We will use this lecture to expore the links. Because several changes have to occur, cancer is more often associated with older people. However, some people have already taken a hit or two by receiving defective alleles for genes encoding particularly important proteins. For these people, cancer generally strikes earlier. Viruses are involved in some cancers Viruses cause some cancers.
Tumor suppressor genes generally slow down the cell cycle.
One example is the protein p53. A person inheriting a mutant recessive allele needs only a mutation in the other allele to acquire the phenotype of loss of regulation of cell division. An oncogene, not meant to be abundantly transcribed, is now present in a region of DNA that is highly transcribed. Perhaps this is what happens in some of the breast cancers in which cyclin is overexpressed. Another way translocations could lead to cancer is if a tumor suppressor protein was inactivated by having a translocation occur into its regulatory region, preventing transcription of its gene.