Cancer patients can attribute their condition to environmental factors such as poor lifestyle, and inherited genes. However, a new study suggests that two thirds of those who develop the disease can blame it on bad luck.

Researchers from the Johns Hopkins Kimmel Cancer Center found evidence that majority of the risks for developing cancer, a condition marked by the abnormal and uncontrollable growth of cells, is due to random genetic mutations that occur when stem cells make chance mistakes during cell division and that this sheer bad luck is a more crucial contributor to the likelihood of developing cancer compared with hereditary and environmental factors.

"Only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions," wrote study researchers Cristian Tomasetti and Bert Vogelstein, from the Johns Hopkins Kimmel Cancer Center. "The majority is due to 'bad luck,' that is, random mutations arising during DNA replication in normal, noncancerous stem cells."

The researchers based their conclusion on the results of their research, which was reported in the journal Science on Jan. 2. For this study, Tomasetti and Vogelstein looked at published scientific studies to identify the number of stem cell divisions in 31 different types of body tissues excluding those of breast and prostate and then compared the number of stem-cell divisions in each tissue to a person's lifetime risks for developing cancer in that particular area.

The researchers found that 22 types of cancer including small intestine cancers, pancreatic cancers and Glioblastoma, or brain cancers, could be attributed to random mutations in the DNA that occur during stem cell divisions, when stem cells regenerate and replace old cells. The study investigators explained that cancer can develop when chance mutations happen and that the more mistakes that occur, the higher risks a person has that his cells will divide uncontrollably and become cancer.

A combination of bad luck as well as hereditary and environmental factors, on the other hand, only account for the remaining nine forms of cancer, which include lung cancer, which is strongly tied with smoking; colon cancer, which is linked with poor diet and inherited risks; and Basal cell carcinoma, a form of skin cancer that became widespread due to too much exposure to ultraviolet light.

Tomasetti and Vogelstein likewise observed that the areas of the body with more stem cell division were associated with increased odds for cancer. The human colon, also known as the large intestine, for instance, goes through four times the number of stem cell divisions as the small intestine, which could explain why colon cancer is more prevalent than the cancer of the small intestine.

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