Synergistic growth inhibition of cancer cells harboring the RET/PTC1 oncogene by staurosporine and rotenone involves enhanced cell death.

TPC-1 is a highly proliferative thyroid papillary carcinoma-derived cell line. These cells express the RET/PTC1 fusion protein, whose isoforms are characterized in this work. The bacterial alkaloid staurosporine and the plant extract rotenone are death-inducing drugs that have an inhibitory synergistic effect on the growth of TPC-1 cells. We show that this synergism is accompanied by an enhancement of the induction of cell death. Staurosporine alone induces cell cycle arrest in G1, whereas rotenone induces arrest in G2/M. We suggest that this additive pressure may drive cells to die, resulting in the synergistic interaction of the drug combination. These data emphasize the potential use of the staurosporine plus rotenone combination as an anticancer tool.