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1.  An optimized technology platform for the rapid multiplex molecular analysis of genetic alterations associated with leukemia 
Cancer genetics  2012;205(10):488-500.
Molecular methods play a critical role in the accurate diagnosis of leukemia by complementing morphologic, cytochemical, immunophenotypic, and cytogenetic analyses. We developed a multiplex RT-PCR method combined with liquid bead array cytometry for the rapid detection of genetic alterations associated with leukemia. Fusion transcripts corresponding to the most common recurrent chromosomal translocations were reproducibly detected in as low as 0.1 to 10 ng of total RNA with an analytical sensitivity of 0.01 to 1%. Multi-day, -lot, -operator, and -instrument precision studies for a total of 678 independent measures in 46 runs showed a very high reproducibility with 100% agreement between replicates. Using multiplex panels for four to twenty independent targets, we demonstrate the flexibility of the method to co-detect rare splicing isoforms, discriminate between multiple variants generated by unique cytogenetic abnormalities, identify distinct chromosomal partners involved with 11q23 or 17q21 rearrangements, and assess cryptic abnormalities not detectable by standard cytogenetics such as t(12;21), del(1p32), or NPM1 mutations. Overall, three different internal control transcripts and 34 variants resulting from eighteen abnormal chromosomal sites were evaluated. These results underscore the value of the multiplex assay system as a sensitive and reliable technology platform for the characterization of relevant genetic alterations in leukemia.
PMCID: PMC3478406  PMID: 23026076
leukemia; fusion transcript; multiplex; RT-PCR; molecular diagnosis
2.  Rapid and Reliable Confirmation of Acute Promyelocytic Leukemia by Immunofluorescence Staining With an Antipromyelocytic Leukemia Antibody 
Cancer  2010;116(2):369-376.
The authors evaluated the utility of immunofluorescence staining with an antipromyelocytic leukemia (anti-PML) antibody for patients with a suspected diagnosis of new or relapsed acute promyelocytic leukemia (APL) and correlated the findings with the results of other established diagnostic modalities.
Bone marrow (BM) and/or peripheral blood (PB) smears from 349 patients in whom the diagnosis of APL was considered were assessed with the anti-PML antibody using immunofluorescence. The study group included 199 patients with confirmed APL and 150 with other conditions. The results of conventional cytogenetics, reverse transcription polymerase chain reaction (RT-PCR), and fluorescence in situ hybridization (FISH) performed on these patients were correlated with the PML results.
Among patients with confirmed APL, anti-PML antibody was positive in 182 of 184 BM and 32 of 33 PB smears. Conventional cytogenetics demonstrated t(15;17)(q22;q12) in 166 of 182 (91%) patients; 10 had a normal karyotype, 4 had insufficient mitoses to grow in culture, 1 was inconclusive, and 1 was 48, XX, +8, +8. Anti-PML staining was positive in 9 of 10 with a normal karyotype and in all 4 cases with insufficient mitoses. RT-PCR and FISH were positive for PML–retinoic acid receptor-α in 169 of 172 (98%) and 90 of 94 (96%) cases, respectively. Among the patients without APL, 148 of 150 (98.6%) were negative with anti-PML antibody. The sensitivity and specificity of the test were 98.9% and 98.7%, respectively.
PML immunofluorescence staining is a rapid (<4 hours turnaround time) and reliable frontline diagnostic approach that can facilitate initiation of targeted therapy, particularly in clinical settings where cytogenetic and molecular testing are not readily available.
PMCID: PMC4180261  PMID: 19950129
acute promyelocytic leukemia; rapid diagnosis; promyelocytic leukemia oncogenic domain; immunofluorescence
3.  Array comparative genomic hybridization and cytogenetic analysis in pediatric acute leukemias 
Current Oncology  2011;18(5):e210-e217.
Most patients with acute lymphocytic leukemia (all) are reported to have acquired chromosomal abnormalities in their leukemic bone marrow cells. Many established chromosome rearrangements have been described, and their associations with specific clinical, biologic, and prognostic features are well defined. However, approximately 30% of pediatric and 50% of adult patients with all do not have cytogenetic abnormalities of clinical significance. Despite significant improvements in outcome for pediatric all, therapy fails in approximately 25% of patients, and these failures often occur unpredictably in patients with a favorable prognosis and “good” cytogenetics at diagnosis.
