Compared to the normal bronchial epithelial cells (HBEC), the expression of PD1 mRNA was upregulated in six lung cancer cell lines, including H1299, H23, COLO677, H1975, H82, and H2228, with the expression level being more than 326-fold higher in COLO677 (Figure 1(ai)). This evidence concerns the gene PDCD1 and lung cancer.