Oncogene database

2261

FGFR3

fibroblast growth factor receptor 3;FGFR3;fibroblast growth factor receptor 3

FGFR-3|fibroblast growth factor receptor 3 variant 4|hydroxyaryl-protein kinase|tyrosine kinase JTK4

4p16.3

protein-coding

The t(4;14) translocation occurs frequently in multiple myeloma (MM) and results in the simultaneous dysregulated expression of 2 potential oncogenes, FGFR3 (fibroblast growth factor receptor 3) from der(14) and multiple myeloma SET domain protein/Wolf-Hirschhorn syndrome candidate gene 1 from der(4). It is now shown that myeloma cells carrying a t(4;14) translocation express a functional FGFR3 that in some cases is constitutively activated by the same mutations that cause thanatophoric dysplasia. As with activating mutations of K-ras and N-ras, which are reported in approximately 40% of patients with MM, activating mutations of FGFR3 occur during tumor progression. However, the constitutive activation of ras and FGFR3 does not occur in the same myeloma cells. Thus the activated forms of these proteins appear to share an overlapping role in tumor progression, suggesting that they also share the signaling cascade. Consistent with this prediction, it is shown that activated FGFR3-when expressed at levels similar to those seen in t(4;14) myeloma-is an oncogene that acts through the MAP kinase pathway to transform NIH 3T3 cells, which can then generate tumors in nude mice. Thus, FGFR3, when overexpressed in MM, may be not only oncogenic when stimulated by FGF ligands in the bone marrow microenvironment, but is also a target for activating mutations that enable FGFR3 to play a ras-like role in tumor progression.

Translocations involving fibroblast growth factor receptor 3 (fgfr3) have been identified in about 25% of patients with myeloma. To directly examine the oncogenic potential of fgfr3, murine bone marrow (BM) cells were transduced with retroviral vectors containing either wild-type fgfr3 or an activated mutant form of the receptor, fgfr3-TD. Mice transplanted with FGFR3-TD-expressing BM developed a marked leukocytosis and lethal hematopoietic cell infiltration of multiple tissues within 6 weeks of transplantation. Secondary and tertiary recipients of spleen or BM from primary fgfr3-TD mice also developed tumors within 6 to 8 weeks. Analysis of the circulating tumor cells revealed a pre-B-cell phenotype in most mice, although immature T-lymphoid or mature myeloid populations also predominated in some animals. Enhanced lymphoid but not myeloid colony formation was observed in the early posttransplantation period and only interleukin 7 and FGF-responsive pre-B-cell lines could be established from tumors. Cell expansions in primary recipients appeared polyclonal, whereas tumors in later passages exhibited either clonal B- or T-cell receptor gene rearrangements. Mice transplanted with wild-type FGFR3-expressing BM developed delayed pro-B-cell lymphoma/leukemias approximately 1 year after transplantation. These studies confirm that FGFR3 is transforming and can produce lymphoid malignancies in mice.

Translocations involving the immunoglobulin heavy-chain switch region and fibroblast growth factor receptor 3 (FGFR3) are identified in 10% to 15% of patients with myeloma. In previous research we overexpressed FGFR3 or the constitutively active FGFR3-TD mutant in an interleukin-6 (IL-6)-dependent murine myeloma cell line, B9. FGFR3-enhanced IL-6 responsiveness increased phosphorylation of STAT3 and up-regulated Bcl-x(L). Since Bcl-x(L) was up-regulated, we have tested FGFR3-expressing B9 cells for chemotherapy sensitivity. FGFR3 expression did not alter sensitivity to melphalan or doxorubicin. In contrast, B9 cells overexpressing FGFR3 were resistant to treatment with dexamethasone, a phenomenon successfully reversed using a Bcl-x(L) antisense oligonucleotide. These data demonstrate that the overexpression of FGFR3 in B9 cells confers resistance to dexamethasone but not to anthracyclines or alkylating agents, at least in part through the up-regulation of Bcl-x(L). This finding has potential implications for the use of chemotherapy in t(4;14)-positive myeloma.

