Abstract P4-04-13: Comparison of tumor and stroma CD73 expression with TLR9 and survival in breast cancer

CD73 is a 59 ectonuclease that catalyzes the conversion of cyclic AMP into the highly immunosuppressive adenosine in extracellular space. In addition to the cells of the immune system, CD73 is highly expressed in various cancer cell lines and clinical cancer tissues. Toll like receptor-9 (TLR9) is a cellular DNA-receptor that is highly expressed in breast cancer. Both CD73 and TLR9 expression have recently been associated with TNBC prognosis but the mechanisms how these proteins possibly contribute to TNBC pathophysiology remains poorly understood. TLR9 and CD73 expression has been shown to be mutually regulated in various cell types. Whether this is the case in cancer is unknown. The aim of this study was to investigate the mutual role of TLR9 and CD73 in breast cancer (BC). Specifically our hypothesis was that TLR9 and CD73 expression correlate in TNBC. We compared immunohistological tumor TLR9 and CD73 expression scores using a previously characterized breast cancer (BC) cohort (n=184) with follow-up time of > 10 years. We did not discover a connection between TLR9 and CD73 expression in tumor cells in BC. There was a trend for increased survival among patients that had high tumor cell CD73 expression, as compared with the lower tumor cell CD73 expression groups. There was a trend for a better survival among TNBC patients that had lower stromal CD73 expression, as compared with those TNBC patients that had higher stromal CD73 expression. No such difference was detected among patients with non-TNBC tumors. Our results suggest that stromal vs. tumor cell CD73 expression have opposite effects on survival in TNBC, but there is no connection between CD73 and TLR9 expression. Our conclusions are limited by low sample numbers. Citation Format: Selander K, Mella M, Kauppila J, Karihtala P, Jukkola-Vuorinen A, Auvinen P, Soini Y, Kauppila S, Haapasaari K-M, Harris K, Vuopala K. Comparison of tumor and stroma CD73 expression with TLR9 and survival in breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-04-13.