Data from Knockdown of <i>Apolipoprotein E</i> Enhanced Sensitivity of Hep3B Cells to Cardiac Steroids via Regulating Na<sup>+</sup>/K<sup>+</sup>-ATPase Signalosome

Abstract

<div>Abstract<p>This study compared the sensitivity of human hepatoma Hep3B, SK-HEP-1, SMMC-7721, and BEL-7402 cells to cardiac steroids, including bufalin (BF), a bufalin derivative (BF211), ouabain (OUA), and digitoxin (DIG). Hep3B cells exhibited relatively low sensitivity to cardiac steroids. Expression levels of subunits of Na<sup>+</sup>/K<sup>+</sup>-ATPase were high in Hep3B cells. However, colocalization of Na<sup>+</sup>/K<sup>+</sup>-ATPase and caveolin was nearly undetectable in Hep3B cells. By using RNA-Seq technology, we found a total of 36 genes to be differentially expressed between Hep3B cells and SK-HEP-1 cells, which are highly sensitive to cardiac steroids. Our bioinformatics analysis determined that these genes were mostly comprised of extracellular space, protein binding, and extracellular region. Among these 36 genes, <i>apolipoprotein E</i> (<i>APOE</i>) played a critical role, as knockdown <i>APOE</i> expression induced colocalization of Na<sup>+</sup>/K<sup>+</sup>-ATPase and caveolin and increased sensitivity of Hep3B cells to both proliferation-inhibiting and cytotoxic effects of BF or BF211. Also, the effects of BF on PI3K/AKT/GSK3β and apoptosis signal cascades were enhanced in <i>APOE</i> knockdown cells. The results of our study confirmed the role of Na<sup>+</sup>/K<sup>+</sup>-ATPase signalosome in cytotoxicity of cardiac steroids and suggested that <i>APOE</i> regulated the sensitivity of cells to cardiac steroids by affecting formation and function of Na<sup>+</sup>/K<sup>+</sup>-ATPase signalosome. In addition, intercellular interaction with high level of Na<sup>+</sup>/K<sup>+</sup>-ATPase β1 subunit may be also a factor in the low sensitivity of Hep3B cells to cardiac steroids. <i>Mol Cancer Ther; 15(12); 2955–65. ©2016 AACR</i>.</p></div>