FGFR3 protein expression and its relationship to mutation status and prognostic variables in bladder cancer

Abstract

FGFR3 is frequently activated by mutation in urothelial carcinoma (UC) and represents a potential target for therapy. In multiple myeloma, both over-expression and mutation of FGFR3 contribute to tumour development. To define the population of UC patients who may benefit from FGFRtargeted therapy, we assessed both mutation and receptor over-expression in primary UCs from a population of new patients. Manual or laser capture microdissection was used to isolate pure tumour cell populations. Where present, non-invasive and invasive components in the same section were microdissected. A screen of the region of highest tumour stage in each sample yielded a mutation frequency of 42%. Mutations comprised 61 single and 5 double mutations, all in hotspot codons previously identified in UC. There was a significant association of mutation with low tumour grade and stage. Subsequently, non-invasive areas from the 43 tumours with both non-invasive and invasive components were analysed separately. Eighteen of these had mutation in at least one region, including 9 with mutation in all regions examined, 8 with mutation in only the non-invasive component and one with different mutations in different regions. Of the 8 with mutation in only the non-invasive component, 6 were predicted to represent a single tumour and 2 showed morphological dissimilarity of fragments within the block, indicating possible presence of distinct tumour clones. Immunohistochemistry showed over-expression of FGFR3 protein in many tumours compared to normal bladder and ureteric controls. Increased expression was associated with mutation (85% of mutant tumours showed high-level expression). Overall, 42% of tumours with no detectable mutation showed over-expression including many muscle invasive tumours. This may represent a non-mutant subset of tumours in which FGFR3 signalling contributes to the transformed phenotype and which may benefit from FGFR-targeted therapies.

Frequent phosphatidylinositol-3-kinase mutations in proliferative breast lesions

“…FGFR3 mutations are seen in B60% of in situ bladder lesions, but in o20% of T2-stage invasive carcinomas. 48,49 Further, genotyping of multiple regions from the same bladder cancer specimen revealed FGFR3 mutations in the non-invasive component with paired wild-type invasive carcinoma from eight discordant specimens, and different point mutations in one sample (of 43 specimens with multiple areas tested). 48,49 With regard to these findings, the authors suggest that FGFR3 contributes early in the process of tumor development, and either the FGFR3 mutant allele was lost in the high stage lesion or it is a small subpopulation of FGFR3 wild-type cells in the non-invasive lesion that progresses to invasive carcinoma.…”

“…48,49 Further, genotyping of multiple regions from the same bladder cancer specimen revealed FGFR3 mutations in the non-invasive component with paired wild-type invasive carcinoma from eight discordant specimens, and different point mutations in one sample (of 43 specimens with multiple areas tested). 48,49 With regard to these findings, the authors suggest that FGFR3 contributes early in the process of tumor development, and either the FGFR3 mutant allele was lost in the high stage lesion or it is a small subpopulation of FGFR3 wild-type cells in the non-invasive lesion that progresses to invasive carcinoma. 48,49 In conclusion, we have screened a spectrum of 192 breast lesions with emphasis on proliferative lesions, and found that PIK3CA mutations were very frequent and were heterogeneous between multiple lesions in the same specimen.…”

“…48,49 With regard to these findings, the authors suggest that FGFR3 contributes early in the process of tumor development, and either the FGFR3 mutant allele was lost in the high stage lesion or it is a small subpopulation of FGFR3 wild-type cells in the non-invasive lesion that progresses to invasive carcinoma. 48,49 In conclusion, we have screened a spectrum of 192 breast lesions with emphasis on proliferative lesions, and found that PIK3CA mutations were very frequent and were heterogeneous between multiple lesions in the same specimen. Importantly, point mutations in proliferative lesions were often paired with wild-type carcinomas.…”

FGFR3 and TP53 mutation analysis in inverted urothelial papilloma: incidence and etiological considerations

“…[8][9][10] PCR was performed with 3 ml of isolated genomic DNA in a final volume of 50 ml containing 2.3 mM MgCl 2 , 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 2 mM deoxynucleotide triphosphates, 2 mM each primer, and 2 U Taq DNA polymerase (Bio-Rad, Hercules, CA, USA). Each PCR protocol had an initial denaturing step of 951C for 5 min, followed by 40 cycles at 951C for 30 s, at 551C (exons 7 and 15) for 30 s or at 581C (exon 10) for 30 s, and at 721C for 30 s, and then followed by a single final extension step at 721C for 7 min.…”

Novel targeted agents for the treatment of bladder cancer: translating laboratory advances into clinical application

“…In the FGFR family, FGFR3 is most prominent in normal urothelial cells, with only low levels of FGFR 1, 2 and 4 observed by real-time reverse transcriptase PCR (20). Further, mutations of FGFR3 are common in urothelial papillomas, which are considered to be a precursor for papillary bladder cancer, suggesting that FGFR3 mutation occurs early in the process of tumor development (21).…”