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Questions and Answers
Cancer is characterized by uncontrolled cell ______.
Cancer is characterized by uncontrolled cell ______.
division
Most cancers originate from a single ______.
Most cancers originate from a single ______.
cell
Cancers can be categorized into benign and ______ types.
Cancers can be categorized into benign and ______ types.
malignant
The process of cancer development is often referred to as a ______ process.
The process of cancer development is often referred to as a ______ process.
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Tumor ______ are viruses known to directly cause cancer.
Tumor ______ are viruses known to directly cause cancer.
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Examples of DNA viruses that may cause cancer include hepatitis B and ______.
Examples of DNA viruses that may cause cancer include hepatitis B and ______.
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Rous sarcoma virus (RSV) causes sarcomas in ______.
Rous sarcoma virus (RSV) causes sarcomas in ______.
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Chemical ______ can contribute to cancer by damaging DNA.
Chemical ______ can contribute to cancer by damaging DNA.
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Epstein-Barr virus is a causative agent in ______ lymphoma.
Epstein-Barr virus is a causative agent in ______ lymphoma.
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Approximately ______% of human cancers are not induced by viruses.
Approximately ______% of human cancers are not induced by viruses.
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Specific genes capable of inducing cell transformation are called ______.
Specific genes capable of inducing cell transformation are called ______.
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The first oncogene to be identified was the ______ gene of RSV.
The first oncogene to be identified was the ______ gene of RSV.
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Mutations in proto-oncogenes are typically ______ in nature.
Mutations in proto-oncogenes are typically ______ in nature.
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The prototype tumor suppressor gene is ______.
The prototype tumor suppressor gene is ______.
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______ is required for apoptosis induced by DNA damage.
______ is required for apoptosis induced by DNA damage.
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Tumor suppressor genes act to inhibit cell ______ and tumor development.
Tumor suppressor genes act to inhibit cell ______ and tumor development.
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Rb inhibits progression past the restriction point in ______.
Rb inhibits progression past the restriction point in ______.
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Cdk4, 6/cyclin D complexes promote passage through the restriction point by ______ and inactivating Rb.
Cdk4, 6/cyclin D complexes promote passage through the restriction point by ______ and inactivating Rb.
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The activity of Cdk4, 6/cyclin D is inhibited by ______.
The activity of Cdk4, 6/cyclin D is inhibited by ______.
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Wild-type p53 is required for both cell cycle arrest and ______ induced by DNA damage.
Wild-type p53 is required for both cell cycle arrest and ______ induced by DNA damage.
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Cell cycle arrest is mediated by induction of the Cdk inhibitor ______.
Cell cycle arrest is mediated by induction of the Cdk inhibitor ______.
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Loss-of-function in a tumor-suppressor gene can allow ______ growth to occur.
Loss-of-function in a tumor-suppressor gene can allow ______ growth to occur.
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Normal, nonmutated genes with the potential to become oncogenes are known as ______.
Normal, nonmutated genes with the potential to become oncogenes are known as ______.
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Missense mutations in ras genes are frequently found in a large number of different ______.
Missense mutations in ras genes are frequently found in a large number of different ______.
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Gains-of-function mutations generally increase the ______ of protein or alter its structure.
Gains-of-function mutations generally increase the ______ of protein or alter its structure.
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The ______ family members PUMA and Noxa are involved in the apoptosis pathway.
The ______ family members PUMA and Noxa are involved in the apoptosis pathway.
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The first human tumor-suppressor gene identified was the ______ gene.
The first human tumor-suppressor gene identified was the ______ gene.
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Alfred Knudson proposed a 'two-hit' model for ______.
Alfred Knudson proposed a 'two-hit' model for ______.
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About ______% of all human cancers are associated with defects in the p53 gene.
About ______% of all human cancers are associated with defects in the p53 gene.
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The Rb protein regulates the transcription factor ______, which is essential for cell cycle progression.
The Rb protein regulates the transcription factor ______, which is essential for cell cycle progression.
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Apoptosis is facilitated by proteases known as ______.
Apoptosis is facilitated by proteases known as ______.
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Tumor-suppressor genes prevent ______ growth.
Tumor-suppressor genes prevent ______ growth.
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The functions of tumor-suppressor genes include negatively regulating cell ______.
