Malignant progression results from a dynamic cross-talk between stromal and cancer cells. Recent evidence suggests that this cross-talk is mediated to a significant extent by exosomes, nanovesicles secreted by most cell types and which allow the transfer of proteins, lipids, and nucleic acids between cells. Adipocytes are a major component of several tumor microenvironments, including that of invasive melanoma, where cells have migrated to the adipocyte-rich hypodermic layer of the skin. We show that adipocytes secrete exosomes in abundance, which are then taken up by tumor cells, leading to increased migration and invasion. Using mass spectrometry, we analyzed the proteome of adipocyte exosomes. Interestingly, these vesicles carry proteins implicated in fatty acid oxidation (FAO), a feature highly specific to adipocyte exosomes. We further show that, in the presence of adipocyte exosomes, FAO is increased in melanoma cells. Inhibition of this metabolic pathway completely abrogates the exosome-mediated increase in migration. Moreover, in obese mice and humans, both the number of exosomes secreted by adipocytes as well as their effect on FAO-dependent cell migration are amplified. These observations might in part explain why obese melanoma patients have a poorer prognosis than their nonobese counterparts. Cancer Res; 76(14); 4051-7. Ó2016 AACR.

Exosomes are important mediators in cell-to-cell communication and, recently, their role in melanoma progression has been brought to light. Here, we characterized exosomes secreted by seven melanoma cell lines with varying degrees of aggressivity. Extensive proteomic analysis of their exosomes confirmed the presence of characteristic exosomal markers as well as melanoma-specific antigens and oncogenic proteins. Importantly, the protein composition differed among exosomes from different lines. Exosomes from aggressive cells contained specific proteins involved in cell motility, angiogenesis, and immune response, while these proteins were less abundant or absent in exosomes from less aggressive cells. Interestingly, when exposed to exosomes from metastatic lines, less aggressive cells increased their migratory capacities, likely due to transfer of pro-migratory exosomal proteins to recipient cells. Hence, this study shows that the specific protein composition of melanoma exosomes depends on the cells' aggressivity and suggests that exosomes influence the behavior of other tumor cells and their microenvironment.

Bone deficits are frequent in HIV-1-infected patients. We report here that osteoclasts, the cells specialized in bone resorption, are infected by HIV-1 in vivo in humanized mice and ex vivo in human joint biopsies. In vitro, infection of human osteoclasts occurs at different stages of osteoclastogenesis via cell-free viruses and, more efficiently, by transfer from infected T cells. HIV-1 infection markedly enhances adhesion and osteolytic activity of human osteoclasts by modifying the structure and function of the sealing zone, the osteoclast-specific bone degradation machinery. Indeed, the sealing zone is broader due to F-actin enrichment of its basal units (i.e., the podosomes). The viral protein Nef is involved in all HIV-1-induced effects partly through the activation of Src, a regulator of podosomes and of their assembly as a sealing zone. Supporting these results, Nef-transgenic mice exhibit an increased osteoclast density and bone defects, and osteoclasts derived from these animals display high osteolytic activity. Altogether, our study evidences osteoclasts as host cells for HIV-1 and their pathological contribution to bone disorders induced by this virus, in part via Nef.

Autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of monogenic genodermatoses that encompasses non-syndromic disorders of keratinization. The pathophysiology of ARCI has been linked to a disturbance in epidermal lipid metabolism that impaired the stratum corneum function, leading to permeability barrier defects. Functional characterization of some genes involved in ARCI contributed to the identification of molecular actors involved in epidermal lipid synthesis, transport or processing. Recently, PNPLA1 has been identified as a gene causing ARCI. While other members of PNPLA family are key elements in lipid metabolism, the function of PNPLA1 remained unclear. We identified 5 novel PNPLA1 mutations in ARCI patients, mainly localized in the putative active enzymatic domain of PNPLA1. To investigate Pnpla1 biological role, we analysed Pnpla1-deficient mice. KO mice died soon after birth from severe epidermal permeability defects. Pnpla1-deficient skin presented an important impairment in the composition and organization of the epidermal lipids. Quantification of epidermal ceramide species highlighted a blockade in the production of ω-O-acylceramides with a concomitant accumulation of their precursors in the KO. The virtually loss of ω-O-acylceramides in the stratum corneum was linked to a defective lipid coverage of the resistant pericellular shell encapsulating corneocytes, the so-called cornified envelope, and most probably disorganized the extracellular lipid matrix. Finally, these defects in ω-O-acylceramides synthesis and cornified envelope formation were also evidenced in the stratum corneum from PNPLA1-mutated patients. Overall, our data support that PNPLA1/Pnpla1 is a key player in the formation of ω-O-acylceramide, a crucial process for the epidermal permeability barrier function.