Ionizing Radiation (IR) downregulates CD31 and enhances HIF1α levels in human lung cancer tumours. ( A) Lysates from control and irradiated tumours were subjected to immunoblot analysis using CD31 and HIF1α antibodies. A representative immunoblot from 6 independent experiments is shown. ( B) Average normalized densitometric values are shown as percent change in protein expression relative to the control group (*p < 0.05; **p < 0.001). ( C) A549 tumours were fixed and immunohistochemistry analysis was performed using a specific anti-CD31 antibody.