Georgetown medical researchers discover genetic link to cancer

Researchers at the Georgetown University School of Medicine have recentlyuncovered a genetic irregularity that causes cancer in some individuals. David Solomon, an M.D./Ph.D. student in the group of Dr. Todd Waldman, an associate professor of oncology at the Lombardi Comprehensive Cancer Center, found that a mutation of the STAG2 gene causes an abnormal number of chromosomes during cell division, which in turn causes cancer, as he published in the August 19 issue of Science magazine.

Solomon explains that the STAG2 gene encodes a protein subunit of the “cohesin complex” that holds together chromosomes before they are pulled apart during mitosis, or cell division. Abnormal STAG2 genes cause problems in how chromosomes are held together, and this results in a phenomenon called aneuploidy, where some cells have too many chromosomes and others have too few. Aneuploidy is a driving factor in creating carcinogenic tumors.

Why is this significant? “This is the first gene that has ever been proven to directly cause aneuploidy when mutated or inactivated in human cancers,” Solomon said. “Aneuploidy is one hallmark of cancer, [but] researchers in the past have not known the mechanism and why this happens in cancer cells.”

Abnormalities in the STAG2 gene are acquired, rather than inherited.  The researchers have found that 20 percent of brain, skin, and bone cancer samples had a missing or abnormal STAG2 gene.

This is where cancer treatment drugs come in. The Waldman lab is currently working on finding compounds that will kill cells with the abnormal STAG2 gene, and leave normal cells unscathed. They are currently testing cells with normal and mutated STAG2 genes against a drug library of 10,000 different compounds to see how the cells would react with the different chemicals. “[The testing process] doesn’t take very long,” Solomon said.

However, the cure for cancer will not come in the next six months. “Once you identify a compound, it takes years for a drug to move through clinical trials and become an available treatment option.”

At the moment, Solomon and other researchers in the Waldman lab are also looking for genetic mutations that lead to breast, prostate, and lung cancer.

Solomon, who has been interested in science since high school and double majored in biology and chemistry as an undergraduate at the College of William and Mary, is now in his final year of study at Georgetown. After completing his MD/PhD degree from Georgetown, Solomon is looking to join a pathology residency program and to continue clinical study of cancer there.

Photo from the Lombardi Cancer Center website.

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