• Cancer cells do not respond normally to the body's control mechanism.

o They divide excessively and invade other tissues.
o If left unchecked, they can kill the organism.

• Cancer cells do not exhibit contact inhibition

o If cultured, they continue to grow on top of each other when the total area of the petri dish has been covered
o They may produce required external growth factor (or override factors) themselves or possess abnormal signal transduction sequences which falsely convey growth signals thereby bypassing normal growth checks.

• Cancer cells exhibit irregular growth sequences

o If growth of cancer cells does cease, it does so at random points of the cell cycle
o Cancer cells can go on dividing indefinitely if they are given a continual supply of nutrients
o Normal mammalian cells growing in culture only divide 20-50 times before they stop dividing.