CXCR4 is a G-Protein coupled receptor that is expressed nearly ubiquitously and is known to control cell migration via its interaction with CXCL12, the most ancient chemokine. The functions of CXCR4/CXCL12 extend beyond cell migration and involve the recognition and disposal of unhealthy or tumor cells. The CXCR4/CXCL12 axis plays a relevant role in shaping the tumor microenvironment (TME), mainly towards dampening immune responses. Notably, CXCR4/CXCL12 cross-signal via the T and B cell receptors (TCR and BCR) and co-internalize with CD47, promoting tumor cell phagocytosis by macrophages in an anti-tumor immune process called ImmunoGenic Surrender (IGS). These specific activities in shaping the immune response might be exploited to improve current immunotherapies.

Chemokine heterodimers activate or dampen their cognate receptors during inflammation. The CXCL12 chemokine forms with the fully reduced (fr) alarmin HMGB1 a physiologically relevant heterocomplex (frHMGB1•CXCL12) that synergically promotes the inflammatory response elicited by the G-protein coupled receptor CXCR4. The molecular details of complex formation were still elusive. Here we show by an integrated structural approach that frHMGB1•CXCL12 is a fuzzy heterocomplex. Unlike previous assumptions, frHMGB1 and CXCL12 form a dynamic equimolar assembly, with structured and unstructured frHMGB1 regions recognizing the CXCL12 dimerization surface. We uncover an unexpected role of the acidic intrinsically disordered region (IDR) of HMGB1 in heterocomplex formation and its binding to CXCR4 on the cell surface. Our work shows that the interaction of frHMGB1 with CXCL12 diverges from the classical rigid heterophilic chemokines dimerization. Simultaneous interference with multiple interactions within frHMGB1•CXCL12 might offer pharmacological strategies against inflammatory conditions.

Pleural mesothelioma (PM) is an aggressive cancer that originates from mesothelial cells lining the pleura. To identify the different cell types in mesothelioma and their relationships, we performed single-cell RNAseq analyses of non-malignant pleura biopsies, PM biopsies and PM patient-derived organoids. Gene expression profiles of mesothelial and mesothelioma cells are very similar, suggesting that mesothelioma cells retain most properties of mesothelial cells. Surprisingly, in PM patient-derived organoids mesothelioma cells can acquire a fibroblast-like gene expression profile. Indeed, in most of the original PM biopsies a fraction of cells within the cluster of cancer-associated fibroblasts (CAFs) appear derived from tumor cells, with which they share the same genomic rearrangements. We confirmed by immunohistochemistry, and thus at the protein level, that cancer-derived fibroblast-like cells (CDFs) express smooth muscle actin, as most CAFs do, but have lost the same tumor suppressor proteins as the cognate mesothelioma cells. We propose that mesothelioma cells can become CDFs because they retain the ability of mesothelial cells to differentiate into fibroblasts. CDFs are thus tumor cells with fibroblast-like gene expression associated to tumors, and fulfil the definition of CAFs. CAFs generally support tumor progression, and in most tumors derive from resident fibroblasts or circulating mesenchymal cells. Our finding that a subset of CAFs derive from tumor cells, at least in mesothelioma, challenges current understanding of CAF origin. We suggest that interfering with the mesothelioma-to-CAF transition might offer an avenue to moderate tumor progression and resistance to therapy.

Mesothelioma is a rare and aggressive malignancy arising from mesothelial cells. Despite recent advances in systemic therapies, overall survival remains limited, underscoring the need for a deeper mechanistic understanding of disease pathogenesis and novel therapeutic strategies. In mesothelioma, chronic tissue injury induced by asbestos fibers leads to sustained activation of innate immune pathways and chronic inflammation that actively promote tumorigenesis. The release of Damage-Associated Molecular Patterns (DAMPs)—endogenous molecules that signal cellular stress and damage—contributes to establishing a self-sustaining inflammatory circuit within the pleural microenvironment that promotes tumor initiation and progression and immune evasion. Among DAMPs, High-Mobility Group Box 1 (HMGB1) has emerged as a key regulator of mesothelioma pathogenesis. Several studies demonstrated that mesothelial cells actively secrete HMGB1 in response to asbestos exposure, driving macrophage recruitment, cytokine production, and chronic inflammation. Beyond HMGB1, additional DAMPs—including IL-33, extracellular ATP, cell-free nucleic acids, heat shock proteins, and calreticulin—contribute to inflammasome activation, stromal remodeling, and immune dysregulation. Recent evidence suggests that DAMP signaling in mesothelioma is dysregulated, resulting in chronic inflammation coupled with ineffective antitumor immunity. This review provides a comprehensive synthesis of DAMP biology in mesothelioma, highlighting the emerging therapeutic opportunities targeting DAMP-associated pathways.