A.T. and H.P.K contributed equally to this work.
Novel CUX1 missense mutation in association with 7q− at leukemic transformation of MPN†
Article first published online: 14 JUN 2011
Copyright © 2011 Wiley-Liss, Inc.
American Journal of Hematology
Volume 86, Issue 8, pages 703–705, August 2011
How to Cite
Thoennissen, N. H., Lasho, T., Thoennissen, G. B., Ogawa, S., Tefferi, A. and Koeffler, H. P. (2011), Novel CUX1 missense mutation in association with 7q− at leukemic transformation of MPN. Am. J. Hematol., 86: 703–705. doi: 10.1002/ajh.22069
Conflict of interest: Nothing to report.
- Issue published online: 14 JUL 2011
- Article first published online: 14 JUN 2011
- Accepted manuscript online: 27 APR 2011 11:14AM EST
- Deutsche Forschungsgemeinschaft (DFG, Bonn, Germany). Grant Number: TH 1438/1-1
- National Institutes of Health (NIH, Bethesda, MD). Grant Number: 5R01CA026038-32
- National University of Singapore (A*STAR grant of Singapore)
Patients with monosomy 7 (−7) or del(7q) comprise a heterogeneous subgroup in acute myeloid leukemia (AML) but no specific target genes have been identified [1–4]. Recently, we detected a commonly deleted region on the long arm of chromosome 7 in a large cohort of Philadelphia chromosome-negative myeloproliferative neoplasms (MPN) at the time of leukemic transformation using single-nucleotide polymorphism array (SNP-A) [5, 6]. This region was located on 7q22.1 encompassing only two genes, CUX1 and SH2B2. Currently, we screened for acquired mutations in these two candidate genes using 15 secondary AML cases with preceding MPN and loss-of-heterozygosity (LOH) on chromosome 7q. We detected a novel hemizygous missense mutation (V1288L) in the HOX domain of the transcriptional regulator CUX1 in one case with primary myelofibrosis (PMF) at time of leukemic evolution. Although only detected in 1/15 (6.5%) of the cases with secondary AML, an acquired mutation of CUX1 may play a critical role in myeloid malignancies with 7q aberrations.
Abnormalities involving chromosome 7q are frequently detectable in myeloid malignancies [1–4]. The association of losses in 7q with AML suggests that this region contains a tumor suppressor gene or genes whose loss of function contributes to leukemic transformation or tumor progression. Based on several preceding chromosome banding studies, two minimal deleted regions have been identified; one locus at centromeric band 7q22 and the other at telomeric breakpoint varying from q32 to q36 [7–9]. The complexity of 7q rearrangements suggests that a synergy of different genetic factors, rather than the alteration of a single tumor suppressor gene, could be involved in the pathogenesis of 7q− in myeloid disorders. Two recent studies identified monoallelic or biallelic loss-of-function mutations in the histone H3 methyltransferase EZH2 on 7q36.1 in patients with myelodysplastic/s (12%) and in those with myelofibrosis (13%); the authors suggested EZH2 functions as a tumor-suppressor gene in these malignancies rather than an oncogene as in some other malignancies [10, 11]. Notably, no EZH2 mutations were found so far in de novo or secondary patients with AML having complete or partial monosomy for chromosome 7.
Using high-density SNP-A provides a robust and detailed approach to detect large and small copy-number changes, as well as copy-number neutral (CNN-) LOH. We recently applied this interrogational method and performed a systemic analysis of 159 samples obtained from patients with either MPN or secondary AML with preceding MPN to obtain a comprehensive profile of genomic alterations associated with leukemic transformation in MPN disease . Complete or partial deletion (−7/7q−) and CNN-LOH of the long arm of chromosome 7 were one of the most common abnormalities detected by SNP-A analysis in 25% of samples with secondary AML, and associated with inferior outcome. The minimal deleted region spanned a small region at 7q22.1.
