title: RAS-Mitogen-Activated Protein Kinase Signal Is Required for Enhanced PD-L1 Expression in Human Lung Cancers.
abstract: Ectopic programmed cell death ligand 1 (PD-L1) expression in non-small cell lung cancers (NSCLCs) is related to immune evasion by cancer, and it is a molecular target of immune checkpoint therapies. Although some altered signals in NSCLCs are responsible for ectopic PD-L1 expression, the precise mechanisms remain obscure. Because we found a higher frequency of EGFR/KRAS mutations in NSCLC cell lines with high PD-L1 expression (p < 0.001), we evaluated the relationships between downstream signals and PD-L1 expression, particularly in three KRAS-mutant adenocarcinoma cell lines. The MEK inhibitor U0126 (20 μM) significantly decreased the surface PD-L1 levels by 50-60% compared with dimethyl sulfoxide (p < 0.0001). Phorbol 12-myristate 13-acetate stimulation (100 nM, 15 min) increased (p < 0.05) and two ERK2 siRNAs as well as KRAS siRNAs decreased (p < 0.05) PD-L1 expression. The transcriptional activity of the potential AP-1 site (+4785 to +5056 from the transcription start site) in the PD-L1 gene was demonstrated by luciferase assays, which was inhibited by U0126. The chromatin immunoprecipitation assay demonstrated the binding of cJUN to the AP-1 site. Two STAT3 siRNAs decreased PD-L1 expression by 10-32% in two of the three KRAS-mutant lung adenocarcinoma cell lines (p < 0.05), while the PI3K inhibitor LY294002 (40 μM) did not change the expression level. Supervised cluster analysis and gene set enrichment analysis between the PD-L1-high and -low NSCLCs revealed a correlation between PD-L1 expression and genes/pathways related to cell motility/adhesion. These results indicate that MAPK signaling is the dominant downstream signal responsible for ectopic PD-L1 expression, in which STAT3 is also involved to some extent. Furthermore, MAPK signaling may control the expression of PD-L1 and several genes related to enhanced cell motility. Our findings suggest that MAPK, along with STAT3, is important for determining PD-L1 expression, which could be useful for targeted therapies against lung cancers.
authors.affiliation: Department of Medical Oncology and Cancer Center, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Sumimoto
authors.affiliation: Department of Medical Oncology and Cancer Center, Shiga University of Medical Science, Otsu, Shiga, Japan.|Center for Antibody and Vaccine Therapy, Research Hospital, Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Takano
authors.affiliation: Department of Medical Oncology and Cancer Center, Shiga University of Medical Science, Otsu, Shiga, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Teramoto
authors.affiliation: Department of Medical Oncology and Cancer Center, Shiga University of Medical Science, Otsu, Shiga, Japan.|Center for Antibody and Vaccine Therapy, Research Hospital, Institute of Medical Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Yataro
authors.initials: Y
authors.lastname: Daigo
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D000077192:Adenocarcinoma of Lung; D060890:B7-H1 Antigen / Q000235:genetics*; D002070:Butadienes / Q000008:administration & dosage; D002448:Cell Adhesion / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D066246:ErbB Receptors / Q000235:genetics; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D020935:MAP Kinase Signaling System / Q000187:drug effects; D020928:Mitogen-Activated Protein Kinases / Q000096:biosynthesis / Q000235:genetics*; D009154:Mutation; D009570:Nitriles / Q000008:administration & dosage; D010704:Phorbols / Q000008:administration & dosage; D047428:Protein Kinase Inhibitors / Q000008:administration & dosage; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000096:biosynthesis / Q000235:genetics*; D018808:Transcription Factor AP-1 / Q000235:genetics; D024363:Transcription Initiation Site
chemical_list: D060890:B7-H1 Antigen; D002070:Butadienes; C423236:CD274 protein, human; C117307:KRAS protein, human; D009570:Nitriles; D010704:Phorbols; D047428:Protein Kinase Inhibitors; D034741:RNA, Small Interfering; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D018808:Transcription Factor AP-1; C113580:U 0126; C512478:EGFR protein, human; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D016283:Proto-Oncogene Proteins p21(ras); C033085:phorbol