Abstract 4101: Stromal cell-induced alterations in the response of colorectal cancer cell to demethylating agents

Abstract

Abstract Epigenetic mechanisms such as DNA hypermethylation, that results in gene silencing, is closely associated with resistance to platinum-based chemotherapy for colorectal cancer (CRC). DNA methyltransferase inhibitors (DNMTi) that reactivate and induce reexpression of silenced gene have the potential to improve the outcome of platinum-based and other therapies in CRC. In fact, non-cytotoxic concentrations of azacitidine, a clinically used DNMTi, has been reported to resensitize platinum-resistant ovarian cells to carboplatin. Hypomethylating agents, such as azacitidine and decitabine have shown significant promise in hematologic malignancies; however, studies on their application to CRC and other solid tumors have yielded ambivalent results potentially due to the complexities of the tumor microenvironment that result from the numerous cell type interactions. In this study, we analyzed the impact of different tumor-stroma ratios on cancer cell response to azacitidine, decitabine, and two lead compounds identified by in vitro screens in two-dimensional (2D) and three-dimensional (3D) co-cultures of colorectal HCT116 carcinoma demethylation reporter cells and adipose-derived mesenchymal stromal cells (MSCs) isolated from healthy individuals undergoing elective lipoaspiration. Each subject provided informed consent. Activity of hypomethylating drugs was examined in 2D and 3D cultures of different tumor-stroma ratios using confocal microscopy, flow cytometry, and MTT analyses. Our preliminary flow cytometry results show an altered response of hypomethylating agents in cocultures of HCT116 and MSCs compared to monocultures of HCT116 cells alone. There was an increase in demethylation of HCT116 cells in 3D cultures containing a higher ratio of stromal cells following treatment with low concentration of decitabine. Furthermore, confocal analysis 3D co-cultures at various z-plane heights revealed increased demethylation at low concentrations of all drugs in cultures with high stromal cell numbers. These results indicate that intratumoral stroma may alter the sensitivity of cancer cells to demethylating agents and warrant further studies. Citation Format: Viswanath Das, Svetlana Skolekova, Khushboo Agrawal, Jan Gursky, Lucia Kučerová, Marián Hajdúch. Stromal cell-induced alterations in the response of colorectal cancer cell to demethylating agents. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4101.