Tumor suppressors

Definition

Tumor suppressors are genes that help regulate cell growth and division, acting as safeguards against uncontrolled cell proliferation that can lead to cancer. These genes produce proteins that can repair DNA, control the cell cycle, and initiate apoptosis (programmed cell death) when necessary. When tumor suppressor genes are mutated or inactivated, their protective functions are lost, increasing the risk of cancer development.

5 Must Know Facts For Your Next Test

1. Common tumor suppressor genes include TP53, BRCA1, and APC, each playing a critical role in preventing cancer by regulating cell cycle checkpoints.
2. Tumor suppressors act primarily by slowing down cell division or triggering apoptosis in cells with damaged DNA.
3. Loss of function mutations in tumor suppressor genes can be inherited (germline mutations) or acquired (somatic mutations), both contributing to cancer risk.
4. The 'two-hit hypothesis' suggests that both copies of a tumor suppressor gene must be inactivated for cancer to develop, explaining how recessive mutations lead to tumorigenesis.
5. Screening for mutations in tumor suppressor genes is important for understanding hereditary cancer syndromes and guiding treatment options.

Review Questions

• How do tumor suppressor genes contribute to the regulation of the cell cycle and prevent cancer development?
  • Tumor suppressor genes play a crucial role in controlling the cell cycle by producing proteins that monitor DNA integrity and regulate progression through various phases. They can halt the cell cycle in response to DNA damage or other stress signals, allowing for repair or triggering apoptosis if damage is irreparable. This regulatory mechanism prevents abnormal cell division and ensures that only healthy cells continue to proliferate, thus reducing the risk of cancer.
• Discuss the significance of common tumor suppressor genes like TP53 and BRCA1 in relation to cancer prevention and treatment strategies.
  • TP53 is known as the 'guardian of the genome' because it regulates the cell cycle and initiates apoptosis in response to DNA damage. Mutations in TP53 are found in many cancers, highlighting its critical role in maintaining genomic stability. BRCA1 is associated with hereditary breast and ovarian cancers; individuals with mutations in this gene have a significantly higher risk of developing these cancers. Understanding these tumor suppressors aids in developing targeted therapies and informs screening protocols for at-risk individuals.
• Evaluate how the loss of function of tumor suppressor genes affects cellular mechanisms and contributes to tumorigenesis.
  • When tumor suppressor genes lose their function due to mutations, the cellular mechanisms that normally prevent uncontrolled growth become compromised. This leads to unregulated cell division and survival, allowing cells with genetic abnormalities to proliferate unchecked. The loss of these regulatory mechanisms can result in a variety of malignancies, as seen with conditions like familial adenomatous polyposis linked to APC mutations. By understanding this process, researchers can better design interventions that restore the functions of these crucial genes or target pathways affected by their loss.

Related terms

Oncogenes: Oncogenes are mutated forms of proto-oncogenes that promote cell growth and division, leading to cancer when overactive.

Apoptosis: Apoptosis is the process of programmed cell death that eliminates damaged or unnecessary cells, preventing the development of tumors.

Cell Cycle: The cell cycle is a series of phases that a cell goes through as it grows and divides, regulated by tumor suppressors and other proteins.