The Mechanism of a Novel Mitochondrial-Targeted Icaritin Derivative in Regulating Apoptosis of BEL-7402 Cells Based on the SIRT3 and CypD-Mediated ROS/p38 MAPK Signaling Pathway

Tumorigenesis and progression are closely associated with apoptosis and primarily regulated by mitochondria, which are considered major targets for cancer therapy. In this study, twelve novel icaritin (ICT) derivatives were designed and synthesized, four of which were specifically targeted to mitochondria. Biological studies demonstrated that all compounds containing triphenylphosphine (TPP⁺) exhibited a substantial increase in antitumor activity compared to ICT and control compounds while also exhibiting notable selectivity for tumor cells over normal cells. Among these derivatives, Mito-ICT-4 exhibited the strongest antiproliferative effect, with an IC₅₀ value of 0.73 ± 0.06 μM for BEL-7402 cells, which is 29 times lower than that of ICT, and an IC₅₀ value of 67.11 ± 2.09 μM for HEK293 cells, indicating approximately 33-fold selectivity for tumor cells. High-performance liquid chromatography (HPLC) analysis revealed that Mito-ICT-4 significantly accumulated in the mitochondria of BEL-7402 cells, with the level of accumulation approximately 2.5 times greater than that of ICT. Further investigations demonstrated that upon entering the mitochondria of tumor cells, Mito-ICT-4 downregulated SIRT3 protein expression, disrupted intracellular redox homeostasis, and led to a substantial increase in mitochondrial ROS levels, abnormal CypD-dependent MPTP opening, mitochondrial membrane potential depolarization, and ROS release into the cytoplasm, ultimately triggering ROS-mediated apoptosis in BEL-7402 cells. Transcriptomic analysis identified differentially expressed genes and enriched pathways, highlighting the ROS-mediated p38-MAPK signaling pathway as a key mediator of Mito-ICT-4-induced mitochondria-dependent apoptosis. The effects of Mito-ICT-4 on the expression of key genes (SIRT3, CypD, P-MKK6, P-P38, and DDIT3) were further validated by qRT-PCR and Western blot analysis, with results aligning with transcriptomic data. The novel ICT derivatives synthesized in this study, with mitochondria-targeting functionality, provide a basis for the development of targeted antitumor drugs.