Compared to normal lung tissues, the expression of the MOR in tumor tissues of patients with non-small-cell lung cancer (NSCLC) was 5∼10 times increased, which was consistent with that in the NSCLC cell line, which indicates that high expression of the MOR may have regulated a series of biological characteristics including cell proliferation and differentiation (75, 76). This evidence concerns the gene OPRM1 and neoplasm.