Effects of Citrus-derived Diosmetin on Melanoma: Induction of Apoptosis and Autophagy Mediated by PI3K/Akt/mTOR Pathway Inhibition.

Background: Diosmetin (DIOS) is a naturally abundant flavonoid and possesses various biological activities that hold promise as an anti-cancer agent. However, the anti-cancer activities and underlying mechanism of DIOS on cutaneous melanoma remain unclear.

Objective: This study seeks to explore the anti-tumor effect and mechanism of DIOS in cutaneous melanoma.

Methods: Here, a variety of in vitro and in vivo experiments, combined with RNA sequencing (RNA-seq), were employed to ascertain the potential anti-cutaneous melanoma capacity and mechanism of DIOS.

Results: The results demonstrated that DIOS considerably impeded cell proliferation and triggered cell apoptosis in a dose- and time-dependent manner. Concurrently, DIOS markedly elevated the expression of pro-apoptotic proteins (Cleaved caspase-3, Bax, Cleaved PARP, and Cleaved caspase-9) and downregulated the expression of Bcl-2. Additionally, DIOS markedly upregulated the protein expressions of LC3B-II and Atg5, while downregulating p62 protein expression. Notably, pre-treatment with an autophagy inhibitor significantly inhibited DIOSinduced cell apoptosis and autophagy. Mechanistically, DIOS was identified to repress the PI3K/Akt/mTOR signaling pathway by western blot analyses and RNA-seq. Finally, in vivo experiments using a syngeneic mouse model confirmed the anti-tumor effect of DIOS, which exhibited high levels of apoptosis and autophagy.

Conclusion: These findings propose that DIOS acts as a potential melanoma therapy that exerts its anti-tumor effects by triggering apoptosis and autophagy via inhibition of the PI3K/Akt/mTOR pathway.