MODULE 45

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Questions and Answers

What is the primary characteristic of growth signal autonomy in cancer cells?

Enhanced requirement for systemic signals

Dependence on neighboring cells for growth signals

Predominance of autocrine signaling (correct)

Reduced expression of signaling receptors

Which alteration is NOT associated with growth signal autonomy in cancer cells?

Overexpression of growth factor receptors

Increased dependence on external apoptosis signals (correct)

Changes in intracellular signaling cascades

Alterations in integrin types

How do normal bystanders contribute to cancer cell proliferation?

They suppress autocrine signaling

They eliminate apoptotic signals

They provide growth and transformation signals (correct)

They promote receptor mutations

What is the role of pRB in cancer cell growth inhibition?

It blocks progression from G1 to S phase when active Signup and view all the answers

Which mechanism can lead to insensitivity to antigrowth signals?

Sequestration of pRB by oncoproteins Signup and view all the answers

What happens to E2F transcription factors when bound by pRB?

They become inactive and inhibit cell cycle progression Signup and view all the answers

Which of the following factors is associated with resistance to apoptosis in cancer cells?

Inactivation of apoptotic machinery sensors Signup and view all the answers

What feature of RAS proteins contributes to growth signal autonomy in cancer?

Structural alterations enabling independent activation Signup and view all the answers

How does modulated phosphorylation of pRB affect its function?

Hypophosphorylated pRB blocks E2F activity Signup and view all the answers

What is a common feature of cancer cells regarding antigrowth signals?

They show insensitivity to these signals Signup and view all the answers

Which property of cancer cells refers to their ability to grow without limits?

Limitless replicative potential Signup and view all the answers

What type of mutations are crucial for the initiation and progression of cancer?

Driver gene mutations Signup and view all the answers

Which of the following is an example of a tumor suppressor gene mutation?

Rb tumor suppressor loss Signup and view all the answers

Which hallmark of cancer enables it to resist adverse conditions?

Counteracting growth-inhibiting factors Signup and view all the answers

How many mutations are typically required to inactivate tumor suppressor genes according to the two-hit hypothesis?

Two Signup and view all the answers

What is the main metabolic characteristic of most cancers described by Otto Warburg?

Enhanced glycolysis Signup and view all the answers

What process describes the cancer cell's ability to form new blood vessels?

Angiogenesis Signup and view all the answers

The acquisition of new resources and spaces by cancer cells is akin to what concept in business?

Market penetration Signup and view all the answers

What term describes mutations that do not contribute to cancer development?

Passenger mutations Signup and view all the answers

Which of these hallmarks of cancer refers to the ability to invade tissues and spread?

Tissue invasion and metastasis Signup and view all the answers

What role do sensors play in cellular processes?

Monitor cues for cell survival or death Signup and view all the answers

Which protein is considered the major sensor of apoptotic signals?

p53 Signup and view all the answers

What is the effect of p53 when it senses DNA damage?

It induces an apoptotic effector cascade Signup and view all the answers

Which of the following correctly describes the apoptotic cascade?

Cytochrome C activates caspases in the cytosol Signup and view all the answers

How does the BCL-2 family influence apoptosis?

By modulating the release of cytochrome C Signup and view all the answers

What common mutation occurs in more than 50% of human cancers?

p53 mutation Signup and view all the answers

What is a characteristic of cancer cells in terms of apoptosis?

They evade apoptosis Signup and view all the answers

What occurs when BAX is upregulated in response to DNA damage?

It stimulates the release of cytochrome C Signup and view all the answers

What signaling characteristic do cancer cells demonstrate regarding growth signals?

They are self-sufficient for growth signaling Signup and view all the answers

Which of the following signaling pathways is associated with tumor growth?

Decreased anti-growth signaling Signup and view all the answers

What type of signaling is predominantly observed in cancer cells compared to normal cells?

Autocrine signaling Signup and view all the answers

What is the main function of pRB in relation to antigrowth signals?

Inhibits E2F transcription factors Signup and view all the answers

How does the alteration in the intracellular cascades contribute to cancer cell autonomy?

By allowing RAS proteins to remain active without stimulation Signup and view all the answers

Which modifications to pRB can lead to insensitivity to antigrowth signals?

Sequestration by viral oncoproteins Signup and view all the answers

What role do normal bystander cells play in cancer cell proliferation?

They contribute additional growth signals Signup and view all the answers

What is a common mechanism through which cancer cells develop resistance to apoptosis?

Alteration of apoptotic sensors Signup and view all the answers

Which of the following statements about integrins in cancer cells is true?

They determine cell commitment to quiescence, apoptosis, or proliferation Signup and view all the answers

What is the effect of structural changes in growth factor receptors in cancer cells?

Enhanced growth factor binding affinity Signup and view all the answers

What defines the relationship between RAS proteins and upstream regulators in cancer cells?

RAS proteins can be active independent of upstream regulators Signup and view all the answers

Which alteration is typically observed in cancer cells type that affects the extracellular matrix receptors?

Alteration of receptor structure Signup and view all the answers

What characteristic allows cancer cells to grow independently of external growth signals?

Self-sufficiency in growth signals Signup and view all the answers

Which factor contributes to cancer cell metabolism, according to the Warburg effect?

Enhanced glycolysis Signup and view all the answers

What is a key difference between driver and passenger mutations in cancer?

