What are the proto-oncogenes?
- Genes whose function becomes enhanced in carcinogenesis.
- Usually play an essential role in controlling cell proliferation, encoding growth factors, growth factor receptors, transcription factors, etc.
- Mutations of oncogenes may impede normal cell cycle regulation, causing uncontrolled cellular replication.
- Mutation in only one of the proto-oncogene alleles is needed for the mutant gene product to influence downstream events, i.e. mutations are dominant at the cellular level.
- An example of a proto-oncogene—the Ras gene:
- encodes a membrane-associated G protein responsible for cellular signal transduction
- mutated Ras products remain activated, even in the absence of the appropriate growth factor receptor signal
- mutations in Ras are implicated in 30% of all cancers, including melanoma, lung, and pancreas