Well-known tumor supressor has a surprise double role: Killing cancer cells

These ovarian cancer cells may be ignoring their neighbors, who are telling them to stop dividing.

Lawrence Berkeley Lab

Most cancers result from a combination of mutations in genes that normally control a cell's growth. Some of these, called oncogenes, normally push a cell to divide; mutations in these tend to make them more active, pushing the cell to divide ever faster. Then there are tumor suppressors. Their normal role is to put a check on growth, and mutations in these genes tend to eliminate their function, easing off the brakes on a cell's division.

Now, scientists have discovered a well-known tumor suppressor gene doesn't only slow down the growth of the cells it's produced by. Instead, a previously undiscovered form of the protein gets shipped out of the cell and inserts itself into other cells, where it also shuts down growth. In the case of some tumor cells, this sudden shutdown appears to be sufficient to kill them.

The PTEN tumor suppressor gene has been studied for well over a decade. Many of the signaling pathways that help push a cell to divide involve proteins that chemically link a phosphorous to other proteins (these are called "kinases"). The product of the PTEN works by undoing this chemical modification, removing phosphates from proteins and some signaling molecules (technically, it's a "phosphatase"). In doing so, it blocks a variety of growth-stimulating signals. It plays such an essential role in shutting down growth that many cancers from many different cell types have been found to have mutations that wipe out PTEN activity.