Driver mutations are essential for cancer progression Signup and view all the answers

Which process describes the ability of cancer cells to form new blood vessels?

Angiogenesis Signup and view all the answers

What mechanism typically initiates oncogenic activation?

Mutation of one allele of a proto-oncogene Signup and view all the answers

How do cancer cells typically resist apoptosis?

By activating anti-apoptotic pathways Signup and view all the answers

What does the 'two-hit hypothesis' suggest about tumor suppressor gene mutations?

Both alleles must be mutated for cancer to develop Signup and view all the answers

What is a consequence of limitless replicative potential in cancer cells?

Uncontrolled cell division Signup and view all the answers

Which property of cancer cells facilitates their spread to other tissues?

Tissue invasion and metastasis Signup and view all the answers

What role do mitogens play in cancer cell behavior?

They stimulate uncontrolled cell division Signup and view all the answers

What role do cell surface receptors play in cell survival or death?

They bind to survival or death signals to regulate cell fate. Signup and view all the answers

What is one of the main functions of p53 in cellular processes?

To induce apoptosis in response to specific stress signals. Signup and view all the answers

Which proteins are classified as pro-apoptotic members of the BCL-2 family?

BAX and BAK Signup and view all the answers

How does BAX contribute to apoptosis when activated?

By promoting the release of cytochrome C from mitochondria. Signup and view all the answers

What condition typically leads to the activation of p53?

Hypoxia and DNA damage. Signup and view all the answers

What is the function of caspases in the apoptotic process?

They are key effectors in the execution of apoptosis. Signup and view all the answers

Which phenomenon would likely contribute to a cancer cell's ability to evade apoptosis?

Mutation of apoptotic regulators like p53. Signup and view all the answers

What mechanism do cancer cells exploit in relation to growth signaling?

They develop insensitivity to anti-growth signals. Signup and view all the answers

What is a significant effect of cytochrome C release into the cytosol?

It activates apoptotic cascades including caspases. Signup and view all the answers

Why are cancer cells described as self-sufficient for growth signaling?

They can produce their own growth signals. Signup and view all the answers

Study Notes

Cancer as a Corporation

Cancer cells exhibit self-sufficiency in growth, overcoming growth-inhibitory factors, and resisting outside and inside adverse conditions.
They have unlimited growth potential and build their own infrastructure.
Cancer cells acquire new resources/spaces (markets).

Six Basic Properties of Cancer

Self-sufficiency in growth signals: Cancer cells are independent of external growth signals.
Insensitivity to anti-growth signals: Cancer cells ignore signals that normally stop their growth.
Sustained angiogenesis: Formation of new blood vessels to nourish tumor growth.
Evasion of apoptosis: Cancer cells avoid programmed cell death.
Tissue invasion and metastasis: Cancer cells spread to other parts of the body.
Limitless replicative potential: Cancer cells can divide indefinitely.

Role of Mutations in Causing Hallmarks

Driver gene mutations: Essential to cancer initiation, progression, and survival.
Passenger mutations: Occur but do not contribute to cancer development.
Oncogenes: Mutated versions of proto-oncogenes that stimulate excessive cell growth (e.g., RAS).
Tumor suppressor genes: Mutated genes that lose their ability to control cell growth, leading to uncontrolled proliferation. Mutated tumor suppressor genes typically need two "hits."
Multiple hits across genes often contribute to widespread cancer.

Cancer Cell Metabolism

Otto Warburg identified altered metabolism in cancer cells, often characterized by increased glycolysis as an energy source.
Additional deregulated metabolic pathways contribute to uncontrolled proliferation.

Growth Signal Autonomy

Cancer cells exhibit reduced dependence on external growth stimulation.
Strategies include alterations in extracellular signals, receptors, intracellular cascades, and ECM receptors that transmit growth signals.
Autocrine signaling is a prominent component of cancer cell growth autonomy: cells produce signals to stimulate their own growth.
Normal cells use paracrine signaling to respond to neighbor cells.
Cancer cells use alterations in signaling pathways (such as Ras protein activation), to achieve growth independence.
External components (fibroblasts, endothelial, immune, fat cells). can act as accomplices to cancer cell growth.

Insensitivity to Antigrowth Signals

Almost all anti-growth signals are processed through pRB proteins.
pRB, along with p107 and p130, control cell-cycle progression.
E2F transcription factors are suppressed by pRB.
Mutations in pRB or related genes can lead to unregulated cell-cycle progression.
Viruses can also sequester pRB to promote cancer growth

Avoidance of Apoptosis

Tumor growth relies on resistance to apoptosis.
Cells signal to either live or die based on cues within and outside the cells.
Abnormal activation/deactivation of intracellular signaling sensors can alter apoptotic processes.
p53 is a major sensor of apoptotic signals. Mutated p53 is often observed in cancer cells.
Apoptosis pathways involve mitochondria, BCL-2 proteins, and caspases.
Mutations/alterations in these pathway components disrupt programmed cell death/apoptosis in cancer cells.

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Description

Explore the key properties and hallmarks of cancer as a corporation. This quiz covers the self-sufficiency of cancer cells, their insensitivity to signals, and the role of mutations in cancer progression. Test your knowledge on the mechanisms that enable cancer cells to thrive and spread.