Growing evidence indicates that the antiapoptotic protein survivin is a major factor of drug and radiation resistance in cancer cells. However, application of this finding to therapeutic drug combination is largely unexplored. In this study, breast cancer cells were used for treatment with anticancer compounds alone or in combination. We report that T138067, a better drug against multiple drug resistance (MDR) tumor cells than taxol (Shan et al., PNAS 96:5686-91,1999), induces survivin expression and consequently decreases its effectiveness on the induction of cancer cell death. Treatment of breast cancer cells with T138067 induced survivin expression in these cells while showing no effect on Bcl-2, indicating its specificity. Upregulation of survivin by T138067 was concomitant with an increased drug resistance and associated with an increased phosphorylation of Akt and Erk1/2 MAPK, and a decreased phosphorylation of p38 MAPK without affecting the phosphorylation of ErbB2. Therefore, it is possible that inhibition of T138067-induced survivin expression by alternative approaches may sensitize cells to T138067-induced cell death. We found that treatment of breast cancer cells with SN38, the active metabolite of irinotecan, inhibits survivin expression. Intriguingly, inhibition of survivin expression by SN38 was more effective at a low concentration than at the high concentration, which makes SN38 a good survivin modulator. Furthermore, in contrast with the decreased phosphorylation of p38 MAPK after T138067 treatment, inhibition of survivin expression by SN38 was associated with an increased phosphorylation of the p38 MAPK, suggesting opposing signals converging to survivin. Consistent with these observations, T138067 in combination with SN38 strongly induced cell death in comparison with each drug alone. Similarly, sequential combination of resveratrol, a component of red grapes that inhibits survivin expression, with T138067 also provoked massive breast cancer cell death compared with T138067 alone. Together, these results highlight a new concept that unique signaling cross talk converged to survivin may be considered for rational drug combination in the clinic.
Keywords: SN38; Survivin; T138067; breast cancer cells; irinotecan; resveratrol.