[Action of catechin on Pseudomonas fluorescens]

A novel ETV6-miR-429-CRKL regulatory circuitry contributes to aggressiveness of hepatocellular carcinoma

BACKGROUND

Tumor metastasis is one of the main causes of the high mortality of hepatocellular carcinoma (HCC). E-Twenty Six variant gene 6 (ETV6) is a strong transcriptional repressor, associated with the development and progression of tumors. However, the exact role and underlying mechanism of ETV6 in HCC remain unclear.

METHODS

Western blotting, quantitative real-time PCR and immunohistochemistry were used to detect the expression levels of ETV6, CRKL (v-crk sarcoma virus CT10 oncogene homologue (avian)-like) and miR-429 in HCC tissues and cells; Transwell chamber and F-actin cytoskeleton staining assay to examine the effects of ETV6 and CRKL deregulation on the migration, invasion and cytoskeleton of HCC cells; Co-immunoprecipitation assay to determine the interaction between CRKL and ETV6; Chromatin immunoprecipitation assay to investigate the interaction between ETV6 and miR-429.

RESULTS

We established a novel ETV6-miR-429-CRKL regulatory circuitry contributes to HCC metastasis. ETV6 and CRKL were frequently increased, while miR-429 was downregulated in both hepatocarcinoma tissues and hepatocarcinoma cells. Moreover, ETV6 upregulation was positively correlated with CRKL upregulation, and two negative correlations were also established for ETV6 and CRKL upregulation with miR-429 downregulation in both hepatocarcinoma patients' tumorous tissues and hepatocarcinoma cells. Functional investigations revealed that overexpression and knockdown of ETV6 was remarkably effective in promoting and suppressing HCC cell migration, invasion, cytoskeleton F-actin expression and arrangement, whereas, CRKL overexpression exhibited similar effects to the overexpression of ETV6. Mechanistically, ETV6 negatively regulates miR-429 expression by directly binding to the promoter region of miR-429; miR-429 negatively regulates CRKL expression by selectively targeting CRKL-3'-UTR; ETV6 directly binds to CRKL and positively regulates its expression, which in turn CRKL positively regulates ETV6 expression.

CONCLUSIONS

Our data demonstrated that ETV6 promotes migration and invasion of HCC cells by directly binding to promoter region of miR-429 via modulating CRKL expression. The newly identified ETV6-miR-429-CRKL regulatory circuitry contributes to the aggressiveness of HCC, which provides new clues for fundamental research on diagnosis and treatment parameters for HCC.

Influence of the flavonoid (+)-catechin on the permeability of Ehrlich mouse ascites tumour cell membranes

The effect of the flavonoid (+)-catechin and its hydrophilic derivative epicatechinsulphonate on the permeability of Ehrlich mouse ascites tumour cells (EMAT) was investigated. As a sensitive assay, the transmembrane fluxes of two different solutes were measured, the inwardly directed free diffusion of 14C-thiourea, and the carrier-mediated efflux of intracellularly accumulated 12C-1-aminocyclopentane-1-carboxylic acid. (+)-Catechn was found to reduce the permeability of EMAT membranes for both solutes. The primary target of the drug appears to be the membrane itself. The effectiveness of the drug was dependent on its concentration. Inhibition of fluxes was observed at 0.86 mM; the inhibition gradually increased as the concentration was increased. In contrast to (+)-catechin, epicatechinsulphonate was rather ineffective, even at a concentration as large as 10 mM. The effect of (+)-catechin was seen within a few minutes after its addition. However, it was considerably intensified as the incubation was prolonged. The effectivity of (+)-catechin decreased with increasing cell density. Thus, the drug appears to be absorbed by the cells. From the various data and the observation that incorporation of a strong lipophobic sulphonate residue into the moderately lipophilic catechin molecule markedly lowers the effectivity of the flavonoid, it is concluded that (+)-catechin, as a membrane stabilizing drug, interacts directly with certain constituents of the cell envelope, presumably membrane lipids.