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Tumor cells express and maintain HMGB1 in the reduced isoform to enhance CXCR4-mediated migration

ABSTRACT: During inflammation and tissue regeneration, the alarmin High Mobility Group Box 1 (HMGB1), in its reduced isoform, enhances the activity of the chemokine CXCL12, forming a heterocomplex that acts via the chemokine receptor CXCR4. Despite the established roles of both HMGB1 and CXCL12 in tumor progression and metastatic spread to distal sites, the role of the CXCL12/HMGB1 heterocomplex in cancer has never been investigated. By employing a newly established mass spectrometry protocol that allows an unambiguous distinction between reduced (red HMGB1) and oxidized (ox HMGB1) HMGB1 isoforms in cell lysates, we demonstrate that human epithelial cells derived from breast (MCF-7 and MDA-MB-231) and prostate (PC-3) cancer predominantly express red-HMGB1, while primary CD3+ T lymphocytes from peripheral blood express both HMGB1 isoforms. All these cancer cells release HMGB1 in the extracellular microenvironment together with varying concentrations of thioredoxin and thioredoxin reductase. The CXCL12/HMGB1 heterocomplex enhances, via CXCR4, the directional migration and invasiveness of cancer cells characterized by high metastatic potential that possess a fully active thioredoxin system, contributing to maintain red-HMGB1. On the contrary, cancer cells with low metastatic potential, lack thioredoxin reductase, promptly uptake CXCL12 and fail to respond to the heterocomplex. Our study demonstrates that the responsiveness of cancer cells to the CXCL12/HMGB1 heterocomplex, resulting in enhanced cell migration and invasiveness, depends on the maintenance of HMGB1 in its reduced isoform, and suggests disruption of the heterocomplex as a potential therapeutic target to inhibit invasion and metastatic spread in cancer therapies.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Matteo Pecoraro

LAB HEAD: Mariagrazia Uguccioni

PROVIDER: PXD048091 | Pride | 2024-05-02

REPOSITORIES: Pride

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Project description:Endogenous damage associated molecular pattern molecules (DAMPs) released from necrotic, damaged or stressed cells are associated with an inflammatory response. Whether the microRNA expression signature of this response is different from that of a PAMP-stimulated inflammatory response is unknown. We report here that miR-34c and miR-214 are significantly expressed in fresh human PBMCs exposed to DAMPcontaining freeze-thaw lysates, or to conditioned media from serum-starved and glucose-deprived cells (p<6x10-4 and p<3.7x10-3), respectively. Interestingly, only miR-34c expression was differentially expressed in PBMCs exposed to freeze-thaw lysates or conditioned media from HMGB1+/+ mouse embryonic fibroblast (MEF) cells, when compared to cultures exposed to lysates or conditioned media from HMGB1-/- MEFs. miR-155 expression in these cultures was negligible, but was significantly higher in PBMCs stimulated with LPS or most other TLR ligands, making it the prototypic PAMPmiR. Exposure to a damaged human colorectal carcinoma cell line lysate (HCT116) similarly resulted in increased miR-34c and miR-214 levels. When PBMCs were pre-transfected with anti-miR-34c and then exposed to lysate, expression levels of IKKgamma mRNA, a putative target of miR-34c, increased, while protein levels of IKKgamma in cultures transfected with a pre-miR-34c were abrogated. Levels of miR-34c expression (as well as pro-inflammatory cytokines, IL-1beta and TNFalpha) decreased when PBMC cultures were briefly pre-incubated with the K+ channel (inflammasome) inhibitor, glybenclamide, suggesting that miR-34c is involved in the inflammasome pathway in response to DAMPs. Our findings suggest that a specific microRNA expression signature is associated with the inflammatory response to damaged/injured cells and carries implications for many acute and chronic inflammatory disorders. Human PBMC (peripheral blood mononuclear cells) were exposed to 4 conditions for 48 hours. In the first condition, PBMCs were exposed to conditioned media from serum-starved and glucose-deprived and heat shocked HMGB1-/- MEF cells (mouse embryonic fibroblast cells). In the second condition, PBMCs were exposed to conditioned media from serum-starved and glucose-deprived and heat shocked HMGB1+/+ MEF cells (mouse embryonic fibroblast cells). In the third condition, PBMCs were exposed to LPS (Lipopolysaccharide). In the fourth condition, the PBMCs where left untreated. Four biological repeats were done for each condition for a total of 16 samples.

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Tumor cells express and maintain HMGB1 in the reduced isoform to enhance CXCR4-mediated migration

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