Abstract 5909: Inhibition of Cd39 and Cd73 by 3rd-generation antisense oligonucleotides to improve immunity against tumors

Abstract

Abstract During the last decades it became obvious that the immune system can be utilized to evoke effective antitumor responses. However, cancer cells develop mechanisms to circumvent this. The two ectonucleotidases CD39 and CD73 are promising drug targets, as they act in concert to convert extracellular immune-stimulating ATP to immunosuppressive adenosine. CD39 and CD73 are expressed on different immune cells as well as on a range of cancer cells and the latter are recognized to co-opt both ectonucelotidases for circumventing antitumor immune responses. In order to enhance immunity against tumors it would be favorable to increase extracellular ATP- and to simultaneously reduce adenosine concentrations in the tumor microenvironment. We designed antisense oligonucleotides (ASOs) with specificity for human and mouse CD39 and CD73. Knockdown efficacy of ASOs on mRNA and protein level was investigated in cancer cell lines and primary human T cells. CD39 and CD73 activity was evaluated by measuring levels of ATP, AMP and adenosine in cell supernatants. As functional readout we analyzed T cell proliferation and viability in presence of extracellular ATP and adenosine. The impact of ASO-mediated target knockdown in vivo on antitumor immune responses was analyzed in a syngeneic mouse tumor model. CD39- and CD73-specific ASOs suppressed expression of CD39 and CD73 mRNA and protein in different cancer cell lines and in primary human T cells without the need of any transfection reagent in vitro. Furthermore, degradation of extracellular ATP or AMP was significantly blocked by CD39- or CD73-specific ASOs while formation of adenosine was suppressed. Supplementation of cell culture medium with ATP impaired proliferation and viability of CD39- expressing CD8+ T cells. Strikingly, CD39-knockdown by ASO reversed the inhibitory effects of ATP on cell proliferation and viability. Extracellular AMP strongly inhibited proliferation and viability of CD73-expressing CD4+ T cells. Notably, AMP-mediated inhibition of proliferation was considerably less pronounced in cells treated with CD73-specific ASO. Systemic treatment of mice with CD39- and CD73-specific ASOs resulted in a knockdown of CD39 and CD73 mRNA expression in spleen and liver. Moreover, CD39-ASO treatment of tumor-bearing mice significantly reduced CD39-protein expression on tumor-associated macrophages, as well as intratumoral CD8+ T cells and Tregs. Remarkably, frequency of intratumoral Tregs was potently reduced by ASO-mediated CD39 knockdown. Taken together, targeting of CD39 and CD73 by ASOs represents a very promising state-of-the art therapeutic approach to improve immunity against tumors. Citation Format: Tamara Hilmenyuk, Sandra Kallert, Richard Klar, Lisa Hinterwimmer, Monika Schell, Marina Van Ark, Alfred Zippelius, Frank Jaschinski. Inhibition of Cd39 and Cd73 by 3rd-generation antisense oligonucleotides to improve immunity against tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5909.