Abstract 1714A: TGF-beta signaling on myeloid cells regulates ECM deposition in mammary carcinoma via adenosine dependent mechanisms

TGF-beta plays a crucial role in tumor microenvironment by regulating cell-cell and cell-stroma interactions. We previously demonstrated that TGF-beta signaling on myeloid cells regulates expression of CD73, a key enzyme for production of adenosine, a pro-tumorigenic metabolite implicated in regulation of tumor cell behaviors, immune response and angiogenesis. Using MMTV-PyMT mouse mammary tumor model, we discovered that deletion of TGF-beta signaling on myeloid cells (PyMT/TGFbRII-LysM) affects ECM formation in tumor tissue, specifically increases collagen and decreases fibronectin deposition, and these changes associate with mitigated tumor growth and reduced metastases. Using multiplexed five-color immunofluorescent staining and spatial analysis on a single-cell level, we discovered that reduced TGF-beta signaling on fibroblasts associates with their proximity to CD73 positive myeloid cells in tumor tissue. Consistent with these findings, in vitro gel contraction assay and Western blotting for Collagen I and pSMAD proteins confirmed that adenosine significantly downregulates TGF-beta signaling on fibroblasts. Using in vitro pharmacological approach, we found that this effect is regulated by A2a and A2b adenosine receptors. TCGA data base analysis revealed that patients with triple negative breast cancer and basal type have similar signature of adenosine and ECM profiles: high expression of A2b adenosine receptors correlates with decreased expression of Col1 and is associates with poor outcome. Taken together, our studies reveal a new role for TGF-beta signaling on myeloid cells in tumorigenesis. Discovered crosstalk between TGF-beta/CD73 on myeloid cells and TGF-beta signaling on fibroblasts can contribute to ECM remodeling and pro-tumorigenic actions of CAFs. Citation Format: Georgii Vasiukov, Tatiana Novitskaya, Samantha Schwager, Harold Moses, Timothy Blackwell, Igor Feoktistov, Sergey Novitskiy. TGF-beta signaling on myeloid cells regulates ECM deposition in mammary carcinoma via adenosine dependent mechanisms [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1714A.