Combined treatment of pancreatic cancer xenograft with 90Y-ITGA6B4-mediated radioimmunotherapy and PI3K/m TOR inhibitor

• Published in: 世界胃肠病学杂志：英文版 2017 (42), p.7551-7562
• Main Author: Winn Aung Atsushi B Tsuji Hitomi Sudo Aya Sugyo Yoshinori Ukai Katsushi Kouda Yoshikazu Kurosawa Takako Furukawa Tsuneo Saga Tatsuya Higashi
• Format: Article
• Language: English
• ISSN: 1007-9327; 2219-2840

AIM To investigate the therapeutic effect of combined integrin α6β4-targeted radioimmunotherapy（RIT） and PI3 K/m TOR inhibitor BEZ235 in a pancreatic cancer model.METHODS Phosphorylation of Akt, m TOR, the downstream effectors eukaryotic initiation factor 4 E binding protein 1（4 EBP1） and S6 ribosomal protein（S6） were evaluated in Bx PC-3 human pancreatic cancer cells treated with Yttrium-90(90 Y) labeled anti-integrin α6β4 antibody（ITGA6 B4） and BEZ235 by western blotting. The cytotoxic effect of BEZ235 was investigated using a colony formation assay. Therapeutic efficacy enhancement by oral BEZ235 administration was assessed using mice bearing Bx PC-3 xenograft tumors. Tumor volume measurements and immunohistochemical analyses（cell proliferation marker Ki-67, DNA damage marker p-H2 AX and p-4 EBP1 staining） of tumors were performed for evaluation of combined treatment with 90 Y-ITGA6 B4 plus BEZ235, or each arm alone.RESULTS We found that phosphorylation of Akt（p-Akt）, 4 EBP1（p-4 EBP1） and S6（p-S6） was inhibited by BEZ235. Colony formation in Bx PC-3 cells was additively suppressed by the combination of 90 Y-ITGA6 B4 and BEZ235. Pretreatment with BEZ235 before 90 Y-ITGA6 B4 exposure resulted in significant reduction of cells plating efficiency（PE）(0.54 ± 0.11 vs 2.81 ± 0.14 with 185 k Bq/m L 90 Y-ITGA6 B4 exposure, P < 0.01; 0.39 ± 0.08 vs 1.88 ± 0.09 with 370 k Bq/m L 90 Y-ITGA6 B4 exposure, P < 0.01) when 5 × 103 cells per dish were plated. In vivo, the combined treatment with 90 Y-ITGA6 B4 plus BEZ235 enhanced the inhibition of tumor growth and statistically significant differences of relative tumor volume were observed for 27 d after the treatment start date when compared with the 90 Y-ITGA6 B4 single injection treatment（1.03 ± 0.38 vs 1.5 ± 0.15 at Day 27, P < 0.05）, and for 41 d when compared with the BEZ235 treatment alone（1.8 ± 0.7 vs 3.14 ± 1.19 at Day 41, P < 0.05）. Tumors from treatment groups showed reduction in volumes, decreased Ki-67-positive cells, increased p-H2 AX-positive cells and decreased p-4 EBP1 expression. CONCLUSION The therapeutic efficacy of 90 Y-ITGA6 B4-RIT can be improved by combining with dual PI3 K and m TOR inhibitor, BEZ235, in a pancreatic cancer model suggesting potential clinical application.