Garcinol sensitizes human head and neck carcinoma to cisplatin in a xenograft mouse model despite downregulation of proliferative biomarkers

OBJECTIVE Platinum compounds such as cisplatin and carboplatin are frequently used as the first-line chemotherapy for the treatment of the head and neck squamous cell carcinoma(HNSCC).In the present study,we investigated whether garcinol,apolyisoprenylated benzophenone can chemosensitize HNSCC to cisplatin.METHODS The effect of garcinol and cisplatin on HNSCC was assessed by MTT,Western blotting,real time PCR,FACS,immunohistochemistry,DNA binding assay and xenograft mouse model.RESULTS We found that garcinol inhibited the viability of a panel of diverse HNSCC cell lines,enhanced the apoptotic effect of cisplatin,suppressed constitutive as well as cisplatin-induced NF-κB activation,and downregulated the expression of various oncogenic gene products(cyclin D1,Bcl-2,survivin and VEGF).In vivo study showed that administration of garcinol alone(0.5 mg·kg-1,ip five times/week)significantly suppressed the growth of the tumor,and this effect was further increased by cisplatin.Both the markers of proliferation index(Ki-67)and microvessel density(CD31)were downregulated in tumor tissues by the combination of cisplatin and garcinol.The pharmacokinetic results of garcinol indicated that good systemic exposure was achievable after ip administration of garcinol at 0.5and 2mg·kg-1 with mean peak concentration(cmax)of 1825.4 and 6635.7nmol·L-1 in the mouse serum,respectively.CONCLUSION Overall,our results suggest that garcinol can indeed potentiate the effects of cisplatin by negative regulation of various inflammatory and proliferative biomarkers.