To clarify the potential function of NRP1 in the radio-sensitivity of NSCLC, we attempted to use small interfering RNA (siRNA) technology to inhibit expression of the NRP1 gene in NSCLC cells (A549) and analysed the effect of NRP1 inhibition on growth, survival and radio-sensitivity of NSCLC cells both in vitro and in vivo. Here, NRP1 is linked to non-small cell lung carcinoma.