Novel mutation and RNA splice variant of fibroblast growth factor receptor 3 in multiple myeloma patients at diagnosis

• Published in: Haematologica (Roma) 2002-10, Vol.87 (10), p.1036-1040
• Main Authors: Soverini, S, Terragna, C, Testoni, N, Ruggeri, D, Tosi, P, Zamagni, E, Cellini, C, Cavo, M, Baccarani, M, Tura, S, Martinelli, G
• Format: Article
• Language: English
• Subjects: Alternative Splicing; Amino Acid Sequence; Biological and medical sciences; DNA Mutational Analysis; Humans; Immunodeficiencies. Immunoglobulinopathies; Immunoglobulinopathies; Immunopathology; In Situ Hybridization, Fluorescence; Medical sciences; Models, Genetic; Molecular Sequence Data; Multiple Myeloma - diagnosis; Multiple Myeloma - genetics; Multiple Myeloma - metabolism; Mutation; Protein-Tyrosine Kinases; Receptor, Fibroblast Growth Factor, Type 3; Receptors, Fibroblast Growth Factor - genetics; Receptors, Fibroblast Growth Factor - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA - metabolism; RNA, Messenger - metabolism; Sequence Homology, Amino Acid
• ISSN: 0390-6078; 1592-8721

Institute of Hematology and Medical Oncology Seragnoli , University of Bologna, Italy. BACKGROUND AND OBJECTIVES: The karyotypically silent t(4;14)(p16.3;q32) translocation can be found in approximately 15-20% of multiple myeloma (MM) patients and results in the ectopic expression of fibroblast growth factor receptor 3 (FGFR3) from der4. Point mutations in specific FGFR3 domains can be found in the translocated allele, and have been recently proven to be oncogenic. These mutations produce a constitutively activated receptor, which shows dimerization and autophosphorylation even in the absence of ligand. We investigated the presence of FGFR3 expression and activating mutations in a series of newly diagnosed MM patients. DESIGN AND METHODS: We validated a new sensitive and specific Taqman real-time reverse-transcription polymerase-chain-reaction (RT-PCR) set up to evaluate FGFR3 mRNA expression, and applied it to 78 newly diagnosed patients; in positive cases, FGFR3 mRNA transcripts were sequenced. Fluorescence in situ hybridization (FISH) was done in 32 cases with sufficient material. RESULTS: Real-time RT-PCR revealed FGFR3 mRNA expression in 10/78 (13%) patients. In two cases, sequence analysis revealed novel FGFR3 mutations. In a patient with FISH evidence of the t(4;14), a CGC to TGC transition was detected in codon 248. In a patient without the t(4;14), three additional, abnormal-sized transcripts were detected, corresponding to truncated transcripts originating from cryptic splice donor sites located within exon 7. INTERPRETATION AND CONCLUSIONS: We describe a novel FGFR3 mutation (with a demonstrated deregulatory mechanism), as well as a case of alternative splicing in the absence of t(4;14), detected in newly diagnosed MM patients overexpressing FGFR3. This implies that FGFR3 mutation can occur at an early stage of myelomagenesis and even in the absence of the t(4;14).