Icaritin induces paraptosis in hepatocellular carcinoma cells by targeting BHLHE40 via endoplasmic reticulum stress and mitochondrial dysfunction.

[OBJECTIVE] Icaritin, a flavonoid derived from the traditional Chinese medicine Epimedium, exhibits diverse biological activities; however, the mechanisms underlying its effects against hepatocellular carcinoma (HCC) remain unclear. This study aimed to investigate the anticancer properties of icaritin and elucidate the mechanisms of icaritin-induced cell death.

[METHODS] The effects of icaritin-induced paraptosis were assessed using CellTiter-Glo, EdU, and colony formation assays, and phenotypic observations. Transcriptome analysis was performed to identify the dysregulated genes associated with icaritin-induced paraptosis. Western blotting and qRT-PCR were used to analyze icaritin-induced changes in protein and mRNA levels, respectively. Mito-GFP, ROS, and MMP assays were conducted to monitor the mitochondrial status. IPA, molecular docking, CETSA, shRNA and cell-derived xenografts confirmed the role of BHLHE40 in icaritin-induced paraptosis in vivo and in vitro RESULTS: Icaritin induced paraptosis in HCC cells, which was characterized by cytoplasmic vacuolation and caspase-independent. Transcriptomic analysis indicated that icaritin triggered ER stress and mitochondrial dysfunction, validated by molecular and biochemical assays. IPA, molecular docking, and CETSA analyses identified BHLHE40 as a crucial mediator of this process. BHLHE40 knockdown inhibited ER stress and mitochondrial dysfunction, significantly reducing icaritin-induced paraptosis in HCC cells. Animal experiments demonstrated that silencing of BHLHE40 diminished the inhibitory effects of icaritin on tumor growth in xenograft models.

[CONCLUSION] These results highlight the potent anticancer effects of icaritin, particularly its ability to induce paraptosis by targeting BHLHE40. This study provides a comprehensive understanding of the anticancer mechanisms of icaritin and suggests that targeting BHLHE40 represents a novel therapeutic strategy for enhancing the efficacy of cancer treatment.

[ABBREVIATIONS] HCC: Hepatocellular carcinoma; TCM: Traditional Chinese Medicine; ER: Endoplasmic Reticulum; MMP: Mitochondrial Membrane Potential; ROS: Reactive Oxygen Species; CTG: CellTiter-Glo; EdU: 5-ethynyl-2'-deoxyuridine; UPR: Unfolded Protein Response; BHLHE40: Basic helix-loop-helix family member E40; IPA: Ingenuity Pathway Analysis; CETSA: Cellular Thermal Shift Assay; PI: Propidium Iodide;PCR: Polymerase Chain Reaction; qRT-PCR: Quantitative Reverse Transcription PCR; GFP: Green Fluorescent Protein; JC-1: 5,5',6,6'-Tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide; ATF4: Activating Transcription Factor 4; PERK: Protein kinase RNA-like ER kinase; DDIT3: DNA Damage Inducible Transcript 3; LMNA: Lamin A/C; IC50: Half Maximal Inhibitory Concentration; PEG300: Polyethylene glycol 300; PBS: Phosphate Buffered Saline; BSA: Bovine Serum Albumin; HRP: Horseradish Peroxidase; SRA: Sequence Read Archive; PCD: Programmed Cell Death; COX8A: Cytochrome c oxidase subunit 8A; DCFH-DA: 2',7'-Dichlorodihydrofluorescein diacetate; CHX: Cycloheximide; zVAD-FMK: Carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone; PARP: Poly (ADP-ribose) polymerase; DMSO: Dimethyl sulfoxide; SPF: Specific Pathogen-Free; IACUC: Institutional Animal Care and Use Committee.