Histopathological And Expression Profiling Studies Of Early Tumor Responses To Near-Infrared Pdt Treatment In Scid Mice

A novel class of porphyrin-based near-infrared photodynamic therapy (PDT) sensitizers is studied. We achieve regressions of human small cell lung cancer (NCI-H69), non-small cell lung cancer (A 459) and breast cancer (MDA-MB-231) xenografts in SCID mice at significant tissue depth by irradiation with an amplified femtosecond pulsed laser at 800 nm wavelength. Significant tumor regressions were observed during the first 10-14 days post treatment. Tumor histopathology was consistent with known PDT effects, while no significant changes were noted in irradiated normal tissues. In vivo imaging studies using intravenous injections of fluorescent dextran demonstrated an early loss of tumor blood flow. RNA was isolated from NCI-H69 PDT treated SCID mouse xenografts and paired untreated xenografts at 4 hours post laser irradiation. Similarly RNA was isolated from PDT treated and untreated Lewis lung carcinomas growing in C57/B16 mice. Expression profiling was carried out using Affymetrix(TM) human and mouse GeneChips(R). Cluster analysis of microarray expression profiling results demonstrated reproducible increases in transcripts associated with apoptosis, stress, oxygen transport and gene regulation in the PDT treated NCI-H69 samples. In addition, PDT treated Lewis lung carcinomas showed reproducible increases in transcripts associated with immune response and lipid biosynthesis. PDT treated C57/B16 mice developed cytotoxic T cell activity towards this tumor, while untreated tumor bearing mice failed to do so.