FGFR1 over-expression in primary rhabdomyosarcoma tumors is associated with hypomethylation of a 5′ CpG wand and abnormal expression of the AKT1, NOG, and BMP4 genes

Rhabdomyosarcoma (RMS), the most common pediatric soft tissue sarcoma likely results from abnormal proliferation and differentiation during skeletal myogenesis. Multiple genetic alterations are associated with the three RMS histopathological subtypes, embryonal, alveolar, and pleomorphic adult variant. Recently, we reported the novel amplification of the FGFR I gene in a RIMS tumor. The involvement of FGFRI in RMS was now further studied in primary tumors and RMS cell lines by mutation screening, quantitative RNA expression, and methylation analyses. No mutation was found by DHPLC and sequencing of the entire FGFR/coding sequence and exon-intron boundaries. However, FGFR I over-expression was detected in all primary RMS tumors and cell lines tested. A hypomethylation of a CpG island upstream to FGFRI exon I was identified in the primary RIMS tumors, using sodium bisulfite modification method, suggesting a molecular mechanism to FGFRI over-expression. Expression analysis of additional genes, AKTI, NOG and its antagonist BMP4, which interact downstream to FGFR I, demonstrated expression differences between primary RMS tumors and normal skeletal muscles. Our data suggest an important role for FGFR I and FGFRI-downstream genes in RMS tumorigenesis and a possible association with the deregulation of proliferation and differentiation of skeletal myoblasts in RMS. (C) 2007 Wiley-Liss, Inc.