Elsevier

Lung Cancer

Volume 88, Issue 1, April 2015, Pages 24-33
Lung Cancer

Clinicopathological analysis of PD-L1 and PD-L2 expression in pulmonary squamous cell carcinoma: Comparison with tumor-infiltrating T cells and the status of oncogenic drivers

https://doi.org/10.1016/j.lungcan.2015.01.016Get rights and content

Highlights

  • We examine PD-L1, L2 expression and PD-1+, CD8+ cell in lung squamous cell carcinoma.

  • PD-L1 and L2 are expressed in approximately one-fourth of patients.

  • PD-L1 expression is significantly and consistently related with increased CD8+ cell.

  • MET expression is correlated with PD-L2 expression and increased PD-1+ cells.

  • This provides rationale for anti-PD-1/PD-L1 immunotherapy in squamous cell carcinoma.

Abstract

Purpose

Programmed cell death-1 (PD-1)/programmed cell death-ligand-1 (PD-L1) pathway-targeted immunotherapy has beneficial therapeutic effects in pulmonary squamous cell carcinoma (SqCC) patients. However, the expression patterns of PD-1 and PD-1 ligands (PD-Ls) in pulmonary SqCC remain unclear. Moreover, the association between the PD-1/PD-Ls pathway and the status of oncogenic drivers in pulmonary SqCC is unknown.

Methods

PD-L1 and PD-L2 expression in tumor cells and the numbers of PD-1+ and CD8+ tumor-infiltrating lymphocytes (TILs) were examined in 331 resected SqCC tumors along with matched lymph node metastases from 77 cases using immunohistochemistry. EGFR and FGFR1 and MET expression and genetic status were also examined.

Results

PD-L1 and PD-L2 expression was detected in 26.9% and 23.9% of the pulmonary SqCC samples, respectively. PD-L1 and PD-L2 expression was maintained or increased in the metastatic lymph node tumors in 81.1% and 93.5% of the 77 cases, respectively. The numbers of PD-1+ and CD8+ TILs were significantly positively correlated (P < 0.001). Cases displaying high PD-L1 expression exhibited consistently high CD8+ T cell infiltration (P < 0.001), even in subgroup analyses according to age, smoking status, tumor size, lymph node metastasis, stage, and the EGFR, MET and FGFR1 status. Moreover, MET expression in the tumors was significantly correlated with high PD-L2 expression and increased PD-1+ TILs (P = 0.001 for both). Increased numbers of CD8+ or PD-1+ TILs were significantly associated with prolonged disease-free survival of these patients, whereas PD-L1 and PD-L2 expression had no significant prognostic implications.

Conclusion

PD-L1 and PD-L2 expression in pulmonary SqCC is associated with an increased number of CD8+ TILs and increased MET expression, which might provide therapeutic insight into targeting the PD-1/PD-Ls pathway in pulmonary SqCC.

Introduction

Non-small cell lung cancer (NSCLC), which accounts for 85% of all lung cancers, is the leading cause of cancer-related death worldwide [1]. Among NSCLCs, adenocarcinoma (ADC) and squamous cell carcinoma (SqCC) are two major histological subtypes that exhibit distinct epidemiologic, biological and genetic characteristics [2]. SqCC frequently occurs in males in the central pulmonary airway, and it is etiologically closely associated with tobacco smoking [3].

In the past decade, the management of NSCLC has evolved from conventional therapy to personalized targeted therapy based on the status of oncogenic drivers in the tumor cells. Particularly, small molecule inhibitors targeting EGFR or ALK prolonged the survival of pulmonary ADC patients carrying an EGFR mutation or an ALK translocation [4], [5], [6]. Moreover, various genetic alterations involving ROS1, RET, BRAF, HER2, and MET have been identified in pulmonary ADC [7]. In contrast, SqCC has been associated with recurrent genetic alterations of FGFR1, PI3K, DDR2, and MET, and these associations have provided the rationale for targeted therapies in pulmonary SqCC (pSqCC) [7], [8], [9]. Recently, immune checkpoint-targeted immunotherapy has demonstrated a favorable clinical outcome in NSCLCs, thereby emerging as an alternative therapeutic strategy [10], [11].

