How are cancer cells different from normal cells?
Answers
cancer cells divides indefinitely and forms tumor...
Difference Between Cancerous and Normal Cells
Growth—Normal cells stop growing (reproducing) when enough cells are present. For example, if cells are being produced to repair a cut in the skin, new cells are no longer produced when there are enough cells present to fill the hole; when the repair work is done. In contrast, cancer cells don’t stop growing when there are enough cells present. This continued growth often results in a tumor (a cluster of cancer cells) being formed. Each gene in the body carries a blueprint that codes for a different protein. Some of these proteins are growth factors, chemicals that tell cells to grow and divide. If the gene that codes for one of these proteins is stuck in the “on” position by a mutation (an oncogene)—the growth factor proteins continue to be produced. In response, the cells continue to grow.
Communication—Cancer cells don’t interact with other cells as normal cells do. Normal cells respond to signals sent from other nearby cells that say, essentially, “you’ve reached your boundary.” When normal cells “hear” these signals they stop growing. Cancer cells do not respond to these signals.
Cell repair and cell death—Normal cells are either repaired or die (undergo apoptosis) when they are damaged or get old. Cancer cells are either not repaired or do not undergo apoptosis. For example, one protein called p53 has the job of checking to see if a cell is too damaged to repair and if so, advise the cell to kill itself. If this protein p53 is abnormal or inactive (for example, from a mutation in the p53 gene,) then old or damaged cells are allowed to reproduce. The p53 gene is one type of tumor suppressor gene that code for proteins that suppress the growth of cells.
Stickiness—Normal cells secrete substances that make them stick together in a group. Cancer cells fail to make these substances, and can “float away” to locations nearby, or through the bloodstream or system of lymph channels to distant regions in the body.
Ability to Metastasize (Spread)—Normal cells stay in the area of the body where they belong. For example, lung cells remain in the lungs. Cancer cells, because they lack the adhesion molecules that cause stickiness, are able to travel via the bloodstream and lymphatic system to other regions of the body—they have the ability to metastasize. Once they arrive in a new region (such as lymph nodes, the lungs, the liver, or the bones) they begin to grow, often forming tumors far removed from the original tumour.
Appearance—Under a microscope, normal cells and cancer cells may look quite different. In contrast to normal cells, cancer cells often exhibit much more variability in cell size—some are larger than normal and some are smaller than normal. In addition, cancer cells often have an abnormal shape, both of the cell, and of the nucleus.The nucleus appears both larger and darker than normal cells. The reason for the darkness is that the nucleus of cancer cells contains excess DNA.Up close, cancer cells often have an abnormal number of chromosomes that are arranged in a disorganized fashion.
Evading the immune system—When normal cells become damaged, the immune system (via lymphocytes) identifies and removes them. Cancer cells are able to evade (trick) the immune system long enough to grow into a tumor by either by escaping detection or by secreting chemicals that inactivate immune cells that come to the scene.
Functioning—Normal cells perform the function they are meant to perform, whereas cancer cells may not be functional. For example, normal white blood cells help fight off infections. In leukemia, the number of white blood cells may be very high, but since the cancerous white blood cells are not functioning as they should, people can be more at risk for infection even with an elevated white blood cell count. The same can be true of substances produced. For example, normal thyroid cells produce thyroid hormone. Cancerous thyroid cells (thyroid cancer) may not produce thyroid hormone. In this case, the body may lack enough thyroid hormone (hypothyroidism) despite an increased amount of thyroid tissue.
Blood supply—Angiogenesis is the process by which cells attract blood vessels to grow and feed the tissue. Normal cells undergo a process called angiogenesis only as part of normal growth and development and when new tissue is needed to repair damaged tissue. Cancer cells undergo angiogenesis even when growth is not necessary. One type of cancer treatment involves the use of angiogenesis inhibitors—medications that block angiogenesis in the body in an effort to keep tumors from growing.
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