Biology subjects

Burd, C. J.

Publications and source records attributed to Burd, C. J..

6 recordsLinked to original sources

bioRxiv2026

In utero Bisphenol A exposure developmentally reprograms mammary gland fibroblasts

In utero exposure to estrogens is known to increase breast cancer risk in adulthood. The plasticizer bisphenol A (BPA) increases tumor susceptibility in rodent models of in utero exposure, but the mechanism of this increase is unclear. Our lab has previously shown that in utero BPA exposure causes alterations to the tissue microenvironment that are conducive to tumor initiation. We thus sought to understand when these alterations arise and how they are regulated using bulk and single-nuclei epigenomics in adult mammary glands following in utero BPA exposure. Our results indicate that in utero BPA exposure causes developmental reprogramming of mammary fibroblasts that is initiated during puberty and persists into adulthood. Fibroblast-specific changes in chromatin accessibility were identified at enhancers and annotated to genes involved in fibroblast differentiation, suggesting that BPA may exert its effects by reprogramming fibroblast heterogeneity. Single-nuclei multiomics confirmed changes in fibroblast heterogeneity and uncovered estrogen signaling as a putative regulator of the fibroblast cell state that is altered by BPA exposure. Together, these studies support a model whereby BPA acts on mesenchymal ER to reprogram the chromatin landscape of mammary fibroblasts, leading to their altered differentiation.

molecular biology↗

bioRxiv2022

The OSUMMER lines: a series of ultraviolet-accelerated NRAS-mutant mouse melanoma cell lines syngeneic to C57BL/6

An increasing number of cancer subtypes are treated with front-line immunotherapy. However, approaches to overcome primary and acquired resistance remain limited. Pre-clinical mouse models are often used to investigate resistance mechanisms, novel drug combinations, and delivery methods; yet most of these models lack the genetic diversity and mutational patterns observed in human tumors. Here we describe a series of thirteen C57BL/6J melanoma cell lines to address this gap in the field. The Ohio State University-Moffitt Melanoma Exposed to Radiation (OSUMMER) cell lines are derived from mice expressing endogenous, melanocyte-specific, and clinically relevant Nras driver mutations (Q61R, Q61K, or Q61L). Exposure of these animals to a single, non-burning dose of ultraviolet B accelerates the onset of spontaneous melanomas with mutational patterns akin to human disease. Furthermore, in vivo irradiation selects against potent tumor antigens, which could prevent the outgrowth of syngeneic cell transfers. Each OSUMMER cell line possesses distinct in vitro growth properties, trametinib sensitivity, mutational signatures, and predicted antigenicity. Analysis of OSUMMER allografts shows a correlation between strong, predicted antigenicity and poor tumor outgrowth. These data suggest that the OSUMMER lines will be a valuable tool for modeling the heterogeneous responses of human melanomas to targeted and immune-based therapies. SIGNIFICANCENRAS-activating mutations are the second most common genetic driver event in cutaneous melanoma, occurring in 15% to 25% of cases. With few therapeutic options beyond immunotherapy, patients with NRAS-mutant melanoma have a poorer prognosis. Pre-clinical mouse models that mimic the high mutational burden of human NRAS-mutant melanomas are lacking in the field. Here, we describe a series of NRAS-mutant melanoma cell lines, derived from ultraviolet (UV)-induced, spontaneous tumors. These lines permit the study of targeted, NRAS mutant-specific, immune, and combination therapies in C57BL/6J mice. With the release of this resource, we hope to catalyze new therapeutic approaches for NRAS-mutant melanoma.

cancer biology↗

bioRxiv2021

Functional differences drive the selection of NRAS mutants in melanoma

Distinct NRAS mutants are enriched in various tumor types. Here, we generated a suite of fully congenic, conditional, Nras knock-in mouse models (LSL-Nras Q61R, -K, -L, -H, -P, -Q; G12D and G13D, -R) to test the hypothesis that melanocyte transformation requires functions specific to the NRAS mutants enriched in human melanoma (Q61R and Q61K). Consistent with the rarity of NRAS codon 12 and 13 mutants in human melanoma, spontaneous melanomas were rare or absent in mice expressing NRAS G12D, G13D or G13R. Mice expressing less common codon 61 alleles (Q61H, Q61P) also developed few or no tumors. NRAS Q61R, Q61K, or Q61L expression, by contrast, induced rapid melanoma onset with high penetrance. Cohorts of heterozygous mice containing one LSL-Nras Q61R and one LSL-Nras Q61K, -L, -H, -P, or -Q allele were generated to assess potential interactions between NRAS mutants. The ability of each Nras variant to substitute for an Nras Q61R allele was consistent with its own ability to drive spontaneous melanoma formation. However, LSL-Nras Q61Q/Q61R mice rarely developed tumors. In vitro experiments in mouse embryonic fibroblasts (MEFs) highlighted activation of the MAPK pathway as a defining difference between tumorigenic and non-tumorigenic NRAS mutants. Enhanced MAPK activation was associated with the promotion of BRAF-BRAF and BRAF-CRAF dimers. These results support the development of cancer preventative strategies specific to the properties of the commonly observed RAS mutants in each tumor type.

