Biology subjects

Lazar, A. J.

Publications and source records attributed to Lazar, A. J..

11 recordsLinked to original sources

bioRxiv2026

Cross-species Study of Canine and Human Peripheral Nerve Sheath Tumors: Clinical and Molecular Perspectives

Malignant peripheral nerve sheath tumors (MPNSTs) are aggressive sarcomas. An obstacle to treating MPNSTs is a lack of effective systemic therapies. Although over 70% of human MPNSTs have lost or inactivated the epigenome regulator polycomb repressive complex 2 (PRC2), its activity and contribution to canine PNST progression remain unclear. This study compared canine peripheral nerve sheath tumors (PNSTs) and human MPNSTs across biological and clinical features, including PRC2 activity. Immunohistochemical analysis was performed for a human tissue microarray of 54 neurofibromas and 139 MPNSTs, and 63 canine PNSTs for H3K27me3, a repressive histone mark deposited by intact PRC2, and H3K27ac, which increases globally upon H3K27me3 loss. To understand the genomic alterations present in canine PNSTs, we analyzed tumor mutation burden, copy number alteration, and transcriptomes of eight canine PNST/normal pairs. The results suggested that H3K27me3 loss and associated gain of H3K27ac epigenetically drive human and canine tumors. These findings warrant further studies to evaluate whether these epigenetic deregulations alter similar gene signatures across species.

cancer biology↗

bioRxiv2026

Spatially-Resolved Multiomic Atlas of Leiomyosarcoma Identifies Two Clinically Relevant Epigenetically-Driven Cell States

Leiomyosarcoma is a smooth muscle-derived malignancy marked by significant clinical heterogeneity. The extent and nature of cellular heterogeneity and molecular underpinnings remain poorly understood. To address this at transcriptomic and epigenomic levels, we performed single-nucleus multiome sequencing on untreated primary leiomyosarcoma tissues. Malignant cells segregated almost exclusively into two previously unrecognized and epigenetically distinct states: a dedifferentiated, mesenchymal-like subtype (MES) and a differentiated smooth muscle-enriched subtype (SMC). Chromatin accessibility profiling revealed strong enrichment of nuclear factor I (NFI) transcription factor motifs in MES cells, whereas AP-1 family motifs--most prominently FOSL2--were selectively accessible in SMC cells. Established leiomyosarcoma cell lines faithfully recapitulated these subtypes, and targeted depletion of NFI or AP-1 factors suppressed proliferation, invasion, and in vivo tumor growth, demonstrating functional dependency on these transcriptional programs. Spatial transcriptomics across 328 tissue cores from 128 leiomyosarcomas showed that immunosuppressive macrophages preferentially cluster around MES regions, revealing a subtype-specific tumor-immune niche. Clinically, MES-dominant tumors were associated with significantly worse patient outcomes. Through an epigenetic inhibitor screen, we identify and validate SMARCA4/2 inhibition as a promising therapeutic vulnerability for MES leiomyosarcomas. Together, this work defines two epigenetically driven, transcription factor-regulated, and clinically relevant states of leiomyosarcoma, revealing mechanistic underpinnings of tumor heterogeneity and uncovering actionable therapeutic strategies. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=93 HEIGHT=200 SRC="FIGDIR/small/726988v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@132928eorg.highwire.dtl.DTLVardef@133e3b7org.highwire.dtl.DTLVardef@1ab4398org.highwire.dtl.DTLVardef@e2de25_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2026

Spatially-resolved single cell atlas of liposarcoma reveals lineage hierarchies, immune niches, and regulatory circuits

