The heart of why so few get cancer: myocardial cells hardly divide

  Only one or two per 100,000 cases of human tumors in certain parts of the body are more common, such as liver cancer, lung cancer, skin cancer, colorectal cancer and so on, while others are rarely long tumor tissues and organs, such as our body blood transportation Center – the heart。
Early in the 16th century, humans have been reported diagnosis of cardiac tumors, but because of cardiac tumors are rare, human cases related to the accumulation of cardiac tumors and treatment programs is not as rich in a number of other common tumors。
  Indeed, the incidence of primary cardiac tumors can be as low%, in other words, one in every one hundred thousand people, only one or two people will suffer from cardiac tumors may。
And these people, about 75% of benign and malignant tumors account for only about 25% and, including one called benign cardiac myxoma is the most common primary cardiac tumor type, accounting for about half of all cardiac tumors。
Heart cancer, the most common types of vascular sarcoma and rhabdomyosarcoma, the patient had two tumors, the survival rate is very low, and the transfer earlier, when under normal circumstances, these two tumors once found has been transferred to the lungs, liver and brain and other parts, if not quickly removed by surgery, 90% of patients will die within 9-12 months after diagnosis。
Of course, on the other hand, other tissues and organs suffering from cancer may also be transferred to the heart "root", which is called metastasis, is the heart of the most common melanoma metastasis to the heart of metastases, accounting for cardiac metastases 50% -70%。
  As the major organs of the human heart, its volume and weight than many tumor tissues often a lot bigger, but it rarely happens tumor, how the reason behind this?How to explain this phenomenon it?  Gene mutation accumulation and tumor tissues and organs to understand why some tumors less frequent, you first need to understand what causes tumorigenesis。 Although it is possible to explore the causes of tumors from external factors (environmental factors), even evolutionary point of view, but in the final analysis it should be focused on the cells of the tissues and organs of the basic unit up。 After all, the tumor tissue is composed of cells, but they are "rebellion" of normal cells transformed from a limited number of normal cell division and proliferation, and tumor cell proliferation can be unlimited, uncontrolled。   So, how normal cells are "mutiny" has become tumor cells do?Mutations are the root cause of tumor cells immortalized。
Usually, the incidence of cancer is the result of interaction of a plurality of mutated tumor-associated genes, mutation, i.e., a plurality of tumor associated genes resulted in the accumulation of uncontrolled cell division and proliferation, and finally into a tumor cell; single gene mutation and the insufficient to cause tumor cells because the cells have DNA repair and replication error correction mechanism, generally can be effectively repair gene mutation, gene mutation prevents continue to divide。 But if the cell contains a gene mutation associated escaped DNA repair and replication error correction and continue to proliferate, they will have more opportunities to accumulate more mutations, so that "rebellion" for the tumor cells。   Myocardial cells hardly divide zebrafish and salamanders and a few other vertebrates have the ability to regenerate limbs and internal organs, such as the adult zebrafish ventricles are cut by 20%, its heart tissue can regenerate completely within 2 months。
For mouse embryonic day 10 to day 12, and about 4 days to 14 days after birth, which can proliferate cardiomyocytes, myocytes and adult mice caught almost no proliferation state therefore generally no adult mouse heart tissue regeneration having。
Mankind is also true, even though studies have shown that adult cardiomyocytes have very low levels of update, however, the vast majority of myocardial cells no longer proliferate。
  Therefore, for an adult mammal such as mice and humans, because of the proliferation of cardiomyocytes has almost stopped, their heart tissue lifetime update rate is very low。
The cells do not proliferate, does not accumulate associated mutations in the genome of the cell, a myocardial cell does not become tumor cells。
On the contrary, such as the liver, intestinal epithelium, skin and other tissue and organ regeneration capacity, strong cell division and proliferation, resulting in tumor-associated mutations in the cell genome cumulative probability of a substantial increase, and thus more prone to cancer。   (The author is Dr. Chen wind Shanghai Tongji University School of Medicine)。