Alexandre André B. A. da Costa

PARG inhibitor sensitivity correlates with accumulation of single-stranded DNA gaps in preclinical models of ovarian cancer

Poly (ADP-ribose) glycohydrolase (PARG) is a dePARylating enzyme which promotes DNA repair by removal of poly (ADP-ribose) (PAR) from PARylated proteins. Loss or inhibition of PARG results in replication stress and sensitizes cancer cells to DNA-damaging agents. PARG inhibitors are now undergoing clinical development for patients having tumors with homologous recombination deficiency (HRD), such as cancer patients with germline or somaticBRCA1/2-mutations. PARP inhibitors kill BRCA-deficient cancer cells by increasing single-stranded DNA gaps (ssGAPs) during replication. Here, we report that, like PARP inhibitor (PARPi), PARG inhibitor (PARGi) treatment also causes an accumulation of ssGAPs in sensitive cells. PARGi exposure increased accumulation of S-phase-specific PAR, a marker for Okazaki fragment processing (OFP) defects on lagging strands and induced ssGAPs, in sensitive cells but not in resistant cells. PARGi also caused accumulation of PAR at the replication forks and at the ssDNA sites in sensitive cells. Additionally, PARGi exhibited monotherapy activity in specific HR-deficient, as well as HR-proficient, patient-derived, or patient-derived xenograft (PDX)-derived organoids of ovarian cancer, and drug sensitivity directly correlated with the accumulation of ssGAPs. Taken together, PARGi treatment results in toxic accumulation of PAR at replication forks resulting in ssGAPs due to OFP defects during replication. Regardless of theBRCA/HRD-status, the induction of ssGAPs in preclinical models of ovarian cancer cells correlates with PARGi sensitivity. Patient-derived organoids (PDOs) may be a useful model system for testing PARGi sensitivity and functional biomarkers.

Single-Stranded DNA Gap Accumulation Is a Functional Biomarker for USP1 Inhibitor Sensitivity

Abstract Recent studies suggest that PARP and POLQ inhibitors confer synthetic lethality in BRCA1-deficient tumors by accumulation of single-stranded DNA (ssDNA) gaps at replication forks. Loss of USP1, a deubiquitinating enzyme, is also synthetically lethal with BRCA1 deficiency, and USP1 inhibitors are now undergoing clinical development for these cancers. Herein, we show that USP1 inhibitors also promote the accumulation of ssDNA gaps during replication in BRCA1-deficient cells, and this phenotype correlates with drug sensitivity. USP1 inhibition increased monoubiquitinated proliferating cell nuclear antigen at replication forks, mediated by the ubiquitin ligase RAD18, and knockdown of RAD18 caused USP1 inhibitor resistance and suppression of ssDNA gaps. USP1 inhibition overcame PARP inhibitor resistance in a BRCA1-mutated xenograft model and induced ssDNA gaps. Furthermore, USP1 inhibition was synergistic with PARP and POLQ inhibition in BRCA1-mutant cells, with enhanced ssDNA gap accumulation. Finally, in patient-derived ovarian tumor organoids, sensitivity to USP1 inhibition alone or in combination correlated with the accumulation of ssDNA gaps. Assessment of ssDNA gaps in ovarian tumor organoids represents a rapid approach for predicting response to USP1 inhibition in ongoing clinical trials. Significance: USP1 inhibitors kill BRCA1-deficient cells and cause ssDNA gap accumulation, supporting the potential of using ssDNA gap detection as a functional biomarker for clinical trials on USP1 inhibitors.

Subclonal loss of DNA mismatch repair proteins in endometrial carcinomas: an unusual pattern with distinct molecular characteristics

Subclonal loss of mismatch repair (MMR) proteins in endometrial carcinoma has recently been identified through immunohistochemistry (IHC) evaluations, characterized by discrete areas of tumors with complete loss of nuclear expression adjacent to tumor cells with retaining expression. Controversies persist regarding reporting findings and managing such cases. Therefore, we conducted a detailed clinicopathological and molecular analysis on a large cohort of endometrial carcinoma cases with subclonal loss of MMR proteins to explore potential reclassification into different molecular categories that could influence diagnostic and treatment strategies. Eligible endometrial carcinoma cases underwent IHC evaluation for PMS2/MLH1/MSH2/MSH6. Cases showing subclonal loss of MMR proteins underwent macrodissection of both proficient and deficient MMR expression areas, followed by testing for microsatellite instability (Idylla), MLH1 promoter methylation (next-generation sequencing), POLE mutations (next-generation sequencing), and p53 expression (IHC). The proposed molecular evaluation was performed in both proficient and deficient areas. Clinical and pathological data for patients with subclonal loss were also analyzed. We evaluated 356 cases of endometrial carcinoma, identifying subclonal loss in 16 patients (4.4%), predominantly endometrioid (15 cases, 93.75%) and International Federation of Gynecology and Obstetrics stage I (13 cases, 81.25%). Subclonal loss of MSH6 occurred independently in 6 cases (37.5%), and concurrently with subclonal loss of MLH1 in 2 cases (12.5%). Complete loss of MLH1/PMS2 was observed in 2 cases (12.5%). MLH1 promoter methylation was detected in 6 cases (37.5%), with 4 cases showing methylation in both areas analyzed. POLE mutations were found in 3 cases (18.75%), occurring in both deficient and proficient areas. The correlation between IHC findings and molecular results varied, providing valuable predictive and prognostic insights that could guide treatment decisions in some patients. Molecular evaluation should be standard practice in all endometrial carcinoma cases exhibiting subclonal loss of MMR proteins to accurately delineate tumor characteristics. Subclonal loss should be reported distinctly, warranting a more comprehensive diagnostic approach to enhance tumor classification.

