Abstract 3189: Aggressive renal cancer cell behavior is partly mediated by CD98hc

Abstract

Abstract CD98, a heteromeric transmembrane protein, consists of a heavy subunit (4F2hc, SLC3A2), extracellular linked to a light subunit. The light chains provide amino acid transport activity of CD98. Recently, we could show that CD98hc directly interacts with a conserved motif in integrin beta subunits, thereby mediating outside - in signaling. A genetic knockout of CD98hc in animals is embryonic lethal, whereas overexpression of CD98hc in somatic cells leads to malignant transformation. Recently, we reported that high CD98hc expression is a novel and reliable diagnostic marker for the more malignant subtype II papillary renal cell cancer marker (pRCC). Thereby, CD98hc expression directly correlated with grade of differentiation. In the present study, we identified the functional role of CD98hc in clear cell renal cell cancer (ccRCC) behavior. First, we generated stable low CD98hc ccRCCs by the use of a shRNA lentiviral construct and compared tumor cell behavior with high CD98hc expressing mock infected ccRCCs. We found that downregulation of CD98hc led to an altered tumor cell behavior including tumor cell survival, migration and proliferation. Expression of a silent mutation - lacking shRNA binding motif - reconstituted CD98hc expression in lowCD98hc ccRCC, thereby restoring aggressive tumor cell behavior. By introducing CD98hc mutations either lacking integrin binding capacities or light chain interactions, we could identify the functional role of leucine amino acid transport in tumor cell proliferation, as affected C14-leucine uptake was directly correlated with tumor cell proliferative activity. In contrast, mutants lacking interaction sites for integrins showed defects adhesion-induced FAK phosphorylation and c-src activation, leading to reduced tumor cell adhesion and spreading. A biological relevance of the in vitro finding was confirmed in in vivo tumor xenotransplant assays, whereby stable low CD98hc/ccRCCs either reconstituted with wild type CD98hc or with mutated CD98hc were used. Only wild type reconstitution was capable to restore full aggressiveness of tumor growth and metastasis formation. From our data we conclude that CD98 partially mediates functional activity of renal cancer cell behavior. Thus, CD98hc-mediated tumor cell behavior may offer a potential novel therapeutic target for the treatment of cancer. Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3189.