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Normal Cells Versus Cancer Cells

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Normal Cells Versus Cancer Cells
Normal Cells Versus Cancer Cells

Photo credit: National Cancer Institute

Breast Cancer Cell

Normal Cells Versus Cancer Cells

All living organisms are composed of cells. These cells grow and divide in a controlled manner in order for the organism to function properly. Changes in normal cells can cause them to grow uncontrollably. This uncontrollable growth is the hallmark of cancer cells.

Normal Cell Properties

Normal cells have certain characteristics that are important for the proper functioning of tissues, organs, and body systems. These cells have the ability to reproduce correctly, stop reproducing when necessary, remain in a specific location, become specialized for specific functions, and self destruct when necessary.
  • Cell Reproduction: Cell reproduction is needed to replenish the cell population that ages or becomes damaged or destroyed. Normal cells reproduce properly. Except for sex cells, all cells of the body reproduce by mitosis. Sex cells reproduce through a process called meiosis.
     
  • Cell Communication: Cells communicate with other cells through chemical signals. These signals help normal cells to know when to reproduce and when to stop reproducing. Cell signals are usually transmitted into a cell by specific proteins.
     
  • Cell Adhesion: Cells have adhesion molecules on their surface that allow them to stick to the cell membranes of other cells. This adhesion helps cells to stay in their proper location and also aids in the passage of signals between cells.
     
  • Cell Specialization: Normal cells have the ability to differentiate or develop into specialized cells. For example, cells can develop into heart cells, brain cells, lung cells or any other cell of a specific type.
     
  • Cell Death: Normal cells have the ability to self destruct when they become damaged or diseased. They undergo a process called apoptosis in which cells break down and are disposed of by white blood cells.

Cancer Cell Properties

Cancer cells have characteristics that differ from normal cells.
  • Cell Reproduction: Cancer cells acquire the ability to reproduce uncontrollably. These cells may have gene mutations or chromosome mutations that affect the reproductive properties of the cells. Cancer cells gain control of their own growth signals and continue to multiply unchecked. They don't experience biological aging and maintain their ability to replicate and grow.
     
  • Cell Communication: Cancer cells lose the ability to communicate with other cells through chemical signals. They also lose sensitivity to anti-growth signals from surrounding cells. These signals normally restrict cellular growth.
     
  • Cell Adhesion: Cancer cells lose the adhesion molecules that keep them bonded to neighboring cells. Some cells have the ability to metastasize or spread to other areas of the body through the blood or lymph fluid. Once in the bloodstream, cancer cells release chemical messengers called chemokines that enable them to pass through blood vessels into the surrounding tissues.
     
  • Cell Specialization: Cancer cells are unspecialized and do not develop into cells of a specific type. Similar to stem cells, cancer cells proliferate or replicate many times, for long periods of time. Cancer cell proliferation is rapid and excessive as these cells spread through out the body.
     
  • Cell Death: When the genes in a normal cell are damaged beyond repair, certain DNA checking mechanisms signal for cell destruction. Mutations that occur in gene checking mechanisms allow for the damages to go undetected. This results in the loss of the cell's ability to undergo programmed cell death.

Causes of Cancer

Cancer results from the development of abnormal properties in normal cells that enable them to grow excessively and spread to other locations. This abnormal development can be caused by mutations that occur from factors such as chemicals, radiation, ultraviolet light, and chromosome replication errors. These mutagens alter DNA by changing nucleotide bases and can even change the shape of DNA. The altered DNA produces errors in DNA replication, as well as errors in protein synthesis. These changes influence cell growth, cell division, and cell aging.

Viruses also have the ability to cause cancer by altering cell genes. Cancer viruses change cells by integrating their genetic material with the host cell's DNA. The infected cell is regulated by the viral genes and gains the ability to undergo abnormal new growth. Several viruses have been linked to certain types of cancer in humans. The Epstein-Barr virus has been linked to Burkitt's lymphoma, the hepatitis B virus has been linked to liver cancer, and the human papilloma viruses have been linked to cervical cancer.

Sources:
  • Cancer Research UK. The Cancer Cell. Accessed 04/18/13. (http://www.cancerresearchuk.org/cancer-help/about-cancer/what-is-cancer/cells/the-cancer-cell)
     
  • Science Museum. How do healthy cells become cancerous? Accessed 04/18/13. (http://www.sciencemuseum.org.uk/WhoAmI/FindOutMore/Yourbody/Whatiscancer/Whathappensincancer/Howdohealthycellsbecomecancerous.aspx)
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