Targeting MET Receptor in Rhabdomyosarcoma: Rationale and Progress.

MET is a tyrosine kinase receptor, which binds hepatocyte growth factor (HGF). It regulates many physiological processes and participates in the regulation of proliferation, differentiation and motility of various cells. It plays an important role in embryogenesis as well as in adult life. Aberrations within the regulatory pathways activated by MET can be one of the causes of tumor development. Recently novel important functions of MET signaling in tumor development have been described, such as maintenance of cancer stem cells or importance of endosomal localization of MET. Moreover, MET is considered as one of the important factors responsible for development of rhabdomyosarcoma (RMS), a soft tissue sarcoma related to myogenic lineage. Its origin remains debatable but it is suggested that it derives from defect in differentiation of the satellite cells or of the mesenchymal stem cells. In RMS MET downregulation induces differentiation of tumor cells and in consequence, metastatic potential of RMS cells is diminished. Therefore, blocking of MET may be clinically useful in novel differentiationbased therapies of RMS in future.