Sophocarpine Inhibits Proliferation and Triggers Apoptosis in Breast Cancer Cells by Modulating the miR-21/PTEN/AKT and ERK1/2 Signaling Networks

Background: Sophocarpine (SC), a tetracyclic quinolizidine alkaloid, has shown antitumor potential, yet its activity and underlying mechanisms in breast cancer remain unexplored. This study aimed to investigate the anticancer effects of SC and the molecular mechanism, focusing on the involvement of microRNA-21 (miR-21) and AKT/mTOR and ERK1/2 signaling networks. Methods: In MDA-MB-231 and T-47D breast cancer cells, SC cytotoxicity and growth-inhibitory effects were evaluated using MTT viability, colony formation, migration assays, and flow cytometry for cell cycle and apoptosis analysis. RT-qPCR analysis, Western blotting, and immunofluorescence staining were performed to measure RNA and protein expression, respectively. Molecular docking analysis was performed to explore SC’s interaction with the miR-21 precursor. Results: SC treatment effectively inhibited the proliferation, survival, and migration of breast cancer cells. It also induced cell cycle arrest and triggered apoptosis in both cell lines. Mechanistically, SC downregulated oncogenic miR-21 transcription, thereby enhancing tumor suppressors PTEN and PDCD4 and suppressing AKT/mTOR and ERK1/2 signaling. Interestingly, restoration of miR-21 reversed SC’s effects on PTEN and PDCD4, confirming SC’s miR-21 dependency. Docking analysis suggested that SC may bind the miR-21 precursor and interfere with its maturation. SC also increased long noncoding RNA GAS5 while reducing miR-196a-5p and HIF-1α transcripts. It shifted the Bcl2/Bax/Bad/caspases balance toward apoptosis. Conclusions: These findings identify SC as a potential structural scaffold exhibiting preliminary anti-tumor activity against breast cancer cells, at least in part, through modulating miR-21 and inhibition of the AKT/mTOR/ERK1/2 survival network.