Cytotoxicity of a naturally occuring spirostanol saponin, progenin III, towards a broad range of cancer cell lines by induction of apoptosis, autophagy and necroptosis

This study was aimed to investigate the cytotoxic potential of a natural compound, progenin III on a broad range of cancer cell lines, including various sensitive and drug-resistant phenotypes. The cytotoxicity, progenin III-induced autophagic, ferroptotic and necroptotic cell death were evaluated by the resazurin reduction assay (RRA). Spectrophotometric analysis of caspases activity was performed using caspase-Glo assay. Flow cytometry was applied for cell cycle analysis (PI staining), apoptosis (annexin V/PI staining), mitochondrial membrane potential (MMP) (JC-1) and reactive oxygen species (ROS) (H₂DCFH-DA). Progenin III and the reference molecule, doxorubicin exerted cytotoxic effects towards the 18 cancer cell lines tested including animal and human cell lines. The IC₅₀ values obtained ranged from 1.59 μM (towards CCRF-CEM leukemia cells) to 31.61 μM (against the BRAF-V600E homozygous mutant SKMel-28 melanoma cells) for progenin III. Normal sensitivity was achieved with CEM/ADR5000 cells and HCT116p53^-/- adenocarcinoma cells respectively compared to their sensitive congeners CCRF-CEM cells and HCT116 p53^+/+ cells. Progenin III induced apoptosis in CCRF-CEM cells mediated by caspases 3/7 activation, MMP alteration and increase ROS production, and otherwise autophagy and necroptosis. Progenin III is a potential anticancer molecule that deserves further investigations to develop a novel drug to combat malignant diseases including refractory cancers.

Keywords: Cell death; Multi-drug resistance; Natural product; Progenin III; Steroidal saponin.