Ovarian cancer is the gynecological cancer with the worst prognosis and the highest mortality rate because 75% of patients are diagnosed with advanced stage III–IV disease. About 50% of patients are now treated with neoadjuvant chemotherapy followed by interval debulking surgery (IDS). In that context, there is a need for accurate predictors of tumor primary chemosensitivity, as it may impact the feasibility of subsequent IDS. Across seven studies with more than 12,000 patients, including six large randomized clinical trials and a national cancer registry, along with a mega-analysis database with 5842 patients, the modeled CA-125 ELIMination rate constant K (KELIM), the calculation of which is based on the longitudinal kinetics during the first three cycles of platinum-based chemotherapy, was shown to be a reproducible indicator of tumor intrinsic chemosensitivity. Indeed, KELIM is strongly associated with the likelihood of complete IDS, subsequent platinum-free interval, progression-free survival, and overall survival, along with the efficacy of maintenance treatment with bevacizumab or veliparib. As a consequence, KELIM might be used to guide more subtly the medical and surgical treatments in a first-line setting. Moreover, it could be used to identify the patients with poorly chemosensitive disease, who will be the best candidates for innovative treatments meant to reverse the chemoresistance, such as cell cycle inhibitors or immunotherapy.

Resistance to platinum-based chemotherapy represents a major clinical challenge for many tumors, including epithelial ovarian cancer. Patients often experience several response-relapse events, until tumors become resistant and life expectancy drops to 12–15 months. Despite improved knowledge of the molecular determinants of platinum resistance, the lack of clinical applicability limits exploitation of many potential targets, leaving patients with limited options. Serine biosynthesis has been linked to cancer growth and poor prognosis in various cancer types, however its role in platinum-resistant ovarian cancer is not known. Here, we show that a subgroup of resistant tumors decreases phosphoglycerate dehydrogenase (PHGDH) expression at relapse after platinum-based chemotherapy. Mechanistically, we observe that this phenomenon is accompanied by a specific oxidized nicotinamide adenine dinucleotide (NAD⁺) regenerating phenotype, which helps tumor cells in sustaining Poly (ADP-ribose) polymerase (PARP) activity under platinum treatment. Our findings reveal metabolic vulnerabilities with clinical implications for a subset of platinum resistant ovarian cancers.

Background: How molecular profiles are associated with tumor microenvironment (TME) in high-grade serous ovarian cancer (HGSOC) is incompletely understood. Therefore, we analyzed the TME and molecular profiles of HGSOC and assessed their associations with overall survival (OS). Methods: Patients with advanced-stage HGSOC treated in three Dutch hospitals between 2008–2015 were included. Patient data were collected from medical records. BRCA1/2 mutation, BRCA1 promotor methylation analyses, and copy number variations were used to define molecular profiles. Immune cells were assessed with immunohistochemical staining. Results: 348 patients were categorized as BRCA mutation (BRCAm) (BRCAm or promotor methylation) (30%), non-BRCA mutated HRD (19%), Cyclin E1 (CCNE1)-amplification (13%), non-BRCAmut HRD and CCNE1-amplification (double classifier) (20%), and no specific molecular profile (NSMP) (18%). BRCAm showed highest immune cell densities and CCNE1-amplification lowest. BRCAm showed the most favorable OS (52.5 months), compared to non-BRCAmut HRD (41.0 months), CCNE1-amplification (28.0 months), double classifier (27.8 months), and NSMP (35.4 months). Higher immune cell densities showed a favorable OS compared to lower, also within the profiles. CD8+, CD20+, and CD103+ cells remained associated with OS in multivariable analysis. Conclusions: Molecular profiles and TME are associated with OS. TME differs per profile, with higher immune cell densities showing a favorable OS, even within the profiles. HGSOC does not reflect one entity but comprises different entities based on molecular profiles and TME.

Van Wagensveld L, et al. J Gynecol Oncol. 2024 Jan;35:e34. https://doi.org/10.3802/jgo.2024.35.e34

The tumor microenvironment in high-grade serous ovarian carcinoma (HGSC) is a complex network of malignant–host cell interactions, yet its orchestration remains poorly understood. We present a single-cell spatial atlas of metastatic HGSC from 280 patients, integrating high-dimensional imaging and molecular profiling. Analyzing 929 single-cell maps, we identify spatial domains with diverse cell compositions and show that immune cell coinfiltration at the tumor–stroma interface affects clinical outcomes. Using Cell Feature Importance Identification by RAndom forest (CEFIIRA), we find that tumor cell MHC class II (MHCII) expression is a key predictor of prolonged survival. Validation with deconvoluted single-cell and two distinct spatial transcriptomic datasets, along with immunopeptidomic analysis, confirms that MHCII expression correlates with immune activation, antigen presentation, and T-cell receptor clonality. Using a patient-derived immuno-oncology platform, we demonstrate that tumor MHCII expression associates with increased CD8+ T-cell cytotoxicity after PD-1 blockade, whereas blocking MHCII inhibits this activation. Our atlas offers new insights into immune activation, potentially improving patient stratification in HGSC. Significance: This study delivers the first large-scale single-cell spatial atlas of HGSC, revealing how tumor–immune organization shapes outcomes. We identify tumor-intrinsic MHCII as a key driver of local immune activation and immunotherapy responsiveness, providing a mechanistic biomarker that can immediately inform improved patient stratification and therapeutic decision-making in ovarian cancer. See related commentary by Conejo-Garcia and Dangaj Laniti, p. 1041