PD-L1表达对晚期肺腺癌患者培美曲塞化疗效果的影响及其机制

Effect of PD-L1 expression on the efficacy of pemetrexed-based chemotherapy in patients with advanced lung adenocarcinoma and its mechanism

背景与目的:肺癌组织程序性死亡配体-1(programmed death ligand-1,PD-L1)表达水平不仅是程序性死亡[蛋白]-1(programmed death-1,PD-1)/PD-L1抑制剂最主要的疗效预测生物标志物,还可能影响表皮生长因子受体-酪氨酸激酶抑制剂(epidermal growth factor receptor-tyrosine kinase inhibitor,EGFR-TKI)的疗效。然而,肺癌组织PD-L1表达水平能否影响肺腺癌患者化疗效果,目前相关文献报道较少。探讨肺腺癌组织PD-L1表达对培美曲塞为基础的化疗效果的影响及其潜在机制。方法:2015年10月—2018年12月于中国人民解放军西部战区总医院肿瘤诊治中心确诊为肺腺癌且符合研究入组条件的患者共185例。应用免疫组织化学法分别检测肺腺癌组织中PD-L1和培美曲塞疗效预测分子胸苷酸合酶(thymidylate synthase,TS)的表达。采用Kaplan-Meier法绘制患者的生存曲线,采用log-rank检验和COX回归模型分析影响患者无疾病进展生存(progression-free survival,PFS)的临床病理学因素,采用log-rank检验分别分析PD-L1和TS表达对患者PFS和总生存(overall survival,OS)的影响,采用Spearman秩相关性检验分析肺腺癌组织中PD-L1表达与TS表达的相关性。应用蛋白质印迹法(Western blot)及实时荧光定量聚合酶链反应(real-time fluorescent quantitative polymerase chain reaction,RTFQ-PCR)分别检测6种肺腺癌细胞系中PD-L1、TS的蛋白水平和mRNA表达。采用Pearson相关性检验分析PD-L1和TS在蛋白表达水平及mRNA表达水平的相关性。结果:在51例一线接受培美曲塞为基础化疗的晚期肺腺癌患者中,PD-L1表达阳性患者的客观有效率(objective response rate,ORR)和疾病控制率(disease control rate,DCR)与PD-L1表达阴性患者相比差异无统计学意义(ORR:20.0%vs 35.5%,χ~2=1.404,P=0.236;DCR:60.0%vs 80.6%,χ~2=2.602,P=0.107)。PD-L1表达阴性患者的中位无疾病进展生存(median progression-free survival,mPFS)显著优于PD-L1表达阳性患者(mPFS:5.6个月vs 4.1个月,log-rank=5.406,P=0.020),两组患者中位总生存(median overall survival,mOS)差异无统计学意义(mOS:15.9个月vs 12.7个月,log-rank=0.525,P=0.469)。单因素分析发现PD-L1和TS表达阳性是影响患者PFS的危险因素(P=0.023和P=0.003),多因素分析发现TS表达阳性是影响患者PFS的独立危险因素(P=0.034)。在51例一线接受培美曲塞为基础化疗的晚期肺腺癌患者中,患者肺腺癌组织PD-L1表达与TS表达呈显著正相关性(r_s=0.691,P<0.001);进一步扩大样本检测发现:在不同肿瘤分期和一线治疗模式的185例肺腺癌患者中,癌组织PD-L1表达与TS表达仍然呈显著正相关(r_s=0.588,P<0.001)。在包括A549在内的6种肺腺癌细胞系中PD-L1与TS在蛋白水平和mRNA表达均呈显著正相关(蛋白水平:r_s=0.899,P<0.05;mRNA表达:r_s=0.861,P<0.05)。结论:在一线接受培美曲塞为基础化疗的晚期肺腺癌患者中,PD-L1表达阳性患者的mPFS较PD-L1表达阴性患者显著缩短,提示PD-L1表达可能作为晚期肺腺癌患者培美曲塞为基础化疗的潜在疗效预测生物标志物。PD-L1和TS的表达不论在肺腺癌组织水平还是细胞系水平均存在显著相关性,可能是PD-L1表达影响培美曲塞化疗效果的潜在原因之一。

