Functional screening of FGFR4-driven tumorigenesis identifies PI3K/mTOR inhibition as a therapeutic strategy in rhabdomyosarcoma

• Published in: Oncogene Vol. 37; no. 20; pp. 2630 - 2644
• Main Authors: McKinnon, Timothy, Venier, Rosemarie, Yohe, Marielle, Sindiri, Sivasish, Gryder, Berkley E., Shern, Jack F., Kabaroff, Leah, Dickson, Brendan, Schleicher, Krista, Chouinard-Pelletier, Guillaume, Menezes, Serena, Gupta, Abha, Zhang, Xiaohu, Guha, Rajarashi, Ferrer, Marc, Thomas, Craig J., Wei, Yuhong, Davani, Dariush, Guidos, Cynthia J., Khan, Javed, Gladdy, Rebecca A.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2018; Nature Publishing Group
• Subjects: 13/31; 13/51; 13/95; 38/39; 631/154; 631/67/1798; 64/60; 96/1; 96/106; 96/98; Animals; Apoptosis; Area Under Curve; Cell Biology; Cell Line; Cell Survival - drug effects; Development and progression; Drug screening; Drug therapy; Genetic aspects; Growth factor receptors; Health aspects; Human Genetics; Humans; Identification and classification; Internal Medicine; Medicine; Medicine & Public Health; Mice; Mutation; Neoplasm Transplantation; Oncology; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation - drug effects; Protein tyrosine kinase; Pyridazines; Quinolines - administration & dosage; Quinolines - pharmacology; Receptor, Fibroblast Growth Factor, Type 4 - genetics; Receptor, Fibroblast Growth Factor, Type 4 - metabolism; Rhabdomyosarcoma; Rhabdomyosarcoma - drug therapy; Rhabdomyosarcoma - genetics; Rhabdomyosarcoma - pathology; Signal Transduction - drug effects; Sulfonamides - administration & dosage; Sulfonamides - pharmacology; TOR Serine-Threonine Kinases - antagonists & inhibitors; Tumors in children; Up-Regulation - drug effects; Xenograft Model Antitumor Assays; Canada; United States
• ISSN: 0950-9232; 1476-5594; 1476-5594
• DOI: 10.1038/s41388-017-0122-y

Rhabdomyosarcoma (RMS) is the most common pediatric soft tissue sarcoma and outcomes have stagnated, highlighting a need for novel therapies. Genomic analysis of RMS has revealed that alterations in the receptor tyrosine kinase (RTK)/RAS/PI3K axis are common and that FGFR4 is frequently mutated or overexpressed. Although FGFR4 is a potentially druggable receptor tyrosine kinase, its functions in RMS are undefined. This study tested FGFR4-activating mutations and overexpression for the ability to generate RMS in mice. Murine tumor models were subsequently used to discover potential therapeutic targets and to test a dual PI3K/mTOR inhibitor in a preclinical setting. Specifically, we provide the first mechanistic evidence of differential potency in the most common human RMS mutations, V550E or N535K, compared to FGFR4 wt overexpression as murine myoblasts expressing FGFR4 V550E undergo higher rates of cellular transformation, engraftment into mice, and rapidly form sarcomas that highly resemble human RMS. Murine tumor cells overexpressing FGFR4 V550E were tested in an in vitro dose–response drug screen along with human RMS cell lines. Compounds were grouped by target class, and potency was determined using average percentage of area under the dose–response curve (AUC). RMS cells were highly sensitive to PI3K/mTOR inhibitors, in particular, GSK2126458 (omipalisib) was a potent inhibitor of FGFR4 V550E tumor-derived cell and human RMS cell viability. FGFR4 V550E -overexpressing myoblasts and tumor cells had low nanomolar GSK2126458 EC 50 values. Mass cytometry using mouse and human RMS cell lines validated GSK2126458 specificity at single-cell resolution, decreasing the abundance of phosphorylated Akt as well as decreasing phosphorylation of the downstream mTOR effectors 4ebp1, Eif4e, and S6. Moreover, PI3K/mTOR inhibition also robustly decreased the growth of RMS tumors in vivo. Thus, by developing a preclinical platform for testing novel therapies, we identified PI3K/mTOR inhibition as a promising new therapy for this devastating pediatric cancer.