Abstract 4241: Development of stroma cells-rich oral cancer organoid for functional analysis of tumor microenvironment

Abstract Background: Tumor microenvironment (TME), composed of cancer cells, endothelial cells, fibroblast, immune cells, and etc, plays crucial roles in tumor progression and treatment resistance. Thus, it is extremely important to find its role involved in the interaction of TME. However, it is more difficult to examine the biological activities of those cells in vitro assay. The purpose of this study is to develop stroma cells-incorporating preclinical model, termed stroma cells-rich oral cancer organoid, for functional analysis of TME. Materials and Methods: We have first developed the stroma cells-rich oral cancer organoid by selecting the types of stroma cells such as endothelial cells, fibroblast, ratio of those cells, culture method, 3-D methods, culture media, and supplement of growth factors. Then, growth rate, morphology, radiosensitivity, and drug response were analyzed to investigate the effect of TME. Finally, the function of tumor-associated macrophage was determined using this organoid model. The growth rate of cancer cells and drug response were investigated using the organoid treated with supernatant of M1 and M2 macrophages polarized from THP-1 monocyte. Results: Oral cancer cells were co-cultured with endothelial cells (ECs) and mesenchymal stem cells (MSCs) in a particular ratio in 3D-culture, and the formed organoid became sphere. The vascular formation in the organoid was confirmed by immunofluorescent analysis. The organoid also showed higher tumorigenicity in nude mice when inoculated, compared to cancer cells alone or mixed cells with ECs and MSCs. Cell viability of luciferase-expressing tongue cancer cells (OSC-19-luc) in the organoid was assessed after treatment with cisplatin using the IVIS system showing that OSC-19-luc organoid was resistance to cisplatin compared to 3D-cultured OSC-19-luc alone or OSC-19-luc co-cultured with ECs/MSCs. The supernatant of M1 or M2 macrophage had no effect on cancer cell growth in the organoid. However, when the organoid was treated with cisplatin in the presence of M2 macrophage supernatant, the drug sensitivity was low compared to those of M1 suggesting that secretory factor from M2 macrophage may lead to drug resistance of oral cancer cells in the presence of TME. Conclusions: We have successfully established stroma cells-incorporating preclinical model that recreates the tumor microenvironment by co-culturing stromal cells. This will serve as a platform that can recapitulate the tumor biology and drug response profiles of cancer cells derived from individual oral cancer patients. This will also enable us to elucidate the role of other factors in TME and to identify novel targets for the treatment of chemo-resistant oral cancer. Citation Format: Ami Shimoda, Shizuka Shiiya, Haruka Yoshii, Kenji Mitsudo, Mitomu Kioi. Development of stroma cells-rich oral cancer organoid for functional analysis of tumor microenvironment abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 4241.