Oncogenes and Tumor Suppressor Genes: Review

00:01 A quick review, we certainly covered this in the cell and molecular biology course. We have oncogenes and proto-oncogenes. Oncogenes are those that can potentially become cancerous or they will cause a cell to become cancerous. Then we have proto-oncogenes. Those are the genes before they’ve become oncogenes. A proto-oncogene is an early oncogene that has not yet caused a mutation that results in cancer. So, there are many genes involved in growth factor receptors as well as proteins in signal transduction pathways, the G-protein-coupled receptors, so on and so forth. Then the thing is with the sequencing of the genome, not only are we looking at what these expressed phenotype genes do but we also are now able to get a much closer look on what each of the regulatory pieces of the genome do also. So, as with other fields of genetics, the more we learn, the more there is to discover in essence as we go deeper and deeper into our understanding of the various pieces of the genome. Tumor suppressor genes, some that we have covered that are important for you to know for your exams are involved in preventing proliferation of mutated cells in their regular roles. That’s the whole meaning of tumor suppressor. In their functional form, they suppress development of a tumor by programming a cell for apoptosis, let’s say. So, p53 was one of those and the Rb protein as well as BRCA1 and BRCA2.

02:06 Remember that Rb was the first one that we discovered. BRCA1 and BRCA2 are also tumor suppressor genes that are involved in breast cancer. They’re two that we have characterized fairly well, not to say that they are the only ones. But someone with BRCA 1 or BRCA2 mutations are much more highly likely to develop breast cancer; again, one of the classic multifactorial disorders that we have considered previously. There are also caretaker genes. Caretaker genes are involved in repair of DNA. Let’s say the caretaker genes are there and they’re supposed to be proteins or enzymes that run along on the DNA and make sure that it is all in order. So, one of the polymerases to make sure that all the base pairs are in order. They run into an error, they generally will stop and correct that or prevent cell division. These caretaker genes, if they’re wrong, they just let the mistakes flow on by and the cell continues to divide with this bad copy of the DNA in it.

03:21 When DNA repair enzymes are mutated, we also have issues in cell cycle controls. That’s all that it comes down to. Gatekeeper genes are again another class of genes under the tumor suppressor genes that will act to prevent growth of cancer cells. Let’s say a cancer cell arises with a new mutation, there are so many checks and balances in place. Caretaker genes would say, “Hmn, this one doesn’t look right. We’re not going to let it divide.” Again, those precancer cells would undergo apoptosis and not result in the generation of cancer. If the gatekeeper genes are broken then cancer could very easily develop. Those cells could divide out of control. Oncogenes and tumor suppressor genes are genes that you should certainly be familiar with as a class of genes.

04:21 The three that I mentioned there are important ones for you to understand their roles of.

04:26 If you need to go back and review how each of those types of genes function, I recommend that you take a look again in the cell cycle controls portion of the cell and molecular biology course because all the details are there.