Emodin targets mitochondrial cyclophilin D to induce apoptosis in HepG2 cells

Emodin has demonstrated potent anticancer activity in human hepatocarcinoma cells and animal models, however, the cellular targets of emodin have not been fully defined. Here we report that emodin induces the dysfunction of mitochondria and the apoptosis in HepG2 cells through an enrichment in mitochondria. Specifically, A mitochondrial matrix protein (cyclophilin D, CyPD) is involved in emodin-induced apoptosis, and the inhibitor of CyPD (cyclosporin A) could almost completely suppressing the apoptosis; Moreover, as the expression of CyPD could be effectively inhibited by antioxidant N-acetyl-l-cysteine and epidermal growth factor (the activator of ERK), reactive oxygen species and ERK might be involved in the relevant role of CyPD. A further molecule-docking discloses the existence of three hydrogen-bonds in CyPD-emodin complex. Thus, target localization and CyPD in mitochondria provides an insight into the action of emodin in the treatment of liver cancer.

Screening and identification of target genes differentially expressed in HepG2 cells treated with arsenic trioxide by suppression subtractive hybridization technique

AIM: To clone and identify human genes differentially expressed in human hepatocarcinoma HepG2 cells treated with arsenic trioxide by constructing a subtractive cDNA library with suppression subtractive hybridization (SSH) technique, and to elucidate the molecular mechanism of arsenic trioxide in the regulation of liver cells.

METHODS: The mRNA was isolated from HepG2 cells treated with arsenic trioxide and PBS, respectively, and then cDNA was synthesized. After digestion of restriction enzyme RsaI, small sizes cDNA were obtained. Then the tester cDNA was subdivided into two portions and each was ligated with a different cDNA adaptor. After the tester cDNA was hybridized with driver cDNA (twice) and underwent nested polymerase chain reaction (PCR) (twice), the DNA fragment was subcloned into T/A plasmid vectors to establish the subtractive cDNA library. Amplification of the library was performed in E. coli strain JM109. The amplified cDNA was sequenced and analyzed in GenBank with BLAST search after colony PCR.

RESULTS: The subtractive cDNA library of genes differentially expressed in HepG2 cells treated with arsenic trioxide was constructed successfully. The amplified library contained 109 positive clones. Colony PCR showed that these clones all contained 200-1 000 bp inserts. Thirty-six clones were analyzed by sequencing and bioinformatics. The results showed there were 15 coding sequences with known function and 6 novel ones with unknown function.

CONCLUSION: A subtractive cDNA library of genes differentially expressed in HepG2 cells treated with arsenic trioxide was constructed successfully using SSH technique.