NTRK1 and neoplasm: Works from our laboratory and others have previously demonstrated that radiation response is enhanced by blocking the VEGF signaling pathway using small molecule VEGF receptor tyrosine kinase inhibitors such as ZD6474[11], SU6668[12] and PTK787/ZK222584[13], or by directly targeting tumor blood vessels with vascular targeting agents such as ZD6126[14,15] and combretastatin[16].