Isn’t it unfair that some people, even if they smoke, are still healthy at the age of 80, while others may develop lung cancer before the age of 40? This makes us think: Why do people develop lung cancer? The cells of human body are proliferating and replicating every moment to maintain our life activities. Genetic mutations occur during this process. Genetic mutations are important in evolution, allowing a small number of people to be different, and when a disease or bad weather comes, there is always a percentage of people who can escape the disaster. However, most of the mutations are not beneficial but, on the contrary, harmful. The human body has “molecular police” that are specialized in removing mutated genes – oncogenes such as P53, RB, CDKN2, etc. When this undesirable mutation is out of control, it is likely to form an uncontrolled proliferation, which is a tumor. This is the risk that human beings take in order to evolve. To some extent, the development of a fertilized egg into a fetus is a process of tumor-like proliferation, except that this process is strictly regulated to the point where it expresses which function with great precision. A tumor also multiplies from a mutant cell, although this process is out of constraint. With the development of molecular biology, we believe more and more in the phrase “life, death and sickness are predestined”. Some people are born with lung cancer genes, which is an evolutionary necessity, such as RAS, MYC gene family, CERB-2, c-jun genes, etc. Therefore, we often find that some families are prone to lung cancer. This process includes activation of lung cancer genes, inactivation of oncogenes, and inactivation of apoptotic mechanisms, leading from the surface to uncontrolled cell growth. This process arises gradually and is a long process. In fact, lung cancer genes have existed in our body for thousands of years. Why is it only in the last decade or so that lung cancer has exploded in growth? This is because with these intrinsic genes, external factors are still needed to promote the occurrence of tumor. 1. Smoking, the risk of lung cancer in smokers is 9-10 times higher. Passive smokers also have twice the risk of lung cancer as normal. The peak incidence of lung cancer in the United States has passed in recent years, and the incidence rate is declining, which is related to strict tobacco control. Our country has also begun to focus on smoking bans in the past few years, as it is now recognized that tobacco causes diseases that consume a large amount of medical costs, far greater than the taxes collected from the tobacco industry. In the past, people basically paid for their own medical care, and the country did not strictly control tobacco for the sake of tobacco taxes. Now, most of the cost of medical care needs to be covered by health insurance, so the country began to pay attention to the ban on smoking. 2, occupational environment and air pollution. It is obvious to all, no need to explain. 3. Diet. As mentioned in the previous series one, excess nutrition may be one of the factors leading to the development of lung cancer. Other, carotene may reduce the occurrence of lung cancer. 4 . Tuberculosis, viral infection, and fungal infection may all promote the occurrence of lung cancer. Therefore, if a person is 80 years old and does not have lung cancer gene in his body, it does not matter if he smokes again, at most he will suffer from emphysema. If you have lung cancer gene in your body, if you go back to the days of production teams, clean air, light meals, working at sunrise and resting at sunset, and no TV, you can still live to 80 years old.