Dumbravă, Mihai

Abstract High-grade serous ovarian cancer (HGSOC), the most prevalent and lethal ovarian cancer subtype, is typically diagnosed at an advanced stage due to the absence of effective early detection strategies. Mounting evidence indicates that HGSOC originates from the fallopian tube (FT), particularly from secretory epithelial cells in the fimbria. However, incomplete understanding of the cellular and molecular origins of HGSOC continues to hinder early interception efforts. To address this, we established a clinically and genetically annotated living FT organoid biobank at Mayo Clinic, representing over 200 patient donors. Using optimized enrichment protocols, we isolated FT epithelial stem/progenitor cells from tissue and Tao brushings, generating organoids independent of anatomical site or laterality that recapitulate native FT epithelial architecture and lineage differentiation. We applied integrated multi-omic analyses, including single-cell RNA sequencing, single-nucleus RNA/ATAC sequencing, and bulk RNA-seq, across fresh cells and organoids. Integration with public datasets produced the largest single-cell atlas of normal and high-risk FTs to date. This analysis defined high-specificity gene signatures for secretory and multiciliated lineages that outperform canonical lineage markers (e.g. PAX8, FOXJ1), identified lineage-defining transcription factors and regulatory networks, and showed concordant protein expression in the human FT epithelium. Notably, subcluster-level analysis revealed a rare hybrid epithelial-mesenchymal population transcriptionally and proteomically aligned with the mesenchymal-like subtype of HGSOC. Spatial immunoprofiling demonstrated that these cells express multiple defining markers and reside above the basement membrane, intercalated between epithelial cells and lack luminal contact, reminiscent of the histologically described peg cell population. Comparative analyses with fetal mesonephric tissues uncovered developmental parallels, and this population was stably maintained in 3D organoid cultures, providing a robust ex-vivo model to study early transformation. Together, our findings identify a rare, multipotent epithelial population with mesenchymal features as a candidate origin for mesenchymal-like HGSOC and establish the FT organoid biobank as a powerful platform for mechanistic and translational studies in ovarian carcinogenesis. Citation Format: Megan L. Ritting, Wenmei Yang, Syed Mohammed Musheer Aalam, Hui Zhao, Liang Feng, Jianning Song, Mihai G. Dumbrava, Wazim M. Ismail, Kenneth Schaufelberger, S. John Weroha, Scott H. Kaufmann, Alexandre Gaspar-Maia, Mark E. Sherman, Jamie N. Bakkum-Gamez, Nagarajan Kannan. A rare multipotent peg-like epithelial cell is a candidate cell-of-origin for high-grade serous ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 7636.

Abstract Cancer can recur when a subset of tumor cells, termed persister cells, survive therapy and re-enter the cell cycle. The cellular lineages that give rise to persister cells and the mechanisms that confer the persister state remain poorly understood. Through single-cell multiomic profiling (snRNA-seq and snATAC-seq) on a cohort of (1) non-malignant fallopian tube, (2) treatment-naïve, and (3) neoadjuvant chemotherapy (NACT)-treated high-grade serous ovarian cancer (HGSOC) patient samples, we identified an epigenetic signature that defines the chemotherapy-tolerant persister state. The changes in chromatin accessibility characterizing the signature were identified in residual NACT tumors but are also present in treatment-naive samples from patients who later developed resistance. Furthermore, this epigenetic signature independently predicted chemotherapy response in patient-derived xenograft models of HGSOC and in a separate patient cohort. Cells enriched in the persister state arose from multiple lineages and displayed activation of oncogenic pathways, including altered stress responses, epithelial to mesenchymal transition, and changes to the cell cycle promoting quiescence. Finally, we identified a subset of genes that are epigenetically primed for expression before treatment and are upregulated after treatment. These findings suggest that an intrinsic epigenetic program primes tumor cells towards chemotherapy tolerance and reveal new vulnerabilities that could be exploited to delay or prevent cancer recurrence. Citation Format: Mihai G. Dumbrava, Wazim M. Ismail, Leticia Sandoval, Amelia Mazzone, Syed Mohammed Musheer Aalam, Megan L. Ritting, Xiaonan Hou, Yiwen Xie, Shariska Harrington, Scott H. Kaufmann, Nagarajan Kannan, S. John Weroha, Alexandre Gaspar-Maia. Single cell multiomic analysis of high-grade serous ovarian carcinoma reveals an intrinsic epigenetic program that primes chemotherapy tolerance in persister cells [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr PR008.

