Abstract A078: In vivo tumor micro-environment characterization: preliminary results of an ovarian cancer patients-derived co-colture organoids platform

Abstract Introduction: Most patients with ovarian cancer (OC) are diagnosed at advanced stage. Current standard of care is based on surgery and platinum-based chemotherapy (CHT) in association with target therapies according to molecular characteristics (BRCA status and Homologous Recombination Repair (HRR) status). However, 15-20% progressed to first line CHT and mechanisms of resistance remain far from being completely known. In this scenario the role of tumoral microenvironment (TME) represents an open question. Methods: We designed a study to establish OC patients-derived co-colture organoids (ID PICTURE, IRB approval 4531). Both peripheral Blood Mononuclear Cells (PBMC) and isolated immune infiltrating cells from tumor tissue were planned to be used. The first endpoint of the study was the feasibility of this approach including (i) establishment OC patients-derived organoids (ii) PBMC isolation from whole blood and characterization (iii) immune infiltrate isolation from tumor tissue and characterization. For the latter, the evaluation of the immune phenotype was carried out by cytofluorimetry analyses, through target cells labelling with monoclonal antibodies conjugates with fluorescent molecules (CD45, CD19, CD3, CD4, CD8, 7AAD). Correlation between tumor immune infiltrate and mutational and clinical findings was also accomplished. Results: From January 2022 to May 2023, 36 patients with EOC, 92% with high grade serous OC and 95% with an advanced stage (from stage III according to FIGO, all high tumor load according to the Fagotti’s score) were enrolled. 23 patients (64%) were BRCA wild type while HRR status was available only for 17 patients of whom 28% were deficient. Considering the model feasibility, 5 organoids were obtained, and 8 and 20 million immune cells were isolated from tissue and peripheral blood, respectively. The immune infiltrate analysis was performed on 21 samples obtained from primary debulking surgery and 15 from diagnostic laparoscopies. 75% were treated with carboplatin paclitaxel (weekly or q21) ; among patients undergoing neoadjuvant treatment, 3 had a complete response (CRS3). The infiltration of B and T lymphocytes was described in all patients: 73% were positive for CD3, 20% for CD45, 7% for CD19. The lymphocytes T characterization was available for 7 patients with a median value of CD4+ 51. 3, CD8+ 44. 4, CD8+CD4+ 2, 6 and CD8-CD4- 1. 6. A trend for statistically significant difference was observed for CD45+ in stage IV vs stage I-III (p=0. 021) and in CD19+ B cells in BRCA mutant vs BRCA WT (p=0. 026). Finally, CD3+ T cells showed a significantly higher concentration in the 4 patients experiencing progression of disease at 6 months follow-up (p=0. 014). Conclusion: These preliminary results suggest that patients-derived organoids co-cultured with tumor immune infiltrate could be challenging because of small numbers of overall cell content. Nevertheless, a correlation between specific components of B and T cells and molecular features and cancer progression deserves further investigation. Citation Format: Floriana Camarda, Clara Di Mario, Camilla Nero, Barbara Tolusso, Stefano Alivernini, Francesca Sillano, Sonia Mastrogiovanni, Tina Pasciuto, Elisa Gremese, Eleonora Cesari, Alessandra Ciucci, Claudio Sette, Giovanni Scambia. In vivo tumor micro-environment characterization: preliminary results of an ovarian cancer patients-derived co-colture organoids platform 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 Suppl₂): Abstract nr A078.