Abstract 1224: 3D models of chemotherapy- and PARPi-resistant ovarian cancer indicate essential roles for JAK/STAT signaling in mediating drug resistance

Abstract Ovarian cancer is the deadliest gynecological cancer with a low 5-year overall survival rate that affects over 300, 000 women globally each year. Given lack of routine screening procedures, ovarian cancer patients are frequently diagnosed with late-stage disease that rapidly progress despite initial responses to front line therapy. PARPi and VEGFi targeted therapies have improved progression free survival in small subsets of patients but have largely failed to improve overall survival. Since the robust uptake of PARPis in the front line setting, resistance to this class of drugs is a growing problem. The literature is filled with many novel treatment approaches, but the vast majority fail to gain traction in pre-clinical models and early phase trials. A contributing factor to these disappointments relates to the prevalent use of 2D monoculture model systems that do not recapitulate the tumor microenvironment. To address this issue, we utilized the Rastrum 3D cell printer to grow ovarian cancer cells and PDX models in bio-functional matrices which provide optimal stiffness and extracellular matrix components specific to the ovarian tumor microenvironment. We found that ovarian cancer cells grown under these conditions exhibit dramatic up-regulation of the JAK/STAT signaling pathway, including autocrine/paracrine signaling factors, which correlated with increased sensitivity to JAK/STAT inhibitors. This affect was lost when STAT1 and STAT3 knockout cell lines were grown in this 3D environment. Ovarian tumors are known to be rich in cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs). We incorporated primary CAFs into this 3D culture system and found they could promote ovarian cancer cell growth only in cancer cells with intact JAK/STAT signaling further indicating the essential role of this pathway in mediating tumor progression. Co-culture with M2 macrophages was also found to induce ovarian cancer cell growth, particularly in resistant models. Conversely, co-culture with M1 macrophages inhibited treatment naïve ovarian cancer cell growth but not resistant cell line growth. Single-cell RNAseq of the complex 3D cultures elucidated profound differences in the cross-talk between these cell types that is dependent on cancer cell sensitivity to standard-of-care agents. Finally, the addition of JAK/STAT inhibitors was found to substantially alter this cross-talk between cell types and inhibit cancer cell viability. These data further implicate the importance of JAK/STAT signaling, specifically in clinically relevant 3D models, in supporting ovarian cancer progression and response to chemotherapy and PARPi treatment. Ongoing studies are aimed at confirming these findings in pre-clinical mouse models and to elucidate the most effective JAK/STAT inhibitors in vivo with the goal of informing the design of future clinical trials. Citation Format: Esther Rodman, Xiyin Wang, Hannah Smith, Xiaonan Hou, Scott Kaufmann, John Weroha, John Hawse. 3D models of chemotherapy- and PARPi-resistant ovarian cancer indicate essential roles for JAK/STAT signaling in mediating drug resistance 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 1224.