Receptor tyrosine kinases (RTKs) such as the fibroblast growth factor receptor (FGFR) and the epidermal growth factor receptor are overexpressed in a variety of cancers. In addition to overexpression, the FGFRs are found mutated in some cancers. The Src homology 2 domain-containing phosphotyrosine phosphatase (SHP2) is a critical mediator of RTK signaling, but its role in oncogenic RTK-induced cell transformation and cancer development is largely unknown. In the current report, we demonstrate that constitutively activated FGFR3 (K/E-FR3) transforms NIH-3T3 cells, and that SHP2 is a critical mediator of this transformation. Infection of K/E-FR3-transformed 3T3 cells with a retrovirus carrying a dominant-negative mutant of SHP2 (C/S-SHP2) retarded cell growth, reversed the transformation phenotype and inhibited focus-forming ability. Furthermore, treatment of K/E-FR3-transformed NIH-3T3 cells with PD98059 or LY294002, specific inhibitors of MEK and PI3K, respectively, inhibited focus formation. Biochemical analysis showed that K/E-FR3 activates the Ras-ERK and the PI3K signaling pathways, and that the C/S SHP2 mutant suppressed this effect via competitive displacement of interaction of the endogenous SHP2 with FRS2. However, the C/S SHP2 protein did not show any effect on receptor autophosphorylation, FRS2 tyrosine phosphorylation or interaction of Grb2 with K/E-FR3 or FRS2. Together, the results show that K/E-FR3 is transforming and that the Ras-ERK and the PI3K-Akt signaling pathways, which are positively regulated by SHP2, are important for K/E-FR3-induced transformation.

AIMS: Urothelial tumors of the upper urinary tract (UUTT) frequently display microsatellite Instability (MSI) and a distinct pathway of tumorigenesis resembling MMR-deficient colorectal cancers has been recognized for MSI-UUTT. For MSS-UUTT however oncogenic mechanisms as in bladder cancer (BC) are debated. mutation of the oncogene FGFR3 has been linked to lower stage, lower grade and favourable clinical outcome in BC. The aim of this study was to evaluate FGFR3 mutation in MSI and MSS-UUTT. METHODS: 172 unselected UUTT were screened for MSI using the National cancer Institute Consensus Panel and additional markers; FGFR3 status was studied using mutation analysis. Histopathological and clinical data were reviewed. RESULTS: Microsatellite status had no impact on histopathological or clinical outcome. 52/99 MSS, 10/22 MSI-low and 25/51 MSI-high UUTT displayed mut. FGFR3 respectively. Overall FGFR3 mutation was associated with favourable stage and grade (p <0.0001 and p <0.002), as 62.1% of mut. vs. 23.5 % of wt. FGFR3 UUTT were stage Ta and T1 and graded G3 in 25.3 % vs. 47.1% respectively. That effect depended on MS-status however, as FGFR3 mutation was related to lower stage (pTa and pT1) in MSS/MSI-L (mut 62.9 % vs. wt 18.7%; p <0.01) only as opposed to MSI-H (mut 60% vs. wt. 50%; p = 0,1) UUTTs and as FGFR3 mut UUTTs tended to display lower grade (G1 and G2) provided stable (mut 74,2 % vs. wt. 44.1%; p <0,01) as opposed to instable microsatellite status (mut 76 % vs. wt. 73 %; p = 0.7). There was no marked relation of MS-status or FGFR3 mutation to sex, age or tobacco-exposure; localization in the renal pelvis (p < 0.01) however was more prevalent in the FGFR3 mut group. As opposed to MSI-status FGFR3 mutation had a favourable impact on survival, as 24.1% vs. 54.2 % cancer related deaths occured in the mutated group (p <0.001); this effect was indendent on stage or MSI-status. Neither MSI- nor FGFR3-status had any influence on subsequent bladder tumors. CONCLUSIONS: FGFR3 mutation is frequent in UUTT and appears to be independent of MS-status; however it is related to significantly favourable histopathological parameters and clinical outcome in MSS cases. Thus our findings might back the notion, that MSS and MSI-UUTTs stem from different oncogenic pathways and that their differing molecular character might have some relevance. Further research is warranted to study the clinical behavior of these tumors and to evaluate a potential role for MS-status and FGFR3 as prognostic tools.

The tyrosine kinase c-Src is upregulated in various human cancers, but the molecular mechanisms underlying c-Src-mediated tumor growth remain unclear. Here we examined the involvement of microRNAs in the c-Src-mediated tumor growth. Microarray profiling revealed that c-Src activation downregulates a limited set of microRNAs, including miR-99a, which targets oncogenic mammalian target of rapamycin (mTOR) and fibroblast growth factor receptor 3 (FGFR3). Re-expression of miR-99a suppressed tumor growth of c-Src-transformed cells, and this effect was restored by the overexpression of mTOR. The downregulation of miR-99a was also observed in epidermal growth factor- and Ras-transformed cells, and it was suppressed by inhibiting the mitogen-activated protein kinase (MAPK) pathway. Furthermore, miR-99a downregulation is associated with mTOR/FGFR3 upregulation in various human lung cancer cells/tissues. The tumorigenicity of these cells was suppressed by the introduction of miR-99a. These findings suggest that the miR-99a-mTOR/FGFR3 pathway is crucial for controlling tumor growth in a wide range of human cancers that harbor upregulation of the Src-related oncogenic pathways.

