CYP1B1 is mainly an extrahepatic enzyme which oxidatively metabolizes both endogenous (steroids; eicosanoids) and exogenous xenobiotics such aspolyaromatic hydrocarbons. TMS is a potent and selective inhibitor of CYP1B1, with an IC50 of 6 nM. It is 50-fold selective for the inhibition of CYP1B1 versus CYP1A1, making it a useful tool to differentiate between various CYP450 families. In cultured human colon cancer cells, TMS induces apoptosis and inhibits cell growth with an IC50 of 0.8 μg/ml.
