Elsevier

Lung Cancer

Volume 141, March 2020, Pages 21-31
Lung Cancer

Elucidation of the relationships of MET protein expression and gene copy number status with PD-L1 expression and the immune microenvironment in non-small cell lung cancer

https://doi.org/10.1016/j.lungcan.2020.01.005Get rights and content

Highlights

  • MET-altered NSCLC showed significantly stronger PD-L1 expression and more abundant tumoral TILs than non-MET-altered tumors.

  • MET amplification among MET alterations was the strongest and independently associated with tumoral CD8 + TILs.

  • Unlike EGFR/ALK-altered tumours, MET-amplified tumours might respond to ICI therapy.

Abstract

Objectives

Alterations in the MET gene, such as mutations and high-level amplification, are important drivers of non-small cell lung cancer (NSCLC). The efficacy of immune checkpoint inhibitors (ICIs) in lung cancer with MET abnormalities is unclear. We evaluate the potential relationship between MET alterations and the tumor immune microenvironment and PD-1/PD-L1 axis.

Material and Methods

MET and phospho-MET protein expression were assessed in 622 resected NSCLC specimens. MET amplification was assessed by fluorescence in-situ hybridization in 272 tumors. PD-L1 expression was evaluated by immunohistochemistry. CD8+, Foxp3+, CD45RO, and PD-1+ tumor-infiltrating lymphocytes (TILs) in the tumor nest and surrounding stroma were profiled. Associations with MET alterations were explored.

Results

The cohort comprised 425 male patients (68.3 %), 184 never-smokers (29.6 %), and 408 adenocarcinoma (ADC) patients (65.6 %). Median age was 68 years. MET alteration was observed mainly in ADCs (18.9 % MET-positive, 3.9 % phospho-MET-positive, and 15.1 % with MET amplification). PD-L1 expression was significantly increased in MET-altered ADCs (P < 0.001 for MET; P = 0.002 for phospho-MET; P = 0.019 for MET amplification). Most TIL subset numbers in the tumor nest were significantly increased in MET-altered tumors. Only MET amplification was independently associated with tumoral CD8 + TILs. Three of the six patients responded to ICI treatment; two of them showed MET overexpression and an increase in MET copy number.

Conclusion

MET-altered tumors showed significantly stronger PD-L1 expression and more abundant tumoral TILs than non-MET-altered tumors. Among the MET alterations assessed, MET amplification was particularly implicated in the inflamed microenvironment, suggesting that MET-amplified tumors might respond to ICIs.

Introduction

Driver oncogenic mutations in genes such as EGFR and ALK are currently considered important therapeutic targets in non-small cell lung cancer (NSCLC) [1,2]. Although driver-specific inhibitors have marked treatment effects on tumors with these driver alterations, tumors often develop resistance [3] and thus become difficult to treat. Recent research on immune-checkpoint inhibitor (ICI) immunotherapy has shed light on intractable cases, and ICI therapy has become one of the first-line treatment options of NSCLC without driver mutations [4]. While ICIs are unlikely to exert satisfactory effects on tumors with driver alterations in EGFR and ALK [5,6], the mechanisms underlying innate resistance caused by these drivers remain unclear. A recent clinical study indicated that platinum-based chemotherapy with atezolizumab was beneficial in patients with EGFR-mutant NSCLC [7]. Therefore, ICI therapy should be personalized based on the driver mutations present in the patient and the context of treatment.

