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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 × 10~3 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.
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) 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 analyzes (cell proliferation marker Ki-67, DNA damage The 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 cell plating efficiency (PE) (0.54 ± 0.11 vs 2.81 ± 0.14 with 185 k Bq / m L ~ (90) Y- 0.08 vs 1.88 ± 0.09 with 370 k Bq / m L ~ (90) Y-ITGA6 B4 exposure, P <0.01) when combined 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.