The t(X;7)(q22;q34) in paediatric T‐cell acute lymphoblastic leukaemia results in overexpression of the insulin receptor substrate 4 gene through illegitimate recombination with the T‐cell receptor beta locus

Abstract

Summary The t(X;7)(q22;q34), a translocation not previously reported in a neoplastic disorder, was identified and molecularly characterised in a paediatric T‐cell acute lymphoblastic leukaemia (T‐ALL), subsequently shown also to harbour a deletion of 6q, a STIL/TAL1 fusion and an activating NOTCH1 mutation. The t(X;7) was further investigated using fluorescence in situ hybridisation (FISH), real‐time quantitative polymerase chain reaction (RQ‐PCR) and Western blot analyses. FISH revealed a breakpoint at the T‐cell receptor beta locus at 7q34 and mapped the corresponding breakpoint to Xq22.3. The latter region contains only two known genes, namely insulin receptor substrate 4 (IRS4) and collagen, type IV, alpha 5 (COL4A5), the expressions of which were analysed by the use of RQ‐PCR. COL4A5 was not differentially expressed in the t(X;7)‐positive sample compared to five T‐ALL controls. However, a marked, 1000‐fold overexpression of IRS4 was identified. Western blot analysis with a monoclonal antibody against IRS4 showed overexpression also at the protein level. Considering that forced expression of several members of the IRS family has been shown to result in increased cell proliferation, for example in haematopoietic cells, we hypothesise that the IRS4 up‐regulation in T‐ALL is pathogenetically important as a mitogenic stimulus.

IRS4 induces mammary tumorigenesis and confers resistance to HER2-targeted therapy through constitutive PI3K/AKT-pathway hyperactivation

“…In fact, the inference that IRS4 is a constitutive active IRS is also in line with our finding that the Irs4 gene is a target for retroviral insertional mutagenesis, as this process leads with few exceptions to transcriptional deregulation of the target genes rather than to mutations affecting protein function34. The notion that IRS4 is a constitutive active oncogenic protein primarily regulated transcriptionally also explains the recent observations that chromosomal translocation events can activate Irs4 expression, leading to T-cell acute lymphoblastic leukaemia3536 and subungual exostosis (a benign bone and cartilage producing tumour)37. In addition, in human hepatocellular carcinomas (HCC), IRS4 expression is frequently upregulated compared with hepatocytes38, and its role in this malignancy has been further substantiated in the HEPG2 hepatoblastoma cell line where IRS4 plays an important role in cell proliferation39.…”

Novel principles of gamma-retroviral insertional transcription activation in murine leukemia virus-induced end-stage tumors

“…Col4a5 contains 10 of these sites, one of which is located more than 220 kb from the Irs4 promoter. The finding that IRS4 but not COL4A5 activation in T-ALL involves translocation of both genes to the T-cell receptor beta locus [61] is particularly interesting considering that insertion of the retroviral enhancer mimics such oncogenic rearrangements. We detected an activation pattern at the Wwox locus fairly similar to the patterns observed at the Klf7 , Col4a5/Irs4 and Ccr9 loci (Additional file 1: Figure S3).…”

“…SYN2 encodes a neuronal phosphoprotein (Synapsin 2) and is deregulated in human glioblastoma multiforme and breast cancer [58,79]. As described already, IRS4 is activated in T-ALL following COL4A5/IRS4 translocation involving the T-cell receptor beta locus [61]. The CUGBP-ETR3-like factors and Bruno-like (or CELF/Bruno-like) family of RNA-binding proteins regulate RNA splicing, translation and mRNA stability.…”

The NOTCH signaling pathway: role in the pathogenesis of T-cell acute lymphoblastic leukemia and implication for therapy

“…In addition, genetic alterations in signal transduction pathways can also contribute to the pathogenesis of T-ALL. These include deletions and mutations in PTEN , ABL1 fusion oncogenes (NUP214-ABL1, EML1-ABL1 and ETV6-ABL1) [De Keersmaecker et al 2005;Graux et al 2004]; mutations activating the RAS signaling pathway [Balgobind et al 2008;Bar-Eli et al 1989;Campbell and Der, 2004], activating mutations in JAK1 and JAK3 [Flex et al 2008;Zhang et al 2012], activating mutations in IL7R [Zenatti et al 2011;Zhang et al 2012], FLT3 mutations [Paietta et al 2004], PTPN2 deletions [Kleppe et al 2011] and IRS4 translocations [Karrman et al 2009]. Finally, deletions and loss of function mutations in histone-modifying genes such as SUZ12, EED, EZH2, and SETD2 have been found in T-ALL, which highlight the role of altered epigenetic regulation in T-cell transformation [Ntziachristos et al 2012;Zhang et al 2012].…”