According to a recent study, most of the mutations responsible for the development of cancers occur spontaneously, by simple bad luck, throughout our lives. On the other hand, what will promote the development of cancer or its inhibition is directly linked to our way of life.
It is now established that cancer is the result of an accumulation of mutations in certain key genes which lead to uncontrolled cell proliferation. These mutations are caused by three major factors:
– Random copying errors that occur during cell division. With each division, some 3 billion letters of DNA present in each cell must be replicated and the body produces billions of new cells every hour, which leads to many errors.
– Environmental factors. Substances like cigarette smoke, alcohol or UV rays cause DNA damage. These toxic aggressors are responsible for most cancers of the lung, upper digestive tract, liver and skin.
– Heredity. Some defective genes, containing mutations, are transmitted by the parents and are therefore already present at birth. It is estimated that these inherited mutations are responsible for approximately 5-10% of all cancers.
The origin of cancer is due to chance
The work of the group of Dr. Bert Vogelstein (Johns Hopkins University School of Medicine) indicates that it is the first category, copying errors, produced spontaneously and by simple chance, which are the main sources of cancerous mutations. They showed that there is a strong correlation between the total number of stem cell divisions in an organ and the risk of cancer emerging, which explains why an organ where cells divide frequently, the colon, for example, is more often affected by cancer than an organ like the brain, where the frequency of this division is much lower.
In a recent article, the same authors have extended their observations to 17 types of cancer affecting the inhabitants of 69 different countries and arrive at a similar conclusion, that is to say that two thirds of the mutations present in most cells cancerous would be due to simple chance. The main risk factor for cancer is therefore not heredity, as many mistakenly think, but rather the appearance of mutations caused by errors that occur spontaneously, by simple bad luck, during cell renewal. .
Cancer grows.. or not
These spontaneous mutations have the potential to become cancerous, but, in most cases, they never manage to evolve enough to form a clinically detectable cancer. For example, 50% of women in their forties have precancerous breast lesions, while the incidence of this cancer is 15%. In other words, the appearance of cancer cells is largely due to bad luck, but there are clearly other outside factors that influence the development of these abnormal cells into aggressive tumors.
Lifestyle stimulates or stops the proliferation of cancer
Several observations indicate that lifestyle plays a key role in the progression of these microscopic tumors into mature cancers. The international variations in the incidence of certain cancers are probably the best illustration of this: breast cancer is up to 20 times more common in America than in Asia, for example, while Westerners are 10 times more affected by prostate cancer than the Japanese.
In the latter case, the difference is all the more impressive since the Japanese have a similar incidence of prostate microtumors to those of Westerners, which indicates that additional factors, related to their lifestyle, manage to prevent the development of these microscopic tumors into mature cancer. Since most of these mutations are acquired in the explosion of cell divisions in childhood, associated with the development of the adult body, and since more than 90% of cancers appear after the age of 50, these mutations therefore require decades to be able to reach a threshold of clinical expression. In most cases, it is therefore possible to prevent the development of these microtumors into mature cancer.
Prevent 70% of cancers with a healthy lifestyle
Population studies clearly show that the high incidence of the main cancers affecting our society (lung, colon, breast, prostate) is mainly caused by the Western way of life and that approximately 70% of these cancers can be prevented. by adopting healthy lifestyle habits: no smoking, limited alcohol consumption, diet rich in plants and Omega-3, low in sugar, maintenance of normal body weight and regular physical activity.
Tomasetti C and Vogelstein B. Variation in cancer risk among tissues can be explained by the number of stem cell divisions. Science, 2015; 347: 78-81.
Tomasetti C et al. Stem cell divisions, somatic mutations, cancer etiology, and cancer prevention. Science, 2017; 355:1330-1334.
Wu S et al. Substantial contribution of extrinsic risk factors to cancer development. Nature, 2016; 529: 43-7.