Nevertheless, a study by Yu et al. has revealed that another combination of four factors (Oct3/4, Sox2, NANOG [Nanog ho-meobox], and LIN28 [lin-28 homolog]) is also sufficient to induce pluripotent stem cells from human somatic cells, 4 indicating that more genes are involved in the establishment or maintenance of pluripotency. In this case, the therapy of HCC directing to one or several of these genes may be insufficient to achieve satisfactory efficacy. On the other hand, a recent report by Gupta et al. showed that salinomycin might selectively eliminate breast CSCs and inhibit metastasis by inducing the differentiation of CSCs. They also suggest that it is preferable to treat cancer using agents that target both the CSCs and non-CSCs, because non-CSCs might transform into CSCs and thus eradication of CSCs alone may not obtain complete regression of an established tumor. 5 Interestingly, our study indicated that HNF4 could induce the differentiation of both hepatoma cells and its CSCs. The suppression of CSCs was accompanied by the inhibition of a cluster of genes which contribute to the pluripotency of human stem cells, including-catenin, Oct3/4, SMO(smoothened homolog), Bmi, Sox2, NANOG, c-Myc, Klf4, LIN28, and ESG1 (enhancer of split groucho 1). 3 More recently, we also demonstrated that up-regulation of HNF4 remarkably ameliorated hepatic fibrosis 6 and prevented the development of HCC in rats accompanied by the revision of epithelial-mesenchymal transition (unpublished data). Thus, we believe that differentiation therapy with HNF4, a central regulator for hepatocyte differentiation, might be an ideal strategy for the treatment of human HCC. Moreover, this strategy may be extended to other cancer types through the induction of differentiation using their corresponding key transcription factors.

BackgroundMicroRNA-21 (miR-21) plays an important role in the pathogenesis and progression of liver fibrosis. Here, we determined the serum and hepatic content of miR-21 in patients with liver cirrhosis and rats with dimethylnitrosamine-induced hepatic cirrhosis and examined the effects of miR-21 on SPRY2 and HNF4α in modulating ERK1 signaling in hepatic stellate cells (HSCs) and epithelial-mesenchymal transition (EMT) of hepatocytes.MethodsQuantitative RT-PCR was used to determine miR-21 and the expression of SPRY2, HNF4α and other genes. Immunoblotting assay was carried out to examine the expression of relevant proteins. Luciferase reporter assay was performed to assess the effects of miR-21 on its predicted target genes SPRY2 and HNF4α. Primary HSCs and hepatocytes were treated with miR-21 mimics/inhibitors or appropriate adenoviral vectors to examine the relation between miR-21 and SPRY2 or HNF4α. ResultsThe serum and hepatic content of miR-21 was significantly higher in cirrhotic patients and rats. SPRY2 and HNF4α mRNA levels were markedly lower in the cirrhotic liver. MiR-21 overexpression was associated with enhanced ERK1 signaling and EMT in liver fibrosis. Luciferase assay revealed suppressed SPRY2 and HNF4α expression by miR-21. Ectopic miR-21 stimulated ERK1 signaling in HSCs and induced hepatocyte EMT by targeting SPRY2 or HNF4α. Downregulating miR-21 suppressed ERK1 signaling, inhibited HSC activation, and blocked EMT in TGFβ1-treated hepatocytes.ConclusionsMiR-21 modulates ERK1 signaling and EMT in liver fibrosis by regulating SPRY2 and HNF4α expression. MiR-21 may serve as a potentially biomarker as well as intervention target for hepatic cirrhosis.

MicroRNAs are involved in the regulation of various cellular processes, including cell apoptosis and autophagy. Expression of microRNA-99a (miR-99a) is reduced in apoptotic neonatal mice ventricular myocytes (NMVMs) subjected to hypoxia. We hypothesize that miR-99a might restore cardiac function after myocardial infarction (MI) by up-regulation of myocyte autophagy and apoptosis. We observed down-regulated miR-99a expression in NMVMs exposed to hypoxia using TaqMan quantitative reverse transcriptase-polymerase chain reaction analysis (RT-PCR). We also observed that miR-99a overexpression decreased hypoxia-mediated apoptosis in cultured NMVMs. To investigate whether overexpression of miR-99a in vivo could improve cardiac function in ischaemic heart, adult C57/BL6 mice undergoing MI were randomized into two groups and were intra-myocardially injected with lenti-99a-green fluorescent protein (GFP) or lenti-GFP (control). Four weeks after MI, lenti-99a-GFP group showed significant improvement in both left ventricular (LV) function and survival ratio, as compared to the lenti-GFP group. Histological analysis, western blotting analysis and electron microscopy revealed decreased cellular apoptosis and increased autophagy in cardiomyocytes of lenti-99a-GFP group. Furthermore, western blotting analysis showed inhibited mammalian target of rapamycin (mTOR) expression in the border zones of hearts in miR-99a-treated group. Our results demonstrate that miR-99a overexpression improves both cardiac function and survival ratio in a murine model of MI by preventing cell apoptosis and increasing autophagy via an mTOR/P70/S6K signalling pathway. These findings suggest that miR-99a plays a cardioprotective role in post-infarction LV remodelling and increased expression of miR-99a may have a therapeutic potential in ischaemic heart disease.