Targeting Wild-Type and Mutationally Activated FGFR4 in Rhabdomyosarcoma with the Inhibitor Ponatinib (AP24534)

Samuel Q Li,Jun S Wei,Hongling Liao,Adam T Cheuk,Young K Song,Javed Khan,Jack F Shern,Laura Hurd,Anette Duensing

doi:10.1371/journal.pone.0076551

Abstract

Rhabdomyosarcoma (RMS) is the most common childhood soft tissue sarcoma. Despite advances in modern therapy, patients with relapsed or metastatic disease have a very poor clinical prognosis. Fibroblast Growth Factor Receptor 4 (FGFR4) is a cell surface tyrosine kinase receptor that is involved in normal myogenesis and muscle regeneration, but not commonly expressed in differentiated muscle tissues. Amplification and mutational activation of FGFR4 has been reported in RMS and promotes tumor progression. Therefore, FGFR4 is a tractable therapeutic target for patients with RMS. In this study, we used a chimeric Ba/F3 TEL-FGFR4 construct to test five tyrosine kinase inhibitors reported to specifically inhibit FGFRs in the nanomolar range. We found ponatinib (AP24534) to be the most potent FGFR4 inhibitor with an IC50 in the nanomolar range. Ponatinib inhibited the growth of RMS cells expressing wild-type or mutated FGFR4 through increased apoptosis. Phosphorylation of wild-type and mutated FGFR4 as well as its downstream target STAT3 was also suppressed by ponatinib. Finally, ponatinib treatment inhibited tumor growth in a RMS mouse model expressing mutated FGFR4. Therefore, our data suggests that ponatinib is a potentially effective therapeutic agent for RMS tumors that are driven by a dysregulated FGFR4 signaling pathway.

Highlights

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in childhood, accounting for about 3% of all childhood tumors [1]
RMS cells with overexpressed wild-type Fibroblast Growth Factor Receptor 4 (FGFR4) are more sensitive to ponatinib
This is consistent with the fact that fusion-positive RMS cell lines typically express higher levels of FGFR4 (Figure S3B, p = 0.0005), because it is directly induced by the PAX3-FOXO1 fusion gene [13]

Summary

Introduction

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in childhood, accounting for about 3% of all childhood tumors [1]. Treatment of RMS includes the use of intensive chemotherapeutic regimens in combination with surgical and radiation therapy. This strategy has improved the survival rate for patients with localized disease to 70% albeit with significant toxicity [2]. High risk patients continue to have a poor prognosis with overall survival rates of 20–30% [3]. RMS tumors typically arise from skeletal muscle and are categorized as either of the alveolar (ARMS) or embryonal (ERMS) subtype based on their histology. ERMS tumors commonly harbor loss of heterozygosity at 11p15.5 [5] as well as point mutations in TP53 [6], NRAS, KRAS, HRAS [7], PIK3CA [8] and FGFR4 [9] genes

Methods

Results

Conclusion