The value of PET/CT for cytoreductive surgery selection in recurrent ovarian carcinoma

To evaluate the value of positron emission tomography/computed tomography (PET/CT) in predicting no residual disease (NRD) after secondary cytoreductive surgery (SCS) compared with MSK criteria, the iMODEL, and the AGO score. We analyzed 112 patients with platinum-sensitive ovarian carcinoma who underwent SCS. We excluded patients for whom PET/CT was not performed, those without sufficient data, and who received chemotherapy before SCS. Ultimately, 69 patients were included. Variables that correlated with NRD were peritoneal carcinomatosis index (odds ratio [OR]=0.91; 95% confidence interval [CI]=0.83-0.99; p=0.044), European Cooperative Oncology Group Performance Status (ECOG) 0 (OR=8.0; 95% CI=1.34-47.5; p=0.022), and ≤2 lesions by PET/CT (OR=4.36; 95% CI=1.07-17.7; p=0.039). Of the patients with ≤2 lesions by PET/CT, 48 (92.3%) underwent complete SCS. The sensitivity, positive predictive value, negative predictive value, and accuracy of PET/CT for NRD were 85.7%, 92.3%, 33.3%, and 81.2%, respectively. NRD was achieved after fulfilling the MSK criteria, iMODEL and AGO Score in 89.1%, 88.1% and 85.9%, respectively. The accuracy of the MSK criteria, iMODEL, and AGO score in predicting NRD was 87%, 83.3%, and 77.3%, respectively. The PET/CT findings agreed well with the AGO score and iMODEL. The addition of PET/CT to these models increased the NRD rates (92.2%, 91.8%, and 89.4% for MSK+PET/CT, iMODEL+PET/CT, and AGO+PET/CT, respectively), but lowered their accuracy. We observed NRD in 92.3% of patients with ≤2 lesions by PET/CT, with an accuracy of 81.2%. PET/CT did not increase the accuracy of the MSK criteria, iMODEL, or AGO score models.

ASO Author Reflections: Personalized Surgery in Recurrent Ovarian Cancer Patients

Fusion Cell Markers in Circulating Tumor Cells from Patients with High-Grade Ovarian Serous Carcinoma

Cancer is primarily a disease in which late diagnosis is linked to poor prognosis, and unfortunately, detection and management are still challenging. Circulating tumor cells (CTCs) are a potential resource to address this disease. Cell fusion, an event discovered recently in CTCs expressing carcinoma and leukocyte markers, occurs when ≥2 cells become a single entity (hybrid cell) after the merging of their plasma membranes. Cell fusion is still poorly understood despite continuous evaluations in in vitro/in vivo studies. Blood samples from 14 patients with high-grade serous ovarian cancer (A.C. Camargo Cancer Center, São Paulo, Brazil) were collected with the aim to analyze the CTCs/hybrid cells and their correlation to clinical outcome. The EDTA collected blood (6 mL) from patients was used to isolate/identify CTCs/hybrid cells by ISET. We used markers with possible correlation with the phenomenon of cell fusion, such as MC1-R, EpCAM and CD45, as well as CEN8 expression by CISH analysis. Samples were collected at three timepoints: baseline, after one month (first follow-up) and after three months (second follow-up) of treatment with olaparib (total sample = 38). Fourteen patients were included and in baseline and first follow-up all patients showed at least one CTC. We found expression of MC1-R, EpCAM and CD45 in cells (hybrid) in at least one of the collection moments. Membrane staining with CD45 was found in CTCs from the other cohort, from the other center, evaluated by the CellSearch® system. The presence of circulating tumor microemboli (CTM) in the first follow-up was associated with a poor recurrence-free survival (RFS) (5.2 vs. 12.2 months; p = 0.005). The MC1-R expression in CTM in the first and second follow-ups was associated with a shorter RFS (p = 0.005). CEN8 expression in CTCs was also related to shorter RFS (p = 0.035). Our study identified a high prevalence of CTCs in ovarian cancer patients, as well as hybrid cells. Both cell subtypes demonstrate utility in prognosis and in the assessment of response to treatment. In addition, the expression of MC1-R and EpCAM in hybrid cells brings new perspectives as a possible marker for this phenomenon in ovarian cancer.

