Infrared laser activation of indocyanine green inhibits growth in human pancreatic cancer.

Abstract

Indocyanine green (ICG) is a clinically-approved, water-soluble dye that generates reactive singlet oxygen when activated by infrared light. Infrared light offers the advantage of deeper tissue penetration making ICG photodynamic therapy (PDT) ideal for treatment of intra-abdominal cancers such as pancreatic adenocarcinoma. To determine the cytotoxicity of ICG PDT in human pancreatic cancer. MIA PaCa-2, PANC-1, and BxPC-3 pancreatic cancer cells were incubated for 1 hour with 0 to 50 microg/mL ICG, serially washed to remove unbound dye, and then briefly exposed to infrared light from a diode laser at 0.45 W. MTT cell viability assays were performed at 72 hours post-treatment. Toxicity to ICG or infrared laser alone was not observed in any of the cell lines. Cell viability assays showed an ICG dose-dependent ablation when combined with laser exposure (+L). In all 3 cancer cell lines, significant growth inhibition was seen at 10 microg/mL ICG + L with nearly total ablation at 20 microg/mL ICG + L (P < 0.01). ICG PDT induces consistent and dramatic pancreatic cancer cell death. Since neither ICG nor laser alone caused toxicity, combination therapy may offer effective control of tumor growth with minimal side effects in patients with unresectable primary or metastatic pancreatic cancer.