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| genetic cause of cancer. Mutations in tumor-suppressor genes should be viewed as markers for tumor susceptibility. |
| The most common genetic mutation that occurs in human cancers is in the tumor-suppressor gene p53. About 70 percent of all colon cancers, 30 to 50 percent of breast and ovarian cancers, 50 percent of all lung cancers, all small-cell lung cancers, and most prostate cancers are a result of a defect in the p53 gene. It is worth noting here that one of the many cancer-inhibiting effects of quercetin, a flavone found in onions and broccoli, is to prevent a defect in this gene. |
| An individual may inherit one defective copy of the tumor-suppressor protein gene p53 from a parent, giving that person a predisposition to develop cancer. Since p53 is a repair gene, when it malfunctions damaged DNA is able to escape, proliferate unchecked, and mutate into cancerous cells. As that person ages, she may then be more susceptible to external factors that can cause irregular cell proliferation. However, it sometimes takes an accumulation of ten or more mutations in critical genes before a cell becomes cancerous. Scientists have recently found that there is another gene, p34, that may be responsible for p53's ability to halt cell division. Approximately 90 percent of all breast cancers display abnormal p34 genes. |
| Another tumor-suppressor gene, the Rb, gene, is implicated in a number of childhood cancers, such as Wilms' tumors and neuroblastoma. |
| Tumor-suppressor genes are regulators that control the expression of other genes. For example, normal cells contain dominant suppressor genes that down-regulate cancer genes. These dominant genes are lost, however, during any cell mutations. When this line of defense is lost, it is possible for tumor genes to be reexpressed rather than down-regulateda situation that brings disastrous results. |
| Mutation |
| One well-known cause of cancer is a buildup of oxidative damage and mutations whereby the gene itself is altered and can then initiate the process of malignancy. The human body is composed of sixty-three trillion cells, plus or minus one hundred billion at any given time. Each day a cell undergoes around five thousand mutations, each of which could be capable of causing the |
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