Overview

Cancer, a group of genetic diseases, is development gone wrong in a clone of somatic cells – a tumor. If a tumor destroys adjacent tissue it is malignant. Tumor cells:

• Accumulate mutations and become genetically unstable

• Grow in an unregulated manner

• Lose contact inhibition; i.e., growth is not inhibited by adjacent cells

• Lose the potential to undergo apoptosis

• May metastasize – migrate and establish subclones in other body locations

Characteristics of Cancer

The hallmark of tumors is uncontrolled cell proliferation. Cancer cells proliferate exponentially because they have gained the ability to self-stimulate cell cycling and have lost the ability to respond to extrinsic growth inhibitors. A tumor's potential to be lethal principally depends on its uncontrolled growth. The growth of normal cells is inhibited by contact with adjacent cells, whereas cancer cells have lost contact inhibition. The morphology of cancer cells changes and telomerase synthesis (not present in normal somatic cells) resumes. Cancer cells become immortal – they can go through an indefinite number of cell division cycles – and gain the ability to be cultured; a normal somatic clone can survive for a limited time, ~102 cell division cycles. Cancer cells often lose the ability to undergo apoptosis. Solid tumors may stimulate angiogenesis, the growth of blood vessels supplying the tumor. Many cancer cells metastasize – move into the blood and migrate to other locations in the body. Cancer cells may evolve the ability to evade the immune system.