Background and purpose:The expression of programmed death ligand-1(PD-L1)in lung cancer not only is the most important biomarker for predicting the efficacy of programmed death-1(PD-1)/PD-L1 inhibitors,but also may affect the efficacy of epidermal growth factor receptor-tyrosine kinase inhibitors(EGFR-TKIs)targeted therapy.However,there are currently few reports in the relevant literature on whether the expression of PD-L1 in lung cancer can affect the efficacy of chemotherapy in patients with lung adenocarcinoma.This study mainly explored the effect of PD-L1 expression in lung adenocarcinoma on the efficacy of pemetrexed-based chemotherapy and its underlying mechanism.Methods:From Oct.2015 to Dec.2018,185 eligible lung adenocarcinoma patients treated in Department of Pathology,The General Hospital of Western Theater Command PLA were enrolled.The expressions of PD-L1 and thymidylate synthase(TS),a molecule predicting the efficacy of pemetrexed-based chemotherapy,were detected by immunohistochemistry.The survival curve of patients was drawn by Kaplan-Meier method.The log-rank test and COX regression model were used to analyze the clinicopathological factors affecting the patients’progression-free survival(PFS)and overall survival(OS).The log-rank test was used to analyze the effects of PD-L1 and TS expressions on the patients’PFS and OS.Spearman rank correlation test was used to analyze the correlation between PD-L1 expression and TS expression in lung cancer tissues.Western blot and real-time fluorescent quantitative polymerase chain reaction(RTFQ-PCR)were used to detect the protein and mRNA expressions of PD-L1 and TS in 6 types of lung adenocarcinoma cell lines.The Pearson correlation test was used to analyze the correlation between PD-L1 and TS at protein expression level and mRNA expression level.Results:Among 51 patients with advanced lung adenocarcinoma who received pemetrexed-based chemotherapy as first-line treatment,the objective response rate(ORR)of the PD-L1 positive group was 20.0%,and the disease control rate(DCR)was 60.0%.There was no significant difference compared with the PD-L1 negative group(ORR:20.0%vs 35.5%,χ2=1.404,P=0.236;DCR:60.0%vs 80.6%,χ2=2.602,P=0.107).The median PFS(mPFS)of patients with negative expression of PD-L1 was significantly better than that of patients with positive expression of PD-L1(mPFS:5.6 months vs 4.1 months,log-rank=5.406,P=0.020),and there was no significant difference in median OS(mOS)between them(mOS:15.9 months vs 12.7 months,log-rank=0.525,P=0.469).Univariate analysis found that the positive expressions of PD-L1 and TS were risk factors for PFS[PD-L1 negative vs positive:HR=2.002(1.100-3.645),P=0.023;TS negative vs positive:HR=2.205(1.367-4.587),P=0.003].Multivariate analysis found that TS positive expression was an independent risk factor for PFS[TS negative vs positive:HR=3.245(1.091-9.652),P=0.034].Among the 51 patients with advanced lung adenocarcinoma who received pemetrexed-based chemotherapy as the first-line treatment,the expression of PDL1 in cancer tissues was significantly positively correlated with the expression of TS(rs=0.691,P<0.001).We further compared the subjects after expanding to 185 patients of lung adenocarcinoma with different tumor stages and first-line treatments,and the expressions of PD-L1 and TS in cancer tissues still showed a significant positive correlation(rs=0.588,P<0.001).In 6 types of lung cancer cell lines including A549 and H1437,the expressions of PD-L1 and TS at the protein level and mRNA level were significantly positively correlated(protein expression level:rs=0.899,P<0.05;mRNA expression level:rs=0.861,P<0.05).Conclusion:In patients with advanced lung adenocarcinoma who received pemetrexed as the first-line chemotherapy,the PFS of patients with positive PDL1 expression was significantly shorter than that of patients with negative PD-L1 expression,suggesting that PD-L1 expression may be used as a potential biomarker for predicting the efficacy of pemetrexed-based chemotherapy.There is a significant correlation between the expressions of PD-L1 and TS in both lung adenocarcinoma tissues and lung cancer cell lines,which may be one of the potential reasons why the expression of PD-L1 affects the efficacy of pemetrexed-based chemotherapy.