Cancer evades host immune surveillance via the utilization of immune checkpoints [12]. These checkpoints include PD-1/PD-L1 (or PD-L2)-mediated interactions between T cells and antigen-presenting cells (APCs) or host cells. These pathways deliver inhibitory signals to immune cells, thereby contributing to the maintenance of self-tolerance and the regulation of immune responses under physiologic conditions. PD-1, which is expressed on T cells, attenuates immune responses by inhibiting effector T-cell proliferation and function upon its engagement by PD-L1 or PD-L2 [13]. Furthermore, a blockade of PD-1/PD-L1 interactions restores effector T-cell function and enhances anti-tumor immune responses in vivo [14]. Consistently, blocking antibodies against PD-1 and PD-L1 have exerted clear effect with objective response and disease control in NSCLC patients with squamous or non-squamous histology based on phase 1 clinical trials [10], [15], [16]. Thus, PD-1/PD-L1 pathway-targeted immunotherapy has emerged as a highly promising therapeutic strategy for pSqCC. Consistently, several reports have demonstrated variable positive PD-L1 expression in pSqCC [17], [18], [19], [20], [21]. Given that PD-Ls on tumor cells or APCs interact with PD-1 on T cells in the tumor microenvironment, a comprehensive analysis of PD-1/PD-L-related molecules might provide invaluable information for determining the biological and clinical relevance of the PD-1/PD-Ls pathway to pSqCC. Therefore, we investigated the expression patterns of PD-L1 and PD-L2 in tumor cells and the number of PD-1+ and CD8+ tumor-infiltrating lymphocytes (TILs) in a large cohort of pSqCC cases. Moreover, we analyzed the clinicopathological characteristics of PD-L1- and PD-L2-expressing SqCC and the status of the oncogenic drivers including EGFR, FGFR1, and MET. We demonstrated that PD-L1 and PD-L2 expression in pSqCC was closely associated with increased CD8+ TILs and MET expression.

Section snippets

Patients and samples

A total of 331 patients with primary pSqCC who underwent surgical resection at Seoul National University Hospital (SNUH, Seoul, Korea) from 2004 to 2012 were included in this study. None of the patients had received neoadjuvant chemotherapy or radiotherapy or exhibited distant metastasis at the time of diagnosis. Metastatic tumors were found in the regional lymph nodes of 77 of these patients, which were comparatively analyzed with the primary tumors. Tissue microarrays (TMAs; 2 mm diameter)

Clinicopathological and genetic characteristics of the patients

The clinicopathological and genetic characteristics and expression pattern of PD-1-related molecules in the patients with pSqCC are shown in Table 1 and Supplementary Table S1. In brief, most of the patients (95.8%) were male with an age from 37 to 88 years (mean ± SD = 66.35 ± 8.21 years). The majority of patients (90.9%) were smokers, ranging from 1 to 170 pack years (mean ± SD = 46.75 ± 23.82 pack years). An EGFR mutation and positive EGFR FISH were detected in 3.8% and 30.1% of the patients,

Discussion

This study demonstrated that PD-L1 and PD-L2 expression was observed in 26.9% and 23.9% of pSqCC cases, respectively. This PD-L1 expression rate was similar to previously reported rates (from 19.6 to 36.1%) [18], [21], whereas PD-L2 expression had not yet been explored in pSqCC. Regarding PD-L1 in NSCLC, previous studies focused on ADC rather than SqCC and were not subjected to detailed histological analysis [17], [18], [19], [21]. Furthermore, no previous reports have described the correlation

Conflict of interest statement

The authors have declared no conflicts of interest related directly or indirectly to this paper.

Funding

This study was supported by a grant from the National R&D Program for Cancer Control, Ministry for Health and Welfare, Republic of Korea (1220220).

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    These authors contributed equally to this work.

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