Abstract High-grade serous ovarian cancer (HGSOC), the most prevalent and lethal ovarian cancer subtype, is often diagnosed at an advanced stage due to the lack of effective early detection methods. Current evidence suggests that HGSOC originates from the fallopian tube (FT), specifically from secretory epithelial cells in the fimbriated region, based on the detection of early serous lesions and clonal genetic relationships linking them to HGSOC tumors. However, efforts to improve early diagnosis and interception are hindered by an incomplete understanding of HGSOC’s cellular and molecular origin. To address this, we established a diverse, clinically and genetically annotated living FT organoid biobank at the Mayo Clinic, encompassing specimens from over 200 patient donors. Using robust, multi-step protocols, we enriched FT epithelial stem/progenitor cells from tissue samples and Tao brushings, generating bi-lineage differentiated organoids independent of anatomical site (ampulla, fimbria) or laterality (right, left). To gain deeper insight into FT epithelial lineage dynamics, we applied multi-omic modalities—including single-cell RNA sequencing (scRNA-seq), single-nucleus RNA and ATAC sequencing (snMultiome), and bulk RNA-seq—to fresh cells and pooled organoids, integrating findings with public FT datasets to generate the largest known integrated single-cell atlas of normal and high-risk FTs. This enabled the generation and validation of gene expression-derived signatures for secretory and multiciliated lineages, identification of key lineage-defining transcription factors and their regulatory networks, and validation using immunohistochemistry (IHC) data from the Human Protein Atlas. Subcluster-level analysis of epithelial cells revealed transcriptionally distinct populations with unique biological functions, deepening insight into epithelial heterogeneity and FT lineage differentiation. Further, analysis of FT epithelial subclusters identified a rare population with transcriptomic and proteomic association with the mesenchymal-like HGSOC subtype. These cells retained epithelial identity while expressing mesenchymal and ECM-related genes, forming a hybrid phenotype. Spatial profiling via IHC localized them to a rare, basal, peg-like position within the FT epithelium. Developmental analysis showed shared transcriptional features with fetal mesonephric cells, suggesting both developmental plasticity and potential vulnerability to transformation. Pooled organoid scRNA-seq confirmed that they are preserved in culture, indicating they are stably maintained ex-vivo. Together, these findings suggest that this cell cluster represents a rare, multipotent epithelial population with mesenchymal features, offering a candidate cellular origin for the mesenchyme-like subtype of HGSOC. In conclusion, this living FT organoid biobank serves as a powerful, clinically annotated platform for dissecting epithelial lineage hierarchies, identifying rare cell populations, and uncovering mechanisms that may underlie subtype-specific ovarian carcinogenesis. Citation Format: Megan Ritting, Syed Mohammed Musheer Aalam, Mihai Dumbrava, Wazim Mohammed Ismail, Alexandre Gaspar-Maia, Mark Sherman, Jamie Bakkum-Gamez, Nagarajan Kannan. Tubal organoid biobanking and multi-omics framework uncovers rare basal peg cells as a source of epithelial stemness and a candidate for high-grade serous ovarian cancer origin [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Ovarian Cancer Research; 2025 Sep 19-21; Denver, CO. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl):Abstract nr A078.

Abstract Cancer can recur when a subset of tumor cells, denoted here as persister cells, are able to survive therapy and re-enter the cell cycle. The precise mechanisms that confer the persister state and whether it is characteristic of a subgroup of cells or arises from multiple cellular lineages remain poorly understood. We hypothesize that an epigenetic signature underlies the drug-tolerant persister state, characterized by transcriptional and chromatin accessibility changes that promote survival of residual cancer following chemotherapy. To identify clinically relevant features of persister cells in untreated tumors and residual disease, we performed single-cell multiomic profiling (snRNA+snATAC) on a cohort of non-malignant fallopian tube, treatment-naïve, and neoadjuvant chemotherapy (NACT)-treated high-grade serous ovarian cancer (HGSOC) samples. We identified differences in gene expression and open chromatin between naïve and residual patient tumors following chemotherapy. Although only a small proportion of the differentially expressed genes enriched in residual HGSOC overlapped with established gene sets for chemo-response and patient prognosis, the epigenomic analysis revealed activity of several DNA-binding factors that are both enriched upon chemotherapy and also high in resistant tumors prior to treatment. From this analysis, we identified an epigenetic signature that precedes expression and defines the persister state. This epigenetic signature also correlated with chemotherapy sensitivity and resistance using patient-derived xenograft models of HGSOC. Gene regulatory networks driven by the persister signature are involved in the activation of oncogenic pathways, including changes to the cell cycle promoting quiescence and stress response. Further study of the persister cells identified by this epigenetic signature may increase understanding of the mechanisms underlying persister cell survival and reveal new vulnerabilities that could be exploited to delay or prevent cancer recurrence.

