A non-canonical adenosinergic pathway led by CD38 in human melanoma cells induces suppression of T cell proliferation

// Fabio Morandi 1, * , Barbara Morandi 2, * , Alberto L. Horenstein 3, * , Antonella Chillemi 3 , Valeria Quarona 3 , Gianluca Zaccarello 3 , Paolo Carrega 4 , Guido Ferlazzo 5, 6 , Maria Cristina Mingari 2 , Lorenzo Moretta 4 , Vito Pistoia 1, # , Fabio Malavasi 3, # 1 Laboratory of Oncology, Istituto Giannina Gaslini, Genoa, Italy 2 Department of Experimental Medicine, University of Genoa, Genoa, Italy 3 Department of Medical Sciences, Laboratory of Immunogenetics and CeRMS, University of Torino, and Transplant Immunology, Città della Salute e della Scienza, Torino, Italy 4 Istituto Giannina Gaslini, Genoa, Italy 5 Department of Human Pathology, University of Messina, Italy 6 Cellular Therapy Program, University Hospital - A.O.U. Policlinico, Messina, Italy * These authors have contributed equally to this work # These authors have contributed equally to this work Correspondence to: Fabio Morandi, e-mail: fabiomorandi@ospedale-gaslini.ge.it Keywords: Melanoma, ectoenzymes, adenosine, immunosuppression Received: February 27, 2015      Accepted: July 13, 2015      Published: July 25, 2015 ABSTRACT Nucleotide-metabolizing ectoenzymes are endowed with an extracellular catalytic domain, which is involved in regulating the extracellular nucleotide/nucleoside balance. The tumor microenvironment contains high levels of adenosine (ADO) generated by this enzymatic network, thus promoting tumor growth by inhibiting anti-tumor immune responses. ADO inhibition in melanoma murine models limits tumor metastases and restores anti-tumor immune responses. This work investigates the expression and function of ectoenzymes in primary human melanoma cell lines. All of latter cells expressed CD38, CD39, CD73, and CD203a/PC-1, and produced ADO from AMP and NAD + . Melanoma cells inhibited T cell proliferation through an ADO-dependent mechanism, since such inhibition was reverted using CD38/CD73 specific inhibitors. Melanoma cells abolished the function of effector memory, central memory and reduced naïve CD4 + T cell proliferation. Accordingly, phosphorylation of S6 ribosomal protein, p38 and Stat1 was lower in activated memory cells than in naïve CD4 + T lymphocytes. Melanoma cells also inhibited proliferation of naïve, memory and -to a lesser extent- of effector CD8 + T cells. These different inhibitory effects correlated with distinct patterns of expression of the ADO receptor A2a and A2b. These results show that primary human melanoma cell lines suppress in vitro T cell proliferation through an adenosinergic pathway in which CD38 and CD73 play a prominent role.