In vitro toxicity of camalexin derivatives in human cancer and non-cancer cells.

The aim of the study was to investigate the cytotoxic activity of camalexin and its five synthetic derivatives in cancer and non-cancer cells. In cancer cells the benzocamalexin (BC) displayed the most potent activity with an IC value of 23.3-30.1 μmol/L. On the other hand, minimal toxicity (IC>100.0 μmol/L) in non-cancer cells was observed. Based on these results, BC was selected for further studies. Flow cytometric analysis revealed a BC-induced arrest of the cell cycle in the G2 phase associated with downregulation of α-tubulin, α1-tubulin, β5-tubulin expression. These findings suggest that the inhibitory effect of BC is mediated via inhibition of microtubule formation. Moreover, BC downregulated the expression of microtubule-related protein indicating the effect of this compound on microtubule assembly. After treatment with BC increase of the sub-G DNA content fraction was noted which is considered to be a marker of apoptotic cell death. Apoptosis was also confirmed by DNA fragmentation assay. Moreover, quantitative real-time PCR showed that BC downregulated the expression of antiapoptotic genes Bcl-2 and Bcl-xL and upregulated the expression of proapoptotic Bax. Taken together, our study suggests that the blockade of cell cycle progression and initiation of apoptosis may play an important role in the antiproliferative activity of BC in human cancer cells.