PD-L1 mRNA expression in EGFR-mutant lung adenocarcinoma

Molecular mechanisms of programmed death-ligand 1 (PD-L1) mRNA expression and roles of apoptosis and biomarkers are poorly understood in epidermal growth factor receptor (EGFR)-mutant lung adenocarcinoma patients. Thirty-three patients with recurrent postoperative EGFR-mutant lung adenocarcinoma (exon 19 deletion in 16, L858R in 15, G719C in 2 patients) treated with gefitinib were studied. PD-L1 mRNA expression of formalin-fixed paraffin-embedded paratumoral and intratumoral tissues was quantified by PCR. Correlations of PD-L1 mRNA expression with BIM, p53 upregulated modular of apoptosis (PUMA), human epidermal growth factor receptor 2 (HER2), mesenchymal-epithelial transition (MET), EGFR, and vascular endothelial growth factor A (VEGFA) were determined. Eleven of the 33 patients (33.3%) and 14/33 patients (42.4%) expressed intratumoral and paratumoral PD-L1 mRNA, respectively. Patients with intratumoral PD-L1 mRNA expression had significantly higher BIM and lower VEGFA expression compared with paratumoral PD-L1 mRNA patients (P=0.049, P=0.009). PD-L1 mRNA expression was not associated with the expression of PUMA, HER2, EGFR and MET but was positively correlated with BIM expression (r=0.41, P=0.017) and inversely correlated with VEGFA expression (r=-0.33, P=0.043). Patients with intratumoral PD-L1 mRNA expression had significantly shorter median progression-free survival (PFS) after gefitinib therapy compared with no PD-L1 expression (255 vs. 732 days, respectively; P=0.032). Thus, PD-L1 mRNA expression in EGFR-mutant lung adenocarcinoma was associated with BIM and VEGFA mRNA expression and with shorter PFS after gefitinib therapy.