In this study, we used 15 secondary AML cases with chromosome seven aberrations and prior MPN (Table I) to screen for novel tumor suppressor genes. Using both cytogenetics and SNP-A, 11 samples (73%) showed heterozygous deletions on 7q; three samples (20%) had CNN-LOH on 7q; and the analysis of one case (7%; #138) revealed both CNN-LOH on 7q21.13-qter and a small homozygous deletion on 7q22.1 (0.88 Mbp) encompassing only two candidate genes, CUX1 and SH2B2 (Fig. 1). One of the major protein function of SH2B2 (alias APS) is the recruitment of c-Cbl into the receptor/JAK complex, and thereby inhibiting JAK/STAT signaling activity [12, 13]. CUX1 (alias Cut homeobox 1 or CUTL1) belongs to a family of transcription factors with homeodomain (HOX) involved in the control of cell proliferation and differentiation .
|Case #||Diagnose||JAK2V617F||Prior MPN||Cytogenetics||SNP-A (breakpoints)||Aberration size [Mbp]||Genetic Variation in CUX1|
|34||sAML||Pos.||PV||7q−||del(7)(q11.21 qter)||96||rs76202142 G/T (SNP; Intron 16-17)|
|72||sAML||Neg.||ET||7q−||del(7)(q11 .22 qter)||87||–|
|79||sAML||Neg.||ET||7q−||7qCNN-LOH(q21.3qter)||63||rs73712454 G/T (SNP; Intron 22-23)|
|80||sAML||Pos.||ET||7q−||del(7)(p12 3qter)||109||rs73712454 G/T (SNP; Intron 22-23)|
|90||sAML||Neg.||ET||7q−||del(7)(q11 21 qter)||96||V1288L (rnissense mutation; Exon 24)|
|138||sAML||Pos.||PMF||Normal||7qCNN-LOH(q21.13qter), del7q22.1||69, 0.88||Homozygously deleted|
First, we investigated all coding exons of SH2B2 in the 15 patients with secondary AML by direct sequencing, but no genetic variation, either SNP or mutation, could be detected. Instead, after screening the coding regions of the three Cut domains and the HOX domain of the CUX1 gene, we detected not only a SNP in case #34, #79, and #80 (Table I) but also a genetic variation in a highly conserved nucleotide position in case #90 (V1288L; Table I), which has not been previously described in the “Database of Genomic Variants” (http://projects.tcag.ca/variation/), the “UCSC Genome Browser” (http://genome.ucsc.edu/), or the “Cosmic Catalogue for Somatic Mutations in Cancer” (http://www.sanger.ac.uk/genetics/CGP/cosmic/). We were able to characterize the novel nucleotide variant (GTC CTC) as a somatic mutation by showing a normal genetic code in a serial sample of case #90 originating from the chronic phase of MPN before leukemic evolution (Fig. 2A). Interestingly, not only the V1288L missense mutation in CUX1 was acquired at the time of transformation to secondary AML but also the loss of the normal allele with del(7)(q11.21qter) as indicated by SNP-A . The V1288L mutation is located in the coding region of the DNA-binding HOX domain of CUX1 (Fig. 2B) and has statistically a detrimental effect on the CUX1 protein (non-neutral, reliability index 2, accuracy 70%) according to the SNAP software, a neural-network–based method to make prediction regarding the functionality of a mutated protein .
The human CUX1 spans at least 340 kb, contains 33 exons, and at least three protein isoforms can be expressed as the result of proteolytic processing or transcription initiation at an alternative start site (Fig. 2B) . The full-length protein, p200, is a complex protein with four evolutionarily conserved DNA-binding domains: three Cut repeats and a Cut homeodomain (HOX; Fig. 2B). CUX1 was originally shown to function in precursor cells of various lineages as a transcriptional repressor that down-modulates lineage specific genes that later become expressed in terminally differentiated cells [14, 16]. Noteworthy, homozygous mutant mice expressing a hypomorphic and non-functional HOX domain of the CUX1 protein demonstrated myeloid hyperplasia, suggesting that CUX1 functions as a tumor suppressor and that its loss is a significant event in the generation or progression of myeloid disorders . However, one study performing a mutational analysis of childhood samples with AML and monosomy 7 revealed no somatic mutations in CUX1 . In contrast, transgenic mice expressing the short isoform of CUX1, p75, displayed heightened susceptibility to mammary tumors and a myeloproliferative disease-like myeloid leukemia, pointing to an oncogenic role of CUX1 [19, 20]. In consequence, regarding to present literature, CUX1 has a critical regulatory influence on the myeloid development and may act as either transcriptional repressor or activator depending on its isoform.
In summary, this is the first report of an acquired missense mutation of CUX1 in a patient with secondary AML and 7q−. Although detected in only one case (6.5%), it may contribute to the pathogenesis of AML in a subset of patients including the transformation or progression of chronic myeloid diseases in association with 7q−. Larger cohorts of myeloid diseases and further functional analysis are required to explore the impact of the novel mutation in the CUX1 gene.
