosphorylated and hyperphosphorylated Rb proteins influences cell cycle regulation.
    • DNA damage response mechanisms are vital; activation of p53 due to DNA damage leads to cell cycle arrest and DNA repair induction.
    • Unsuccessful DNA repair results in either apoptosis or senescence, preventing the propagation of genetically damaged cells.

    Diagnostic Imaging in Oncology

    • Positron Emission Tomography (PET) scans detect tumors by visualizing glucose analog uptake; F-fluorodeoxyglucose is commonly used in imaging.
    • Most tumors are PET-positive, indicating high metabolic activity, which is relevant for monitoring tumor growth and response to therapy.

    Metabolic Changes in Cancer Cells

    • Cancer cells exhibit altered metabolism, characterized by the Warburg effect, which shifts energy production towards glycolysis.
    • Various metabolic intermediates are necessary for the proliferation of cancer cells, highlighting the importance of understanding metabolic pathways in cancer progression.

    Important Cancer Genes

    • TP53 (Tumor Suppressor Gene)

      • Functions as a sensor for cellular stress and facilitates DNA repair.
      • Loss of function leads to genomic instability and resistance to pro-apoptotic signals.
      • Associated with diverse cancers.

    • RB (Tumor Suppressor Gene)

      • Acts as a negative regulator of the cell cycle.
      • Loss of function results in increased cell growth and failure to differentiate.
      • Mutated in retinoblastoma and osteosarcoma, with dysregulation noted in various cancers.

    • HER2 (Oncogene)

      • A growth factor receptor involved in signaling pathways.
      • Gain of function causes factor-independent growth signaling.
      • Frequently amplified in a subset of breast cancers and other carcinomas.

    • ABL (Oncogene)

      • Functions as a non-receptor tyrosine kinase.
      • Gain of function leads to growth signaling independence.
      • Activated through translocations in certain types of leukemias.

    • RAS (Oncogene)

      • Serves as an essential signaling molecule.
      • Gain of function results in independent growth signaling.
      • Implicated in a variety of cancers.

    • BRAF (Oncogene)

      • Another critical signaling molecule.
      • Mutations lead to factor-independent signaling.
      • Commonly mutated in melanoma.

    • Cyclin D (Oncogene)

      • Functions as a cell cycle regulator.
      • Overexpression disrupts the action of RB, fostering increased cell proliferation.
      • Frequently overexpressed due to translocations or amplification in lymphoma and breast cancer.

    • MYC, NMYC (Oncogenes)

      • Serve as transcription factors regulating various genes.
      • Overexpression leads to reprogramming of cell metabolism.
      • Translocated in Burkitt lymphoma and amplified in neuroblastoma, with dysregulation in multiple cancers.

    • IDH1, IDH2 (Oncogenes)

      • Encode metabolic enzymes.
      • Mutations lead to the production of oncometabolites.
      • Associated with acute myeloid leukemia, gliomas, chondrosarcoma, and cholangiocarcinoma.

    • BCL2 (Anti-apoptosis Gene)

      • Opposes pro-apoptotic factors.
      • Overexpression leads to resistance against apoptosis.
      • Translocated in follicular lymphoma and noted for dysregulation in diverse cancers.

    • PDL1, PDL2 (Host/Cancer Cell Interactions)

      • Involved in activating immune checkpoint pathways in T cells.
      • Overexpression drives immune evasion mechanisms.
      • Amplified in Hodgkin lymphoma and various other cancers.

    Cellular Transformation and Tumor Progression

    • Inflammation and genomic instability enable cellular transformations and tumor progression involving cellular components like organelles and membrane constituents necessary for cell division.
    • Growth factor receptors can become transiently activated to stimulate similar signaling pathways even when growth factor levels are low.
    • Oncogenic mutations, particularly in ABL and RAS genes, lead to altered signaling that drives uncontrolled cell proliferation.### Cell Cycle Regulation
    • Activation of oscillations is dependent on the cell cycle phase, affecting cell growth and division.
    • Cyclin-dependent kinase (CDK) receptors play a crucial role, with their activity dependent on specific growth factors and sometimes affected by mutations associated with cancer.
    • The exchange of GDP for GTP and specific binding interactions are mediated by cyclins.

