Biology subjects

Ostrander, J. H.

Publications and source records attributed to Ostrander, J. H..

7 recordsLinked to original sources

bioRxiv2026

Advanced models of lobular breast cancer metastasis capture clinical organ tropism, endocrine response, and bone remodeling

Patients with invasive lobular carcinoma of the breast (ILC) are at high risk of long-term recurrence and metastatic progression with poor prognoses due to delayed detection and treatment-refractory disease. Unfortunately, few models are available to investigate metastatic ILC (mILC) and understand the unique metastatic patterns and phenotypes, including abdominal metastases, leptomeningeal disease, and mixed osteosclerotic/lytic bone metastases. Therefore, we expanded upon the previously established mammary intraductal (MIND) cell line xenograft model by supplementing mice with low-dose estradiol to promote disease progression. We observed spontaneous multi-organ spread from the mammary gland to common and mILC-specific tissues, with micro-metastatic disease as early as 12 weeks post-engraftment and macro-metastatic disease in 24-30 weeks, without the need for primary tumor resection. Primary and metastatic tumors remain highly endocrine responsive, allowing for the evaluation of novel therapeutics in the setting of disseminated metastasis. Derivative cell lines were isolated from various metastatic lesions, a total of 13 derivates from 7 sites across three hosts, and were found to have shared gene expression changes related to metabolism and intercellular signaling. Focusing on bone-derived variant cells as bone is the most common site for mILC to present, we found that bone-derived variant lines maintain multi-organ metastatic potential upon rechallenge by MIND or intratibial injection, despite increased aggressiveness and maintained endocrine response. Notably, bone lesions from either challenge route showed mixed osteosclerotic/lytic features characteristic to clinical ILC. Accordingly, we found that conditioned medium from ILC cells and the mILC bone-derived variants induce osteoblast differentiation and suppressed osteoclast differentiation in vitro, consistent with their effect on bone remodeling in vivo and in clinical disease. Together, the models developed herein can be utilized to understand the unique metastatic processes of mILC, and to investigate new therapeutic combinations in the setting of endocrine-responsive primary and metastatic ILC.

cancer biology↗

bioRxiv2025

Viral evolution of T1L mammalian orthoreovirus enhances breast cancer stem-like cell killing

BackgroundBreast cancer is the second leading cause of death in women in the US. Among the different subtypes of breast cancer, estrogen receptor positive (ER+) has a more favorable prognosis; however, patients can experience cancer recurrence 10 years or more after initial diagnosis. Breast cancer stem-like cells (BCSCs) are slowly proliferating cells that drive metastasis and resistance to therapies that target rapidly proliferating tumor cells. BCSC self-renewal and survival pathways make them difficult to eliminate; no selective therapeutics currently exist to target them. Our research aims to use mammalian orthoreovirus (MRV) as an oncolytic agent to eliminate BCSCs. MethodsWe evaluated the effects of three different MRV strains (T3D, T1L and R2) under both 2D and 3D culture conditions (which enrich for BCSCs) in parental and paclitaxel resistant (TaxR) MCF7 cells using cell viability assays, flow cytometry, western blotting, and tumorsphere assays. We identified differentially expressed genes in response to T1L by RNA sequencing. Novel MRV strains were developed by serial passaging of the parental T1L strain in TaxR BCSCs, leading to the isolation and sequencing of three distinct MRV clones. The novel MRV clones were assessed for their oncolytic effects using the aforementioned techniques alongside inhibitor-based studies targeting cell death pathways. ResultsNotably, at least two clones (T1L SP B and T1L SP C) demonstrated enhanced oncolytic potency compared to the parent T1L strain against MCF7 TaxR BCSCs, even though their infectivity and viral protein synthesis was reduced. Whole genome sequencing of the viral clones identified changes in viral protein sequences that correlate with enhanced potency against BCSCs. T1L, T1L SP B and T1L SP C induced apoptosis; however, T1L SP B may induce a more immunogenic form of cell death in the TaxR cells, as indicated by the increased release of extracellular ATP (eATP), a damage-associated molecular pattern (DAMP), which is associated with immunogenic cell death. ConclusionsIn summary, we developed novel oncolytic viruses promote oncolysis in therapy-resistant BCSCs. We found that T1L SP B induces apoptosis in a more immunogenic manner, highlighting the potential of these viruses to eliminate BCSCs and stimulate the immune system.

