KDR and neoplasm: Whereas, studies of VEGFA-VEGFR signaling in tumor cells have reached controversial conclusions (including the idea that p38/AKT phosphorylation regulates VEGFA expression; VEGFA regulates p38/AKT phosphorylation; VEGFA and p38/AKT phosphorylation mutually activate each other through a feedback loop) 59, 63-65.