    CDK Inhibitors and RAS Function

    • CDK inhibitors (CDKIs) regulate CDK complexes by altering conformational states, which generate active RAS proteins.
    • Active RAS functions as a negative regulator of cyclin/CDK complexes, influencing cell cycle progression.

    Phases of the Cell Cycle

    • Transition from G1 phase to S phase is significant for cell cycle regulation, highlighting cellular commitment to DNA synthesis and replication.
    • The progression through the cell cycle is tightly regulated by CDKs and their corresponding cyclins, including the p21 family of CDK inhibitors.

    Key CDKs and Cyclins

    • Important CDKs include CDK1, CDK2, CDK4, and CDK6, each associated with specific cyclins (e.g., Cyclin D, Cyclin B).
    • Cyclin levels fluctuate throughout the cell cycle, activating their respective CDKs and facilitating cell cycle progression.

    Importance of Rb Protein

    • Rb (Retinoblastoma protein) is a key player in cell cycle regulation, controlling the transition from G1 to S phase by inhibiting E2F transcription factors when hypophosphorylated.
    • Phosphorylation of Rb by CDKs allows progression through the cell cycle, highlighting the interplay between Rb and CDK/cyclin complexes.

    Cancer Cell Proliferation Mechanisms

    • Insensitivity to growth-inhibitory signals is a hallmark of cancer cells, leading to unchecked proliferation.
    • Pro-growth pathways like MAPK and oncogene mutations alone are inadequate for unregulated proliferation; they require mutations that also inhibit tumor suppressor genes.

    Role of Tumor Suppressor Genes

    • Tumor suppressor genes act as brakes on cellular proliferation in normal cells, preventing excessive growth.
    • RB (retinoblastoma protein) is a crucial tumor suppressor that regulates the G1-S phase transition of the cell cycle.
    • HPVs E7 protein can bind to RB in its hypo-phosphorylated active form, preventing E2F inhibition and thus promoting cell cycle progression.

    Transcription Regulation and Cancer Progression

    • Increased protein synthesis is observed during cellular proliferation, requiring specific transcription factors from the E2F family.
    • HPV infection is significant for squamous cell carcinomas, affecting the expression of genes vital for progression into the S phase.

    TP53 and the Cellular Stress Response

    • TP53 is known as the "guardian of the genome," being the most frequently mutated tumor suppressor gene in human cancers.
    • Its role includes protecting cells from stress-induced damage and modulating responses to various stresses, such as DNA damage and inappropriate pro-growth signals.

    G1-S Checkpoint Dysregulation

    • Abnormalities in the regulation of the G1-S checkpoint, primarily due to mutations in RB and related phosphorylation pathways, are prevalent in cancer cells.
    • Such dysregulation often results in overactivation of cellular pathways leading to unregulated growth, indicating a connection to oncogenes like RAS.

    The Role of MDM2 and E2F in Cancer

    • MDM2 is involved in the negative regulation of p53, often leading to its degradation and inactivation in cancers where p53 is protective.
    • E2F transcription factors play a critical role in cell cycle progression and are targeted by oncogenic proteins that interfere with their normal regulatory functions.

    HPV and Carcinogenic Mechanisms

    • HPV utilizes viral oncogenes, such as E6, which interact with and destabilize p53, leading to unchecked cellular replication and tumorigenesis.
    • The destruction of crucial proteins such as p53 and RB by HPV contributes significantly to the development of cancer by allowing rapid cell division and mutation accumulation.