cancer biology↗

bioRxiv2025

Progesterone receptors drive advanced breast cancer phenotypes including circulating tumor- and stem-like cell expansion in the context of ESR1 mutation

Endocrine therapy resistance remains a major challenge in the treatment of advanced estrogen receptor positive (ER+) breast cancer. This can be driven by acquired mutations in the estrogen receptor gene (ESR1), such as Y537S or D538G, that primarily emerge in patients with prior aromatase inhibitor therapy and results in constitutive estrogen-independent ER activity. Progesterone receptors (PR) are important modifiers of ER activity, in part via direct binding. We previously showed that PR mediates expansion of cancer stem-like cell (CSC) populations and promotes tamoxifen resistance in nuclear ER/PR transcriptional complexes. In this study, we sought to define whether PR function changes in the context of ESR1 mutations. PR readily interacted with wild type (WT), but not Y537S or D538G ERs. RNA-seq and ChIP-seq studies demonstrated that ER+ breast cancer models expressing Y537S ER exhibited a distinct response to progesterone. CSC populations were enhanced in Y537S ER+ cells compared to WT ER+ cells. PR knockdown demonstrated that this property required PR expression but was unresponsive to antiprogestins. Moreover, we identified PR-dependent transcriptional programs such as the unfolded protein response (UPR) that can be leveraged to target CSC populations in Y537S ESR1-mutant breast cancer. The UPR activator ErSO, but not UPR inhibitors, blocked expansion of CSCs in WT as well as Y537S ER+ models. Together, our findings demonstrate a critical interplay between PR and mutant ER function and provide insight into PR-driven pathways including hyperactivation of the stress-sensing UPR that can be exploited as potential therapeutic avenues in advanced ER+ breast cancer.

cancer biology↗

bioRxiv2025

CDH1 loss remodels gene expression and lineage identity in human mammary epithelial cells

Invasive lobular carcinoma (ILC) is a common subtype of breast cancer, molecularly defined by genetic loss of CDH1, and subsequent loss of cell adhesion protein E-cadherin, in [~]95% of ILC. Though CDH1 loss occurs early in ILC oncogenesis, it is unclear how this facilitates transformation. We modeled early CDH1 loss using "normal" human mammary epithelial cells (HMEC), i.e. finite lifespan cells reflecting early hyperplasia, and targeted E-cadherin signaling using antibodies versus causing genetic CDH1 loss using siRNA or CRISPR/Cas9-knockout. Transcriptome analysis across four HMEC models showed that the mode of E-cadherin targeting is critical for the subsequent phenotype. Antibody-mediated inhibition of cell-cell contacts induced gene signatures of epithelial-mesenchymal transition (EMT), consistent with the role of E-cadherin suppression during the EMT process. Conversely, genetic CDH1 loss - as in ILC oncogenesis - repressed EMT signatures, and instead remodeled gene expression toward a luminal epithelial phenotype. RNA-seq, single cell transcriptomics, flow cytometry, microscopy, and ATACseq analyses support that CDH1 loss induces lineage remodeling to a luminal state, which is mirrored in transcriptomic analysis of clinical ILC precursor lesions. By isolating luminal versus basal cells prior to CDH1 knockout, we found that CDH1 loss led to remodeling of lineage identity in both populations, converging on a new lineage homeostasis with a luminal progenitor-like phenotype. Consistent with the shift to a luminal progenitor phenotype, CDH1 loss enhanced proliferative capacity over the finite lifespan of the HMECs, highlighting a feature of early CDH1 loss that may contribute to clonal advantage during tumor initiation. Moreover, CDH1 loss enhanced anoikis resistance, a defining feature of ILC cells. Our findings support that genetic loss of CDH1 in mammary epithelial cells induces transcriptional and phenotypic changes consistent with lineage identity remodeling toward a luminal progenitor-like state, which may underpin the mechanism by which early CDH1 loss mediates ILC oncogenesis.

cancer biology↗

bioRxiv2025

Isoform-Specific Gene Regulation by Progesterone Receptors Drives Divergent Phenotypes in Breast Cancer Cells

