Narciclasine Exerts Anticancer Activity in Colorectal Cancer Cells in Association with HELLS Downregulation and DNA Damage-Associated Responses

Background/Objectives: Colorectal cancer (CRC) remains a major cause of cancer-related mortality worldwide, largely owing to metastasis, recurrence, and resistance to conventional therapies. Natural-product-derived compounds represent an important source of anticancer drug candidates. This study investigated the anticancer activity of purified narciclasine, which was tentatively annotated as a major detected constituent of Lycoris sanguinea extract, and examined its association with HELLS-associated DNA damage responses in CRC cells. Methods: Human CRC cell lines HT29 and HCT116 were used to evaluate the cytotoxic and mechanistic effects of L. sanguinea extract and narciclasine. Cell viability, clonogenic growth, apoptosis, mitochondrial membrane potential, cell cycle distribution, migration, and invasion were assessed. Western blotting was performed to analyze apoptosis-, cell cycle-, epithelial–mesenchymal transition (EMT)-, and DNA damage-related proteins. UPLC-QTOF/MS analysis was used to identify major phytochemical constituents. HELLS knockdown and γ-H2AX immunofluorescence staining were conducted to examine the involvement of HELLS in narciclasine-associated DNA damage and apoptosis. Results: L. sanguinea extract reduced CRC cell viability, suppressed clonogenic growth, induced mitochondrial dysfunction and caspase-dependent apoptosis, and promoted G2/M cell cycle arrest with decreased cyclin B1 and increased p53/p21 expression. The extract also inhibited migration and invasion, accompanied by reduced β-catenin, N-cadherin, vimentin, slug, and snail expression and increased E-cadherin expression. UPLC-QTOF/MS tentatively annotated narciclasine as a major detected constituent. Purified narciclasine recapitulated several anticancer effects of the extract, accompanied by HELLS downregulation, increased γ-H2AX accumulation, reduced cyclin B1 expression, and enhanced PARP and caspase-3 cleavage. HELLS knockdown further sensitized CRC cells to narciclasine-associated γ-H2AX accumulation, G2/M arrest-associated signaling, and apoptosis. Conclusions: Narciclasine treatment was associated with HELLS downregulation, DNA damage-associated signaling, G2/M cell cycle arrest-associated changes, EMT suppression, and apoptosis in CRC cells. These findings suggest that narciclasine is a promising natural-product-derived lead compound for further preclinical evaluation in HELLS-associated CRC vulnerabilities.