MadSci Network: Cell Biology
Query:

Re: How do cancer cells differ in structure compared to normal cells

Date: Wed May 28 16:11:48 2003
Posted By: Sarah Earley, Graduate student
Area of science: Cell Biology
ID: 1047618519.Cb
Message:

Hi Whitee,

I study cultured breast cancer cells, which means that I grow cancer 
cells in flasks rather than study tumors in animals.  Some of my 
cancer cells do not look much different from normal cells, structurally.  
Others are irregularly shaped.  Often cancer cells have increased 
numbers of chromosomes, which would account for the larger and 
darker nuclei you mentioned in your comments.  Morphological 
analysis can be used to detect cancerous cells in certain areas of the 
body.  For instance, when women have Pap smears, cells from the 
cervix are scraped off and analyzed under the microscope.  Cells with 
large nuclei and irregular shapes are considered abnormal.  For 
some pictures of normal cells and cancer cells, check out  http://pathology2
.jhu.edu/cyto_tutorial/Atlas/Index.cfm  You can 
choose slides and read the captions indicating why the cell was 
considered normal or cancerous.

There are also molecular markers that indicate whether a cell is 
cancerous.  Checking for a variety of proteins or genes expressed in 
cancer cells is another method of detection.  Normal cells may 
express these genes, but often they are modified in cancerous cells.

I am not sure what you mean by "drown out normal cells" but maybe 
you mean that the cancer cells divide rapidly, forming tumors that can 
grow out of control and in a sense take over the body.  When cells 
acquire the ability to migrate, they are malignant.  Malignant cancer 
leads to tumors throughout the body (metastasis).  When normal 
cells are put into a flask, they typically stop growing when they cover 
the bottom of the flask.  This is called contact inhibitionÑthe cells 
stop growing when they come into contact with one another.  But the 
cancer cells will not stop growing, indicating a loss of contact 
inhibition.  A malignant tumor can have similar characteristics.  

Malignant cancer cells tend to proliferate rapidly, so interphase would 
not last as long as a normal cell that does not undergo mitosis as 
frequently.  Many chemotherapy drugs target rapidly proliferating cells 
in hopes of eliminating cancer cells and not normal cells.  
Unfortunately, certain normal cells in the body proliferate rapidly and 
are affected by the chemotherapy drugs.  This is why people with 
cancer who are undergoing chemotherapy can lose their hair.  Trying 
to detect rapidly dividing cells in a human would be difficult in the 
early stages of cancer.  You are right that there might be ways to 
target cancer cells, though.  For example, there are drugs that are 
meant to starve tumors of oxygen and nutrients by cutting of their 
ability to promote the growth of blood vessels around them.  Blood 
vessel growth is called angiogenesis.  Blood transports oxygen and 
nutrients, which a tumor needs just like other cells.  If the tumor 
cannot promote angiogenesis, it will not have blood vessels delivery 
oxygen and nutrients and would theoretically be starved.  A drug 
called Herceptin is regularly used to treat cancers that over-express a 
particular receptor on their surface.  For more information about 
cancer therapy, check out the National Cancer Institute website at  http://www.nci.nih.gov/.  

So although cancer cells might look just like normal cells, there are 
differences that can be exploited when trying to detect and treat 
cancer.  Please write back if you have any questions.  I hope this 
helps!

Sarah Earley




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