Abstract LB236: Utilizing endometrial tumor organoids to model cancer immunomodulation
Authors: Nizam Aaron , Chung Charlie , Goldberg Gary L. , Beyaz Semir 
Published: July 2021

Abstract
Endometrial cancer is the most common gynecologic malignancy in the United States. Most women present with early stage disease and have a favorable prognosis. However, the treatment options for recurrent endometrial cancer is limited. Immunotherapy has become increasingly popular in the treatment of recurrent endometrial cancer. A hallmark of malignant cells is immune-evasion at both the genetic level and in the tumor microenvironment. We hypothesized that an endometrial cancer organoid model could be utilized to study the tumor immune microenvironment.
Major Histocompatibility Complex (MHC) is a protein receptor recognized with its antigen by immune cells to screen either non-self or tumorous cells. It has a crucial role in eliminating non-self cells, such as cancer cells. We first assessed the genes involved in the regulation of MHC I and II in cultured normal and tumor organoids. RNA-Sequencing of fifty-six patients from our living organoid biobank were analyzed and we found an immunologic cluster of high-grade endometrial cancers that display significant downregulation in both MHC I and II. This was confirmed with real time-PCR which showed that high-grade cancers organoids had downregulated MHC I and II compare to organoids derived from low-grade cancer tissues and benign tissues. We next sought to demonstrate that both normal and endometrial cancer organoids retain the ability to present external antigen by using DQ-Ovalbumin. We demonstrated that endometrial organoids retain the ability to present antigen, but cancer organoids display reduced efficiency in the antigen processing. Next, we stimulated endometrial cancer organoids with interferon-gamma (IFNg), a well known cytokine for enhancing immunological response, to increase the expression of MHC I and II in cancer organoids. IFNg led to a 2-6 fold increase in MHC expression in low-grade cancer organoids, but a 5-40 fold increase in expression in high-grade cancer organoids utilizing real time-PCR. Finally, we implement the organoid-immune cell co-culture system with patient-derived organoids and CD8+ cytotoxic T-Cells in the allogeneic and syngeneic settings. Endometrial cancer organoids and matched patient-derived cytotoxic T-Cells were co-cultured for 48 hours and imaged for 16 hours. Both migratory effect and tumor killing effect were compared. As expected, in the allogeneic setting CD8+ T-Cells efficiently colocalized and killed cancer cells in the vehicle and IFNg stimulated groups. In the syngeneic setting, CD8+ T-Cells did not colocalize or kill cancer cells in the vehicle, whereas they significantly colocalized and killed cancer cells when stimulated with IFNg.
Our data demonstrate that high-grade endometrial cancer cells downregulate MHC I and II, suggesting that they can evade the host immune system. We also showed that this effect is patient-specific and can be overcome by stimulating with interferon-gamma. Furthermore, we demonstrated that increasing MHC I and II among cancer organoids enhances the target cell recognition and apoptosis induction by CD8+ T-cells. Collectively, our finding offers an approach to study the tumor microenvironment that can be individualized for each patient through the use of patient-derived cancer organoids. This technology can be further developed to study targeted therapies and provides a much needed pre-clinical model for the study of endometrial cancer.
Citation Format: Aaron Nizam, Charlie Chung, Gary L. Goldberg, Semir Beyaz. Utilizing endometrial tumor organoids to model cancer immunomodulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB236.