17-(Allylamino)-17-Demethoxygeldanamycin Combination with Curcumin Selectively Targets Mitogen Kinase Pathway in A Human Neuroblastoma Cell Line

Pharmacological inhibition of Hsp90 has emerged as a novel anticancer treatment. In this study we have investigated the effect of Hsp90 inhibitor drug 17AAG combination with curcumin on human neuroblastoma cells. The 17AAG treatment of cells for 18 h induced G1/S cell cycle arrest associated with cyclin D1 down regulation, and degradation of Raf-1 and inactivation of Akt. However, 17AAG treatment activated the mitogen kinase, ERK1, and induced the expression of stress proteins, Hsp70 and p53. The curcumin treatment resulted in G2/M cell cycle arrest and activation of both Raf1 and ERK1 kinases. The drugs in combination induced proteolytic degradation of Raf1 and Akt, and surpassed curcumin induced G2/M arrest. The combination treatment additionally inactivated MEK, inhibited activation and nuclear localization of ERK1, and also inhibited the stress protein induction. EGF stimulation induced re-activation of mitogen signaling with individual drug treatments but not in combination. This study highlights that 17AAG combination with curcumin selectively targets mitogen signal transduction mechanism through ERK1 inactivation. In conclusion, our study proposes the beneficial effects of 17AAG combination with curcumin in combating cancer.