Furthermore, nano-Se combined with radiotherapy could induce apoptosis of lung cancer cells (P < 0.05) and nano-Se combined with radiotherapy could significantly inhibit the expression of proliferation-related proteins CCND1, c-Myc, invasion and migration-related proteins MMP2 and MMP9, but conversely promoted the expression of apoptosis-related proteins cleaved caspase-3 and cleaved caspase-9. This evidence concerns the gene MMP9 and lung cancer.