Biology subjects

Gramolelli, S.

Publications and source records attributed to Gramolelli, S..

5 recordsLinked to original sources

bioRxiv2026

Extracellular vesicles from antigen-activated B cells stimulate oncogenic herpesvirus lytic gene expression

B cell-derived extracellular vesicles (B-EVs) have been associated with immunomodulatory functions like antigen presentation, cytokine signaling, and T cell activation. However, little is known about the general composition of B-EVs or how the state of the donor cells affects the B-EV composition or functions. We performed integrated proteomic, lipidomic, and transcriptomic analyses of EVs secreted by B cells in resting conditions or upon 30 min of B cell receptor (BCR) activation. Antigen-driven BCR stimulation led to acute remodeling of the protein and lipid composition, and RNA cargo of the B-EVs, which also translated into differential responses in recipient B cells. Remarkably, EVs from activated B cells stimulated lytic gene expression of latent oncogenic {gamma}-herpesviruses Epstein-Barr virus (EBV) and Kaposi sarcoma-associated herpesvirus (KSHV). These findings suggest a novel mechanism for the potentially oncogenic reactivation of these lifelong-persisting latent herpesviruses, residing in B cells. Our results support a mechanism in which, upon immune activation, B-EVs from antigen-specific B cells induce viral reactivation in bystander B cells in a paracrine manner, providing molecular insights that bridge immune activation and the pathogenesis of {gamma}-herpesvirus infections.

immunology↗

bioRxiv2024

Heat shock factor 2 positively regulates oncogenic herpesvirus gene expression by remodeling the chromatin landscape

Human gamma-herpesviruses, Kaposis sarcoma herpesvirus (KSHV) and Epstein-Barr virus (EBV) are causally associated to a wide range of cancers. While the default infection program for these viruses is latent, sporadic lytic reactivation supports virus dissemination and oncogenesis. Despite its relevance, the repertoire of host factors governing the transition from latent to lytic phase is not yet complete, leaving much of this complex process unresolved. Here, we show that heat shock factor 2 (HSF2), a transcription factor involved in regulation of acute stress responses and specific cell differentiation processes, promotes gamma-herpesvirus lytic gene expression. In lymphatic endothelial cells infected with KSHV and gastric cancer cells positive for EBV, ectopic HSF2 enhances the expression of lytic genes, while knocking down HSF2 significantly decreases their expression. Mechanistically, HSF2 overexpression results in decreased levels of repressive chromatin histone marks, at the promoters of the master regulators of the oncogenic lytic cascade, KSHV ORF50 and EBV BZLF1. Our results demonstrate that endogenous HSF2 binds to the ORF50 promoter in latent cells and sustains a transcriptionally permissive state. In contrast, in lytic cells, HSF2 occupancy at the ORF50 promoter is lost in conjunction with its proteasomal degradation. These findings establish HSF2 as a conserved regulator of gamma-herpesvirus lytic gene expression in latency and offer new functional insights on the cellular role of HSF2 at target promoters.

microbiology↗

bioRxiv2024

Dynamic HSF2 regulation drives breast cancer progression by steering the balance between proliferation and invasion

Phenotypic plasticity is a hallmark of breast carcinogenesis that facilitates the acquisition of invasive properties via epithelial-mesenchymal transition (EMT). Transforming growth factor-beta (TGF-{beta}), a key EMT-inducing cytokine, drives pro-metastatic gene programs through downstream transcription factors. Among mammalian stress-protective transcription factors, heat shock factor 2 (HSF2) has been associated with cancer progression, but the mechanisms regulating HSF2 expression and activity are unknown. Here, we demonstrate that TGF-{beta} stimulation downregulates HSF2 to enable activation of an invasive phenotype. Remarkably, ectopic expression of HSF2 in breast cancer cells inhibited TGF-{beta}-mediated effects on gene expression and cellular properties. By using both in vitro cell models and in vivo zebrafish xenografts, we found that a temporal downregulation of HSF2 is a prerequisite for EMT activation, while ectopically sustained HSF2 promotes rapid cell proliferation and survival. Analyses of human patient tissues corroborated our results by showing that HSF2 is dynamically regulated during breast cancer progression. Specifically, HSF2 expression and nuclear co-localization with the proliferation marker Ki67 are dramatically increased already in ductal carcinoma in situ. Altogether, our findings expand the pathological landscape of HSF2, demonstrating that dynamic regulation of HSF2 is an inherent property of malignant progression and characterizes the distinct stages of breast cancer.

cell biology↗

bioRxiv2023

DLL4-Notch3-WNT5B axis is a novel mediator of bi-directional pro-metastatic crosstalk between melanoma and lymphatic endothelial cells

Despite strong indications that melanoma interaction with lymphatic vessels actively promotes melanoma progression, the molecular mechanisms are not yet completely understood. To characterize molecular factors of this crosstalk we established human primary lymphatic endothelial cell (LEC) co-cultures with human melanoma cell lines. Here, we show that co-culture with melanoma cells induced transcriptomic changes in LECs and led to multiple alterations in their function. WNT5B, a paracrine signaling molecule upregulated in melanoma cells upon LEC interaction, was found contributing to the functional changes in LECs. Moreover, WNT5B transcription was regulated by Notch3 in melanoma cells following the co-culture with LECs, and Notch3 and WNT5B were co-expressed in melanoma patient primary tumor and metastasis samples. Moreover, melanoma cells derived from LEC co-culture escaped efficiently from the primary site to the proximal tumor draining lymph nodes, which was impaired upon WNT5B depletion. This supports the role of WNT5B in promoting the metastatic potential of melanoma cells through its effects on LECs. Finally, DLL4, a Notch ligand expressed in LECs, was identified as an upstream inducer of the Notch3-WNT5B axis in melanoma. This study elucidates WNT5B as a novel molecular factor mediating bi-directional crosstalk between melanoma cells and lymphatic endothelium and promoting melanoma metastasis.

cancer biology↗

bioRxiv2019

Oncogenic herpesvirus engages the endothelial transcription factors SOX18 and PROX1 to increase viral genome copies and virus production

Kaposi sarcoma (KS) is a tumour of endothelial origin caused by KS herpesvirus (KSHV) infection and suggested to originate from lymphatic endothelial cells (LECs). While KSHV establishes latency in virtually all susceptible cell types, LECs support a spontaneous lytic gene expression program with high viral genome copies and release of infectious virus. Here, we investigated the role of PROX1, SOX18 and COUPTF2, drivers of lymphatic endothelial fate during embryogenesis, in this unique KSHV infection program. We found that these factors were co-expressed in KS tumours with the viral lytic marker K8.1, and that SOX18 and PROX1 regulate KSHV infection via two independent mechanisms. SOX18 binds to the viral origins of replication and its depletion or chemical inhibition significantly reduced the KSHV genome copies in LECs. PROX1 interacts with ORF50, the initiator of the lytic cascade, increases lytic gene expression and virus production and its depletion reduces KSHV spontaneous lytic reactivation. Upon lytic replication, PROX1 binds to the KSHV genome in the promoter region of ORF50 and enhances its transactivation activity. These results demonstrate the importance of two endothelial transcription factors in the regulation of the KSHV life cycle and introduce SOX18 inhibition as a potential, novel therapeutic modality for KS.

microbiology↗