Indole-3-carbinol – Induced growth inhibition can be converted to a cytotoxic response in the presence of TPA + Ca2+ in squamous cell carcinoma cell lines

Abstract We examined the possibility that I3C, when combined with a differentiation stimulus (TPA + CaCl 2 ), would sensitise SCC cells to a differentiation stimulus. We report that I3C induces a profound growth inhibition in SCC cells that is dissimilar to the growth inhibition required to initiate differentiation. Moreover, we report that I3C, when combined with TPA + CaCl 2 treatment, induces a loss of colony forming ability that was differentiation and senescence – independent but was due to delayed cytotoxicity. This study shows that I3C in combination with a PKC activator + Ca 2+ may be a useful therapeutic strategy for treating oral SCC.