MYC expression correlates with PD-L1 expression in non-small cell lung cancer.

Objectives Programmed death-ligand 1 (PD-L1) is a widely used biomarker for predicting immune checkpoint inhibitors, but is of limited usefulness in the prediction of drug response. MYC, a transcription factor that is overexpressed in cancers, is involved in preventing immune cells from attacking tumor cells through inducing PD-L1 expression. This study evaluated the relationship between MYC and PD-L1 expression in 84 non-small cell lung cancer (NSCLC) patients who underwent curative surgical resection. Materials and Methods The relationship between MYC and PD-L1 was investigated by introducing pcDNA3-cMYC into A549 and H1299 cells with low PD-L1 expression and siRNA against MYC into H60 and H2009 cells with high PD-L1 expression. Expression of PD-L1 in NSCLC tissues was analyzed by immunostaining using a PD-L1 (22C3) PharmDx protocol using the Dako Automated Link 48 platform and expression of MYC was determined using anti-c-MYC (Y69) (ab320720). Results Of 84 patients, PD-L1 was expressed in 14 (16.7%) and MYC was overexpressed in 30 (35.7%). We investigated the relationship between PD-L1 and MYC expression. There were 49 (58.3%) double-negative patients and 9 (10.7%) double-positive patients. Significant positive correlation was observed between PD-L1 and MYC expression (γ=0.210, P=0.029). Double-negative patients showed better disease free (31.1 vs. 7.1 months, P=0.011) and overall survival (56.1 vs. 14.4 months, P=0.032) than double-positive patients. Conclusion Taken together, MYC expression significantly correlated with PD-L1 expression in NSCLC. The usefulness of MYC expression as a surrogate marker of treatment response assessment is worth evaluating for immune checkpoint inhibitor therapy and special interest are required for the subgroup of NSCLC patients, whose tumor expresses PD-L1 and MYC double positive.