Recycled melanoma-secreted melanosomes regulate tumor-associated macrophage diversification.

Extracellular vesicles (EVs) are important mediators of communication between cells. Here, we reveal a new mode of intercellular communication by melanosomes, large EVs secreted by melanocytes for melanin transport. Unlike small EVs, which are disintegrated within the receiver cell, melanosomes stay intact within them, gain a unique protein signature, and can then be further transferred to another cell as "second-hand" EVs. We show that melanoma-secreted melanosomes passaged through epidermal keratinocytes or dermal fibroblasts can be further engulfed by resident macrophages. This process leads to macrophage polarization into pro-tumor or pro-immune cell infiltration phenotypes. Melanosomes that are transferred through fibroblasts can carry AKT1, which induces VEGF secretion from macrophages in an mTOR-dependent manner, promoting angiogenesis and metastasis in vivo. In melanoma patients, macrophages that are co-localized with AKT1 are correlated with disease aggressiveness, and immunotherapy non-responders are enriched in macrophages containing melanosome markers. Our findings suggest that interactions mediated by second-hand extracellular vesicles contribute to the formation of the metastatic niche, and that blocking the melanosome cues of macrophage diversification could be helpful in halting melanoma progression.

Primary Melanoma miRNA Trafficking Induces Lymphangiogenesis.

Melanoma, the deadliest cutaneous tumor, initiates within the epidermis; during progression, cells invade into the dermis and become metastatic through the lymphatic and blood system. Before melanoma cell invasion into the dermis, an increased density of dermal lymphatic vessels is observed, generated by a mechanism which is not fully understood. In this study, we show that, while at the primary epidermal stage (in situ), melanoma cells secrete extracellular vesicles termed melanosomes, which are uptaken by dermal lymphatic cells, leading to transcriptional and phenotypic pro-lymphangiogenic changes. Mechanistically, melanoma-derived melanosomes traffic mature let-7i to lymphatic endothelial cells, which mediate pro-lymphangiogenic phenotypic changes by the induction of type I IFN signaling. Furthermore, transcriptome analysis upon treatment with melanosomes or let-7i reveals the enhancement of IFI6 expression in lymphatic cells. Because melanoma cells metastasize primarily via lymphatic vessels, our data suggest that blocking lymphangiogenesis by repressing either melanosome release or type I IFN signaling will prevent melanoma progression to the deadly metastatic stage.

Observational outcomes in proliferative diabetic retinopathy patients following treatment with ranibizumab, panretinal laser photocoagulation or combination therapy - The non-interventional second year follow-up to the PRIDE study.

PURPOSE: Ranibizumab monotherapy showed stronger effects on area of retinal neovascularization (NV) reduction while offering better visual acuity (VA) results than panretinal laser photocoagulation (PRP) monotherapy during the first 12 months of the PRIDE study. The second year of PRIDE was an observational, non-interventional follow-up, performed to evaluate long-term anatomical and functional outcomes in proliferative diabetic retinopathy (PDR) patients under real-life conditions, prior to the approval of ranibizumab for PDR. METHODS: Seventy-three PDR patients (28 from the ranibizumab group; 20 from the PRP group; 25 from the combination group) were included in the observational follow-up phase and treated at the investigators discretion. Visual acuity (VA) measurements and retinal imaging were performed at Months 12, 18 and 24. RESULTS: Mean (± SD) NV area in the ranibizumab monotherapy and combination follow-up groups increased from 3.16 ± 4.30 mm2 and 1.13 ± 2.78 mm2 at Month 12 to 6.09 ± 10.79 mm2 and 2.14 ± 4.41 mm2 at Month 18 and 10.00 ± 17.63 mm2 and 3.26 ± 7.05 mm2 at Month 24, respectively. In the PRP follow-up group, NV area declined from 5.44 ± 14.55 mm2 at Month 12 to 1.22 ± 1.67 mm2 at Month 18, but increased again to 4.05 ± 11.66 mm2 at Month 24. During the observational phase, only 2 (6;8) patients in the ranibizumab (PRP;combination) follow-up group were treated with anti-VEGF medications, while 17 (6;10) patients received PRP laser therapy. CONCLUSION: Discontinuation of ranibizumab treatment in PDR patients may result in an increase of NV area and VA loss. Tight monitoring of disease activity and continued treatment beyond the first year is needed to maintain disease control.