RESEARCH ARTICLE Near Infra-Red Photoimmunotherapy with Anti-CEA-IR700 Results in Extensive Tumor Lysis and a Significant Decrease in Tumor Burden in Orthotopic Mouse Models of Pancreatic Cancer

Photoimmunotherapy (PIT) of cancer utilizes tumor-specific monoclonal antibodies conjugat-ed to a photosensitizer phthalocyanine dye IR700 which becomes cytotoxic upon irradiation with near infrared light. In this study, we aimed to evaluate the efficacy of PIT on human pan-creatic cancer cells in vitro and in vivo in an orthotopic nudemouse model. The binding ca-pacity of anti-CEA antibody to BxPC-3 human pancreatic cancer cells was determined by FACS analysis. An in vitro cytotoxicity assay was used to determine cell death following treat-ment with PIT. For in vivo determination of PIT efficacy, nude mice were orthotopically im-planted with BxPC-3 pancreatic tumors expressing green fluorescent protein (GFP). After tumor engraftment, the mice were divided into two groups: (1) treatment with anti-CEA-IR700 + 690 nm laser and (2) treatment with 690 nm laser only. Anti-CEA-IR700 (100 μg) was ad-ministered to group (1) via tail vein injection 24 hours prior to therapy. Tumors were then sur-gically exposed and treated with phototherapy at an intensity of 150 mW/cm2 for 30 minutes. Whole body imaging was done subsequently for 5 weeks using an OV-100 small animal im-aging system. Anti-CEA-IR700 antibody bound to the BxPC3 cells to a high degree as show