Characterization of the role of DPPA3 in stemness regulation in hepatocellular carcinoma by DNA methylation

Abstract

Hepatocellular carcinoma (HCC) is one of the most common cancers in the world with a very poor prognosis, which is closely associated with cancer stem cell (CSC).GlobalRNA-sequencingwas used in different developmental stages of hepatocytes, including embryonic stemcell, endoderm, liver progenitor, and premature hepatocyte, aswell as two pairs of nontumor and tumor tissues fromHCC patients. We found that Developmental Pluripotency Associated 3 (DPPA3) was highest expressed in the stage of liver progenitor cells, and was down-regulated along with development. In HCC patients, DPPA3 was expressed in less than 1% tumor cells, while no staining was detected in normal counterparts. Functional assays revealed thatDPPA3 overexpression increasedHCCcells proliferation rate, the ability of foci formation and colony formation in soft agar, as well as migration and invasion. Furthermore,DPPA3 signifıcantly increasedHCCcells sphere formation frequency and sensitivity to chemotherapeutic agent including cisplatin, 5-Fu, and Sorafenib. In order to investigate the role of DPPA3 in CSCmaintenance and stemness regulation in HCC, whole genome methylation sequencing was applied to compare methylation status between DPPA3- and empty vector-transfected cells. Results showed thatDPPA3 reduced CGmethylation level within functional regions in the genome. Of the 541 differentially methylated regions, the majority of them were involvedindevelopmentalprocess andcelldifferentiation.Overall,our fındings give anovel insight intohowmethylationregulationcontrols the fate of cancer stemcells.