Well-differentiated and dedifferentiated liposarcoma (WDLPS and DDLPS) exhibit markedly different clinical behaviors, with DDLPS showing greater aggressiveness, higher recurrence and metastasis rates, and worse outcomes. Using single-nucleus multiome sequencing, epigenomic profiling, and spatial transcriptomics, we characterized cellular and epigenetic heterogeneity between these subtypes at single-cell and spatial resolution. We found distinct phenotypic states reflecting altered lineage differentiation and plasticity: DDLPS is dominated by early-differentiated progenitor-like cells, sclerotic WDLPS displays broader mesenchymal lineage plasticity, and adipocytic WDLPS contains abundant committed adipocytes. The DDLPS immune microenvironment was dominated by immunosuppressive macrophages, whereas WDLPS harbored more T cells and inflammatory macrophages. Notably, sclerotic WDLPS displayed intermediate cellular and molecular features, suggesting it may represent a distinct WDLPS subtype. Importantly, we identified novel gene regulatory circuits underlying each state, including FABP4/PPARG programs in adipocytic WDLPS, GLI2/TCF7L2/RBPJ/KLF7 programs in sclerotic WDLPS, and KLF7/FOSL2/SP3/GLI2/RBPJ programs in DDLPS. H3K27ac-marked enhancers were enriched near adipocytic marker genes in WDLPS and mesenchymal markers in DDLPS. Together, these findings reveal the cellular heterogeneity of tumor and immune compartments across liposarcoma subtypes and identify regulatory programs driving their differentiation states. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/713651v1_ufig1.gif" ALT="Figure 1"> View larger version (73K): org.highwire.dtl.DTLVardef@1c84ee1org.highwire.dtl.DTLVardef@1b2ad42org.highwire.dtl.DTLVardef@18ce5a6org.highwire.dtl.DTLVardef@138f615_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

ATRX Loss Predicts Poor Outcomes and Reveals a Therapeutic Vulnerability to TEAD Inhibition in Soft Tissue Sarcomas

ATRX is one of the most frequently altered genes in sarcoma and encodes an ATP-dependent chromatin remodeler implicated in maintaining heterochromatin. However, ATRX alterations have not been leveraged for sarcoma treatment. We observed loss of ATRX protein in 14% of soft tissue leiomyosarcoma (STLMS, n =127), 53% of uterine leiomyosarcoma (ULMS, n = 95), 37% of undifferentiated pleomorphic sarcoma (UPS, n = 82), and 8% of dedifferentiated liposarcoma (DDLPS, n = 84). ATRX loss was associated with significantly worse outcomes in ULMS, UPS, and DDLPS. ATRX knockout in sarcoma cells increased proliferation in cooperation with TP53 deletion. ATRX knockout led to chromatin de-repression and enrichment of PRDM4 and NFIX transcription factor (TF) motifs. PRDM4 and NFIX knockdown in ATRX-mutant sarcoma lines resulted in reduced proliferation and invasion suggesting epistatic relationship. Consistent with the known functional relationship between PRMD4 and YAP1, we observed that ATRX/TP53 KO cells were more sensitive to the TEAD inhibitor VT103 compared to TP53 KO and ATRX WT controls. Overall, our results identify ATRX loss as a prognostic factor of worse outcomes, implicate the ATRX-PRDM4-YAP1 axis as a novel underlying mechanism, and suggest use of TEAD inhibition as a potential therapeutic strategy for ATRX-deficient sarcomas. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=45 SRC="FIGDIR/small/689992v1_ufig1.gif" ALT="Figure 1"> View larger version (13K): org.highwire.dtl.DTLVardef@a759ecorg.highwire.dtl.DTLVardef@100c580org.highwire.dtl.DTLVardef@1a675c9org.highwire.dtl.DTLVardef@17f1f91_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2025

Oxidative Phosphorylation (OXPHOS) Promotes the Formation and Growth of Melanoma Lung and Brain Metastases

