Array Comparative Genomic Hybridization Analysis Identifies Recurrent Gain of Chromosome 2p25.3 Involving the ACP1 and MYCN Genes in Chronic Lymphocytic Leukemia
Department of Hematopathology, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA. Clinical lymphoma, myeloma & leukemia
(Impact Factor: 2.02).
06/2011; 11 Suppl 1:S17-24. DOI: 10.1016/j.clml.2011.03.031
Chromosomal aberrations are independent prognostic markers in chronic lymphocytic leukemia (CLL). Recent studies using genomic arrays have shown recurrent gains of the short arm of chromosome 2 (2p) in a subset of CLL. We evaluated 178 CLL cases for 2p gains using custom-designed oligonucleotide array-based comparative genomic hybridization (aCGH). A high frequency of 2p gains was observed in 53 of 178 (30%) cases, which ranged from a small 29-kb region to large segments involving the entire short arm. Besides several common chromosomal aberrations associated with 2p gain, we demonstrated a novel observation that gain of the telomeric region 2p25.3 harboring the ACP1 gene is common in CLL (25%, 44 of 178 cases). The ACP1 gene has been previously shown to regulate T-cell receptor signaling through ZAP-70, and both genes are unfavorable clinical markers for CLL. Quantitative polymerase chain reaction (qPCR) confirmed the presence of 3-6 copies of ACP1 in 35 of 40 (88%) of these cases. Interestingly, none of the aCGH diploid CLL cases showed gain of ACP1. Assessment of 73 healthy individuals by qPCR revealed ACP1 copy number gain in only two cases (2.7%). Gain of 2p25.3 was associated with ZAP-70 expression (P < .002) and unmutated immunoglobulin heavy chain variable (IGHV) gene mutation (P < .0001). A high frequency of MYCN co-amplication with ACP1 was observed (14 of 40 cases, 35%). The frequent 2p25.3 gain involving the ACP1 and MYCN genes may help define the critical region of 2p that contributes to pathogenesis of CLL together with other chromosomal abnormalities.
Available from: Francesco Angrilli
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ABSTRACT: Recent studies have described chromosome 2p gain as a recurrent lesion in chronic lymphocytic leukemia (CLL). We investigated the 2p gain and its relationship with common prognostic biomarkers in a prospective series of 69 clinical monoclonal B-cell lymphocytosis (cMBL) and 218 early stage (Binet A) CLL patients. The 2p gain was detected by FISH in 17 patients (6%, 16 CLL, and 1 cMBL) and further characterized by single nucleotide polymorphism-array. Overall, unfavorable cytogenetic deletions, i.e., del(11)(q23) and del(17)(p13) (P = 0.002), were significantly more frequent in 2p gain cases, as well as unmutated status of IGHV (P < 1 × 10(-4) ) and CD38 (P < 1 × 10(-4) ) and ZAP-70 positive expression (P = 0.003). Furthermore, 2p gain patients had significantly higher utilization of stereotyped B-cell receptors compared with 2p negative patients (P = 0.009), and the incidence of stereotyped subset #1 in 2p gain patients was significantly higher than that found in the remaining CLLs (P = 0.031). Transcriptional profiling analysis identified several genes significantly upregulated in 2p gain CLLs, most of which mapped to 2p. Among these, NCOA1 and ROCK2 are known for their involvement in tumor progression in several human cancers, whereas among those located in different chromosomes, CAV1 at 7q31.1 has been recently identified to play a critical role in CLL progression. Thus, 2p gain can be present since the early stages of the disease, particularly in those cases characterized by other poor prognosis markers. The finding of genes upregulated in the cells with 2p gain provides new insights to define the pathogenic role of this lesion. Am. J. Hematol. 2012. © 2012 Wiley Periodicals, Inc.
Available from: Tadeusz Majewski
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ABSTRACT: Genomic abnormalities, such as deletions in 11q22 or 17p13, are associated with poorer prognosis in patients with chronic lymphocytic leukemia (CLL). We hypothesized that unknown regions of copy number variation (CNV) affect clinical outcome and can be detected by array-based single-nucleotide polymorphism (SNP) genotyping. We compared SNP genotypes from 168 untreated patients with CLL with genotypes from 73 white HapMap controls. We identified 322 regions of recurrent CNV, 82 of which occurred significantly more often in CLL than in HapMap (CLL-specific CNV), including regions typically aberrant in CLL: deletions in 6q21, 11q22, 13q14, and 17p13 and trisomy 12. In univariate analyses, 35 of total and 11 of CLL-specific CNVs were associated with unfavorable time-to-event outcomes, including gains or losses in chromosomes 2p, 4p, 4q, 6p, 6q, 7q, 11p, 11q, and 17p. In multivariate analyses, six CNVs (ie, CLL-specific variations in 11p15.1 to 15.4 or 6q27) predicted time to treatment or overall survival independently of established markers of prognosis. Moreover, genotypic complexity (ie, the number of independent CNVs per patient) significantly predicted prognosis, with a median time to treatment of 64 months versus 23 months in patients with zero to one versus two or more CNVs, respectively (P = 3.3 × 10(-8)). In summary, a comparison of SNP genotypes from patients with CLL with HapMap controls allowed us to identify known and unknown recurrent CNV and to determine regions and rates of CNV that predict poorer prognosis in patients with CLL.
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ABSTRACT: Abstract Array-based comparative genomic hybridization (aCGH) chromosomal analysis facilitates rapid detection of cytogenetic abnormalities previously undetectable by conventional cytogenetics. In this study, we analyze 48 uniformly treated acute myeloid leukemia (AML) patients by 44K aCGH and correlated the findings with clinical outcome. aCGH identified previously undetected aberrations, as small as 5 kb, of currently unknown significance. The 36.7 Mb minimally deleted region on chromosome 5 lies between 5q14.3 to 5q33.3 contains 634 genes and 15 microRNAs whereas loss of chromosome 17 spans 3,194 kb involves 342 genes and 12 microRNAs. Loss of 155 kilobase (kb) region on 5q33.3 (p<0.05) is associated with achievement of complete remission. In contrast, loss of 17p11.2-q11.1 was associated with lower CR rate and poorer overall survival (Kaplan-Meier analysis, p<0.0096). aCGH detected loss of 17p in 12/48 patients as compared to 9/48 by conventional karyotyping. In conclusion, aCGH analysis adds to the prognostic stratification of AML patients.
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