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Cancer may strike due to bad luck, not lifestyle

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Published: 07:02, 25 March 2017   Update: 15:18, 26 July 2020
Cancer may strike due to bad luck, not lifestyle

Risingbd Desk: Why does cancer strike some people and not others? New research shows that random changes or 'mistakes' in DNA when cells are dividing cause nearly two-third of all cancers in humans. These changes are neither caused by external factors like smoking or exposure to harmful chemicals, nor by hereditary factors. They are chance events occurring at the molecular level. In other words, cancer can strike anybody.

This upends prevailing wisdom that cancer is mostly a lifestyle related disease caused by external or environmental factors like smoking, harmful chemicals and conditions like obesity. While all these are valid and important risk increasing factors, random chance may be the real driver, if one goes by this new research.

The study involved a statistical analysis of cancer data from 69 countries including India, representing 4.8 billion people, more than half of the world's population. It was done by scientists from Johns Hopkins Kimmel Cancer Center at Baltimore, US, and published in the peer reviewed journal Science on March 24.

Human bodies grow by constant division of cells, starting from the first cell formed by fusion of the male sperm with the female egg. Every time a cell divides into two, the genetic code carrying DNA is copied. What the scientists are saying is that mistakes occur in this copying process that accumulate over time and ultimately cause cancer.

"These copying mistakes are a potent source of cancer mutations that historically have been scientifically undervalued, and this new work provides the first estimate of the fraction of mutations caused by these mistakes," said the paper's lead author Cristian Tomasetti.

The researchers studied all 32 cancer types and estimated that 66 percent of cancer mutations result from copying errors, 29% can be attributed to lifestyle or environmental factors, and the remaining 5% are inherited. They found a strong correlation between cancer incidence and normal cell divisions among 17 cancer types, regardless of the countries' environment or stage of economic development.

This means that lifestyle factors like smoking or exposure to toxic chemicals are also very important factors causing nearly a third of cancers.

"We need to continue to encourage people to avoid environmental agents and lifestyles that increase their risk of developing cancer mutations," co-author Bert Vogelstein emphasized.

Studies of cancer patients across the world have shown that approximately 40% of cancers can be prevented by avoiding unhealthy environments and lifestyles. But this study explains why cancer is known to strike people who follow all the rules of healthy living — nonsmoker, healthy diet, healthy weight, little or no exposure to known carcinogens — and have no family history of the disease.

Different types of cancers have different origins, the researchers found. For example, in pancreatic cancers, 77% are due to random DNA copying errors, 18% to environmental factors, such as smoking, and the remaining 5% to heredity. In other cancer types, such as those of the prostate, brain or bone, more than 95% of the mutations are due to random copying errors.

Lung cancer is most likely to be caused by environmental factors, mostly smoking. About 65% of all the mutations are due to smoke and 35% due to DNA copying errors. Inherited factors have negligible role.

Source: Times of India




Risingbd/March 25, 2017/Mukul

 

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