Biology subjects

Volovetz, J.

Publications and source records attributed to Volovetz, J..

5 recordsLinked to original sources

bioRxiv2024

miR-644a is a tumor cell-intrinsic mediator of sex bias in glioblastoma

BackgroundBiological sex is an important risk factor for glioblastoma (GBM), with males having a higher incidence and poorer prognosis. The mechanisms for this sex bias are thought to be both tumor intrinsic and tumor extrinsic. MicroRNAs (miRNAs), key post-transcriptional regulators of gene expression, have been previously linked to sex differences in various cell types and diseases, but their role in the sex bias of GBM remains unknown. MethodsWe leveraged previously published paired miRNA and mRNA sequencing of 39 GBM patients (22 male, 17 female) to identify sex-biased miRNAs. We further interrogated a separate single-cell RNA sequencing dataset of 110 GBM patients to examine whether differences in miRNA target gene expression were tumor cell intrinsic or tumor cell extrinsic. Results were validated in a panel of patient-derived cell models. ResultsWe identified 10 sex-biased miRNAs (adjusted < 0.1), of which 3 were more highly expressed in males and 7 more highly expressed in females. Of these, miR-644a was higher in females, and increased expression of miR-644a target genes was significantly associated with decreased overall survival (HR 1.3, p = 0.02). Furthermore, analysis of an independent single-cell RNA sequencing dataset confirmed sex-specific expression of miR-644a target genes in tumor cells (p < 10-15). Among patient derived models, miR-644a was expressed a median of 4.8-fold higher in females compared to males. ConclusionsOur findings implicate miR-644a as a candidate tumor cell-intrinsic regulator of sex-biased gene expression in GBM. Key PointsO_LImiR-644a is more highly expressed in female GBM patients. C_LIO_LILower miR-644a target gene expression is associated with improved overall survival. C_LIO_LImiR-644a target genes are higher in male GBM cells but not in other cell types. C_LI Importance of the StudyMicroRNAs (miRNAs) are non-coding RNAs that regulate gene expression at the post-transcriptional level and were previously linked to glioblastoma (GBM) growth and therapeutic resistance. miRNAs play a role in the sex bias of various cell types and diseases, but how miRNAs contribute to sex differences in GBM is not well elucidated. We show that 10 miRNAs are differentially expressed between males and females and identify miR-644a as more highly expressed in female GBM patients. Using single-cell RNA-seq data, we demonstrate that sex differences in miR-644a target gene expression are tumor cell-intrinsic. Likewise, decreased miR-644a target gene expression is associated with improved overall patient survival. Our findings reveal miR-644a as a novel sex-biased miRNA in GBM, and a possible target for sex-specific precision therapies with limited collateral damage.

cancer biology↗

bioRxiv2023

Tumor cell-derived spermidine promotes a pro-tumorigenic immune microenvironment in glioblastoma via CD8+ T cell inhibition

The glioblastoma microenvironment is enriched in immunosuppressive factors that potently interfere with the function of cytotoxic T lymphocytes. Cancer cells can directly impact the immune system, but the mechanisms driving these interactions are not completely clear. Here we demonstrate that the polyamine metabolite spermidine is elevated in the glioblastoma tumor microenvironment. Exogenous administration of spermidine drives tumor aggressiveness in an immune-dependent manner in pre-clinical mouse models via reduction of CD8+ T cell frequency and phenotype. Knockdown of ornithine decarboxylase, the rate-limiting enzyme in spermidine synthesis, did not impact cancer cell growth in vitro but did result in extended survival. Furthermore, glioblastoma patients with a more favorable outcome had a significant reduction in spermidine compared to patients with a poor prognosis. Our results demonstrate that spermidine functions as a cancer cell-derived metabolite that drives tumor progression by reducing CD8+T cell number and function.

