Hedgehog signal inhibitors suppress the invasion of human rhabdomyosarcoma cells

PURPOSE: In the treatment of rhabdomyosarcoma (RMS), invasion and metastasis remain the most critical determinants of resectability and survival. The objective of this study was to determine whether Hedgehog (Hh) signaling plays a role in the invasion of RMS. METHODS: Two kinds of specific Hh signaling inhibitors, cyclopamine and forskolin, were used to suppress activated Hh signals in three RMS cell lines. The effects of the Hh signaling inhibitors on tumor cell invasion and motility were investigated using Matrigel invasion assays and wound closure assays, respectively. RESULTS: The number of invaded cells counted in six random microscopic fields in the Matrigel chambers was significantly decreased by both cyclopamine and forskolin in every RMS cell line. Furthermore, the wound closure assays revealed that a blockade of the Hh signaling pathway by the Hh inhibitors strongly impairs RMS cell motility, as visualized by the delayed closure of the gaps generated in the cultured cell monolayers of the three RMS cell lines. CONCLUSIONS: Both the invasive capacity and motility of RMS cells are significantly suppressed by Hh signaling inhibitors, demonstrating that the Hh pathway plays an important role in the invasion of RMS. Hh inhibitors may provide a new paradigm for the treatment of RMS.