Combination of tipifarnib and rapamycin synergistically inhibits the growth of leukemia cells and overcomes resistance to tipifarnib via alteration of cellular signaling pathways

Small molecules are attractive agents for the treatment of leukemia. We found that a combination of a farnesyltransferase inhibitor, tipifarnib, and an mTOR inhibitor, rapamycin, synergistically inhibited the growth of myeloid leukemia cell lines and primary leukemia cells by inducing apoptosis and cell-cycle blockage. The combined agents reduced the level of phospho-ERK1/2, suggesting that they altered the network of signaling pathways. They also showed synergistic effects in tipifarnib-resistant K562/RR cells. The results support the utility of this combination as a potential therapy for leukemia. The combination might also be effective in overcoming resistance to tipifarnib.