AbstractBackgroundNeoadjuvant platinum‐based chemotherapy offers a modest survival advantage in muscle‐invasive bladder cancer (MIBC) for patients with pathologic response. B7‐H3 (CD276), an immune checkpoint overexpressed in various cancers, including urothelial‐cell carcinoma (UCC), has been associated with chemoresistance and poor oncologic outcomes. We aimed to explore if B7H3 expression on bladder biopsy samples was a predictive biomarker for pathologic response to neoadjuvant platinum‐based chemotherapy.MethodsThis was a retrospective cohort study among MIBC patients receiving neoadjuvant platinum‐based chemotherapy followed by radical cystectomy. All patients underwent routine preoperative biopsy of their tumour. Immunohistochemistry was used to evaluate B7‐H3 expression from pre‐operative specimens. The primary outcome of interest was pathologic complete response (pCR). Statistical analysis included Mann–Whitney U test, Fisher's exact test, Kaplan–Meier method, and Cox regression for survival analysis.ResultsAmong 87 patients analysed, high B7‐H3 expression was found in 44.8% (n = 39) of patients. The median follow‐up periods were similar between the high and low B7‐H3 groups (high expression; 4.29 years [SD 3.04], low expression 3.94 years [SD 3.04], p = 0.60). Only 20.5% of patients with high B7‐H3 expression achieved pCR, compared to 41.7% in the low expression group (p = 0.04). Cox regression showed no significant differences in recurrence‐free or cancer‐specific survival between the high and low B7‐H3 expression groups (p > 0.05).ConclusionHigh B7‐H3 expression is associated with a reduced likelihood of achieving pCR in MIBC patients undergoing neoadjuvant chemotherapy. This suggests B7‐H3's potential as a predictive biomarker for chemotherapy response. Further research is needed to explore the role of B7‐H3 on platinum‐based chemotherapy response in urothelial cancer.

Introduction: Monoclonal gammopathy of renal significance (MGRS) is characterized by clonal cell deposition of monoclonal immunoglobulin causing renal manifestations without overt malignancy. MIDD is a subtype of MGRS characterized by deposition of monoclonal light (LCDD), heavy chains (HCDD), or both (LHCDD) along the renal glomerular and tubular basement membranes. Virtually all organs can be involved, and if left untreated, MIDD can progress to MM and end stage renal disease. Although these patients classically did not receive treatment, current MIDD management is primarily focused on controlling the underlying clonal plasma cell disorder. Case description: We present a 56-year-old male with atypical MIDD treated successfully with plasma cell directed therapy consisting of daratumumab, cyclophosphamide, bortezomib, and dexamethasone (DARA-CYBOR-D). Despite a primary diagnosis of diabetic kidney disease, renal biopsy suggested myeloma-related MIDD based on linear immunofluorescent staining for IgG and kappa light chains along the tubular and glomerular basement membranes. Notably there were no electron dense deposits in the mesangium or tubular basement membranes typical to MIDD electron microscopy. Despite the presentation of MIDD on IF only, DARA-CYBOR-D treatment led to hematologic and renal improvement and remission from MIDD, with a GFR increase from 22 to 59 mL/min/BSA and a drop in urine protein from up to 9 to 0.6 g/dL. Conclusions: In conclusion, our case illustrates the efficacy of the DARA-CYBOR-D regimen in a patient with IF-only MIDD. We highlight the importance of obtaining a kidney biopsy when there are other potential causes for real decline and enhance our understanding of pathological and clinical spectrum of MIDD.

Background: Approximately 30% of renal cell carcinoma (RCC) cases present with de novo metastatic disease, while 20% to 30% of those with localized disease will develop metastases following surgical resection. Various drug classes have been investigated to treat RCC, including cytokine-based therapies, small molecule Vascular Endothelial Growth Factor (VEGF) tyrosine kinase inhibitors (TKIs) and antibody-based therapies. Up to 58% of patients fail to respond to primary immune checkpoint inhibitor (ICI) therapy, and nearly all initial responders experience disease progression due to the development of secondary resistance. Consequently, novel treatment options are being investigated. Objective: Review the rapidly evolving ADC therapeutic landscape in metastatic RCC including recent trials, emerging ADCs targets, and future directions for ADCs in the treatment of advanced RCC. Methods: Literature review using the MEDLINE database on important trials and presentations from the American Society of Clinical Oncology (ASCO), and the European Society for Medical Oncology (ESMO) conferences. Key words used included “renal cell carcinoma,” “RCC,” “metastatic RCC,” “advanced RCC,” “antibody-based therapies,” “immunotherapy,” “clinical trials,” and “emerging drugs.” Specifically for review of ADCs in RCC, the following search string was used with additional review of bibliographies from retrieved papers: “((antibody drug conjugate) OR (antibody-dependent cellular cytotoxicity) OR (chimeric antigen receptor)) AND ((kidney cancer) OR (renal cell carcinoma))”. Results: Several promising targets including MMP14, EGFR, MCT4, CA9, MET, CDH13, B7-H3, and PSMA were identified with relevant preclinical and clinical studies reviewed. Conclusions: While ADCs therapeutics have not shown benefit to date for renal cell carcinoma, there are ample promising candidates and targets for future research.