Combination of angiogenesis inhibitors increases the anti-tumor efficacy of photodynamic therapy in a human bladder tumor xenograft model

Photodynamic therapy (PDT) is a standard treatment for various malignant and non-malignant conditions. Though therapeutic responses are encouraging, recurrences have been noted, as one of the limitations of PDT is treatment-induced hypoxia that triggers angiogenesis. The present study evaluates the use of angiogenic inhibitors Avastin, that targets vascular endothelial growth factor (VEGF) and Erbitux that targets epidermal growth factor receptor (EGFR) with PDT in an in vivo bladder carcinoma xenograft. Tumor bearing mice were assigned to 6 different categories: control, PDT only, Avastin + Erbitux, PDT + Avastin, PDT + Erbitux and PDT + Avastin and Erbitux. Treated and control tumors were monitored for recurrence for up to 90 days. VEGF and EGFR expression was detected in the tumor tissue. Migratory assay was performed to establish the inhibitory effect of the angiogenesis agents. Using confocal laser endomicroscopy, the tumor microvasculature was assessed. Tumors treated with the combination therapy of PDT + inhibitors showed significantly greater response compared to control and PDT only treated group. Combination therapy treated tumors also showed the most post-treatment damage with reduced tumor vasculature. These results demonstrate that the combination of PDT with inhibitors that target different angiogenesis pathways can improve tumor control.