Cancer is a disease caused due to the abnormal growth of cells. Cancer causes damage in the body by reproducing the cells uncontrollably and starts making tumors. Tumors can only produce in the nervous, circulatory and digestive system of the body and they also damage the real function of these systems. When a cancerous cell produces in the body, it has the ability to move in the body using the blood lymph systems and as a result healthy tissues start destroying. The whole process is called as invasion. In some cases, the cell starts growing along and makes blood vessels so that it can get food. The process is called angiogenesis.

Cancer is caused when cells start growing in an abnormal way and they do not die but accumulate in the body. When the programmed cell death apoptosis disturbs, it results in cancer. Cancer cells do not experience apoptosis. There are various factors which lead to the disease of cancer. For example;

Age is a factor which leads to the cancer because when a person gets old, the cells of the body get old and do not function properly. Actually the changes occur in the genes present in the cell. These changes either occur during the division of the cell or due to the damage to the cell by carcinogens. This damage can transfer to the daughter cells and leads to the birth of cancer in the body. It is fact that changes in the genes depend on the age of the person. If the person is old enough, there are bright chances of occurrence of mistakes in the cells.

Carcinogens are the harmful substances which cause cancer. They cause cancer by directly affecting the cell's DNA. Main carcinogens are arsenic, asbestos, tobacco and radiations like gamma and x-rays. When the body is exposed to carcinogens, the electrons start moving out of the molecules because of the formation of free radicals. These radicals have the ability to damage cell's normal functioning.

Environment is another factor which can trigger the formation of cancer in the body. For example, when a person is smoking, he not only damages his own body cells but the smoke of the cigarette can enter another parson's body and can damage the cells of the body. Sun also causes cancer because sun rays contain strong ultraviolet radiations which penetrate through skin and damage the genetic material of the cell. Radiations can also cause cancer like breast cancer, lung cancer and skin cancer. Ionizing radiations are the major cause of cancers because they contain radiations of x-rays, gamma rays and ultraviolet rays. People who work in areas where they have to get exposed to radiations and chemicals more often they have bright chances that they develop cancer in their body because continuous exposure of their body to radiations and chemicals may change the genetic makeup of the cells or trigger uncontrolled growth of cells. Asbestos are the carcinogens which can also cause cancer.

Immune system:-
If people have weak immune system, they are more likely to have cancer. Those people who have undergone organ transplantation and take some drugs so that their immune system does not reject the organ, they have bright chances that cancer develop in their bodies. Due to medications, their body's cells may start growing abnormally which may result in the cancer. AIDS is a disease which weakens the immune system by causing infections and can also cause cancer.

Cancer can be inherited from a member of the family. In this case, genes do not function properly and this defect can transfer in the daughter cells. Mutations or some mistake in the gene can also cause cancer to develop.

Viral and Bacterial Infections:-
Viruses have the ability to cause infection in the cells which may result in the changes of the genes. It will result in the formation of cancerous cells. There are people who get liver cancer and leukemia due to virus and there are some people who are infected with virus but never suffer from the cancer disease.

Similarly bacteria can cause cancer as the recent studies have shown. Scientists have stated that the people who develop an infection of helicobacter pylori due to which stomach suffers from inflammation may lead to the stomach cancer. Many antibiotics can be used t treat this type of cancer.

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