| Normal versus Cancer Cells (National Cancer Institute, 2015) |
| |
Normal Cells |
Cancer Cells |
| 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. |
| Density-dependent inhibition |
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. |
Genes:
|
- 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. |
| Chromosome quantity |
Normal quantity |
Abnormal quantity |
| 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. |