Department of Pathology, Beijing Chest Hospital, Capital Medical University, 97 Beiguan Machang Rd. Tongzhou District, Beijing, 101147, China.
Department of Pathology, Shanghai General Hospital, Shanghai Jiaotong University School of Medicine, 100 Haining Rd, Hongkou District, Shanghai, 200080, China.
BMC Cancer. 2020 Feb 24;20(1):148. doi: 10.1186/s12885-020-6631-z.
Lung adenocarcinoma (LAC) is composed of lepidic, papillary, mucinous, micropapillary and solid components in its parenchyma. Complex responses to therapeutics result from intratumoral heterogeneity. However, it remains confused that what components in a mixed LAC tumor are responsible to the heterogeneous EGFR mutation and PD-L1 expression.
We investigated EGFR status via laser microdissection to capture spatially separated cancer cell subpopulations and digital droplet PCR to determine the abundance of EGFR sensitizing mutation and naïve T790M. Whilst, PD-L1 expression level via tumor proportion score (TPS) was evaluated by Ventana immunohistochemistry using SP263 antibody. PD-L1 expression levels were tiered in < 1, 1-49% and > =50% groups.
EGFR mutation harbored in 154 (59%) of 261 LAC patients and more frequently occurred in papillary, lepidic and micropapillary constituents. Higher levels of PD-L1 were found in LACs at stage III and IV (68.3%) versus those at stage I and II (31.7%) (P = 0.04). Solid predominant LACs (41.3%) expressed PD-L1 with TPS > =50%, versus mucinous and lepidic LACs (P < 0.01). LACs with solid constituents also had more positive proportion of PD-L1 protein. Cut-offs < 1, 1-49% or > =50% were associated with patients' progression-free survival and longer in the < 1% group (22.9 month, 95% CI 17.6-28.2) (P < 0.05). LACs consisting of two constituents with PD-L1 TPS < 1% had a better prognosis than the groups with single component and more than two components (P < 0.05). Eighteen LACs (6.9%) had concomitantly deletion in exon 19 or L858R and naïve T790M mutation. The abundance of T790M varied diversely with sensitizing mutation. PD-L1 expression was not concordant in same components and usually negative in the EGFR-mutated constituents. Heterogeneous PD-L1 expression occurred in the vicinity of stromal tissues. 58.8, 29.4 and 11.8% in ALK positive LACs (N = 17) were found PD-L1 expression via cutoffs of < 1, 1-49% and > =50%, respectively (P > 0.05).
Intratumoral genetic heterogeneity of LACs was demonstrated associated with histological patterns. Heterogeneous PD-L1 expression in higher level usually occurred in solid component both in EGFR mutated and EGFR wild-typed LACs. EGFR mutated LACs heterogeneously had sensitizing and resistant mutation and was accompanied with PD-L1 expression, but discordant among histological constituents. Immune checkpoint inhibitor combined with third generation EGFR tyrosine kinase inhibitor should be more effective to these LACs.
肺腺癌（LAC）在其实质中由贴壁型、乳头状、黏液型、微乳头状和实体型成分组成。肿瘤内异质性导致对治疗的复杂反应。然而，目前仍不清楚混合 LAC 肿瘤中的哪些成分与异质性 EGFR 突变和 PD-L1 表达有关。
我们通过激光微切割捕获空间分离的癌细胞亚群，通过数字液滴 PCR 确定 EGFR 敏感突变和原始 T790M 的丰度，来检测 EGFR 状态。同时，通过 Ventana 免疫组化使用 SP263 抗体评估 PD-L1 表达水平，通过肿瘤比例评分（TPS）进行评估。PD-L1 表达水平分为<1、1-49%和≥50%三个等级。
在 261 例 LAC 患者中，有 154 例（59%）存在 EGFR 突变，在乳头状、贴壁和微乳头状成分中更常见。III 期和 IV 期 LAC 的 PD-L1 水平较高（68.3%），而 I 期和 II 期 LAC 的 PD-L1 水平较低（31.7%）（P=0.04）。41.3%的实体为主型 LAC 表达 PD-L1，TPS≥50%，与黏液型和贴壁型 LAC 相比（P<0.01）。具有实体成分的 LAC 也有更多的 PD-L1 蛋白阳性比例。<1、1-49%或≥50%的截断值与患者的无进展生存期相关，<1%组的生存期更长（22.9 个月，95%CI 17.6-28.2）（P<0.05）。由 PD-L1 TPS<1%的两个成分组成的 LAC 比单个成分和两个以上成分组成的 LAC 预后更好（P<0.05）。18 例（6.9%）同时存在外显子 19 缺失或 L858R 和原始 T790M 突变。T790M 的丰度与敏感突变差异很大。PD-L1 表达在同一成分中不一致，通常在 EGFR 突变成分中为阴性。异质性 PD-L1 表达发生在间质组织附近。在 ALK 阳性 LAC 中（N=17），分别有 58.8%、29.4%和 11.8%的患者通过<1、1-49%和≥50%的截断值检测到 PD-L1 表达（P>0.05）。
LAC 的肿瘤内遗传异质性与组织学模式有关。在 EGFR 突变和 EGFR 野生型 LAC 中，通常在实体成分中出现高水平的异质性 PD-L1 表达。EGFR 突变的 LAC 具有敏感和耐药突变，并伴有 PD-L1 表达，但在组织学成分中不一致。免疫检查点抑制剂联合第三代 EGFR 酪氨酸激酶抑制剂对这些 LAC 可能更有效。
