FGFR3 has tumor suppressor properties in cells with epithelial phenotype - PubMed (original) (raw)

doi: 10.1186/1476-4598-12-83.

Isabelle Moranvillier, Stéphane Garcia, Evelyne Peuchant, Juan Iovanna, Benoit Rousseau, Pierre Dubus, Véronique Guyonnet-Dupérat, Geneviève Belleannée, Jeanne Ramos, Aurélie Bedel, Hubert de Verneuil, François Moreau-Gaudry, Sandrine Dabernat

Affiliations

FGFR3 has tumor suppressor properties in cells with epithelial phenotype

Marie Lafitte et al. Mol Cancer. 2013.

Abstract

Background: Due to frequent mutations in certain cancers, FGFR3 gene is considered as an oncogene. However, in some normal tissues, FGFR3 can limit cell growth and promote cell differentiation. Thus, FGFR3 action appears paradoxical.

Results: FGFR3 expression was forced in pancreatic cell lines. The receptor exerted dual effects: it suppressed tumor growth in pancreatic epithelial-like cells and had oncogenic properties in pancreatic mesenchymal-like cells. Distinct exclusive pathways were activated, STATs in epithelial-like cells and MAP Kinases in mesenchymal-like cells. Both FGFR3 splice variants had similar effects and used the same intracellular signaling. In human pancreatic carcinoma tissues, levels of FGFR3 dropped in tumors.

Conclusion: In tumors from epithelial origin, FGFR3 signal can limit tumor growth, explaining why the 4p16.3 locus bearing FGFR3 is frequently lost and why activating mutations of FGFR3 in benign or low grade tumors of epithelial origin are associated with good prognosis. The new hypothesis that FGFR3 can harbor both tumor suppressive and oncogenic properties is crucial in the context of targeted therapies involving specific tyrosine kinase inhibitors (TKIs). TKIs against FGFR3 might result in adverse effects if used in the wrong cell context.

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Figures

Figure 1

Figure 1

FGFR3 has tumor suppressor gene properties in BxPC-3 and Capan-2 pancreatic cell lines. A) Capan-2 cells were transduced with either control (a,d), FGFR3-IIIb (b,e) or FGFR3-IIIc ZsGreen lentivectors (c,f) and observed with a fluorescence microscope (original magnification ×40, bright field, a,b,c, green fluorescence, d,e,). Colonies with strong overexpression of either FGFR3-IIIb or –IIIc were smaller (arrows heads, b, c, e, f) than colonies with lower expression (arrows). Right panel: mean fluorescence intensity was determined for colonies transduced with the same lentivectors as in left panel, and were also transduced with a lentivector carrying a FGFR3-IIIc cDNA with the K508M mutation inactivating the kinase domain. B) FGFR3-IIIb and –IIIc overexpression decreased Capan-2 and BxPC-3 cell proliferation and (C) increased apoptosis. (D) FGFR3 forced expression had opposite effect on cell proliferation of Mia PaCa-2 and PANC-1 cells. NS: nor significant, *p = 0.05, **p < 0.01, ***p < 0.001.

Figure 2

Figure 2

Phenotypic properties of PDAC cell lines. A) FGFR3 expression in the PDAC cell lines was determined by western-blot. FGFR3 expression was the highest in BxPC-3 cells and the lowest in Mia PaCa-2 cells. Membranes were reprobed for GAPDH to test equivalent loading. B) FGFR3 splice variants relative mRNA level were determined by RT-qPCR with specific primers and normalized with RPLP0 used as a mRNA expression internal reference. C) Epithelial E-cadherin and mesenchymal vimentin markers mRNA levels were determined by RT-qPCR. Capan-2 and BxPC-3 cells were epithelial, whereas the Mia PaCa-2 cell line was more mesenchymal. PANC-1 cells displayed an intermediate phenotype. D) Light microscope pictures of the four tested cell lines (original magnification ×40). PANC-1 presented an epithelial phenotype despite the strong expression of vimentin.

Figure 3

Figure 3

FGFR3 conveys a negative signal in the pancreatic beta cell line BTC. A) BTC cells were cultured in the absence (CT) or in the presence of the neutralizing anti-FGFR3. Alternatively, cells were transiently transfected with a vector overexpressing FGFR3-IIIc or a control vector (CT). B) Tumors were produced from parental BTC cells (n = 12) or clones of BTC cells overexpressing stably FGFR3-IIIc (n = 17). Tumor masses were determined 6 weeks after cells were injected. ***: p < 0.001, **: p < 0.01.

Figure 4

Figure 4

FGFR3 engaged diverse intracellular pathways. Proteins extracts of tumors from Capan-2 and Mia PaCa-2, were analyzed by western-blot. See text for more details. CKIs: Cyclin-dependant kinase inhibitors. Membranes were reprobed for GAPDH to test equivalent loading. Results shown are representative of one out of at least 3 independent experiments.

Figure 5

Figure 5

FGFR3 expression in normal and pancreatic tumor tissues. A: (a, b) FGFR3 signal was found in islets of normal pancreas. (c) Co-localization of FGFR3 (green) and insulin (red). Nuclei were stained with DAPI (blue). (d-l) FGFR3 expression was assessed according to the signal obtained in normal pancreas (strong in islets, weak in the exocrine tissue). Twelve percent of pancreatic endocrine carcinomas (PEC, n = 25) displayed no FGFR3 signal (d), 56% showed weak (e) and only 32% had strong (normal, f) FGFR3 expression. For Intraductal papillary mucinous neoplasms (IPMN, n = 30), 63.3% had no signal (g), 30% had weak signal (normal, h) and 6.7% showed strong (i) FGFR3 expression. In Pancreatic ductal adenocarcinomas (PDAC, n = 88), 30.6% displayed no FGFR3 signal (j), 48.9% had weak (normal, k) and 20.5% showed strong (l) FGFR3 expression. Bars represent 50 μm. B: Table recapitulating the scoring of pancreatic tumors for FGFR3 signal. Strong signals were as intense as signals obtained in normal pancreatic islets (A: a, b). Weak signals were similar to what was observed in normal pancreatic exocrine tissue (ducts and acinar cells, A: a, b).

Figure 6

Figure 6

FGFR3 actions in pancreatic cancers: a working model. FGFR3 action in cancer cells from epithelial origin limits tumor growth. During tumor progression, FGFR3 disruption or loss of expression promotes cell growth. If epithelial to mesenchymal transition occurs, then FGFR3 will function as an oncogene favoring tumor progression.

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