Enhanced MTT-reducing activity under growth inhibition by resveratrol in CEM-C7H2 lymphocytic leukemia cells.

Inhibition of proliferation by resveratrol of CEM-C7H2 lymphocytic leukemia cells was paradoxically associated with an enhanced cellular 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT)-reducing activity. This phenomenon was most pronounced at the sub-apoptotic concentration range of 5-20 microM resveratrol. The results of our study show that the MTT-reducing activity can be increased by the polyphenolic antioxidant resveratrol without a corresponding increase in the number of living cells and that this occurs at a concentration range of the antioxidant which is not sufficient to induce apoptosis but suffices to slow down cell growth. This phenomenon appears to be restricted to proliferation inhibitors with antioxidant properties and is cell type-specific. Thus, in determining the effects of flavonoids and polyphenols on proliferation, in certain cell types this might represent a pitfall in the MTT proliferation assay.