Why do the majority of people never get cancer?: "In a previous discussion, Klein and his coauthors identified five kinds of anticancer mechanisms. The first type is immunological, which applies to virus-associated cancers. For instance, researchers have compared the antibody responses of the squirrel monkey and the marmoset when infected with Herpesvirus saimri, a virus that is endogenous to squirrel monkeys but that the marmoset never encounters. When exposed to the virus, the marmosets, but not the squirrel monkeys, develop rapidly growing lymphomas. The researchers found a striking difference in the timing of each animal’s antibody response. In the tumor-resistant squirrel monkeys, the antibodies rose to a high level just three days after the infection, but, for the marmosets, the response took three weeks. By that time, the marmosets already had a rapidly growing virus-driven lymphoma. Research has shown that such immunological responses are influenced by genetic variation.
The second mechanism is genetic, and the most common example is DNA repair mechanisms. Studies have shown that there are individual variations in the efficiency of DNA repair, which is highlighted in cases such as the specific DNA repair deficiency called xeroderma pigmentosum. Individuals with this deficiency are highly sensitive to ultraviolet light, and even with careful protection they develop multiple skin carcinomas due to the genetic deficiency."