Melanoma mortality is driven by the formation and growth of distant metastases. Here, we interrogated the role of tumor oxidative phosphorylation (OXPHOS) in the formation of distant metastases in melanoma. OXPHOS was the most upregulated metabolic pathway in primary tumors that formed distant metastases in the RCAS-TVA mouse model of spontaneous lung and brain metastases, and in melanoma patients that developed brain or other distant metastases. Knockout of PGC1 in melanocytes in the RCAS-TVA melanoma mouse model had no impact on primary tumor formation, but markedly reduced the incidence of lung and brain metastases. Genetic knockout of a component of electron transport chain complex I, NDUFS4, in B16-F10 and D4M-UV2 murine melanoma cell lines did not impact tumor incidence following subcutaneous, intravenous, or intracranial injection, but decreased tumor burden specifically in the lungs and brain. Together, these data demonstrate that OXPHOS is critical for the formation of metastases in melanoma. STRUCTURED ABSTRACTO_ST_ABSPurposeC_ST_ABSMelanoma mortality is driven by the formation and growth of distant metastases. However, the process and pathogenesis of melanoma metastasis remain poorly understood. Here, we interrogate the role of tumor oxidative phosphorylation (OXPHOS) in the formation of distant metastases in melanoma. Experimental DesignThis study includes (1) new RNA-seq analysis of primary melanomas from patients characterized for distant metastasis events; (2) RNA-seq analysis and functional testing of genetic OXPHOS inhibition (PGC1 KO) the RCAS-TVA model, which is the only existing immunocompetent murine model of autochthonous lung and brain metastasis formation from primary melanoma tumors; and (3) functional experiments of genetic OXPHOS inhibition (NDUFS4 KO) in the B16-F10 and D4M-UV2 murine melanoma cell lines, including evaluation of subcutaneous, lung, and brain metastatic site dependencies. ResultsOXPHOS was the most upregulated metabolic pathway in primary tumors that formed distant metastases in the RCAS-TVA mouse model of spontaneous lung and brain metastases, and in melanoma patients that developed brain or other distant metastases. Knockout of PGC1a in melanocytes in the RCAS-TVA melanoma mouse model had no impact on primary tumor formation, but markedly reduced the incidence of lung and brain metastases. Genetic knockout of a component of electron transport chain complex I, NDUFS4, in B16-F10 and D4M-UV2 murine melanoma cell lines did not impact tumor incidence following subcutaneous, intravenous, or intracranial injection, but decreased tumor burden specifically in the lungs and brain. ConclusionsTogether, these data demonstrate that OXPHOS is critical for the formation of metastases in melanoma. TRANSLATIONAL RELEVANCEMelanoma is the most aggressive form of skin cancer. One hallmark of this disease is a high risk of distant metastasis formation. The process and pathogenesis of metastasis in this disease remain poorly understood and there is controversy regarding the role of oxidative phosphorylation (OXPHOS) in melanoma metastasis. This study incorporates RNAseq analysis of primary melanoma tumors from patients characterized for distant metastasis events, RNAseq analysis of the only existing immunocompetent murine model of autochthonous lung and brain metastasis formation from primary melanoma tumors, and functional testing in multiple syngeneic models of melanoma at different tissue sites. This integrated analysis consistently demonstrates that melanoma OXPHOS promotes distant metastasis to the lungs and brain, two of the most common and clinically relevant sites of melanoma metastasis. This improved understanding of tumor OXPHOS may represent novel vulnerabilities for therapeutics development and surveillance/preventative strategies for melanoma metastasis.

cancer biology↗

bioRxiv2023

ASPSCR1-TFE3 reprograms transcription by organizing enhancer loops around hexameric VCP/p97

The t(X,17) chromosomal translocation, generating the ASPSCR1-TFE3 fusion oncoprotein, is the singular genetic driver of alveolar soft part sarcoma (ASPS) and some Xp11-rearranged renal cell carcinomas (RCC), frustrating efforts to identify therapeutic targets for these rare cancers. Proteomic analysis showed that VCP/p97, an AAA+ ATPase with known segregase function, was strongly enriched in co-immunoprecipitated nuclear complexes with ASPSCR1-TFE3. We demonstrate that VCP is a likely obligate co-factor of ASPSCR1-TFE3, one of the only such fusion oncoprotein co-factors identified in cancer biology. Specifically, VCP co-distributed with ASPSCR1-TFE3 across chromatin in association with enhancers genome-wide. VCP presence, its hexameric assembly, and its enzymatic function orchestrated the oncogenic transcriptional signature of ASPSCR1-TFE3, by facilitating assembly of higher-order chromatin conformation structures as demonstrated by HiChIP. Finally, ASPSCR1-TFE3 and VCP demonstrated co-dependence for cancer cell proliferation and tumorigenesis in vitro and in ASPS and RCC mouse models, underscoring VCPs potential as a novel therapeutic target.