The functions of tumor-suppressor genes include negatively regulating cell ______.
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The two forms of retinoblastoma are inherited and ______.
The two forms of retinoblastoma are inherited and ______.
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If there is no functional Rb protein, a cell can always progress through the ______ cycle.
If there is no functional Rb protein, a cell can always progress through the ______ cycle.
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P53 promotes pathways that activate genes for DNA ______.
P53 promotes pathways that activate genes for DNA ______.
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The inhibition of E2F prevents the transcription of certain genes required for DNA replication and cell division, and the protein kinase ______ negatively regulates cyclin-dependent kinases.
The inhibition of E2F prevents the transcription of certain genes required for DNA replication and cell division, and the protein kinase ______ negatively regulates cyclin-dependent kinases.
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The NF1 protein stimulates Ras to hydrolyze its GTP to ______.
The NF1 protein stimulates Ras to hydrolyze its GTP to ______.
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APC is a negative regulator of a cell-signaling pathway that leads to the activation of genes that promote ______.
APC is a negative regulator of a cell-signaling pathway that leads to the activation of genes that promote ______.
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P53 acts as a checkpoint protein and positively regulates a few specific target genes while negatively regulating others, acting as a sensor of ______.
P53 acts as a checkpoint protein and positively regulates a few specific target genes while negatively regulating others, acting as a sensor of ______.
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BRCA1 and BRCA2 proteins are involved in the cellular defense against ______.
BRCA1 and BRCA2 proteins are involved in the cellular defense against ______.
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Tumor-suppressor genes fall into two categories: those that negatively regulate cell division and those that maintain ______.
Tumor-suppressor genes fall into two categories: those that negatively regulate cell division and those that maintain ______.
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Checkpoint proteins detect genetic abnormalities and prevent ______.
Checkpoint proteins detect genetic abnormalities and prevent ______.
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Epigenetics is the study of heritable traits that happen without changes to the ______ sequence.
Epigenetics is the study of heritable traits that happen without changes to the ______ sequence.
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Epigenetic changes can lead to functionally relevant alterations in the ______.
Epigenetic changes can lead to functionally relevant alterations in the ______.
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Examples of mechanisms that produce epigenetic changes include DNA ______ and histone modification.
Examples of mechanisms that produce epigenetic changes include DNA ______ and histone modification.
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Epigenetic changes may directly contribute to disease ______.
Epigenetic changes may directly contribute to disease ______.
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One indirect association of epigenetic changes and disease suggests that a third factor may be involved, like a toxic ______.
One indirect association of epigenetic changes and disease suggests that a third factor may be involved, like a toxic ______.
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Abnormal chromatin modifications in cancer cells include DNA methylation and histone ______.
Abnormal chromatin modifications in cancer cells include DNA methylation and histone ______.
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Mutations in genes that encode chromatin-modifying proteins can lead to ______ effects on gene expression.
Mutations in genes that encode chromatin-modifying proteins can lead to ______ effects on gene expression.
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Covalent modification of histones affects how genes are ______.
Covalent modification of histones affects how genes are ______.
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Environmental agents can directly alter the functions of ______ proteins.
Environmental agents can directly alter the functions of ______ proteins.
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Tobacco smoke and charbroiled food contain polycyclic aromatic ______.
Tobacco smoke and charbroiled food contain polycyclic aromatic ______.
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A common type of mutation in cancer involves the gene encoding a DNA ______ enzyme.
A common type of mutation in cancer involves the gene encoding a DNA ______ enzyme.
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Histone demethylases are involved in removing ______ groups from histones.
Histone demethylases are involved in removing ______ groups from histones.
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Acute myeloid leukemia is associated with mutations in genes encoding DNA ______.
Acute myeloid leukemia is associated with mutations in genes encoding DNA ______.
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Endocrine disruptors are associated with cancer of the breast, prostate, and ______.
Endocrine disruptors are associated with cancer of the breast, prostate, and ______.
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5-azacytidine and decitabine are examples of drugs that inhibit ______ to treat cancer.
5-azacytidine and decitabine are examples of drugs that inhibit ______ to treat cancer.
