Overexpression of FGF receptor 3 (FGFR3) is implicated in the development of t(4;14

Fibroblast growth factor receptor 3 (FGFR3) belongs to a family of receptor tyrosine kinases that control cell proliferation, differentiation, and survival. Aberrant activation of FGFR3 via overexpression or mutation is a frequent feature of bladder cancer; however, its molecular and cellular consequences and functional relevance to carcinogenesis are not well understood. Through transcriptional profiling of bladder carcinoma cells subjected to short hairpin RNA knockdown of FGFR3, we identified a gene-signature linking FGFR3 signaling with de novo sterol and lipid biosynthesis and metabolism. We found that FGFR3 signaling promotes the cleavage and activation of the master transcriptional regulator of lipogenesis, sterol regulatory element-binding protein 1 (SREBP1/SREBF1), in a PI3K-mTORC1-dependent fashion. In turn, SREBP1 regulates the expression of key lipogenic enzymes, including stearoyl CoA desaturase 1 (SCD1/SCD). SCD1 is the rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids and is crucial for lipid homeostasis. In human bladder cancer cell lines expressing constitutively active FGFR3, knockdown of SCD1 by siRNA markedly attenuated cell-cycle progression, reduced proliferation, and induced apoptosis. Furthermore, inducible knockdown of SCD1 in a bladder cancer xenograft model substantially inhibited tumor progression. Pharmacologic inhibition of SCD1 blocked fatty acid desaturation and also exerted antitumor activity in vitro and in vivo. Together, these findings reveal a previously unrecognized role of FGFR3 in regulating lipid metabolism to maintain tumor growth and survival, and also identify SCD1 as a potential therapeutic target for FGFR3-driven bladder cancer. Cancer Res; 72(22); 5843-55. Ó2012 AACR.

Purpose: The aim of this study was to identify noninvasive pharmacodynamic biomarkers of FGFR3-targeted therapies in bladder cancer to facilitate the clinical development of experimental agent targeting FGFR3.Experimental Design: Potential soluble pharmacodynamic biomarkers of FGFR3 were identified using a combination of transcriptional profiling and biochemical analyses in preclinical models. Two matrix metalloproteinases (MMP), MMP-1 and MMP-10, were selected for further studies in human bladder cancer xenograft models treated with a specific anti-FGFR3 monoclonal antibody, R3Mab. Serum and urinary levels of MMP-1 and MMP-10 were determined in healthy donors and patients with bladder cancer. The modulation of MMP-1 and MMP-10 by R3Mab in patients with bladder cancer was further evaluated in a phase I dose-escalation study.Results: MMP-1 and MMP-10 mRNA and protein were downmodulated by FGFR3 shRNA and R3Mab in bladder cancer cell lines. FGFR3 signaling promoted the expression and secretion of MMP-1 and pro-MMP-10 in a MEK-dependent fashion. In bladder cancer xenograft models, R3Mab substantially blocked tumor progression and reduced the protein levels of human MMP-1 and pro-MMP-10 in tumor tissues as well as in mouse serum. Furthermore, both MMP-1 and pro-MMP-10 were elevated in the urine of patients with advanced bladder cancer. In a phase I dose-escalation trial, R3Mab administration resulted in an acute reduction of urinary MMP-1 and pro-MMP-10 levels in patients with bladder cancer.Conclusion: These findings reveal a critical role of FGFR3 in regulating MMP-1 and pro-MMP-10 expression and secretion, and identify urinary MMP-1 and pro-MMP-10 as potential pharmacodynamic biomarkers for R3Mab in patients with bladder cancer. Clin Cancer Res; 20(24); 6324-35. Ó2014 AACR.

<p>XLS file - 97KB, List of genes that showed significant changes upon FGFR3 knockdown.</p>

<p>PDF file, 114KB, This section includes Supplemental Materials and Methods. It also contains the legends to Supplemental Figures 1-9.</p>