How come immune system does not fight cancer - Research Paper Example

cancers arising from the connective tissue are known as sarcomas. They originate from the mesenchymal cells that are present outside the bone marrow. examples of this type of cancer are osteosarcoma, liposarcoma, fibrosarcoma and neurosarcoma. Lymphomas and leukemias arise from hematopoietic cells. Germ cell tumors are those which arise from pluripotent cells froms ovaries or testicles. Classical examples of these cancers are dysgerminoma and seminoma. Blastomas are those that are derived from immature cells or embryonic cells.

Hence they are more common in children. Examples of these are neutoblastoma and retinoblastoma (Yarbro, 2011). Pathogenesis of cancer Cancer mainly occurs due to failure of regulation of growth of tissues. This occurs due to alteration of the genes which are involved in the growth and differentiation of cells. There are two categories of genes that can get affected during the process of cancer development. They are oncogenes and tumour supressor genes. Oncogenes cause promotion of cell growth and reproduction.

Tumor supressor genes cause inhibition of cell division. Hence triggering of oncogenes and supression of tumor supressor genes contributes to cancer (Yarbro, 2011). Causes of cancer There are several causes for cancer and they depend on the site of origin of cancer. For example, lung cancer is caused because of exposure to tobacco, asbestos and certain pollutants. Skin cancer is caused by exposure to sunlight or due to chronic skin ulcer. In some cancers, the causative agent can be infection like cervical cancer which is caused by human papilloma virus.

Human T-cell Leukemia Virus-I, a human retro virus is known to cause adult T-cell leukemia. Leukemia, which is a type of blood cancer is caused by chemicals like Benzene and other aromatic hydrocarbons, some insecticides, hexachlorcyclohexane, phenyl butazone (Shafer, 162), alkylating agents, and a few chem-therapeutic drugs. Certain environmental factors also can lead to cancer. Studies have shown that ionizing radiation causes leukemia in experimental animals. There has been increased incidence of leukemia in the survivors of Japanese bomb explosions and those exposed to occupational radiation.

Also, those receiving radiation therapies for various causes including spondylitis may be at increased risk for leukemia. Chromosomal translocations involving the Nucleophosmin gene occur frequently in myeloid and lymphoid cancers. This gene is a multifunctional phosphoprotein to which both tumor-suppressor and oncogenic functions have been attributed. In some cancers, genetic factors play an important role like in breast cancer and leukemias. There are some families with excessive incidence of leukemias.

There is high concordance among identical twins if acute leukemia occurs in the first year of life. Also, the incidence of leukemia is high in various congenital genetic disorders like Down's syndrome, Bloom's Syndrome, Klinefelter's syndrome, etc. In chronic granulocytic leukemia, an abnormality in the chromosome 21 has been detected. This abnormal chromosome is called Philadelphia chromosome (Ph-1) and is characterized by the absence of a part of one of its long arms. Certain pre-existing diseases can lead to cancers.

Fanconi anemia is a risk factor for developing acute myelogenous leukemia. Those with myeloblastic syndrome also are at risk for acute myelogenous leukemia. Colonic polyps can lead to colon cancer. Other contributing factors for cancer are