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It is difficult to treat malignant melanoma because of its high malignancy. New and effective therapies for treating malignant melanoma are urgently needed. Ergosterols are known for specific biological activities and have received widespread attention in cancer therapy. Here, LH-1, a kind of ergosterol from the secondary metabolites of the marine fungus Pestalotiopsis sp., was extracted, isolated, purified, and further investigated the biological activities against melanoma. In vitro experiments, the anti-proliferation effect on tumor cells was detected by MTT and colony formation assay, and the anti-metastatic effect on tumor cells was investigated by wound healing assay and transwell assay. Subcutaneous xenograft models, histopathology, and immunohistochemistry have been used to verify the anti-tumor, toxic, and side effect in vivo. Besides, the anti-tumor mechanism of LH-1 was studied by mRNA sequencing. In vitro, LH-1 could inhibit the proliferation and migration of melanoma cells A375 and B16-F10 in a dose-dependent manner and promote tumor cell apoptosis through the mitochondrial apoptosis pathway. In vivo assays confirmed that LH-1 could suppress melanoma growth by inducing cell apoptosis and reducing cell proliferation, and it did not have any notable toxic effects on normal tissues. LH-1 may play an anti-melanoma role by upregulating OBSCN gene expression. These findings suggest that LH-1 may be a potential for the treatment of melanoma.

The ubiquitin-specific protease 7 (USP7), as a deubiquitinating enzyme, plays an important role in tumor progression by various mechanisms and serves as a potential therapeutic target. However, the functional role of USP7 in melanoma remains elusive. Here, we found that USP7 is overexpressed in human melanoma by tissue microarray. We performed TMT-based quantitative proteomic analysis to evaluate the A375 human melanoma cells treated with siRNA of USP7. Our data revealed specific proteins as well as multiple pathways and processes that are impacted by USP7. We found that the phosphatidylinositol-3-kinases/Akt (PI3K-Akt), forkhead box O (FOXO), and AMP-activated protein kinase (AMPK) signaling pathways may be closely related to USP7 expression in melanoma. Moreover, knockdown of USP7 in A375 cells, particularly USP7 knockout using CRISPR-Cas9, verified that USP7 regulates cell proliferation in vivo and in vitro. The results showed that inhibition of USP7 increases expression of the AMPK beta (PRKAB1), caspase 7(CASP7), and protein phosphatase 2 subunit B R3 isoform (PPP2R3A), while attenuating expression of C subunit of vacuolar ATPase (ATP6V0C), and peroxisomal biogenesis factor 11 beta (PEX11B). In summary, these findings reveal an important role of USP7 in regulating melanoma progression via PI3K/Akt/FOXO and AMPK signaling pathways and implicate USP7 as an attractive anticancer target for melanoma.