cancer biology↗

bioRxiv2019

UVA and UVB elicit distinct mutational signatures in melanoma

BRAF-mutant melanomas are more likely than NRAS-mutant melanomas to arise in anatomical locations protected from chronic sun damage. We hypothesized that this discrepancy in tumor location is a consequence of the differential sensitivity of BRAF and NRAS-mutant melanocytes to ultraviolet light (UV)-mediated carcinogenesis. We tested this hypothesis by comparing the mutagenic consequences of a single, narrow band ultraviolet-A (UVA; 320-400nm) or ultraviolet-B (UVB; 280-320nm) exposure in mouse models predisposed to Braf- or Nras-mutant melanoma. Exposures approximated the amount of UVA or UVB energy contained in ~40 minutes of summer sunlight. Tumor onset was accelerated in all UVB-, but only half of UVA- irradiated mice as compared to unirradiated controls. Melanomas from both mouse models, harbored recurrent mutations affecting the RING domain of MAP3K1 and Actin-binding domain of Filamin A irrespective of UV status. Melanomas from UVB-irradiated, Braf-mutant mice averaged twice as many SNVs (1,025 vs. 435) and five times as many dipyrimidine variants (33.3 vs. 5.7) than tumors from similarly irradiated Nras-mutant mice. We identified a mutational signature enriched in UVB-accelerated tumors which mirrored COSMIC signatures associated with human skin cancer. Notably, this signature was enriched to a greater extent in Braf- than Nras-mutant murine melanomas. These data suggest that oncogenic BRAF may enhance UVB carcinogenesis to promote melanoma formation at anatomic sites with low or intermittent sun exposure.

cancer biology↗

bioRxiv2019

In utero estrogenic endocrine disruption alters the stroma to increase extracellular matrix density and mammary gland stiffness.

In utero endocrine disruption is linked to increased risk of breast cancer later in life. Despite numerous studies establishing this linkage, the long-term molecular changes that predispose mammary cells to carcinogenic transformation are unknown. Several lines of evidence indicate the stroma mediates endocrine disruption following early-life (or in utero) exposure. Herein, we utilized BPA as a model of estrogenic endocrine disruption to analyze the long-term consequences in the stroma. Using RNA-seq transcriptional profiling of adult primary fibroblasts isolated from female mice exposed to BPA in utero, we identified deregulated genes associated with the extracellular matrix. Specifically, multiple collagen genes had increased expression in exposed mice. In line with the transcriptional data, collagen deposition is increased in adult BPA-exposed mice. We further demonstrate in vitro that fibroblasts exposed to BPA in utero remodel a collagen matrix, thereby decreasing permeability of the collagen matrix. These alterations to the mammary gland resulted in increased gland stiffness in the adult mice. Our data connects early life endocrine disruption to breast density. Interestingly, increased collagen deposition and gland stiffness were not observed in the developing glands of younger mice, suggesting risk factors for breast cancer continue to develop throughout life following these exposures. Finally, we assessed whether in utero exposure to two other endocrine disruptors, BPS and DES, also increase breast stiffness in adult mice. While DES increased breast stiffness, BPS did not, suggesting this BPA alternative may in fact pose less breast cancer risk than its predecessor. As breast stiffness, extracellular matrix density, and collagen deposition have been directly linked to breast cancer risk, these data mechanistically link endocrine disruptor exposures and molecular alterations to increased disease susceptibility in the gland.

cancer biology↗

bioRxiv2019

GREB1 regulates proliferation of estrogen receptor positive breast cancer through modulation of PI3K/Akt/mTOR signaling

Over 70% of breast cancers express the estrogen receptor (ER) and depend on ER activity for survival and proliferation. While hormone therapies that target receptor activity are initially effective, patients invariably develop resistance which is often associated with activation of the PI3K/Akt/mTOR pathway. While the mechanism by which estrogen regulates proliferation is not fully understood, one gene target of ER, growth regulation by estrogen in breast cancer 1 (GREB1), is required for hormone-dependent proliferation. However, the molecular function by which GREB1 regulates proliferation is unknown. Herein, we validate that knockdown of GREB1 results in growth arrest and that exogenous GREB1 expression initiates oncogene-induced senescence, suggesting that an optimal level of GREB1 expression is necessary for proliferation of breast cancer cells. Under both of these conditions, GREB1 is able to regulate signaling through the PI3K/Akt/mTOR pathway. GREB1 acts intrinsically through PI3K to regulate PIP3 levels and Akt activity. Critically, growth suppression of estrogen-dependent breast cancer cells by GREB1 knockdown is rescued by expression of constitutively activated Akt. Together, these data identify a novel molecular function by which GREB1 regulates breast cancer proliferation through Akt activation and provides a mechanistic link between estrogen signaling and the PI3K pathway.

cancer biology↗