In summary, this study identifies NRP2 (Neuropilin 2) as a novel biomarker for predicting response to IGF-1R (insulin-like growth factor 1) therapy. A critical finding in this context is that NRP2 is a much more robust biomarker than the IGF-1R itself. This finding is significant because the IGF-1R, is also expressed normal glands, in contrast to NRP2. Importantly, the data presented provide a rationale for initiating clinical trials that combine inhibitors of both NRP2 and IGF-1R.