P18.11.A AMLODIPINE EXERTS SYNERGETIC EFFECT ON CHEMOTHERAPY AGAINST GLIOBLASTOMA BY SUPPRESSING MGMT-AKT/GSK3Β/Β-CATENIN AXIS OF TUMOR STEM CELLS.

Abstract BACKGROUND High chemo-resistance of glioblastoma is still a major clinical challenge, exploring new strategy to enhance tumoricidal activity of chemoresistance, especially against high therapeutic resistant glioma stem cells (GSCs), is crucial to improve patient outcome. As a classical calcium channel blocker (CCB) against hypertension, amlodipine has been reported to have definite anti-tumor effect. However, whether it has synergetic effect with temozolomide (TMZ) against GSCs and the relevant regulatory pathways remains unclear. MATERIAL AND METHODS Glioma stem cell lines and the intracranial orthotopic GSCs-derived tumor model were applied to evaluate the effects of amlodipine alone or combing with TMZ against GSCs in vitro and in vivo, respectively. Then gene transduction, quantitative real-time PCR, Western blot, flow cytometry and immunofluorescence assay were utilized to disclose the relevant regulating signaling pathway and elucidate the underlying mechanisms. RESULTS Amlodipine inhibited tissue remodeling of GSCs. Besides, amlodipine enhanced cytotoxicity of TMZ against GSCs through downregulating MGMT expression both in vitro and in vivo, via down-regulating Akt/GSK3β/β-catenin axis. Overexpression of MGMT reversed the synergistic anti-GSCs effects of amlodipine with TMZ. Pharmacological inhibition of GSK-3β with CHIR-99021 or overexpression of β-catenin reversed amlodipine-induced suppression of cell viability, down-regulation of β-catenin and MGMT and enhancement of TMZ cytotoxicity against GSCs. In vivo studies also demonstrated that the synergetic effect of amlodipine with TMZ against GSCs, which was achieved through down-regulating β-catenin and MGMT, then retarding growth of GSCs-derived intracranial xenografts, and prolonging survival of tumor bearing mice. CONCLUSION Amlodipine had obvious synergetic effect with TMZ against development of glioblastoma via AKT/GSK3β/β-catenin axis inhibit MGMT expression of GSCs. These results indicated that amlodipine has novel potentials of repurposing as synergetic chemotherapy against GSCs to disrupt progression of therapeutic-resistant glioblastoma.