    Cancer Cell Cycle and Progression

    • Mutations in genes responsible for regulating cellular processes can lead to abnormal cell division, commonly observed in cancer.
    • The normal balance of cellular functions relies on proteins that regulate growth and division processes.

    Molecular Mechanisms

    • Key signaling molecules that promote cancer cell cycle progression include growth factors, signaling molecules, and cyclins along with cyclin-dependent kinases.
    • RAS is a pivotal player, activating pathways that promote growth; its function is often disrupted in cancer.
    • RAS activity is regulated by GTPase-activating proteins (GAPs), such as NF1, while PI3 kinase activity is blocked by tumor suppressor PTEN.

    Oncogenes and Tumor Suppressors

    • Oncogenes, depicted in green, are frequently activated by gain-of-function mutations in diverse cancers.
    • Tumor suppressor genes, in red, are often inactivated due to loss-of-function mutations, such as defects in the TP53 gene, which is implicated in over 70% of human cancers.
    • The relevance of TP53 dysregulation is underscored by its frequent inactivation in various cancer types.

    Pathway Activation and Transcription Regulation

    • β-catenin acts as a transcriptional activator and can become hyperactive when associated regulatory genes like APC are lost.
    • Hyperactivity of β-catenin in specific lineages can result in increased transcription of growth-promoting genes.

    Retinoblastoma (RB) Regulation

    • RB protein is crucial for regulating the G1 to S phase transition within the cell cycle via interaction with E2F transcription factors.
    • Hypophosphorylated RB inhibits transcription factors necessary for S phase entry, maintaining cell cycle control.

    Genetic Defects and Cancer Development

    • More than 70% of cancers have mutations reflecting defects in genes that regulate cell cycle, including TP53 and others upstream or downstream of its pathways.
    • Individuals with inherited mutations, such as one defective copy of the RB gene, have a predisposition to developing certain tumor types, like retinoblastoma.

    Summary of Cancer Genetics

    • CDK inhibitors such as p16 and p21 regulate cell cycle by inhibiting cyclin-dependent kinases, thus impacting cancer progression.
    • The complexity of cancer genetics involves both the activation of oncogenes and the inactivation of tumor suppressors, illustrating a dynamic interplay in cancer development.

    Cell Cycle and Cancer

    • Mutations in genes regulating cellular processes are present in all cancers, influencing cell division and the formation of daughter cells.
    • These mutations impact multiple levels of cellular regulation by disrupting the balance between proteins.

    Molecular Mechanisms of Cancer

    • Discussion includes oncogenic mutations in genes encoding growth factors, signaling molecules, and cyclin/cyclin-dependent kinases.
    • The activation of growth factor receptors can stimulate the same pathways even when growth factor levels are low.

    Signal Transduction

    • Signal transmission occurs across the cytosol to the nucleus, using activated proteins or second messengers.
    • Overexpression of structural normal receptors enables signaling to occur despite low growth factor levels.

    Role of Oncogenes and Tumor Suppressors

    • Activation of transcription factors increases the expression of genes that support cell growth, such as cyclins and MYC.
    • Loss of TP53 mutations leads to unregulated cell cycle progression and proliferation of genetically damaged cells, potentially resulting in malignant neoplasms.

    Metabolic Changes in Cancer

    • Tumor cells often exhibit the Warburg effect, favoring glycolysis even in the presence of oxygen.
    • Cancer cells require metabolic intermediates to synthesize cellular components; mitochondrial oxidative phosphorylation is critical for their survival.

    Autophagy and Nutrient Deficiency

    • Autophagy is a response to severe nutrient deficiency, allowing cells to recycle proteins and organelles.
    • Cancer cells can grow under marginal conditions, contrasting with aerobic glycolysis that typically occurs in healthier cells.

    Gene Regulation and Malignancy

    • Several genes promoting autophagy also function as tumor suppressors, highlighting the connection between metabolism and cancer progression.
    • Disruption of pathways inducing autophagy can exacerbate cancer development and progression.

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