TIMP-1 is an activator of MHC-I expression in myeloid dendritic cells with implications for tumor immunogenicity.

Immune checkpoint therapies (ICT) for advanced solid tumors mark a new milestone in cancer therapy. Yet their efficacy is often limited by poor immunogenicity, attributed to inadequate priming and generation of antitumor T cells by dendritic cells (DCs). Identifying biomarkers to enhance DC functions in such tumors is thus crucial. Tissue Inhibitor of Metalloproteinases-1 (TIMP-1), recognized for its influence on immune cells, has an underexplored relationship with DCs. Our research reveals a correlation between high TIMP1 levels in metastatic melanoma and increased CD8 + T cell infiltration and survival. Network studies indicate a functional connection with HLA genes. Spatial transcriptomic analysis of a national melanoma cohort revealed that TIMP1 expression in immune compartments associates with an HLA-A/MHC-I peptide loading signature in lymph nodes. Primary human and bone-marrow-derived DCs secrete TIMP-1, which notably increases MHC-I expression in classical type 1 dendritic cells (cDC1), especially under melanoma antigen exposure. TIMP-1 affects the immunoproteasome/TAP complex, as seen by upregulated PSMB8 and TAP-1 levels of myeloid DCs. This study uncovers the role of TIMP-1 in DC-mediated immunogenicity with insights into CD8 + T cell activation, providing a foundation for mechanistic exploration and highlighting its potential as a new target for combinatorial immunotherapy to enhance ICT effectiveness.

Epigenetic control of CD1D expression as a mechanism of resistance to immune checkpoint therapy in poorly immunogenic melanomas.

Immune Checkpoint Therapies (ICT) have revolutionized the treatment of metastatic melanoma. However, only a subset of patients reaches complete responses. Deficient ß2-microglobulin (ß2M) expression impacts antigen presentation to T cells, leading to ICT resistance. Here, we investigate alternative ß2M-correlated biomarkers that associate with ICT resistance. We shortlisted immune biomarkers interacting with human ß2M using the STRING database. Next, we profiled the transcriptomic expression of these biomarkers in association with clinical and survival outcomes in the melanoma GDC-TCGA-SKCM dataset and a collection of publicly available metastatic melanoma cohorts treated with ICT (anti-PD1). Epigenetic control of identified biomarkers was interrogated using the Illumina Human Methylation 450 dataset from the melanoma GDC-TCGA-SKCM study. We show that ß2M associates with CD1d, CD1b, and FCGRT at the protein level. Co-expression and correlation profile of B2M with CD1D, CD1B, and FCGRT dissociates in melanoma patients following B2M expression loss. Lower CD1D expression is typically found in patients with poor survival outcomes from the GDC-TCGA-SKCM dataset, in patients not responding to anti-PD1 immunotherapies, and in a resistant anti-PD1 pre-clinical model. Immune cell abundance study reveals that B2M and CD1D are both enriched in tumor cells and dendritic cells from patients responding to anti-PD1 immunotherapies. These patients also show increased levels of natural killer T (NKT) cell signatures in the tumor microenvironment (TME). Methylation reactions in the TME of melanoma impact the expression of B2M and SPI1, which controls CD1D expression. These findings suggest that epigenetic changes in the TME of melanoma may impact ß2M and CD1d-mediated functions, such as antigen presentation for T cells and NKT cells. Our hypothesis is grounded in comprehensive bioinformatic analyses of a large transcriptomic dataset from four clinical cohorts and mouse models. It will benefit from further development using well-established functional immune assays to support understanding the molecular processes leading to epigenetic control of ß2M and CD1d. This research line may lead to the rational development of new combinatorial treatments for metastatic melanoma patients that poorly respond to ICT.

Novel prognostication biomarker adipophilin reveals a metabolic shift in uveal melanoma and new therapeutic opportunities.

Metastatic uveal melanoma remains incurable at present. We previously demonstrated that loss of BAP1 gene expression in tumour cells triggers molecular mechanisms of immunosuppression in the tumour microenvironment (TME) of metastatic uveal melanoma. Adipophilin is a structural protein of lipid droplets involved in fat storage within mammalian cells, and its expression has been identified in uveal melanoma. We comprehensively evaluated adipophilin expression at the RNA (PLIN2) and protein levels of 80 patients of the GDC-TCGA-UM study and in a local cohort of 43 primary uveal melanoma samples respectively. PLIN2 expression is a survival prognosticator biomarker in uveal melanoma. Loss of adipophilin expression is significantly associated with monosomy 3 status and nuclear BAP1 losses in uveal melanoma tumours. Integrative transcriptomic and secretome studies show a relationship between transient loss of adipophilin expression and increased levels of tumour-associated macrophages and hypoxia genes, suggesting PLIN2-dependent changes in oxygen and lipid metabolism in the TME of low and high-metastatic risk uveal melanoma. We designed four adipophilin-based multigene signatures for uveal melanoma prognostication using a transcriptomic and secretome survival-functional network approach. Adipophilin-based multigene signatures were validated in BAP1-positive and BAP1-negative uveal melanoma cell lines using a next-generation RNA sequencing approach. We identified existing small molecules, mostly adrenergic, retinoid, and glucocorticoid receptor agonists, MEK, and RAF inhibitors, with the potential to reverse this multigene signature expression in uveal melanoma. Some of these molecules were able to impact tumour cell viability, and carvedilol, an adrenergic receptor antagonist, restored PLIN2 levels, mimicking the expression of normoxia/lipid storage signatures and reversing the expression of hypoxia/lipolysis signatures in co-cultures of uveal melanoma cells with human macrophages. These findings open up a new research line for understanding the lipid metabolic regulation of immune responses, with implications for therapeutic innovation in uveal melanoma. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.