Danshen (Salvia miltiorrhiza) extract suppresses the growth of melanoma cells and induces autophagy by inhibiting the STAT3 pathway

Ethnopharmacological relevance: Danshen (Salvia miltiorrhiza Bunge), a revered traditional Chinese medicine derived from dried roots and rhizomes, has historically been employed to invigorate blood circulation, resolve stasis, and treat cardiovascular disorders. Emerging evidence highlights its ethnopharmacological relevance in cancer therapy, particularly for suppressing tumor progression. While melanoma remains a therapeutic challenge, Danshen's potential mechanisms against this malignancy warrant systematic exploration. 

Aim of the study: This research was designed to evaluate the therapeutic potential of Danshen ethanol extract (DSE) against melanoma cells, with a particular focus on elucidating the regulatory role of signal transducer and activator of transcription 3 (STAT3) signaling pathways in mediating these effects. 

Material and methods: The anti-melanoma effects of Danshen ethanol extract (DSE) were evaluated through in vitro assays (3-(4,5-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide, 5-Ethynyl-2′-deoxyuridine, wound healing, transwell assay, flow cytometry) and in vivo xenograft models. Network pharmacology analysis was utilized. STAT3 pathway activity was assessed via Western blotting, immunofluorescence, and STAT3C plasmid overexpression. Autophagic flux was monitored using RFP-GFP-LC3 dual fluorescence and pharmacological inhibitors chloroquine (CQ) and, 3-Methyladenine (3 MA). 

Results: DSE dose-dependently inhibited melanoma cell proliferation, induced cell cycle arrest and apoptosis, and reduced cell migration and invasion. Network pharmacology-predicted JAK2/STAT inhibition was experimentally confirmed: DSE reduced STAT3 phosphorylation, nuclear translocation, and downstream targets (Cyclin D1, Bcl-2). STAT3 overexpression partially reversed DSE's anti-proliferative and anti-metastatic effects. Mechanistically, DSE triggered protective autophagy through STAT3 suppression. Co-treatment with autophagy inhibitors synergistically enhanced DSE's cytotoxicity. In vivo, DSE attenuated tumor growth and downregulated STAT3 signaling in xenografts. 

Conclusions: This study elucidates that DSE exerts anti-melanoma effects through dual mechanisms: suppressing STAT3-mediated proliferation/metastasis and disrupting STAT3-modulated pro-survival autophagy. These findings bridge the traditional blood-activating applications of Danshen with modern targeted cancer therapy. They not only validate the ethnopharmacological relevance of Salvia miltiorrhiza in oncology but also propose DSE as a multifunctional adjuvant for melanoma treatment.