Exposure to progesterone is a recognized risk factor for breast cancer, and PGR polymorphisms are associated with various malignancies. Two progesterone receptor (PR) isoforms, full length PR-B and truncated PR-A, are expressed from the PGR gene in breast tissue and play crucial roles in normal physiology and breast cancer progression. An imbalance in the expression ratio of these isoforms, favoring increased levels of PR-A, is common in breast cancer and is associated with resistance to tamoxifen in luminal A-type tumors. Notably, PRs have recently been implicated in promoting endocrine resistance and driving the expansion of cancer stem-like cell (CSC) populations. Despite this insight, the isoform-specific molecular and epigenetic mechanisms underlying PR action in estrogen receptor positive (ER+) breast cancers remain understudied. Phenotypic studies of T47D cell lines that express exclusively PR-A or PR-B showed that PR isoforms regulate divergent cell fates. PR-B-expressing cells have a higher proliferation rate, while PR-A-expressing cells produce more mammospheres. We profiled progesterone-driven gene expression in cells grown in both adherent (2D) and mammosphere (3D) growth conditions and found differential gene regulation by PR-A and PR-B that is consistent with the observed divergent phenotypes. Only the PR-A-driven gene signature of ER+ breast cancer cells maintained as non-adherent mammospheres robustly predicted poor clinical outcome in the METABRIC data set. We then performed CUT&RUN to identify the genomic binding patterns unique to each PR isoform and their suite of target genes. Our findings indicate that PR-A acts as a regulator of the cell cycle, while PR-B plays a pivotal role in metabolism and intracellular signaling. Our genomic profiling of PRs in this model system has unveiled novel isoform-specific functions of PR. This work has shifted our prior understanding of the role of PRs in gene regulation, offering potential insights for therapeutic interventions in ER+ breast cancer.

cancer biology↗

bioRxiv2024

Neutrophils exposed to a cholesterol metabolite secrete extracellular vesicles that promote epithelial-mesenchymal transition and stemness in breast cancer cells.

Small extracellular vesicles (sEVs) are emerging as critical mediators of intercellular communication in the tumor microenvironment (TME). Here, we investigate the mechanisms by which sEVs derived from neutrophils treated with the cholesterol metabolite, 27-hydroxycholesterol (27HC), influence breast cancer progression. sEVs released from 27HC treated neutrophils enhance epithelial-mesenchymal transition (EMT) and stem-like properties in breast cancer cells, resulting in loss of adherence, increased migratory capacity and resistance to cytotoxic chemotherapy. Decreased microRNAs (miRs) within the sEVs resulted in activation of the WNT/{beta}-catenin signaling pathway in recipient cells and suggest that this may be a predominant pathway for stem-like phenotype and EMT. Our findings underscore a novel mechanism by which 27HC-modulated neutrophils contribute to breast cancer pathophysiology through EV-mediated intercellular communication, suggesting potential therapeutic targets in cancer treatment.

cancer biology↗

bioRxiv2020

PELP1/SRC-3-dependent regulation of metabolic kinases drives therapy resistant ER+ breast cancer

Recurrence of metastatic breast cancer stemming from acquired endocrine and chemotherapy resistance remains a health burden for women with luminal (ER+) breast cancer. Disseminated ER+ tumor cells can remain viable but quiescent for years to decades. Contributing factors to metastatic spread include the maintenance and expansion of breast cancer stem cells (CSCs). Breast CSCs frequently exist as a minority population in therapy resistant tumors. In this study, we show that cytoplasmic complexes composed of steroid receptor (SR) co-activators, PELP1 and SRC-3, modulate breast CSC expansion through upregulation of the HIF-activated metabolic target genes PFKFB3 and PFKFB4. Seahorse metabolic assays demonstrated that cytoplasmic PELP1 influences cellular metabolism by increasing both glycolysis and mitochondrial respiration. PELP1 interacts with PFKFB3 and PFKFB4 proteins, and inhibition of PFKFB3 and PFKFB4 kinase activity blocks PELP1-induced tumorspheres and protein-protein interactions with SRC-3. PFKFB4 knockdown inhibited in vivo emergence of circulating tumor cell (CTC) populations in mammary intraductal (MIND) models. Application of PFKFB inhibitors in combination with ER targeted therapies blocked tumorsphere formation in multiple models of advanced breast cancer, including tamoxifen (TamR) and paclitaxel (TaxR) resistant models and ER+ patient-derived organoids (PDxO). Together, our data suggest that PELP1, SRC-3, and PFKFBs cooperate to drive ER+ tumor cell populations that include CSCs and CTCs. SignificanceIdentifying non-ER pharmacological targets offers a useful approach to blocking metastatic escape from standard of care ER/estrogen (E2)-targeted strategies to overcome endocrine and chemotherapy resistance.

cancer biology↗