SP600125 overcomes antimitotic drug-resistance in cancer cells by increasing apoptosis with independence of P-gp inhibition

The purpose of this study was to identify conditions that increase the sensitivity of resistant cancer cells to antimitotic drugs. Using MTS assays, microscopic observation, assessment of cleaved PARP, FACS analysis, and Hoechst staining, we found that the c-Jun N-terminal kinase (Jnk) inhibitor SP600125 (SP) sensitized the antimitotic drug-resistant KBV20C cancer cell line. The sensitization mechanism was independent of p-glycoprotein (P-gp) inhibition. Interestingly, SP-induced sensitization was greater in resistant KBV20C cancer cells than in KB parent cells. The mechanism of SP-induced sensitization involved G2 arrest. KBV20C cells treated with SP and antimitotic drugs were more sensitized than cells treated with SP alone. This suggests that SP can restore sensitization for antimitotic drugs in resistant cancer cells. Our findings may contribute to the development of SP-based combination therapies for patients receiving anti-cancer agents that target microtubules.