I was reading some science news, as I am prone to do, and came across this article which just so happens to deal with what we're learning about in class right now--cell organelles and their function. The organelle this particular blog post features is the lysosome. Need to digest a food particle? The lysosome has digestive enzymes that will hydrolyze that food particle right up! Got a mitochondrion or two on their last legs? Lysosomes are right there to digest them and get rid of them. Did your cell engulf a bacterial cell or virus? The lysosome will dispose of the invaders quickly and efficiently. You get the idea...lysosomes are little sacs containing digestive enzymes that must work at a specific pH in order to perform properly.
Now what do lysosomes have to do with cancer cells? Well, quite a lot actually. When we start talking about the death of cells, lysosomes are a key player in aiding a cell's demise. In a study conducted by researchers at M.D. Anderson Cancer Center in Houston, they found that ovarian cancer cells which express a protein known as PEA-15 have a higher rate of autophagy than those that do not. This higher level of PEA-15 causes the cancer cells to basically commit suicide (by causing the lysosomes to open and release their contents) and can lead to an increase in a woman's survival rate from this particular type of cancer, which kills over 15,000 annually. PEA-15 causes cell death by interacting with a protein known as ERK (extracellular signal-regulated kinase, an enzyme). When PEA-15 interacts with ERK in the nucleus, it will move ERK into the cytoplasm, which prevents ERK from having an effect on the growth of the cell. When PEA-15 is in the cytoplasm, it will cause the cell to become autophagic.
It should be noted that PEA-15 is what is known as a "death effector domain" protein; in other words, it is responsible for contributing to cellular death. This leads to some interesting questions that can be asked about this protein and its role in cells. If ovarian cancer cells contain higher levels of PEA-15, would other cells affected by ovarian cancer (such as the cells of the uterus and omentum--the covering over the intestines) also have high levels of PEA-15? How could the presence of PEA-15 in other types of cells affect the survival rate of those cancers? What about ERK? What sorts of treatments could be developed to prevent ERK from doing its job? PEA-15 is also found in astrocytes (a type of brain cell), so could this research be extended to those who suffer from various cancers of the brain?
Posted by scienceguru on November 21, 2008
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