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Study Notes
Genetic Basis of Cancer
- Cancer is a disease of uncontrolled cell division, a genetic disease at the cellular level
- Human cancers are classified by the cell type that becomes cancerous; over 100 types have been identified
- Most cancers originate from a single cell; a characteristic known as clonal in origin. Cancer cells divide to produce more cancer cells
- Cancer is a multistep process; beginning as a benign, non-invasive growth. More genetic changes cause cancerous growth
Characteristics of Cancer
- Most cancers originate from a single cell, a clonal origin
- Cancer is a multistep process beginning as a benign, non-invasive growth
- Additional genetic changes cause cancerous growth
- Cancer may be staged as malignant (invasive, invades surrounding tissues) or metastatic (moves to a different site in the body)
Causes of Cancer
- Radiation and many chemical carcinogens damage DNA and induce mutations
- Other chemical carcinogens contribute to cancer development by stimulating cell proliferation
- Viruses cause cancer in humans and other species
Tumor Viruses
- Several families of animal viruses, known as tumor viruses, are capable of causing cancer in experimental animals and humans
- Different virus families have different human tumor types, different genome sizes
- The majority of human cancers (about 80%) are not induced by viruses; they are caused by other factors
Cancer Results From Alterations in Genes
- Cancer results from alterations in critical regulatory genes that control cell proliferation, differentiation, and survival
Oncogenes
- Specific genes (oncogenes) are capable of inducing cell transformation, providing insights into the molecular basis of cancer
- The identification of viral oncogenes led to the identification of cellular oncogenes involved in non-virus-induced cancers
- The connection between viral and cellular oncogenes was shown in studies of highly oncogenic retroviruses.
- One of the first oncogenes discovered was the src gene of Rous sarcoma virus(RSV). Further studies identified more than 2 dozen oncogenes in various retroviruses.
- Proto-oncogenes are normal genes but can become oncogenes when mutated; mutations in proto-oncogenes are typically dominant
- Oncogenes are abnormally expressed or mutated forms of the related proto-oncogenes
Tumor Suppressor Genes
- Tumor suppressor genes normally inhibit cell growth and development
- The prototype tumor suppressor gene Rb was identified through studies of retinoblastoma inheritance.
- Loss or mutational inactivation of Rb and other tumor suppressor genes (like p53) contributes to the variety of human cancers
- Rb proteins inhibit the cell cycle by not allowing passage from G1 to S
- p53 is needed for apoptosis after DNA damage to initiate programmed cell death. p53 promotes DNA repair and cell division arrest, and activates genes regulating apoptosis as needed.
Apoptosis
- Apoptosis is a programmed cell death characterized by cell shrinkage and chromatin condensation
- Apoptosis is facilitated by proteases called caspases that degrade cell components
- Cells in apoptosis eventually break down into vesicles and are phagocytized(eaten) by immune cells
Mutations in Proto-oncogenes
- Four types of mutations that can change proto-oncogenes to oncogenes are missense mutation, gene amplification, chromosomal translocation, and viral integration.
Rb Protein Regulates Cell Division
- More recent research has detailed how the Rb protein halts the proliferation of cancer cells by regulation of E2F transcription factor
- Binding of Rb to E2F blocks the protein's activity, preventing the progression from G1 phase to S
- Absence of functional Rb protein allows uncontrolled cell division
p53
- The p53 gene is a crucial tumor suppressor gene
- p53 acts as a checkpoint, determining if a damaged cell can repair before division
- Fifty% of human cancers are related to p53 gene defects
- p53 regulates repair mechanisms, arrests cell division, and activates genes that induce apoptosis (programmed cell death)
Epigenetics
- Epigenetics involves heritable traits that don't change DNA sequences
- Epigenetic mechanisms alter gene expression without altering the underlying DNA sequence
- Epigenetic factors can contribute to cancer by changes in DNA methylation and histone modifications
Environmental Agents and Cancer
- Some environmental agents alter chromatin-modifying proteins impacting gene expression.
- Associations between specific agents and types of cancer are noted, but further study may be needed.
- Several examples of environmental agents are provided
Cancer Treatments
- Researchers are investigating drugs that affect DNA methylation and inhibit abnormal cell proliferation.
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Description
Test your knowledge on the genetic foundations of cancer and its characteristics. This quiz covers the multistep process of cancer development, the origin of cancer cells, and various causes of cancer. Challenge yourself to learn more about this complex disease and its implications.
