Our results indicate that both mutations and overexpression of FGFR3 are correlated together, and are more prevalent in early stage (pTa and pT1) and low grade (G1 and G2) bladder tumors.
The phenotypic consequences of constitutive activation of FGFR3 in bladder cancer have not been elucidated and further studies are required to confirm the consequences of inhibiting receptor activity in urothelial cells.
Bladder cancer cell lines were exposed to normoxic or hypoxic conditions and examined for the expression of FGFR3 by quantitative PCR (qPCR) and western blotting, and miR-100 by qPCR.
Further investigation showed that FGFR3 knockdown resulted in downregulation of DAPK1 in bladder cancer cell line, suggesting that FGFR3 may be an upstream factor of DAPK1.
Our findings are consistent with the results of the TCGA data set for the "squamous-like" subtype of bladder cancer (n = 85), which revealed reduced overall expression of FGFR1 and FGFR2 in tumors compared to normal tissue, while expression of FGFR3 remained high.
Knockdown of endogenous FGFR3 impaired the activity of daidzein against bladder cancer, which suggested that the effect of daidzein was mainly mediated by FGFR3 pathway.
Molecular grade (mG) based on fibroblast growth factor receptor 3 (FGFR3) gene mutation status and MIB-1 expression was proposed as an alternative to pathologic grade in bladder cancer (BCa) [1].
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.
Massively parallel sequencing of sperm DNA showed that levels of the FGFR3 mutation increase with paternal age and that the mutation spectrum at the Lys650 codon is similar to that observed in bladder cancer.
In contrast, there are very few studies on the impact of miRNA regulation on signaling by VHL (von Hippel-Lindau tumor suppressor) and vascular endothelial growth factor in renal cell carcinoma or by fibroblast growth factor receptor 3 and p53 in bladder cancer.
The identification of mutations of FGF receptor 3 (FGFR3) in most noninvasive bladder tumors and the recent finding of overexpression of this receptor not only in superficial tumors but also in many invasive bladder cancers has generated optimism that therapies targeting this receptor tyrosine kinase may have major application in the treatment of urothelial cancers.
Whole-genome and whole-exome sequencing of bladder cancer identifies frequent alterations in genes involved in sister chromatid cohesion and segregation.
In conclusion we retain that activated RAS and FGFR3 do not appear to be drivers in bladder cancer but the mutually exclusive relationship between RAS and FGFR3 mutations indicates a possible clonal advantage of modified signaling via a common pathway.
In summary, alternative splicing of FGFR3 IIIb in NHU cells represents a normal mechanism to generate a transcript that regulates proliferation and in bladder cancer, the ratio of FGFR3 isoforms is significantly altered.