Listeria pathogen may be key to understanding cancer development

A research team including University of Central Florida Microbiology Professor Keith Ireton is using the bacterial pathogen Listeria Monocytogenes to understand the mechanisms of cell growth and cancer development.

In research published this month in the Journal of Biological Chemistry, the team found that a Listeria protein called InlB induces internalization and degradation of a human receptor known as Met. Met has been implicated in the development of some cancers.

Lisa A. Elferink at the University of Texas Medical Branch led the team. She and Ireton found that the ability of InlB to induce Met internalization and degradation requires a human protein called Cbl. If scientists could figure out how to control Cbl, such knowledge might lead to the development of drugs that induce the destruction of Met and are useful in treating Met-related cancers.

Ireton is an expert on Listeria monocytogenes, a cause of food poisoning. He has long studied how it enters into cells of the human body, and explains the mechanism in this month's issue of the journal Cellular Microbiology.

We found that Listeria actually provokes human epithelial cells (cells lining the small intestine) into ingesting bacteria, Ireton said.When Listeria contacts an epithelial cell, the bacterium causes changes in the cell's cytoskeleton that allow the cell to swallow up the bacterium. We discovered that a human protein called CrkII plays a critical role in stimulating internalization of Listeria by somehow controlling the cytoskeleton.

Listeria is a potentially deadly pathogen, causing abortions in pregnant women and meningitis in those with compromised immune systems, resulting in about a 25 percent mortality rate.

The findings are important in helping to understand and control the spread of bacteria that are a cause of potentially fatal food poisoning. Ireton said the bacteria can live outside animal hosts. Sources include dead plant matter, fruits and vegetables, unpasteurized diary products and meats that have not been properly cooked. Pregnant women and people with compromised immune systems are particularly susceptible.

To avoid contamination, Ireton suggests cooking all meats thoroughly, avoiding dairy products that are not pasteurized and washing all fruits and vegetables thoroughly before consumption.

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