Macrophages are key participants in melanoma growth and survival. In general, macrophages can be classified as M1 or M2 activation phenotypes. Increasing evidence demonstrates that melanoma exosomes also facilitate tumor survival and metastasis. However, the role of melanoma exosomes in directly influencing macrophage function is poorly understood. Herein, we investigated the hypothesis that natural melanoma exosomes might directly influence macrophage polarization. To explore this hypothesis, ELISA, RT-qPCR, and macrophage functional studies were performed in vitro using an established source of melanoma exosomes (B16-F10). ELISA results for melanoma exosome induction of common M1 and M2 cytokines in RAW 264.7 macrophages, revealed that melanoma exosomes do not polarize macrophages exclusively in the M1 or M2 direction. Melanoma exosomes induced the M1 and M2 representative cytokines TNF-α and IL-10 respectively. Further assessment, using an RT-qPCR array with RAW 264.7 and primary macrophages, confirmed and extended the ELISA findings. Upregulation of markers common to both M1 and M2 polarization phenotypes included CCL22, IL-12B, IL-1β, IL-6, i-NOS, and TNF-α. The M2 cytokine TGF-β was upregulated in primary but not RAW 264.7 macrophages. Pro-tumor functions have been attributed to each of these markers. Macrophage functional assays demonstrated a trend toward increased i-NOS (M1) to arginase (M2) activity. Collectively, the results provide the first evidence that melanoma exosomes can induce a mixed M1 and M2 pro-tumor macrophage activation phenotype.

AS1411 is a quadruplex-forming DNA oligonucleotide that functions as an aptamer to target nucleolin, a protein present on the surface of cancer cells. Clinical trials of AS1411 have indicated it is well tolerated with evidence of therapeutic activity, but improved pharmacology and potency may be required for optimal efficacy. In this report, we describe how conjugating AS1411 to 5 nm gold nanospheres influences its activities in vitro and in vivo. We find that the AS1411-linked gold nanospheres (AS1411-GNS) are stable in aqueous and serum-containing solutions. Compared to unconjugated AS1411 or GNS linked to control oligonucleotides, AS1411-GNS have superior cellular uptake and markedly increased antiproliferative/cytotoxic effects. Similar to AS1411, AS1411-GNS show selectivity for cancer cells compared to non-malignant cells. In a mouse model of breast cancer, systemic administration of AS1411-GNS could completely inhibit tumor growth with no signs of toxicity. These results suggest AS1411-GNS are promising candidates for clinical translation.

The influence of buffer substitution and dilution effects on exosome size and electrophoretic mobility were shown for the first time. Cyclical electrical field flow fractionation (Cy-El-FFF) in various substituted fluids was applied to exosomes and other particles. Tested carrier fluids of deionized (DI) water, 1× phosphate buffered saline (PBS), 0.308 M trehalose, and 2% isopropyl alcohol (IPA) influenced Cy-El-FFF-mediated isolation of A375 melanoma exosomes. All fractograms revealed a crescent-shaped trend in retention times with increasing voltage with the maximum retention time at ∼1.3 V AC. A375 melanoma exosome recovery was approximately 70–80% after each buffer substitution, and recovery was independent of whether the sample was substituted into 1× PBS or DI water. Exosome dilution in deionized water produced a U-shaped dependence on electrophoretic mobility. The effect of dilution using 1× PBS buffer revealed a very gradual change in electrophoretic mobility of exosomes from ∼−1.6 to −0.1 μm cm/s V, as exosome concentration was decreased. This differed from the use of DI water, where a large change from ∼−5.5 to −0.1 μm cm/s V over the same dilution range was observed. Fractograms of separated A375 melanoma exosomes in two substituted low-ionic-strength buffers were compared with synthetic particle fractograms. Overall, the ability of Cy-El-FFF to separate exosomes based on their size and charge is a highly promising, label-free approach to initially catalogue and purify exosome subtypes for biobanking as well as to enable further exosome subtype interrogations.

Melanoma-derived small extracellular vesicles (sEVs) participate in tumor pathogenesis. Tumor pathogenesis is highly dependent on inflammatory processes. Given the potential for melanoma sEVs to carry tumor biomarkers, we explored the hypothesis that they may contain inflammation-related mRNA content. Biophysical characterization showed that human primary melanocyte-derived sEVs trended toward being smaller and having less negative (more neutral) zeta potential than human melanoma sEVs (A-375, SKMEL-28, and C-32). Using primary melanocyte sEVs as the control population, RT-qPCR array results demonstrated similarities and differences in gene expression between melanoma sEV types. Upregulation of pro-angiogenic chemokine ligand CXCL1, CXCL2, and CXCL8 mRNAs in A-375 and SKMEL-28 melanoma sEVs was the most consistent finding. This paralleled increased production of CXCL1, CXCL2, and CXCL8 proteins by A-375 and SKMEL-28 sEV source cells. Overall, the use of primary melanocyte sEVs as a control sEV reference population facilitated the detection of inflammation-related melanoma sEV mRNA content.