Src inhibition potentiates antitumoral effect of paclitaxel by blocking tumor-induced angiogenesis

The protein kinase Src is frequently over-activated in advanced cancers where it modulates the signaling transduction cascade of several growth factors. The feasibility of combination treatment of Src inhibitors with chemotherapy is currently under investigation. We evaluated the anti-tumoral effect of paclitaxel (PTX) in combination with S13, a tyrosine kinase inhibitor with a prevalent specificity for Src, in a hormone-insensible prostate cancer (PCa) cell model. In vivo, combination treatment with PTX and S13 reduced dramatically PCa tumor growth with a relevant difference in the density of new blood vessels with respect to control and single treatments. This reduction was determined by a concomitant impairment of endothelial cell migration and of VEGF release by cancer cells. In fact, S13, when used alone, was sufficient to reduce tubule formation in vivo, and to inhibit VEGFR2 activation and FAK expression in endothelial cells. In addition, the combination treatment determined a significant reduction in ROS production and HIF-1 stabilization in PCa cells respect to single treatments with S13 or PTX. In conclusion, Src-inhibition could be an effective therapeutic strategy aimed at supporting the anti-angiogenic action of PTX in aggressive PCa.