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 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 tumour microenvironment 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 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 cells 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 a new research line for understanding the lipid metabolic regulation of immune responses, with implications for therapeutic innovation in uveal melanoma. This article is protected by copyright. All rights reserved.

BAP1 loss; adipophilin; adrenergic receptor antagonist; drug discovery; immune suppression; immunotherapy; uveal melanoma prognostication.