cancer biology↗

bioRxiv2022

The Androgen Receptor: A Therapeutic Target in Desmoplastic Small Round Cell Sarcoma

Desmoplastic small round cell tumor (DSRCT) is an aggressive, usually incurable sarcoma subtype that predominantly occurs in post-pubertal young males. Recent evidence suggests that the androgen receptor (AR) can promote tumor progression in DSRCTs. However, the mechanism of AR-induced oncogenic stimulation remains undetermined. Herein, we demonstrate that enzalutamide and AR-directed antisense oligonucleotides (AR-ASO) block 5-dihydrotestosterone (DHT)-induced DSRCT cell proliferation and reduce xenograft tumor burden. Gene expression analysis and chromatin immunoprecipitation sequencing (ChIP-seq) were performed to elucidate how AR signaling regulates cellular epigenetic programs. Remarkably, ChIP-seq revealed novel DSRCT-specific AR DNA binding sites adjacent to key oncogenic regulators, including WT1 (the C-terminal partner of the pathognomonic fusion protein) and FOXF1. Additionally, AR occupied enhancer sites that regulate the Wnt pathway, neural differentiation, and embryonic organ development, implicating AR in dysfunctional cell lineage commitment. Our findings have immediate clinical implications given the widespread availability of FDA-approved androgen-targeted agents used for prostate cancer. ONE SENTENCE SUMMARYWe demonstrate that DSRCT, an aggressive pediatric cancer, is an AR-driven malignancy capable of responding to androgen deprivation therapy.

cancer biology↗

bioRxiv2022

Dissociation protocols used for sarcoma tissues bias the transcriptome observed in single-cell and single-nucleus RNA sequencing

BackgroundSingle-cell RNA-seq has emerged as an innovative technology used to study complex tissues and characterize cell types, states, and lineages at a single-cell level. Classification of bulk tumors by their individual cellular constituents has also created new opportunities to generate single-cell atlases for many organs, cancers, and developmental models. Despite the tremendous promise of this technology, recent evidence studying epithelial tissues and diverse carcinomas suggests the methods used for tissue processing, cell disaggregation, and preservation can significantly bias gene expression and alter the observed cell types. To determine whether sarcomas - tumors of mesenchymal origin - are subject to the same technical artifacts, we profiled patient-derived tumor explants (PDXs) propagated from three aggressive subtypes: osteosarcoma, Ewing sarcoma (ES), desmoplastic small round cell tumor (DSRCT). Given the rarity of these sarcoma subtypes, we explored whether single-nuclei RNA-seq from more widely available archival frozen specimens could accurately be identified by gene expression signatures linked to tissue phenotype or pathognomonic fusion proteins. ResultsWe systematically assessed dissociation methods across different sarcoma subtypes. We compared gene expression from single-cell and single-nucleus RNA-sequencing of 125,831 whole-cells and nuclei from ES, DSRCT, and osteosarcoma PDXs. We detected warm dissociation artifacts in single-cell samples and gene length bias in single-nucleus samples. Classic sarcoma gene signatures were observed regardless of dissociation method. In addition, we showed that dissociation method biases can be computationally corrected. ConclusionsWe highlighted transcriptional biases, including warm dissociation and gene-length biases, introduced by the dissociation method for various sarcoma subtypes. This work is the first to characterize how the dissociation methods used for sc/snRNA-seq may affect the interpretation of the molecular features in sarcoma PDXs.

cancer biology↗

bioRxiv2021

New cellular models of undifferentiated pleomorphic sarcoma and malignant peripheral nerve sheath tumor

