Tetrazolium violet induces G0/G1 arrest and apoptosis in brain tumor cells.

Tetrazolium violet (TV), a potent anticancer agent, has been shown to induce cell growth-inhibition in tumor cells. However, the related mechanism has not been revealed yet. In this report we assessed the influence of TV on cell growth and cell cycle in brain tumor cells. Treatment of C6 tumor cells with TV (5-15 microM for 24-72 h) resulted in a growth inhibition in a dose and time-dependent manner and G0/G1 phase arrest, determined by flow cytometry analysis. These effects were accompanied by apoptosis other than necrosis, evidenced by nuclear condensation, terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) assay and trypan blue exclusion assay plus lactate dehydrogenase (LDH) release assay. Treatment of cells with TV at 15 microM for 24 h resulted in an increase in the activity of caspase-3, evidenced by colorimetric assay, and a dramatic up-regulation of p53, accompanied with a significant increase of Bax/Bcl-2 ratio, as evidenced by immunofluorescence assay. These results suggest that TV induces growth inhibition of C6 cells through p53-midiated apoptotic pathway and G0/G1 checkpoint mechanism. Although detailed mechanisms remain to be explored, selective blockage of tumor cells in G0/G1 phase accompanied by p53-associated apoptosis makes tetrazolium violet a promising anticancer agent, meriting further investigations.