Comparison of dose-dense vs. 3-weekly paclitaxel and carboplatin in the first-line treatment of ovarian cancer in a propensity score-matched cohort

Abstract Background Benefit of carboplatin and dose-dense weekly paclitaxel (ddCT) in first line treatment of ovarian cancer patients has been different in Western and Asian studies. In the present study we compare progression-free survival (PFS) of ddCT to three-weekly carboplatin and paclitaxel (CT) in first-line treatment of ovarian carcinoma in a single institution in a Western population. Materials and methods We conducted a retrospective review of medical records from patients with ovarian carcinoma treated in a tertiary cancer center from 2007 to 2018. All patients treated with ddCT or CT in the first-line setting were included. Patients who received first-line bevacizumab were not included. PFS and overall survival (OS) were compared in a propensity score-matched cohort to address selection bias. Patients were matched according to age, ECOG performance status, CA 125, FIGO stage, residual disease, and histological subtype, in a 1:2 ratio. Results Five hundred eighty-eight patients were eligible for propensity score matching, the final cohort consisted of 69 patients treated with ddCT and 138 CT group. Baseline characteristics were well-balanced. After a median follow-up of 65.1 months, median PFS was 29.3 vs 20.0 months, favouring ddCT treatment (p = 0.035). In the multivariate cox regression ddCT showed a 18% lower risk of progression (HR 0.82, 95% CI 0.68–0.99, p = 0.04). Overall survival data is immature, but suggested better outcomes for ddCT (not reached versus 78.8 months; p = 0.07). Conclusion Our retrospective study has shown superior PFS of ddCT over CT regimen in first-line treatment of ovarian carcinoma in a Western population not treated with bevacizumab.

Case Report of Small Cell Carcinoma of the Ovary, Hypercalcemic Type (Ovarian Rhabdoid Tumor) with SMARCB1 Mutation: A Literature Review of a Rare and Aggressive Condition

Small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) is a rare and aggressive condition that is associated with the SMARCA4 mutation and has a dismal prognosis. It is generally diagnosed in young women. Here, we report a case of a young woman with SCCOHT harboring a rare molecular finding with a highly aggressive biological behavior. The patient had a somatic SMARCB1 mutation instead of an expected SMARCA4 alteration. Even though the patient was treated with high-dose chemotherapy followed by stem cell transplantation, she evolved with disease progression and died 11 months after her first symptoms appeared. We present a literature review of this rare disease and discuss the findings in the present patient in comparison to expected molecular alterations and options for SCCOHT treatment.

Randomized Phase II Study of Gemcitabine With or Without ATR Inhibitor Berzosertib in Platinum-Resistant Ovarian Cancer: Final Overall Survival and Biomarker Analyses

PURPOSE The multicenter, open-label, randomized phase 2 NCI-9944 study ( NCT02595892 ) demonstrated that addition of ATR inhibitor (ATRi) berzosertib to gemcitabine increased progression-free survival (PFS) compared to gemcitabine alone (hazard ratio [HR]=0.57, one-sided log-rank P = .044, which met the one-sided significance level of 0.1 used for sample size calculation). METHODS We report here the final overall survival (OS) analysis and biomarker correlations (ATM expression by immunohistochemistry, mutational signature 3 and a genomic biomarker of replication stress) along with post-hoc exploratory analyses to adjust for crossover from gemcitabine to gemcitabine/berzosertib. RESULTS At the data cutoff of January 27, 2023 (>30 months of additional follow-up from the primary analysis), median OS was 59.4 weeks with gemcitabine/berzosertib versus 43.0 weeks with gemcitabine alone (HR 0.79, 90% CI 0.52 to 1.2, one-sided log-rank P = .18). An OS benefit with addition of berzosertib to gemcitabine was suggested in patients stratified into the platinum-free interval ≤3 months (N = 26) subgroup (HR, 0.48, 90% CI 0.22 to 1.01, one-sided log-rank P =.04) and in patients with ATM-negative/low (N = 24) tumors (HR, 0.50, 90% CI 0.23 to 1.08, one-sided log-rank P = .06). CONCLUSION The results of this follow-up analysis continue to support the promise of combined gemcitabine/ATRi therapy in platinum resistant ovarian cancer, an active area of investigation with several ongoing clinical trials.