Abstract 1985: The activation of GSK3 by HGF-MET axis is responsible for differentiation of rhabdomyosarcoma cells

Abstract

Abstract Introduction: Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma among children. At the late stages (metastatic) the outcome for the patients is very poor. The molecular basis for loss of cell differentiation in the process of carcinogenesis is not well understood. Differentiation status of rhabdomyosarcoma cells strongly influences its progression and metastatic ability and therefore the overall patient survival. At the onset of myogenic differentiation MET receptor is rapidly downregulated and on the other hand the activation of MET receptor in rhabdomyosarcoma has been shown to influence proliferation, survival and migration. Aim: Dissecting the role of HGF-MET receptor axis and GSK3 activation in the process of RMS differentiation. Materials and methods: Cell lines used in experiments: RH30 (ARMS), SMS-CTR (ERMS). Real time RT-PCR and western blotting were used to evaluate gene expression and the activation of various intracellular signaling pathways, respectively. The evaluation of protein activation in RMS cell lines was performed after stimulation with HGF. Results: We found that, during differentiation process the expression of MyoD, characteristic for poorly differentiated rhabdomyosarcoma cells decreased and the expression of myogenin, protein characteristic for differentiated/ matured muscle cells increased. That was paralleled by decreased expression of MET receptor. In RMS cell lines with stable downregulation of MET receptor the expression of differentiation related genes was similar to differentiated RMS cells. When we study the activation of GSK3 we observed the phosphorylation of GSK3 beta on serine 9 after HGF stimulation. The intracellular pathway responsible for GSK3 beta phosphorylation turn out to be PI3K-AKT dependent. We observed also the accumulation of beta-catenin in the nucleus of RMS cells stimulated with HGF. This effect was father augmented when HGF was used together with BIO, small molecular inhibitor of GSK3 beta. Conclusion and future directions: In this study we have shown that the expression and signaling of MET receptor is responsible for differentiation of RMS cells. Moreover we postulate that MET receptor exerts its influence on RMS cells differentiation through GSK3 beta activation. These findings might have the significant clinical implication for the treatment of RMS cells because they suggest that induction of differentiation of RMS cells by blocking MET receptor could inhibit growth of RMS tumors. Finally, we think that also GSK3 beta could be used as the new therapeutic target to induce differentiation of RMS. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1985. doi:10.1158/1538-7445.AM2011-1985