The t(8;22) in chronic myeloid leukemia fuses BCR to FGFR1: transforming activity and specific inhibition of FGFR1 fusion proteins

Abstract

This report describes 2 patients with a clinical and hematologic diagnosis of chronic myeloid leukemia (CML) in chronic phase who had an acquired t(8;22)(p11;q11). Analysis by fluorescence in situ hybridization (FISH) and reverse transcription-polymerase chain reaction (RT-PCR) indicated that both patients were negative for the BCR-ABL fusion, but suggested that the BCR gene was disrupted. Further FISH indicated a breakpoint within fibroblast growth factor receptor 1 (FGFR1), the receptor tyrosine kinase that is known to be disrupted in a distinctive myeloproliferative disorder, most commonly by fusion to ZNF198. RT-PCR confirmed the presence in both cases of an in-frame messenger RNA fusion between BCR exon 4 and FGFR1 exon 9. Expression of BCR-FGFR1 in the factor-dependent cell line Ba/F3 resulted in interleukin 3-independent clones that grew at a comparable rate to cells transformed with ZNF198-FGFR1. The growth of transformed cells was inhibited by the phosphatidylinositol 3-kinase inhibitor LY294002, the farnesyltransferase inhibitors L744832 and manumycin A, the p38 inhibitors SB202190 and SB203580 but not by the MEK inhibitor PD98059. The growth of BaF3/BCR-FGFR1 and BaF3/ZNF198-FGFR1 was not significantly inhibited by treatment with STI571, but was inhibited by SU5402, a compound with inhibitory activity against FGFR1. Inhibition with this compound was associated with decreased phosphorylation of ERK1/2 and BCR-FGFR1 or ZNF198-FGFR1, and was dose dependent with an inhibitory concentration of 50% of approximately 5 microM. As expected, growth of BaF3/BCR-ABL was inhibited by STI571 but not by SU5402. The study demonstrates that the BCR-FGFR1 fusion may occur in patients with apparently typical CML. Patients with constitutively active FGFR1 fusion genes may be amenable to treatment with specific FGFR1 inhibitors.

Targeting FGFR3 in multiple myeloma: inhibition of t(4;14)-positive cells by SU5402 and PD173074

“…The IC 50 for SU5402 was similar to that previously reported at approximately 5 mM, as estimated from the day 4 readings. 18 In contrast, the IC 50 for PD173074 was 5 nm indicating that this compound is 1000 times more active. SU6668 gave inconsistent results and was not clearly inhibitory even at concentrations of 50 mM (data not shown) and was therefore not pursued further.…”

“…18 Using the MTS cell proliferation assay, both SU5402 and PD173074 inhibited the growth of BaF3/ZNF198-FGFR1 cells in a dosedependent fashion (Figure 1a,c). The IC 50 for SU5402 was similar to that previously reported at approximately 5 mM, as estimated from the day 4 readings.…”

Fusion tyrosine kinases: a result and cause of genomic instability

“…It is present in chronic myelogenous leukemia (CML) and a cohort of acute lymphoblastic leukemia (ALL) patients (Shtivelman et al, 1986;Clark et al, 1988;Epner and Koeffler, 1990). BCR/FGFR1 is produced by the fusion between BCR exon 4 and FGFR1 exon 9 and was reported in a spectrum of myeloproliferative disorders that include CML-like disease (Demiroglu et al, 2001;Fioretos et al, 2001). TEL/ABL originates from a t(9;12) translocation reported in ALL, acute myelogenous leukemia (AML) and atypical CML.…”

Tyrosine kinase fusion genes in chronic myeloproliferative diseases

“…10 Strikingly, the three patients that have been described with a t(8;22) and a BCR-FGFR1 fusion had a clinical and morphological picture that was very similar to typical, BCR-ABL positive CML. 18,19 All three patients had basophilia, a feature that is uncommon in BCR-ABL-negative MPDs and, as noted above, is rare in EMS with other FGFR1 partner genes. It is possible, therefore, that the BCR moiety of the fusion might directly contribute to the specific clinical features that are characteristic of CML.…”