Dense breasts may increase cancer risk

NASHVILLE, Aug. 25 (UPI) -- Women with denser breasts have an increased risk for developing breast cancer and having breast cancers with invasive characteristics, U.S. researchers said.

Vanderbilt-Ingram Cancer Center researchers said breast cancer cells grown in dense, rigid surroundings step up their invasive activities.

Lead author Dr. Alissa Weaver said the findings suggest a cellular mechanism for the correlation between human breast tissue density and tumor aggressiveness.

Weaver and colleagues were interested in invadopodia -- the finger-like protrusions that a cancer cell uses to make holes in the extracellular matrix -- matrix-degrading enzymes are associated with invadopodia. These structures are believed to be important for cancer invasion.

The study, published in the journal Current Biology, found that breast cancer cells cultured on a denser -- and thus, more rigid -- matrix had a greater number of active invadopodia than breast cancer cells cultured on a less dense matrix.

"If you have enough invadopodia, over time they'll make large holes that cells can move through to invade and metastasize," Weaver said in a statement.

"We thought that more 'stuff' for the cells to get through was going to make it harder, so we expected to see less matrix degradation but instead we found cells actually sense the rigidity and degrade more."