NTRK1 and neoplasm: Furthermore, effective angiogenesis must occur for tumor survival, and this process is mediated both via VEGF secretion by tumor and stromal cells [38, 39] and by secretion of angiopoietins which sustain and augment the vasculogenic process by binding the receptor tyrosine kinase Tie-2, expressed by endothelial lineage cells [67, 68, 71, 77–79].