Scientists at Fox Chase Cancer Center have found that estrogen may increase the movement of precancerous cells in the mouth and thus promote the spread of the disease within the oral cavity. Margie Clapper, co-leader of the Cancer Prevention and Control Program at Fox Chase Cancer Center and colleagues had previously reported that estrogen metabolism changes following smoke exposure in the lungs and may contribute to lung cancer.To find out if this hormone influences scientists examined the impact of estrogen on precancerous and cancerous cells. They found that estrogen induces the expression of an enzyme called cytochrome P450 1B1 (CYP1B1), which is responsible for breaking down toxins and metabolizing estrogen. CYP1B1 induction occurred only in precancerous cells, which are neither totally normal nor cancerous. Surprisingly, estrogen did not induce CYP1B1 in cancer cells. With closer investigation, the researchers found that depleting the expression of CYP1B1 diminished the ability of precancerous cells to move and divide, as compared to similar cells with normal levels of CYP1B1.