Data from An Imbalance in TAZ and YAP Expression in Hepatocellular Carcinoma Confers Cancer Stem Cell–like Behaviors Contributing to Disease Progression

Abstract

<div>Abstract<p>Transcriptional coactivator with PDZ-binding motif (TAZ) and yes-associated protein (YAP) are equivalently placed downstream effectors of the Hippo pathway with oncogenic roles in human cancers. However, the expression profiles of TAZ/YAP differ depending on the cancer cell type, suggesting that these proteins have different roles during cancer progression, yet no studies have examined the biologic significance of the balance between TAZ and YAP expression levels. Here we examined the functional roles of TAZ/YAP in hepatocellular carcinoma progression. We found that TAZ, but not YAP, was predominantly expressed in HCC. <i>TAZ</i> knockdown under normal conditions attenuated cell growth in HCC cells; however, <i>TAZ</i> knockdown combined with 5-fluorouracil treatment significantly increased chemoresistance compared with control cells. Notably, <i>TAZ</i> knockdown induced compensatory YAP expression and was accompanied by upregulation of CD90, a HCC–specific cancer stem cell marker. Continuous treatment with 5-fluorouracil also induced YAP expression and promoted tumor formation in <i>vivo</i>. Conversely, double knockdown of <i>TAZ/YAP</i> reduced chemoresistance and tumorigenicity. Moreover, <i>YAP</i> knockdown aggravated HCC cell growth to a greater degree than <i>TAZ</i> knockdown, and <i>YAP</i> overexpression was strongly associated with poor prognoses in patients with HCC. Collectively, these studies demonstrate that TAZ and YAP exhibit different functional roles in cancer progression, and a shift to predominant YAP expression upon TAZ depletion conferred cancer stem cell–like properties including chemoresistance and tumorigenicity in HCC. Therefore, targeting of both TAZ/YAP will be required for a complete antitumor response in HCC. <i>Cancer Res; 75(22); 4985–97. ©2015 AACR</i>.</p></div>