Explain at least three causes of Cancer in detail.

Explanation

Causes of Cancer. Study of cancer cells is called oncology. Chemical and physical agents that can cause cancer are called carcinogens, which belong to three categories.
(i) Oncogenic Transformations. They are agents or factors which bring about changes in genetic material. They are of two types, radiations and chemicals.
(ii) Tumour Promoters. They promote proliferation of cells which have undergone oncogenic transformation, e.g., some growth factors, hormones.
(iii) Tumour Viruses. Some viruses are known to be connected with oncogenic transformations. Another classification of carcinogens is as follows:
1. Physical irritants, (i) Use of Kangri (an earthen pot containing burning coal) by Kashmiris causes abdominal skin cancer as these poeple keep Kangri close to their abdomen during winter, (ii) Betel and tobacco chewing causes oral cancer, (iii) Heavy smoking causes lung cancer and may also cause cancer of oral cavity, pharynx (throat) and larynx, (iv) Jagged teeth may cause tongue cancer, (v) Excessive exposure to sun light can cause skin cancer.
2. Chemical Agents. Several chemicals are known to cause cancer. These are caffeine, nicotine, products of combustion of coal and oil and pesticides, constant use of artificial sweetener can cause cancer. An animal protein-rich diet is known to cause cancer of large intestine. Breast cancer has hormonal relationship. Thus, some sex hormones and" steroids if secreted or given in large amounts may cause cancer. Chimney sweepers can develop cancer of scrotum. Dye workers have a high rate of bladder cancer.
3. Radiations. The X-rays, cosmic rays, ultra-violet rays, etc. can cause cancer. Japanese people exposed to radiations from World War II nuclear bombing show five times the incidence of leukemia seen in the rest of the population.
4. Biological Agents. Some viruses and other parasites, excessive secretion of certain hormones are believed to cause cancers.