Radioimmunotherapy of pancreatic cancer xenografts in nude mice using (90)Y-labeled anti-α(6)β(4) integrin antibody

The contribution of integrin α(6)β(4) (α(6)β(4)) overexpression to the pancreatic cancer invasion and metastasis has been previously shown. We have reported immunotargeting of α(6)β(4) for radionuclide-based and near-infrared fluorescence imaging in a pancreatic cancer model. In this study, we prepared yttrium-90 labeled anti-α(6)β(4) antibody ((90)Y-ITGA6B4) and evaluated its radioimmunotherapeutic efficacy against pancreatic cancer xenografts in nude mice. Mice bearing xenograft tumors were randomly divided into 5 groups: (1) single administration of (90)Y-ITGA6B4 (3.7MBq), (2) double administrations of (90)Y-ITGA6B4 with once-weekly schedule (3.7MBq × 2), (3) single administration of unlabeled ITGA6B4, (4) double administrations of unlabeled ITGA6B4 with once-weekly schedule and (5) the untreated control. Biweekly tumor volume measurements and immunohistochemical analyses of tumors at 2 days post-administration were performed to monitor the response to treatments. To assess the toxicity, body weight was measured biweekly. Additionally, at 27 days post-administration, blood samples were collected through cardiac puncture, and hematological parameters, hepatic and renal functions were analyzed. Both (90)Y-ITGA6B4 treatment groups showed reduction in tumor volumes (P < 0.04), decreased cell proliferation marker Ki-67-positive cells and increased DNA damage marker p-H2AX-positive cells, compared with the other groups. Mice treated with double administrations of (90)Y-ITGA6B4, exhibited myelosuppression. There were no significant differences in hepatic and renal functions between the 2 treatment groups and the other groups. Our results suggest that (90)Y-ITGA6B4 is a promising radioimmunotherapeutic agent against α(6)β(4) overexpressing tumors. In the future studies, dose adjustment for fractionated RIT should be considered carefully in order to get the optimal effect while avoiding myelotoxicity.