Quantitative analysis of lymphangiogenic markers for predicting metastasis of human gastric carcinoma to lymph nodes

4636 Introduction: Photodynamic therapy (PDT) appears to hold promise for the treatment of localized recurrent prostate cancer. However, the long-term effects remain to be evaluated. We have observed that, in an animal model, subcurative PDT of prostate cancer increases distant metastasis, a side effect also reported after brachytherapy, hyperthermia and surgery. The objectives of this study are to evaluate the effect of PDT on the microcirculation of human prostate tumors as well as its potential role in vascular permeability and angiogenesis. Materials and Methods: This study was performed with the androgen responsive human LNCaP cells. 3x10 6 cells in 50% Matrigel was inoculated in SCID mice prostate, 3 weeks later experiments were performed. BPD was used at a concentration of 140 nM for in vitro assays and at concentration of 0.25 mg/kg body weight for in vivo treatment. PDT is performed 1 hr after incubation or injection of BPD. At various times following PDT treatment we have used, an ELISA to measured VEGF-A protein levels and RT-PCR to measure RNA levels. A modified Miles assay using FITC-Dextran was used to monitor in real time vascular leakage, and IHC was used to image VEGF. Results: PDT treatment of prostate tumors shows significant area of necrosis (H&E staining) as well as an increase in VEGF-A (IHC) 24 h post treatment. Quantification using an ELISA shows a 1,8 fold increase in VEGF-A levels 24 h following subcurative treatment. Using a modified Miles assay we were able to observe, in real time, an immediate increase in vascular permeability following PDT. Next we performed in vitro experiments to identify the mechanism of this increase. ELISA performed 24 h post PDT shows an increase in both intracellular and secreted VEGF-A levels (1,4x and 2,5x respectively). RT-PCR shows an increase in all 3 VEGF-A isoforms expressed in LNCaP cells 24 h following subcurative PDT (1,7x).Conclusion: Together the results presented in this study establishes that PDT alters tumor microcirculation, as well as transcription and synthesis of VEGF-A in vivo and in vitro at subcurative doses. Based on the current observations we conclude that the most effective application of PDT for long-term cure, may involve combined therapeutic regimens that counteract the potential metastatic effect of PDT, while retaining its impressive local tumor control.