title: PD-L1 up-regulation in melanoma increases disease aggressiveness and is mediated through miR-17-5p.
abstract: PD-L1 is expressed by a subset of patients with metastatic melanoma (MM) with an unfavorable outcome. Its expression is increased in cells resistant to BRAF or MEK inhibitors (BRAFi or MEKi). However, the function and regulation of expression of PD-L1 remain incompletely understood.After generating BRAFi- and MEKi-resistant cell lines, we observed marked up-regulation of PD-L1 expression. These cells were characterized by a common gene expression profile with up-regulation of genes involved in cell movement. Consistently, in vitro they showed significantly increased invasive properties. This phenotype was controlled in part by PD-L1, as determined after silencing the molecule. Up-regulation of PD-L1 was due to post-transcriptional events controlled by miR-17-5p, which showed an inverse correlation with PD-L1 mRNA. Direct binding between miR-17-5p and the 3'-UTR of PD-L1 mRNA was demonstrated using luciferase reporter assays.In a cohort of 80 BRAF-mutated MM patients treated with BRAFi or MEKi, constitutive expression of PD-L1 in the absence of immune infiltrate, defined the patient subset with the worst prognosis. Furthermore, PD-L1 expression increased in tissue biopsies after the metastatic lesions became resistant to BRAFi or MEKi. Lastly, plasmatic miR-17-5p levels were higher in patients with PD-L1+ than PD-L1- lesions.In conclusion, our findings indicate that PD-L1 expression induces a more aggressive behavior in melanoma cells. We also show that PD-L1 up-regulation in BRAFi or MEKi-resistant cells is partly due to post-transcriptional mechanisms that involve miR-17-5p, suggesting that miR-17-5p may be used as a marker of PD-L1 expression by metastatic lesions and ultimately a predictor of responses to BRAFi or MEKi.
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.|Department of Medical Sciences, University of Turin, Turin, Italy.
authors.forename: Valentina
authors.initials: V
authors.lastname: Audrito
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.|Department of Medical Sciences, University of Turin, Turin, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Serra
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.|Department of Medical Sciences, University of Turin, Turin, Italy.
authors.forename: Aureliano
authors.initials: A
authors.lastname: Stingi
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Orso
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.|Department of Medical Sciences, University of Turin, Turin, Italy.
authors.forename: Federica
authors.initials: F
authors.lastname: Gaudino
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.|Department of Medical Sciences, University of Turin, Turin, Italy.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Bologna
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Neri
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Garaffo
authors.affiliation: Department of Health Sciences, University of Florence, Italy.
authors.forename: Romina
authors.initials: R
authors.lastname: Nassini
authors.affiliation: Department of Surgery and Translational Medicine, University of Florence, Italy.
authors.forename: Gianna
authors.initials: G
authors.lastname: Baroni
authors.affiliation: Methodology for Clinical Research Laboratory, IRCCS - Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
authors.forename: Eliana
authors.initials: E
authors.lastname: Rulli
authors.affiliation: Department of Surgery and Translational Medicine, University of Florence, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Massi
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.|Department of Life Sciences and Systems Biology, University of Turin, Turin, Italy.
authors.forename: Salvatore
authors.initials: S
authors.lastname: Oliviero
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Piva
authors.affiliation: Department of Molecular Biotechnology and Health Sciences, University of Turin, Turin, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Taverna
authors.affiliation: Department of Oncology and Hematology, Papa Giovanni XXIII Hospital, Bergamo, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Mandalà
authors.affiliation: Human Genetics Foundation (HuGeF), Turin, Italy.|Department of Medical Sciences, University of Turin, Turin, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Deaglio
mesh_terms: D060890:B7-H1 Antigen / Q000235:genetics*; D018450:Disease Progression; D005260:Female; D015870:Gene Expression / Q000235:genetics*; D006801:Humans; D008545:Melanoma / Q000235:genetics; D035683:MicroRNAs / Q000235:genetics*; D014162:Transfection; D015854:Up-Regulation
chemical_list: D060890:B7-H1 Antigen; C423236:CD274 protein, human; C524941:MIRN17 microRNA, human; D035683:MicroRNAs
keywords: melanoma; microRNA; regulation of gene expression; resistance to therapy; targeted therapy