We’ve always wondered. How do carcinogens in cigarettes cause cancer? The answer is genetic mutations. And not just one. Or two. Or ten. Or a even hundred. We are talking thousands of mutations – tens of thousands, in fact.
This is according to researchers at Genentech, the biotech daughter company of Roche in California. The researchers compared the genetic status of healthy tissue and a piece of lung tumor from 51-year old male patient who smoked on average 25 sticks of cigarettes per day for 15 years before tumor removal. Using state-of-the art genetic technology that looks at whole genomes rather than a few genes, the researchers were able to find mutations fast. They detected as many 50,000 mutations in the tumor cells.
According to study author Zemin Zhang of Genentech:
Doing some calculations based on the number of genetic mutations and the number of cigarettes smoked over the last 15 years, the researchers estimated one genetic mutation for every 3 sticks of cigarettes smoked. The smoking rate of 25 sticks per day results in about 8 genetic mutations occurring daily.
However, the calculations are actually an oversimplification because they did not take into consideration the defence mechanisms of the body that helps repair damaged DNA. Thus, there could actually be more mutations occurring each day but are rapidly repaired. However, over time, the DNA repair mechanisms become overused and less efficient and can no longer provide ample protection against the damage of smoking. This is when tumors develop.
The patient whose lung tumor was analyzed was a typical lung cancer patient with no unusual characteristics and can therefore represent the average smoker patient diagnosed with cancer of the lung.
The next step is to find out which of these mutations are linked to smoking-related cancer. In the meantime, next time you smoke a cigarette, think of the cells in your lungs and what cigarette smoking is doing to them. Think of those mutations happening each day. Maybe then you’ll be motivated to stop.