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Genetic Linkage

Prostate and Colon Cancer News: The 2-Hit Hypothesis Revisited

The 2-hit hypothesis of cancer was based on retinoblastoma, the first example of a tumor suppressor mutation.
A report and a case published in two major medical journals this week suggest that relatives of certain people with cancer may be at higher risk, due to inherited (germline) mutations in DNA repair genes.

Only 5 to 10 percent of cancers are inherited. Such individuals inherit a cancer-predisposing mutation in all their cells, and then a somatic (body) cell undergoes a second mutation that initiates the disease. The second mutation may be spontaneous or in response to an environmental factor such as smoking.

The one-two punch of inherited cancers, called the 2-hit hypothesis, was first described in 1971. Read More 
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Second Gene Causes Retinoblastoma

This little boy has heritable retinoblastoma. The mutation originated in him, so he didn't inherit it, but he can pass it on.
In a list of famous genes, RB1 would probably be #1. It’s the tumor suppressor gene whose “loss of function” is behind the childhood eye cancer retinoblastoma, and that Alfred Knudson investigated to deduce the 2-hit mechanism of cancer.

In 1971, the idea that the normal function of a gene could be to prevent cancer was revolutionary. Now a study in Lancet Oncology finds that an amplified oncogene can cause the eye cancer too, with just one “hit.” Read More 
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