MET is an important oncogene in NSCLC [8,9]. It encodes a tyrosine kinase receptor that activates downstream signaling by binding to its ligand hepatocyte growth factor (HGF), followed by dimerization and auto-phosphorylation [8]. MET overexpression is observed in 25–75 % of NSCLC cases [9], and reportedly predicts worse outcomes in NSCLC [10,11]. Besides activation via HGF, various MET alterations, including gene mutations [8,12,13], fusions [13], and amplification [8,13], cause constitutive MET activation. Among these alterations, high-level MET amplification and MET exon 14 skipping (METex14) mutation have been intensively studied and are regarded as oncogenic drivers in NSCLC [8,12,14]. Both alterations are targeted by MET inhibitors such as crizotinib and cabozantinib [14,15]. The prevalence of de-novo MET amplification in NSCLC ranges from 1 % to 5 % [8,16], depending on the definition of gene amplification and the technology used. In addition, MET amplification is known as a potent and prevalent acquired resistance mechanism to EGFR tyrosine kinase inhibitors (TKIs)—especially to those of the third-generation (observed in 19–30 % of patients) [3,[17], [18], [19]]. Despite being recognized as important oncogenic alterations, compared to that on EGFR mutations, information on how MET alterations are related with tumor PD-L1 expression and the tumor immune microenvironment (TME) is relatively scant [5,6,[20], [21], [22]]. Tumor PD-L1 expression and TME are important factors in understanding treatment mechanisms of ICIs [[23], [24], [25], [26]], and have been suggested as predictive markers of ICI efficacy [27]. There is currently no basis for the efficacy of ICIs in MET-altered tumors. Although recent studies in a small cohort have reported relationships between MET alterations (including altered MET expression) and METex14 and both PD-L1 expression and clinical efficacy of ICIs [[28], [29], [30]], the relationships between MET amplification and the PD-1/PD-L1 axis and TME have not been fully unraveled. Given that MET and EGFR alterations occur in different populations in terms of age, sex, and smoking status [8,12], the relationship between tumors with MET alterations, especially MET amplification, and the PD-L1/PD-1 axis and TME should be urgently characterized.

In this study, we explored the associations between MET alterations, with special focus on MET amplification, and PD-L1 expression and the TME as well as patient characteristics and prognoses in patients with NSCLC. In addition, we described the association between MET alterations and ICI reponse in six patients.

Section snippets

Patients and tumor specimens

This study was approved by the ethics committees of Hamamatsu University School of Medicine and Seirei Mikatahara General Hospital. All analyses were conducted in compliance with ethical standards and according to the Helsinki Declaration. The need for patient approval and informed consent was waived because this study was based on reviews of patients’ records. We collected 622 NSCLC tumor tissues in total, 406 of which had been resected at Hamamatsu University Hospital between January 1990 and

MET alterations and their mutual associations in NSCLC

In total, 622 NSCLC specimens, comprising 408 (65.6 %) ADCs 169 (27.2 %) squamous cell carcinomas (SCCs), and 45 (7.2 %) tumors with other histologies, were used in this study (Supplementary Table S1). The median age was 68 years (range 23–88 years), and 425 (68.3 %) patients were male. One hundred eighty-four (29.6 %) patients were never-smokers. Regarding pathological stages, there were 392 (63.0 %) stage I, 107 (17.2 %) stage II, and 123 (19.8 %) stage III cases. Two hundred fifty-four (40.8

Discussion

We evaluated relationships between three MET alterations, i.e. MET overexpression, phospho-MET expression, and MET amplification, with PD-L1 expression and four subsets of TILs in the TME of a relatively large NSCLC cohort. The study revealed a strong association between MET overexpression/MET amplification and PD-L1 expression, and indicated that MET amplification, but not MET expression, was independently associated with tumoral CD8 + TILs. Two out of six patients responsive to ICIs had

Data availability

All data and supplementary information within the article are available from the corresponding author upon reasonable request.

Author’s contributions

Study design: K.Y. Study conduct: K.Y. Data collection: K.Y., M.K., H.Y., A.K., M.T., H.O., Data analysis: KY, Y.I. K.T., K.S. Data interpretation: K.Y., K.T., N.I., K.F., H.N., T.S., H.S. Drafting the manuscript: K.Y., Y.I., K.T. Revising the manuscript content: K.Y., Y.I., Y.I., T.K., T.S., H.S. Approving final version of the manuscript: all authors.

Funding

This work was partly supported by grants from the Japanese Ministry of Health, Labor and Welfare (19–19, 10103838), the Japan Society for the Promotion of Science (22590356, 23790396), the Ministry of Education, Culture, Sports, Science and Technology (S-001), the National Cancer Center Research and Development Fund (25-A-1), and Research on Global Health Issues from the Japanese Ministry of Health, Labor and Welfare, Japan Agency for Medical Research and Development (AMED).

Conflicts of interest

The authors declare no competing interests.

Acknowledgments

We thank Mrs. Naoko Yoshida and Mr. Hisaki Igarashi (Hamamatsu University School of Medicine) for technical assistance.

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