Abstract PR-007: Patient-derived immunocompetent cultures reveal personalized immunotherapies and new treatment options for therapy resistant patients with high-grade serous ovarian cancer
Authors: Färkkilä Anniina , Nagaraj Ashwini S. , Pietilä Elina A. , Salko Matilda , Erkan Erdogan P. , Niemiec Iga , Sirsikar Aditi , Bao Jie , Marchi Giovanni , Nowlan Kirsten , Hautaniemi Sampsa , Vähärautio Anna , Tang Jing , Haltia Ulla-Maija , Kekäläinen Eliisa , Virtanen Anni , Salo Tuula 
Published: March 2024

Abstract
Introduction: Single agent immunotherapies have shown poor responses in high-grade serous ovarian cancer (HGSC), highlighting the importance of combinatorial approaches. However, identifying patients who will benefit from different combinatorial approaches requires representative ex vivo models containing the native immune microenvironment. Here, we established HGSC patient-derived immunocompetent cultures (iPDCs) for high-throughput testing of targeted agents and immunotherapy combinations at single cell level. Material and methods: Freshly resected HGSC patient tumor tissue samples were collected under the approval of ethical board of the Women’s Hospital, Helsinki University Hospital. Tumors were enzymatically dissociated and cultured in a patient-derived matrix with customized growth medium. Immune cell abundance and composition in the source tumor and matched cultures were evaluated using flow cytometry. The genetic landscapes of the iPDCs were profiled using whole-exome sequencing. iPDC responses to combination of DNA damaging, and immunotherapy agents were evaluated using single cell fluorescent imaging, and multiparameter flow cytometry. Results: We show that our novel patient-derived matrix significantly improved the growth of iPDCs compared to the conventional matrix. Importantly, we validate that the iPDCs morphologically and genetically match the source tumor and contain functional immune cells of the native tumor, including T cells, NK cells, and a subset of myeloid cells relevant for response to immunotherapies. Importantly, iPDCs with homologous recombination DNA repair deficiency responded to poly ADP-ribose polymerase inhibitor (PARPi), and to anti-PD1 antibody treatment measured by decreased tumor cell count. Further, the iPDC responses to PARPi or cisplatin corresponded to the clinical responses in PARPi and/or chemo-resistant patients. Interestingly, while iPDCs from the BRCA1 mutant and PARPi resistant patient showed sensitivity to the WEE1 and Chk1/2 inhibitors, iPDCs from another PARPi resistant patient with BRCA1 reversion mutation did not respond to these agents, suggesting distinct mechanisms driving drug sensitivities following PARPi resistance. Importantly, single-cell RNA sequencing revealed distinct epithelial and immune cell pathway activity in PARPi and chemo-resistant patients correlating with drug responses from iPDC. Furthermore, we identify patient-specific responses to novel immunotherapy and DNA damaging agents including drugs targeting the cyclic GMP–AMP synthase (cGAS) stimulator of interferon gene (STING), and Lysophosphatidic acid (LPA) pathways. In summary, these results highlight the utility of iPDCs for the investigation of patient-specific drug sensitivity and resistance in HGSC. Conclusion: Our novel iPDC culture system harboring physiologically relevant patient-derived matrix combined with patient-specific tumor infiltrating immune cells provide a platform for high- throughput testing of immuno-oncology agents and combination treatments in HGSC.
Citation Format: Anniina Färkkilä, Ashwini S. Nagaraj, Elina A. Pietilä, Matilda Salko, Erdogan P. Erkan, Iga Niemiec, Aditi Sirsikar, Jie Bao, Giovanni Marchi, Kirsten Nowlan, Sampsa Hautaniemi, Anna Vähärautio, Jing Tang, Ulla-Maija Haltia, Eliisa Kekäläinen, Anni Virtanen, Tuula Salo. Patient-derived immunocompetent cultures reveal personalized immunotherapies and new treatment options for therapy resistant patients with high-grade serous ovarian cancer [abstract]. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(5 Suppl_2):Abstract nr PR-007.