Biology subjects

Ritting, M. L.

Publications and source records attributed to Ritting, M. L..

4 recordsLinked to original sources

bioRxiv2026

The Human Male Mammary Gland has Similar Epithelial Populations to Female but Distinct Composition and Transcriptional Properties

The normal adult male breast has not been characterized at single-cell resolution, leaving the cellular basis of male breast cancer (MBC) biology undefined. Here we present an integrated single-cell RNA sequencing atlas of the adult human breast comprising 174,471 cells from 17 donors (3 male, 14 female), including 18,117 male-derived cells. This revealed that the male breast retains all three epithelial populations, basal (BC), luminal progenitor (LP), and luminal committed cells (LC), but with an increase in LC at the expense of BC and LP across all three male donors. Male LC were distinguished from female by elevated ESR1 and PGR mRNA, enrichment of RNA processing and ribosome biogenesis programs, reduced inflammatory cytokine and growth factor signaling, elevated estradiol gene set enrichment scores, and higher inferred activity of developmental patterning transcription factors. This pattern was observed across differential expression, gene ontology, ligand profiling, and regulon-based analyses, and was not restricted to sex chromosome-linked gene expression. This is consistent with the near-universal estrogen receptor (ER) positivity that characterizes MBC clinically. This atlas provides the first cellular and transcriptional reference for the normal male breast and a resource for investigating sex differences in mammary biology, germline susceptibility variant interpretation, and modeling breast malignancies.

cancer biology↗

bioRxiv2025

A Rare Multipotent Peg-like Epithelial Cell is a Candidate Cell-of-Origin for High-Grade Serous Ovarian Cancer

To illuminate the origins of high-grade serous ovarian cancer (HGSOC), the most lethal and common form of ovarian cancer, we have created a comprehensive living organoid biobank of human fallopian tube tissue, which is thought to be the origin of this cancer. Through optimized culture protocols and integrated multi-omic profiling--including single-cell RNA sequencing, chromatin accessibility (ATAC) analysis, proteomics, and secretomics--we assembled the largest molecular atlas of the fallopian tube epithelium to date. This resource revealed diverse epithelial lineages and regulatory networks, including a rare, multipotent epithelial subpopulation with hybrid epithelial-mesenchymal features. Spatially localized to the basal epithelium and resembling mesonephric developmental precursors, these cells exhibit transcriptomic and proteomic similarities to the mesenchyme-like subtype of HGSOC, implicating them as potential cells-of-origin. Their molecular identity is preserved in organoid models, enabling future mechanistic and translational studies. This resource, which advances fundamental understanding of epithelial hierarchy and cancer susceptibility, provides a platform to inform early detection and prevention strategies for aggressive forms of ovarian cancer. HighlightsO_LIEstablishment of a clinically annotated fallopian tube organoid biobank enables delineation of epithelial lineage hierarchies and differentiation capacity. C_LIO_LIMulti-omics integration defines robust, lineage-specific transcriptional and regulatory networks in the fallopian tube epithelium. C_LIO_LIA rare basal epithelial subpopulation with mesenchymal features aligns with a mesenchyme-like subtype of high-grade serous ovarian cancer. C_LIO_LIRare basal peg cells exhibit fetal mesonephric developmental transcriptional programs and are maintained ex-vivo in fallopian tube organoids. C_LI

cancer biology↗

bioRxiv2025

Receptor Tyrosine Kinase Profiling Identifies Chronic Constitutive Floodgate Oxidative Signaling in Glutathione-Independent Human Mammary Luminal Progenitor Cells

The human mammary epithelium contains a subset of luminal progenitor (LP) cells that are distinct from basal cells in both lineage potential and redox biology. LPs are uniquely equipped to tolerate oxidative stress through glutathione-independent mechanisms and have been implicated as candidate cells of origin in basal-like breast cancers. In this study, we identify the receptor tyrosine kinase (RTK) cKIT (CD117), as a defining feature of LPs and a key mediator of their expansion. cKIT is developmentally restricted to the LP compartment via Polycomb-mediated epigenetic repression in basal and luminal-committed cells. It is expressed in scattered epithelial cells within both ductal and alveolar regions of resting human mammary glands. Using RTK-engineered MCF10A models, we demonstrate that cKIT ligand/stem cell factor (SCF)-activated wildtype cKIT signaling is sufficient to drive proliferation in the absence of epidermal growth factor (EGF) and that cKIT is responsive not only to canonical ligands but also to hydrogen peroxide (H2O2). In primary human LPs, cKIT is rapidly phosphorylated upon exposure to SCF and H2O2, with concomitant AKT activation. These responses are enhanced when cKIT and EGFR signaling are co-engaged, suggesting a cooperative mitogenic program. In mammary gland, phosphorylation of the antioxidant enzyme PRDX1 is selectively detected in LPs, consistent with a floodgate model of redox signaling in which transient oxidative inactivation of peroxiredoxins (PRDXs) facilitates RTK signaling under elevated intracellular reactive oxygen species conditions. Clinically, elevated cKIT expression is associated with shorter progression-free survival in certain basal-like breast cancer, supporting a link between LP-like redox signaling states and aggressive tumor behavior. Together, these findings define a redox-integrated RTK signaling axis centered on cKIT that drives LP expansion and is associated with poor outcomes in a subset of basal breast cancers. This work establishes a mechanistic framework for targeting redox-responsive progenitor populations in both regenerative and oncologic context.

cancer biology↗

bioRxiv2025

Single cell resolution of an epigenetic signature of persister tumor cell

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-naive, and neoadjuvant chemotherapy (NACT)-treated high-grade serous ovarian cancer (HGSOC) samples. We identified differences in gene expression and open chromatin between naive 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.

genomics↗