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Background Information
Problem
Hypothesis
Variables
 
 
Background Information

          Cancer is a leading cause of death in the world. More than 10 million people are diagnosed with cancer every year. The World Health Organization estimates that there will be 15 million new cases every year by 2020. Cancer causes 6 million deaths every year-or 12% of deaths worldwide. Only a third of cancers are preventable or curable(World Health Organization, 2003).

          In many cancers, high levels of a protein called bcl-2 protects the cells from apoptosis, which is programmed cell death. The bcl-2 protein suppresses apoptosis by preventing the activation of the caspases that carry out the process of killing the cell. This inhibition of apoptosis is a key pathway in the survival of many cancers(Dubois et al., 2003).

          Cyclooxygenase-2, or COX-2, is an enzyme found in all tissues of the body. After testing in rats, it has been shown to upregulate bcl-2, thus inhibiting apoptosis of cells(Liu C. et al, 2003). The exact mechanism by which COX-2 upregulates bcl-2 is still being investigated, however, it is thought that prostaglandins(the group of chemicals produced by COX-2), have a direct role in bcl-2 upregulation. In many cancers, especially those of the breast, cervix, stomach and colon, COX-2 is expressed in unusually high concentrations compared to normal tissues, where COX-2 is almost non-existent.

          A group of chemicals known as non-steroidal anti-inflammatory drugs, or NSAIDs, inhibit COX-2. Meloxicam is one such chemical and is a competitive, time dependent, irreversible inhibitor that forms an enzyme inhibitor complex after a covalent conformational change in the protein. Meloxicam is highly selective for COX-2, making it ideal for inhibiting COX-2(Sigma Aldrich, 2003).

Structure of meloxicam.

                The cells that were used for the experiment were 184-A1, HTB-129 and HTB-132 cell lines. 184-A1 are normal mammary epithelial cells. HTB-129 are a pleural ductal mammary carcinoma. HTB-132 are cancerous mammary gland cells.(American Type Culture Collection, 2004)

Left - The 184-A1 cell line.	Middle - The HTB-129 cell line.	Right - The HTB-132 cell line.

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Problem
What effect will inhibiting the COX-2 enzyme have on the viability of human cancer cells?

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Hypothesis
 
          As the concentration of meloxicam increases, the more COX-2 is inhibited in the cancer cells where COX-2 is overexpressed. As a result, bcl-2 upregulation by the COX-2 will go down and the cancer cells will start to die from apoptosis, whereas the normal cells, where COX-2 is not overexpressed, will not be affected.
          The following animation illustrates the principle presented in the hypothesis. Click the black button at the bottom right corner to progress to the next section of the animation each time.

 

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Variables
 
Manipulated:Concentration of meloxicam.
 
Responding: Cell viability.
 
Controls:

• Length of incubation.

 

• Medium used on cells.

 

• Temperature cells incubated in.

 

• Number of initial cells per well plate.

 

• Substances cells are exposed to.

 

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