Proteomic identification of proteins involved in the anticancer activities of oridonin in HepG2 cells

Oridonin is the main bioactive constituent of the Chinese medicinal herb Isodon rubescens and has been shown to have anti-neoplastic effects against a number of cancers in vitro and in vivo. Here we report the proteomic identification of proteins involved in the anticancer properties of oridonin in hepatocarcinoma HepG2 cells. Cell viability assay showed that oridonin dose-dependently inhibited cell growth with an IC₅₀ of 41.77 μM. Treatment with oridonin at 44 μM for 24 h induced apoptosis and G2/M cell cycle arrest, which were associated with nine differentially expressed proteins identified by proteomic analysis. The proteomic expression patterns of Hsp70.1, Sti1 and hnRNP-E1 were confirmed by quantitative real-time PCR and/or immunoblotting. Eight of the nine identified proteins are shown, for the first time, to be involved in the anticancer activities of oridonin. Up-regulation of Hsp70.1, STRAP, TCTP, Sti1 and PPase, as well as the down-regulation of hnRNP-E1 could be responsible for the apoptotic and G2/M-arresting effects of oridonin observed in this study. Up-regulation of HP1 beta and GlyRS might contribute to inhibitory effects of oridonin on telomerase and tyrosine kinase, respectively. These findings shed new insights into the molecular mechanisms underlying the anticancer properties of oridonin in liver cancer cells.