VEGF/Neuropilin-2 Regulation of Bmi-1 and Consequent Repression of IGF-1R Define a Novel Mechanism of Aggressive Prostate Cancer

We demonstrate that the VEGF receptor, neuropilin-2 (NRP2) is associated with high-grade, PTEN-null prostate cancer and that its expression in tumor cells is induced by PTEN loss as a consequence of c-Jun activation. VEGF/NRP2 signaling represses IGF-1R expression and signaling and the mechanism involves Bmi-1-mediated transcriptional repression of the IGF-1R. This mechanism has significant functional and therapeutic implications that were evaluated. IGF-1R expression correlates with PTEN and inversely with NRP2 in prostate tumors. NRP2 is a robust biomarker for predicting response to IGF-1R therapy because prostate carcinomas that express NRP2 exhibit low levels of IGF-1R. Conversely, targeting NRP2 is only modestly effective because NRP2 inhibition induces compensatory IGF-1R signaling. Inhibition of both NRP2 and IGF-1R, however, completely blocks tumor growth in vivo .