This is very costly and still experimental but it is helping many people. A cell that is not programmed to divide generally stays in G1. Key proteins that regulate whether a cell stays in G1 or goes to S phase include p53 and the cyclin-Cdk complex. Mutant p53 fails to inhibit cells from leaving G1 and thereby leads to excessive replication and division. 14.15 for potential places where regulation can go wrong.
Mutations can cause overproduction of growth factors.
These growth factors act on their target cells and cause increased cell division. One way is if key transcription factors were somehow changed. This could mean that instead of the genes for the highly differentiated cell being expressed, genes for a less differentiated cell were expressed. In the lecture on development, we saw that a cascade of transcriptional activation occurred. One gene product was a transcriptional activator that caused the expression of another transcriptional activator that caused the expression of still another set of transcriptional activators, etc.