Origin of Cancer

 

In most organs and tissues of a mature animal, a balance is maintained between cell renewal and cell death. The various types of mature cells in the body have a given life span; as these cells die, new cells are generated by the proliferation and differentiation of various types of stem cells. Under normal circumstances, the production of new cells is regulated so that the number of any particular type of cell remains constant. Occasionally, cells arise that no longer respond to normal growth control mechanism. These cells give rise to clones of cells that can expand to a considerable size, producing tumour which ultimately leads to cancer.

Cancer is a dreadful disease and is one of the chief killers today. It commonly originates in the tissues in which the cells are regularly replaced by mitosis. Cancer or malignant neoplasm is a disease of uncontrolled proliferation of cells without any differentiation. The cancer cells invade and destroy the surrounding tissues.

Normal cells shows a property called contact inhibition. Due to this property they contact with other cells amd inhibit their uncontrolled growth. Cancer cells seem to have lost this property .

Theories of origin of cancer-:

Mutation theory-: This theory states that the accumulation of mutations over the years cause the normal cells to turn into cancer cells.

Selective gene activation theory-: This theory states that certain genes that are not normally expessed, suddenly become active and their products cause cancer.