How does cancer begin in a human body? What causes it?

Question

Why are cancer cells immortal?

Answer 1

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Look up HeLa cells http://en.wikipedia.org/wiki/HeLa

These cells are immortal. Not all cancer cells are immortal.

Cancers begin when there is damage to the genetic material

in a cell that makes the cell lose the "brakes" that normally

inhibit cellular replication after a certain number of cells

have been made be cell division/mitosis.

The injury may be caused by a chemical - numerous carcinogenic

chemicals are present in tobacco smoke, or radiation exposure.

Even sunlight is carcinogenic. The initial tumor cells have to evade

the immune system to get a "foothold."

Source(s): MD Medical Oncologist and Hematologist - a cancer and blood specialist doctor - with twenty years experience