Tumor Suppressor Genes and Oncogenesis

These flashcards cover key concepts related to tumor suppressor genes, oncogenesis, cellular proliferation, and the role of specific proteins in cancer development.

What is the role of tumor suppressor genes in the human body?

They act as significant physiological barriers to prevent clonal expansion and genetic mutations, inhibiting uncontrolled cell proliferation.

What happens when tumor suppressor genes lose their function?

Their inactivation contributes to oncogenesis by allowing uncontrolled cell growth and proliferation.

What is oncogenesis?

A complex process characterized by inadequate activation of oncogenes and inactivation of tumor-suppressor genes.

What key roles do the retinoblastoma gene (Rb-1) and p53 play in tumor suppression?

Rb-1 inhibits transcription factor E2F and p53 enhances p21 expression to stop cell proliferation.

How does p53 respond to DNA damage?

p53 becomes stabilized, increases concentration, and extends its half-life, leading to cell cycle arrest or apoptosis.

What characteristic is associated with tumors in terms of cell proliferation?

Tumors exhibit uncontrolled proliferation due to genetic mutations that affect cell regulation.

What is the function of cyclin-CDK complexes in the cell cycle?

They promote cell cycle progression but can be inhibited by anti-oncogenes.

Why is the p53 gene significant in cancer?

It is frequently mutated in human cancers and acts as a guardian of the genome by regulating cell division.

What is the result of hyperactivity in proto-oncogenes?

It can lead to disturbances in the regulation of cell proliferation, contributing to malignancies.

What type of mutations in the p53 gene affect its function?

Missense mutations and nonsense mutations can alter the p53 activity or create dominant-negative alleles.

Which proteins inhibit the activity of cyclin-dependent kinases (CDK)?

Proteins like p16INK4A, p15INK4B, p18INK4C, p19INK4D, p21, p27, and p57 act as CDK inhibitors.

How does TGF-β influence the cell cycle?

TGF-β increases the levels of p15INK4B and p21, inhibiting CDK activity and blocking cell cycle progression.

What is the 'Hayflick limit' related to cellular division?

The Hayflick limit refers to the finite number of divisions a normal somatic cell undergoes before cell death.

What is the consequence of increased telomerase activity in tumors?

It can lead to extended lifespan and immortality of tumor cells.

What triggers the expression of p53?

DNA damage, hypoxia, and other genotoxic stresses can induce p53 expressions.

What is the role of autophagy in tumor development?

Autophagy can reduce mutation rates and suppress oncogenesis by eliminating damaged organelles and providing metabolic support.

How does oncogenic signaling affect p53 function?

Oncogenic signals can result in the sequestration or destabilization of normal p53, impairing its function.

What effect does the Bcl-2 protein have on apoptosis?

Bcl-2 inhibits apoptosis by blocking pro-apoptotic proteins and maintaining mitochondrial integrity.

What role does p21Cip have in cell cycle control?

p21Cip inhibits CDK activity and halts cell cycle progression in response to DNA damage.

What is the relationship between oncogenes and tumor suppressor genes?

Oncogenes promote cell proliferation, whereas tumor suppressor genes counteract these effects to regulate growth.

How can malignant cells control apoptosis?

Malignant cells block apoptosis through anti-apoptotic proteins, allowing survival despite mutations.

What is loss of heterozygosity in tumor suppressor genes?

It refers to the requirement of mutations in both alleles of a tumor suppressor gene for tumor development.

Which phase of the cell cycle is most affected by p53?

The G1 phase is heavily regulated by p53 to ensure repair or eliminate damaged cells.