β-Sitosterol Inhibits Osteosarcoma Cell Proliferation through Regulating Caspase-3

Abstract

Background: β-sitosterol, a plant-derived sterol, shows anti-cancer properties in multiple cancers. However, its biological effects on osteosarcoma are unclear. This study aims to decipher β-sitosterols biological function in osteosarcoma and its regulatory mechanism. Methods: Osteosarcoma cell lines 143B and HOS were used as the in vitro models. They were treated with β-sitosterol, and cell counting kit-8 was adopted to assess cell proliferation. Flow cytometry was conducted to examine cell cycle; apoptosis was detected through Terminal Deoxynucleotidyl Transferase dUTP Nick end Labeling (TUNEL) assay and flow cytometry. The targets of β-sitosterol were predicted in the Traditional Chinese Medicine Systems Pharmacology database, and osteosarcoma-associated genes were analyzed with GeneCards database. Cytoscape software and Search Tool for the Retrieval of Interaction Gene/Proteins (STRING) database were applied to establish a protein-protein interaction network and perform modular analysis to screen hub genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology pathway enrichment analyses were then performed with the hub genes with DAVID database. Caspase-3 mRNA expression level was determined via quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was performed to detect the expression level of cleaved caspase-3 protein. Results: β-sitosterol could inhibit 143B and HOS cell growth, and induce cell apoptosis and cell cycle arrest in G1 phase. Caspase-3 was identified as a target of β-sitosterol in osteosarcoma. Additionally, β-sitosterol could significantly promote cleaved caspase-3 expression, and caspase-3 knockdown could markedly reverse the suppressive effect of β-sitosterol on the malignant phenotypes of 143B and HOS cells. Conclusion: β-sitosterol can suppress osteosarcoma cell proliferation and induce apoptosis by facilitating caspase-3 expression.