The new idea of cancer immunotherapy: the expression of PD-L1 may reveal the immunological mechanism of resistance of EGFR-TKIs
Authors: Jia Ying , Li Shi , Wang Xinran , Liu Junying , Fan Xiaojie , Yin Danjing , Han Dandan , Zhao Hang , Yu Shiyang , Liu Yueping 
Published: December 2023

Abstract
INTRODUCTION: Lung cancer is one of the most common and deadly cancers worldwide. Immunotherapy has penetrated into various stages of non-small cell lung cancer diagnosis and treatment.Immunotherapy has become the standard treatment choice for first-line and second-line advanced lung cancer, significantly prolonging the adverse prognosis caused by EGFR resistance. There is currently insufficient evidence to determine whether the expression of PD-1/PD-L1 is related to EGFR mutations or EGFR-TKIs resistance.
METHODS: 1352 cases of NSCLC patients collected for EGFR, PD-L1(Ventana SP263),MET,ERBB2,PIK3CA,RAS detections simultaneously from the medical records of Fourth Hospital of Hebei Medical University between January 2017 and April 2019, 275 cases had PD-L1 expression (> 0%) in positive EGFR mutations（275/737,57.7%）. Real-time quantitative polymerase chain reaction (RT-qPCR) and Next-generation sequencing (NGS) were mainly used for molecular detection , such as EGFR and MET. ERBB2 results were verified in Fluorescence in situ hybridization (FISH) while immunohistochemical staining were decided to be 2+. ALL the test results were confirmed by gold standard method. PD-L1 immunohistochemistry was performed using the 22C3 antibody for tumor cell (TPS，Tumor Proportion Score). Statistical analyses were performed using IBM SPSS software. The chi-square test was used to analyze the objective response rates according to PD-L1 expression.
RESULTS: There were 24 cases (24/196, 12.24%) with high expression of PD-L1 as well as T790M mutation, which was significantly higher than that of 36 cases in low expression group (36/546, 6.59%) or 6 cases in moderate group (6/111,5.41%), P = 0.039, X2 = 6.478. The number of patients with high expression of PD-L1 and ERBB2 amplification was 5 (5/196, 2.55%；P = 0.008, X2 = 9.729), had positive correlation with PD-L1 overexpression. Among 91 EGFR-TKI resistant cases, the positive rate of high expression of PD-L1 in 17 cases of primary resistance to EGFR was higher than that of acquired resistance to EGFR-TKI (58.82% vs 29.73%, X2 = 5.132, P = 0.046). In addition, the primary drug resistance always accompanies the high expression level of PD-L1(positive ratio≥50%).The patients with primary drug-resistant and high expression level of PD-L1 had a shorter progression-free survival (PFS) ( P = 0.040).According to our statistics, the high expression level of PD-L1 is related to poor clinical pathological feature, size, lymph node or distant metastasis rate were all include(P <0.000).In EGFR positive cases, the number of patients with high expression of PD-L1 was different in adenocarcinoma, squamous cell carcinoma, adenosquamous cell carcinoma and mucinous adenocarcinoma (X2 = 157.241, P=0.000). The overexpression of PD-L1 happened in mucinous adenocarcinoma more often.
CONCLUSIONS: It can be inferred that the high expression of PD-L1 is related to poor prognosis and EGFR-TKI resistance. The high expression of PD-L1 may speculate the existence of drug resistance mutation, especially the mutation before medicated, and the resistance mechanism may be related to immunity.