Undifferentiated pleomorphic sarcoma (UPS) and malignant peripheral nerve sheath tumor (MPNST) are aggressive soft tissue sarcomas that do not respond well to current treatment modalities. The limited availability of UPS and MPNST cell lines makes it challenging to identify potential therapeutic targets in a laboratory setting. Understanding the urgent need for improved treatments for these tumors and the limited cellular models led us to generate additional cell lines to study these rare cancers further. Patient-derived tumors were used to establish 5 new UPS models, including one radiation-associated UPS--UPS060.1, UPS271.1, UPS511, UPS0103, and RIS620--and 3 new models of MPNST--MPNST007, MPNST3813E, and MPNST4970. This study examined the utility of the new cell lines as sarcoma models by assessing tumorigenic potential and mutation status for known sarcoma-related genes. All the cell lines formed colonies and migrated in vitro. The in vivo tumorigenic potential of each cell line was determined by either subcutaneous injection of cells or implantation of tumor tissue into immunocompromised mice. UPS060.1, UPS271.1, and UPS511 cells formed tumors in mice upon subcutaneous injection. UPS0103 and RIS620 tumor implants formed tumors in vivo, as did MPNST007 and MPNST3813E tumor implants. Mutation analysis of a panel of genes frequently mutated in sarcomas showed that two of the three MPNST cell lines had NF1 mutations. Two of the three MPNST cell lines had mutations in polycomb repressive complex 2 members. These new cellular models provide the scientific community with powerful tools for detailed studies of sarcomagenesis and investigate novel therapies for UPS and MPNST.

cancer biology↗

bioRxiv2019

Cell-of-Origin Analysis of Metastatic Gastric Cancer Uncovers the Origin of Inherent Intratumor Heterogeneity and a Fundamental Prognostic Signature

Intra-tumoral heterogeneity (ITH) is the fundamental property of cancer, however, the origin of ITH remains poorly understood. Here we performed single-cell RNA sequencing of peritoneal carcinomatosis (PC) from 20 patients with advanced gastric adenocarcinoma (GAC), constructed a transcriptome map of 45,048 PC cells, determined the cell-of-origin of each tumor cell, and incisively explored ITH of PC tumor cells at single-cell resolution. The links between cell-of-origin and ITH was illustrated at transcriptomic, genotypic, molecular, and phenotypic levels. This study characterized the origins of PC tumor cells that populate and thrive in the peritoneal cavity, uncovered the diversity in tumor cell-of-origins and defined it as a key determinant of ITH. Furthermore, cell-of-origin-based analysis classified PC into two cellular subtypes that were prognostic independent of clinical variables, and a 12-gene prognostic signature was then derived and validated in multiple large-scale GAC cohorts. The prognostic signature appears fundamental to GAC carcinogenesis/progression and could be practical for patient stratification.

cancer biology↗

bioRxiv2019

Bivalent and Broad Chromatin Domains Regulate Pro-metastatic Drivers in Melanoma

Chromatin deregulation is an emerging hallmark of cancer. However, the extent of epigenetic aberrations during tumorigenesis and their relationship with genetic aberrations are poorly understood. Using ChIP-sequencing for enhancers (H3K27ac and H3K4me1), promoters (H3K4me3), active transcription (H3K79me2) and polycomb (H3K27me3) or heterochromatin (H3K9me3) repression we generated chromatin state profiles in metastatic melanoma using 46 tumor samples and cell lines. We identified a strong association of NRAS, but not BRAF mutations, with bivalent states harboring H3K4me3 and H3K27me3 marks. Importantly, the loss and gain of bivalent states occurred on important pro-metastasis regulators including master transcription factor drivers of mesenchymal phenotype including ZEB1, TWIST1, SNAI1 and CDH1. Unexpectedly, a subset of these and additional pro-metastatic drivers (e.g. POU3F2, SOX9 and PDGFRA) as well as melanocyte-specific master regulators (e.g. MITF, ZEB2, and TFAP2A) were regulated by exceptionally wide H3K4me3 domains that can span tens of thousands of kilobases suggesting roles of this new epigenetic element in melanoma metastasis. Overall, we find that BRAF, NRAS and WT melanomas may use bivalent states and broad H3K4me3 domains in a specific manner to regulate pro-metastatic drivers. We propose that specific epigenetic traits - such as bivalent and broad domains - get assimilated in the epigenome of pro-metastatic clones to drive evolution of cancer cells to metastasis.

cancer biology↗