cancer biology↗

bioRxiv2021

SerpinB3 drives cancer stem cell survival in glioblastoma

Despite therapeutic interventions for glioblastoma (GBM), cancer stem cells (CSCs) drive recurrence. The precise mechanisms underlying CSC therapeutic resistance, namely inhibition of cell death, are unclear. We built on previous observations that the high cell surface expression of junctional adhesion molecule-A drives CSC maintenance and identified downstream signaling networks, including the cysteine protease inhibitor SerpinB3. Using genetic depletion approaches, we found that SerpinB3 is necessary for CSC maintenance, survival, and tumor growth, as well as CSC pathway activation. The knockdown of SerpinB3 also increased apoptosis and susceptibility to radiation therapy. Mechanistically, SerpinB3 was essential to buffer cathepsin L-mediated cell death, which was enhanced with radiation. Finally, we found that SerpinB3 knockdown dramatically increased the efficacy of radiation in pre-clinical models. Taken together, our findings identify a novel GBM CSC-specific survival mechanism involving a previously uninvestigated cysteine protease inhibitor, SerpinB3, and provide a potential target to improve the efficacy of standard-of-care GBM therapies against therapeutically resistant CSCs. SummaryLauko et al. demonstrate a functional role for SerpinB3, which is elevated in glioblastoma cancer stem cells and protects against lysosomal-mediated cell death. SerpinB3 can be targeted to increase the efficacy of radiation in glioblastoma pre-clinical models.

cancer biology↗

bioRxiv2019

Identifying conserved molecular targets required for cell migration of glioblastoma cancer stem cells

Glioblastoma (GBM) is the most prevalent primary malignant brain tumor and is associated with extensive tumor cell infiltration into the adjacent brain parenchyma. However, there are limited targeted therapies that address this disease hallmark. While the invasive capacity of self-renewing cancer stem cells (CSCs) and their non-CSC progeny has been investigated, the mode(s) of migration used by CSCs during invasion is currently unknown. Here we used time-lapse microscopy to evaluate the migratory behavior of CSCs, with a focus on identifying key regulators of migration. A head-to-head migration assay demonstrated that CSCs are more invasive than non-CSCs. Time-lapse live cell imaging further revealed that GBM patient-derived CSC models either migrate in a collective manner or in a single cell fashion. To uncover conserved molecular regulators responsible for collective cell invasion, we utilized the genetically tractable Drosophila border cell collective migration model. Candidates for functional studies were generated using results from a targeted Drosophila genetic screen followed by gene expression analysis of the human homologs in GBM tumors and associated GBM patient prognosis. This strategy identified the highly conserved small GTPase, Rap1a, as a potential regulator of cell invasion. Alteration of Rap1a activity impaired the forward progress of Drosophila border cells during development. Rap1a expression was elevated in GBM and associated with higher tumor grade. Functionally, the levels of activated Rap1a impacted CSC migration speed out of spheres onto extracellular matrix. The data presented here demonstrate that CSCs are more invasive than non-CSCs, are capable of both collective and single cell migration, and express conserved genes that are required for migration and invasion. Using this integrated approach, we identified a new role for Rap1a in the migration of GBM CSCs.

cancer biology↗

bioRxiv2018

Global immune fingerprinting in glioblastoma reveals immune-suppression signatures associated with prognosis

Abstract/SummaryGlioblastoma (GBM) remains uniformly lethal, and, despite a large accumulation of immune cells in the microenvironment, there is limited anti-tumor immune response, even with newly developed immune checkpoint therapies. To overcome these challenges and enhance the efficacy of immunotherapies, a comprehensive understanding of the immune system in GBM and changes during disease progression is required. Here, we integrated multi-parameter flow cytometry and mass cytometry time of flight (CyTOF) analysis of patient blood to determine changes in the immune system among tumor types and over disease progression. Utilizing multi-parameter flow cytometry analysis in a cohort of over 250 patients with brain tumors ranging from benign to malignant primary and metastatic, we found that GBM patients had a significant elevation in myeloid-derived suppressor cells (MDSCs) in blood, but not immunosuppressive T regulatory cells. We validated these findings in GBM patient tissue and found that increased numbers of MDSCs in recurrent GBM portended poor prognosis. CyTOF analysis of peripheral blood from a cohort of newly diagnosed GBM patients revealed that reduction in MDSC frequency over time is accompanied by a concomitant increase in dendritic cells and natural killer cells. This reduced MDSC profile was present in GBM patients with extended survival and was similar to that of low-grade glioma (LGG) patients. Our findings provide a rationale for developing strategies to target MDSCs, which are elevated in GBM patients and predict poor prognosis, either by directly targeting or by shifting the immune profile to induce differentiation toward the immune profile of LGGs.

cancer biology↗