Question

Oncogenes, Tumor-suppressor genes, and tumors

For each of the following situations, provide a plausible explanation for how it could lead to unrestricted cell division.

Colon cancer cells often contain mutations in the gene encoding the prostaglandin E2 (PGE2) receptor. PGE2 is a growth factor required for the division of cells in the gastrointestinal tract.

Adenovirus, a tumor virus carries a gene for the protein E1A, which binds to the retinoblastoma protein (Rb).  

Answer 1

Since, PGE2 is a growth factor required for the division of cells in the gastrointestinal tract, it binds to its receptor prostaglandin E2 (PGE2) receptor and activation signaling mechanism leading to transcription of growth related genes. Mutation in this receptor gene leads to constitutive activation and continuous signaling leading to continuous expression of cancer promoting genes thus responsible for colon cancer.

The adenovirus (Ad) transforming E1A protein binds to Rb protein and induce the S-phase entry in quiescent cells leading to uncontrolled cell division. The binding of E1A to Rb release growth promoting E2F family transcription factors which binds and transcribe the genes involved in S-phase leading to entry in S-phase and uncontrolled cell division.