Chemotherapy resistance is a critical contributor to cancer mortality and thus an urgent unmet challenge in oncology. To characterize chemotherapy resistance processes in high-grade serous ovarian cancer, we prospectively collected tissue samples before and after chemotherapy and analyzed their transcriptomic profiles at a single-cell resolution. After removing patient-specific signals by a novel analysis approach, PRIMUS, we found a consistent increase in stress-associated cell state during chemotherapy, which was validated by RNA in situ hybridization and bulk RNA sequencing. The stress-associated state exists before chemotherapy, is subclonally enriched during the treatment, and associates with poor progression-free survival. Co-occurrence with an inflammatory cancer–associated fibroblast subtype in tumors implies that chemotherapy is associated with stress response in both cancer cells and stroma, driving a paracrine feed-forward loop. In summary, we have found a resistant state that integrates stromal signaling and subclonal evolution and offers targets to overcome chemotherapy resistance.

Homologous recombination deficiency (HRD) correlates with platinum sensitivity in patients with ovarian cancer, which clinically is the most useful predictor of sensitivity to PARPi. To date, there are no reliable diagnostic tools to anticipate response to platinum-based chemotherapy, thus we aimed to develop an functional HRD detection test that could predict both platinum-sensitivity and patient eligibility to targeted drug treatments. We obtained a functional HR score by quantifying homologous recombination (HR) repair after ionizing radiation-induced DNA damage in primary ovarian cancer samples ( = 32). Samples clustered in 3 categories: HR-deficient, HR-low, and HR-proficient. We analyzed the HR score association with platinum sensitivity and treatment response, platinum-free interval (PFI) and overall survival (OS), and compared it with other clinical parameters. In parallel, we performed DNA-sequencing of HR genes to assess if functional HRD can be predicted by currently offered genetic screening. Low HR scores predicted primary platinum sensitivity with high statistical significance ( = 0.0103), associated with longer PFI (HR-deficient vs. HR-proficient: 531 vs. 53 days), and significantly correlated with improved OS (HR score <35 vs. ≥35, hazard ratio = 0.08, = 0.0116). At the genomic level, we identified a few unclear mutations in HR genes and the mutational signature associated with HRD, but, overall, genetic screening failed to predict functional HRD. We developed an assay that detects tumor functional HRD and an HR score able to predict platinum sensitivity, which holds the clinically relevant potential to become the routine companion diagnostic in the management of patients with ovarian cancer..

have patents pending. P.T.H. is a co-founder and member of the Board of Directors of LayerBio, Inc. She is on the Scientific Advisory Board of Moderna, Inc. and the Board of Directors of Alector, Inc., and she receives consulting fees and holds equity in these companies. P.T.H. is not aware of any conflicts of interest concerning the manuscript's content and topic and these entities. B.G.N. is a cofounder, holds equity in, and is a member of the Scientific Advisory Board at Navire Pharmaceuticals. He also has equity in and is a member of the Scientific Advisory Board at Avrinas, Inc. B.G.N. was an expert witness for the Johnson and Johnson ovarian cancer talc litigation in U.S. Federal Court. His spouse has equity in Amgen, Avrinas, Inc, Gilead Sciences, and Regeneron. R.A.W. is a scientific advisor for and holds an equity interest in Verastem, Inc. The other authors declare no conflicts of interest. Research.

Due to its dynamic nature, the evolution of cancer cell-extracellular matrix (ECM) crosstalk, critically affecting metastasis and treatment resistance, remains elusive. Our results show that platinum-chemotherapy itself enhances resistance by progressively changing the cancer cell-intrinsic adhesion signaling and cell-surrounding ECM. Examining ovarian high-grade serous carcinoma (HGSC) transcriptome and histology, we describe the fibrotic ECM heterogeneity at primary tumors and distinct metastatic sites, prior and after chemotherapy. Using cell models from systematic ECM screen to collagen-based 2D and 3D cultures, we demonstrate that both specific ECM substrates and stiffness increase resistance to platinum-mediated, apoptosis-inducing DNA damage via FAK and β1 integrin-pMLC-YAP signaling. Among such substrates around metastatic HGSCs, COL6 was upregulated by chemotherapy and enhanced the resistance of relapse, but not treatment-naïve, HGSC organoids. These results identify matrix adhesion as an adaptive response, driving HGSC aggressiveness via co-evolving ECM composition and sensing, suggesting stromal and tumor strategies for ECM pathway targeting.

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Human epididymis protein 4 (HE4) is a novel tumour marker in epithelial ovarian cancer (EOC). Data on its profile and predictive potential for subsequent outcome after neoadjuvant chemotherapy (NACT) are still under investigation. The aim of this study was to compare CA125 and HE4 profiles with radiologic response after NACT and to evaluate their potential as predictors of clinical outcome in a primarily inoperable EOC patient cohort. Twenty-five EOC patients of high-grade subtype (HGSC) treated with NACT were enrolled in the study. Serum HE4 and CA125 samples were taken at the time of diagnosis and before interval debulking surgery (IDS). Pre-NACT and pre-IDS HE4 and CA125 and their percentage changes were compared with NACT response seen on CT and surgical outcome in IDS. We also evaluated the biomarkers' abilities to predict platinum-free interval (PFI), progression-free survival (PFS) and overall survival (OS). All 25 patients were considered inoperable in laparoscopy at the time of diagnosis. HE4 and CA125 changes during NACT did not correlate with the changes seen on CT. Surgical outcome in IDS was associated with pre-IDS biomarker values but not with those taken before diagnosis. In IDS, 87 % had <1-cm residual tumour. In patients with HE4 change >80 and <80 % during NACT, the median OS was 3.38 and 1.60 years (p = 0.01), respectively. Serum HE4 is a promising additional tool when evaluating advanced HGSC patient's response to NACT. It may be helpful when deciding whether to proceed to IDS or to second-line chemotherapy.