H.P.K. is the holder of the Mark Goodson endowed Chair in Oncology Research at Cedars Sinai Medical Center and is a member of the Jonsson Cancer Center and the Molecular Biology Institute, UCLA.
- 1The predictive value of hierarchical cytogenetic classification in older adults with acute myeloid leukemia (AML): Analysis of 1065 patients entered into the United Kingdom Medical Research Council AML11 trial. Blood 2001; 98: 1312–1320., , , et al.
- 2Is secondary leukemia an independent poor prognostic factor in acute myeloid leukemia? Best Pract Res Clin Haematol 2007; 20: 29–37..
- 3Structural aberrations of chromosome 7 revealed by a combination of molecular cytogenetic techniques in myeloid malignancies. Cancer Genet Cytogenet 2007; 173: 10–16., , , et al.
- 4Therapy-related Acute myelogenous leukemia. In: Neoplastic Diseases of the Blood, 5th ed. Cambridge University Press. 2011, p 370–394., , .
- 5Prevalence and prognostic impact of allelic imbalances associated with leukemic transformation of Philadelphia chromosome-negative myeloproliferative neoplasms. Blood 2010; 115: 2882–2890., , , et al.
- 6Leukaemic transformation of philadelphia-chromosome-negative myeloproliferative neoplasms—A review of the molecular background. Euro Oncol Haematol 2011; 7: 59–62., .
- 7Molecular cytogenetic delineation of deletions and translocations involving chromosome band 7q22 in myeloid leukemias. Blood 1997; 89: 2036–2041., , , et al.
- 8Molecular anatomy of chromosome 7q deletions in myeloid neoplasms: Evidence for multiple critical loci. Proc Natl Acad Sci USA 1998; 95: 3781–3785., , , et al.
- 9Heterogeneity of structural abnormalities in the 7q31.3 approximately q34 region in myeloid malignancies. Cancer Genet Cytogenet 2004; 150: 136–143., , , et al.
- 10Inactivating mutations of the histone methyltransferase gene EZH2 in myeloid disorders. Nat Genet 2010; 42: 722–726., , , et al.
- 11Somatic mutations of the histone methyltransferase gene EZH2 in myelodysplastic syndromes. Nat Genet 2010; 42: 665–667., , , et al.
- 12APS, an adaptor protein containing Pleckstrin homology (PH) and Src homology-2 (SH2) domains inhibits the JAK-STAT pathway in collaboration with c-Cbl. Leukemia 1999; 13: 760–767., , , et al.
- 13Structural characterization of a novel Cbl phosphotyrosine recognition motif in the APS family of adapter proteins. J Biol Chem 2005; 280: 18943–18949., .
- 14Exon/intron structure and alternative transcripts of the CUTL1 gene. Gene 2000; 241: 75–85., , , et al.
- 15SNAP predicts effect of mutations on protein function. Bioinformatics. 2008; 24: 2397–2398., , .
- 16The multiple roles of CUX1: Insights from mouse models and cell-based assays. Gene 2008; 412: 84–94., .
- 17Lymphoid apoptosis and myeloid hyperplasia in CCAAT displacement protein mutant mice. Blood 2001; 98: 3658–3667., , , et al.
- 18Mutation analysis of CUTL1 in childhood myeloid neoplasias with monosomy 7. Leuk Res 2007; 31: 1323–1324., , , et al.
- 19Mouse mammary tumor virus p75 and p110 CUX1 transgenic mice develop mammary tumors of various histologic types. Cancer Res 2009; 69: 7188–7197., , , et al.
- 20Transgenic mice expressing the p75 CCAAT-displacement protein/Cut homeobox isoform develop a myeloproliferative disease-like myeloid leukemia. Cancer Res 2006; 66: 9492–9501., , , et al.
Nils H. Thoennissen* , Terra Lasho, Gabriela H. Thoennissen* , Seishi Ogawa§, Ayalew Tefferi, H. Phillip Koeffler* ¶, * Division of Hematology and Oncology, Cedars-Sinai Medical Center, UCLA School of Medicine, Los Angeles, California, Department of Hematology and Oncology, University Hospital of Münster, Münster, Germany, Department of Hematology, Mayo Clinic, Rochester, Minnesota, § Department of Regeneration Medicine for Hematopoiesis, Graduate School of Medicine, University of Tokyo, University of Tokyo Hospital, Tokyo, Japan, ¶ National Cancer Institute of Singapore, National University of Singapore, Singapore.