FGF receptor 3 (FGFR3) is activated by mutation or over-expression in many bladder cancers. Here, we identify an additional mechanism of activation via chromosomal re-arrangement to generate constitutively activated fusion genes. FGFR3-transforming acid coiled coil 3 (TACC3) fusions resulting from 4p16.3 re-arrangements and a t(4;7) that generates a FGFR3-BAI1-associated protein 2-like 1 (BAIAP2L1) fusion were identified in 4 of 43 bladder tumour cell lines and 2 of 32 selected tissue samples including the tumour from which one of the cell lines was derived. These are highly activated and transform NIH-3T3 cells. The FGFR3 component is identical in ALL cases and lacks the final exon that includes the phospholipase C gamma 1 (PLCgamma1) binding site. expression of the fusions in immortalized normal human urothelial cells (NHUC) induced activation of the mitogen-activated protein kinase pathway but not PLCgamma1. A protein with loss of the terminal region alone was not as highly activated as the fusion proteins, indicating that the fusion partners are essential. The TACC3 fusions retain the TACC domain that mediates microtubule binding and the BAIAP2L1 fusion retains the IRSp53/MIM domain (IMD) that mediates actin binding and Rac interaction. As urothelial cell lines with FGFR3 fusions are extremely sensitive to FGFR-selective agents, the presence of a fusion gene may aid in selection of patients for FGFR-targeted therapy.

Activating mutations of FGFR3 are a common and early event in bladder cancer. Ectopic expression of mutant FGFR3 in normal urothelial cells has both pro-proliferative and antiapoptotic effects at confluence, suggesting that mutant cells are insensitive to cell-cell contact inhibition. Herein, detailed analysis revealed that these cells have reduced cell-cell adhesion, with large intercellular spaces observable at confluence, and diminished cell-substrate adhesion to collagen IV, collagen I, and fibronectin. These phenotypic alterations are accompanied by changes in the expression of genes involved in cell adhesion and extracellular matrix remodeling. Silencing of endogenous mutant FGFR3 in bladder cancer cells induced converse changes in transcript levels of CDH16, PLAU, MMP10, EPCAM, TNC, and HAS3, confirming them as downstream gene targets of mutant FGFR3. Overexpression of EPCAM, HAS3, and MMP10 transcripts was found in a large fraction of primary bladder tumors analyzed, supporting their key role in bladder tumorigenesis in vivo. However, no correlation was found between their protein and/or mRNA expression and FGFR3 mutation status in tumor specimens, indicating that these genes may be targeted by several converging oncogenic pathways. Overall, these results indicate that mutant FGFR3 favors the development and progression of premalignant bladder lesions by altering key genes regulating the cell-cell and cell-matrix adhesive properties of urothelial cells. IMPLICATIONS: The ability of mutant FGFR3 to drive transcriptional expression profiles involved in tumor cell adhesion suggests a mechanism for expansion of premalignant urothelial lesions.

Recent cancer genome profiling studies have identified many novel genetic alterations, including rearrangements of genes encoding FGFR family members. However, most fusion genes are not functionally characterized, and their potentials in targeted therapy are unclear. We investigated a recently discovered gene fusion between FGFR3 and BAI1-associated protein 2-like 1 (BAIAP2L1). We identified 4 patients with bladder cancer and 2 patients with lung cancer harboring the FGFR3-BAIAP2L1 fusion through PCR and FISH assay screens. To investigate the oncogenic potential of the fusion gene, we established an FGFR3-BAIAP2L1 transfectant with Rat-2 fibroblast cells (Rat-2_F3-B). The FGFR3-BAIAP2L1 fusion had transforming activity in Rat2 cells, and Rat-2_F3-B cells were highly tumorigenic in mice. Rat-2_F3-B cells showed in vitro and in vivo sensitivity in the selective FGFR inhibitor CH5183284/Debio 1347, indicating that FGFR3 kinase activity is critical for tumorigenesis. Gene signature analysis revealed that FGFR3-BAIAP2L1 activates growth signals, such as the MAPK pathway, and inhibits tumor-suppressive signals, such as the p53, RB1, and CDKN2A pathways. We also established Rat-2_F3-B-DeltaBAR cells expressing an FGFR3-BAIAP2L1 variant lacking the Bin-Amphiphysin-Rvs (BAR) dimerization domain of BAIAP2L1, which exhibited decreased tumorigenic activity, FGFR3 phosphorylation, and F3-B-DeltaBAR dimerization, compared with Rat-2_F3-B cells. Collectively, these data suggest that constitutive dimerization through the BAR domain promotes constitutive FGFR3 kinase activation and is essential for its potent oncogenic activity.