|Normal versus Cancer Cells (National Cancer Institute, 2015)
|Growth Factor Proteins
||Stop growing and dividing when they stop producing growth factors, when they have reached their limit, or grown to their maximum.
||May produce their own growth factors that stimulate reproduction and are less dependent on growth factors from other sources.
||Stop growing when the cell has reached a finite cell density.
||Continue to divide despite cell density.
|Specialization and maturity
||Mature into distinct cell types with specific functions; cell division stops once they become fully differentiated.
||Do not specialize or differentiate; divide quickly before maturing and remain immature and undifferentiated.
|Cell-cell interactions (Contact inhibition)
||Respond to signals from adjacent cells telling them they have reached their limit or boundary, causing them to stop growing.
||Do not respond to signals from other cells to stop growing; will grow in a disorganized manner, invading other tissues or migrating over adjacent cells.
|Apoptosis (programmed cell death)
||Occurs when a cell is no longer needed, grows old or when DNA damage cannot be repaired.
||Do not repair themselves and do not undergo apoptosis, and thus live longer.
- Help normal cells grow and divide
- Slow cell growth and division, repair genes, or tell cells when to die
- Mutated proto-oncogenes become oncogenes that permanently activate causing cells to grow out of control
- When tumor suppressor genes are inactivated, they do not tell an old or damaged cell to die
|Cell adhesion molecules
||Secrete cell surface adhesion molecules that make them “stick” to other cells.
||Do not secrete surface adhesion molecules, allowing them to invade other cells and metastasize to distant parts of the body through the bloodstream or lymphatic system.
|Morphology (shape and appearance of the cell)
||Uniform in size and shape.
||Vary in size and often have an abnormal shape; nucleus may appear darker due to increased number of DNA strands.
|Response to the immune system
||When damaged, lymphocytes remove the cells.
||Evade the immune system by hiding or secreting chemicals that inactivate immune cells.
|Angiogenesis (development of new blood vessels)
||Develop new blood vessels to grow and repair damaged tissues.
||Secrete growth factors that promote angiogenesis to support growth.
|Telomeres (caps at the end of each strand of DNA that protects the chromosomes)
||When cells divide, telomeres shorten; once they become too short, a cell can’t divide and dies.
||Capable of regenerating telomeres and continue to divide.