Spherical cell shape of FLC-4 cell, a human hepatoma cell, enhances hepatocyte-specific function and suppresses tumor phenotype through the integration of mRNA-microRNA interaction

The induction mechanism of HNF-4 alpha by spherical cell shape in human hepatoma cells, FLC-4, was investigated. To get insight into the induction mechanism of HNF-4 alpha in three-dimensional FLC-4 cells, mRNA microarray analysis was performed. The gene expression related to drug metabolism and nuclear receptors, such as LXR alpha, was elevated in spherical FLC-4 cells. We found the first time that the expressions of genes related to malignancy of hepatoma cells, such as HIF-1 alpha, c-Myc and VEGFC, were downregulated by spherical cell shape. Network analysis revealed that HNF-4 alpha would elicit both the enhancement of hepatocyte-specific gene expression and suppression of malignancy. Since HNF-4 alpha gene expression was known to be regulated by microRNA, we inferred that spherical cell shape would induce HNF-4 alpha gene expression through microRNA. To investigate the possibility of such a mechanism, mRNA-microRNA interactions were examined using microRNA microarray and bioinformatics analysis. The level of miR-24, a microRNA targeting HNF-4 alpha, was reduced in spherical FLC-4 cells. On the other hand, spherical cell shape-induced miR-194 and miR-320c would directly downregulate SLC7A5 and E2F1 gene expression, respectively, which are both related to malignancy. Our study suggested that spherical cell shape would induce HNF-4 alpha gene expression and consequent enhancement hepatocyte-specific functions. Spherical cell shape itself would suppress malignancy in FLC-4 cells through microRNA, such as miR-194 and miR-320c. (C) 2012. Published by The Company of Biologists Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial Share Alike License (http://creativecommons.org/licenses/by-nc-sa/3.0).