A gene implicated in the development of cancer cells can be switched on using drugs, report researchers from the University of Michigan Comprehensive Cancer Center.
The finding could lead to a new class of targeted cancer therapies with potential to benefit many different cancer types.
Popular new drugs such as Herceptin and Gleevec more effectively treat cancer by targeting genetic mutations that express themselves in large amounts, causing cancer to develop. But cancers also arise because genes that control growth are turned off. While researchers can use these turned-off genes to identify or monitor cancer, currently no treatments actually target these genes.
U-M researchers found that a gene called Brahma, or BRM, is silent , but not missing , in some cancer cells. By exposing the BRM protein to an inhibitor drug, the researchers were able to turn the gene back on, allowing BRM to be expressed. The researchers found this gene is turned off in about 15 percent of tumors studied, including cells from lung, esophageal, ovarian, bladder, colon and breast cancers.
The researchers were able to use existing drugs, which showed some usefulness in turning on the BRM gene. But new drugs would need to be developed to be more effective in reactivating this gene in cancer cells. Still, researchers are excited about the potential this finding could have in leading to new targets for cancer treatment.
"This is a targetable target. We can detect it, but we need to find a better way to turn it back on. No drugs are designed to deal with a gene that's turned off. But it's a straightforward extension of current therapies that target genes that are turned on," says lead study author David Reisman, M.D., Ph.D., assistant professor of internal medicine at the U-M Medical School.
Results of the study appear in the advanced online publication of the journal Oncogene.
The researchers sought to understand why BRM is not expressed in certain cancer cell lines. They found no mutations to the gene but rather that it was just silent , essentially like a switch that had been turned off. Knowing that a class of drugs called histone deacetylase inhibitors, or HDAC inhibitors, can affect gene expression, the researchers applied these drugs to the cells and found the BRM expression could be restored , like flipping the switch back on.
While the existing HDAC inhibitors did return BRM expression, the effect was short-lived. Once the drugs were taken away, BRM expression decreased.
"The HDAC inhibitors are not the perfect answer, but in principle this tells us we can turn our gene back on. If we can turn the gene back on, it may not be a cure for cancer, but it could slow it down or make it responsive to existing drugs," Reisman says.