It is well known that karyotype analysis in hematologic malignancies, although genome-wide, is limited because of altered cell kinetics (mitotic rate), a propensity of leukemic blasts to undergo apoptosis in culture, overgrowth by normal cells, and chromosomes of poor quality in the abnormal clone. Array comparative genomic hybridization (acgh—“microarray”) has a greatly increased genomic resolution over classical cytogenetics. Cytogenetic microarray, which uses genomic dna, is a powerful tool in the analysis of unbalanced chromosome rearrangements, such as copy number gains and losses, and it is the method of choice when the mitotic index is low and the quality of metaphases is suboptimal. The copy number profile obtained by microarray is often called a “molecular karyotype.”
In the present study, microarray was applied to 9 retrospective cases of pediatric all either with initial high-risk features or with at least 1 relapse. The conventional karyotype was compared to the “molecular karyotype” to assess abnormalities as interpreted by classical cytogenetics. Not only were previously undetected chromosome losses and gains identified by microarray, but several karyotypes interpreted by classical cytogenetics were shown to be discordant with the microarray results. The complementary use of microarray and conventional cytogenetics would allow for more sensitive, comprehensive, and accurate analysis of the underlying genetic profile, with concomitant improvement in prognosis and treatment, not only for pediatric all, but for neoplastic disorders in general.
PMCID: PMC3185902  PMID: 21980252
Acute lymphoblastic leukemia; chromosomes; microarray; acgh
4.  A novel insertion ins(18;5)(q21.1;q31.2q35.1) in acute myeloid leukemia associated with microdeletions at 5q31.2, 5q35.1q35.2 and 18q12.3q21.1 detected by oligobased array comparative genomic hybridization 
Molecular Cytogenetics  2014;7(1):63.
Nonrandom clonal chromosomal aberrations can be detected in approximately 55% of adult patients with acute myeloid leukemia (AML). Recurrent cytogenetic abnormalities play an important role in diagnosis, classification and prognosis of AML. However, several chromosomal abnormalities have not been completely determined or characterized, primarily because of their low incidence and limited amount of data.
We characterized an AML patient with a novel apparently balanced insertion ins(18;5)(q21;q31.2q35.1) that was cryptic by G-banding. The rearrangement was further examined by molecular cytogenetic methods and oligobased high-resolution array CGH (oaCGH) analysis. We show that an approximately 31.8 Mb large segment from chromosome 5 bands q31.2 to q35.1 has been inserted, by a direct mechanism, into chromosome 18 between bands q12.3 and q21.1. The insertion was unbalanced with concurrent submicroscopic deletions at 5q31.2 (approximately 0.37 Mb in size), 5q35.1q35.2 (approximately 1.98 Mb in size), and 18q12.3q21.1 (approximately 2.07 Mb in size). The microdeletions affect genes on 5q and 18q that have been associated with hematological malignancy and other cancers. A novel juxtaposition of the genes NPM1 and HAUS1 at 5q35.1 and 18q21.1, respectively, was detected by FISH analysis. Searching the literature and the Mitelman database revealed no previously reported ins(18;5) cases. Interestingly, however, two AML patients with translocation t(5;18)(q35;q21) encompassing the 5q35 and 18q21 breakpoint regions as detected in our present ins(18;5) patient have been reported.
It is well-known that cytogenetic abnormalities on the long arm of chromosome 5 affect hematopoiesis. However, the precise mechanism of their involvement in myeloid transformation is elusive. Our present data shed new light onto the frequent abnormalities on 5q as well as to the less frequent abnormalities observed on 18q in myeloid malignancies. In addition, we show that oaCGH analysis is a useful adjunct to revealing submicroscopic aberrations in regions of clinical importance. Reporting rare and nonrandom chromosomal abnormalities contribute to the identification of the whole spectrum of cytogenetic abnormalities in AML and their prognostic significance.
PMCID: PMC4180307  PMID: 25279000
Acute myeloid leukemia; ins(18;5); oaCGH analysis; Chromosomal insertion; Microdeletion; Cryptic chromosomal aberration; del(5q); add(18q)
5.  A Case of Therapy-related Acute Lymphoblastic Leukemia with t(11;19)(q23;p13.3) and MLL/MLLT1 Gene Rearrangement 
Therapy-related ALL (t-ALL) is a rare secondary leukemia that develops after chemotherapy and/or radiotherapy for primary malignancies. Chromosomal 11q23 abnormalities are the most common karyotypic alterations in t-ALL. The t(11;19)(q23;p13) aberration is extremely rare and has not been confirmed at the molecular genetic level. Here, we report a case of t-ALL with t(11;19)(q23;p13.3) and MLL-MLLT1 (alias ENL) gene rearrangement confirmed by cytogenetic analysis, multiplex reverse transcription-PCR (multiplex RT-PCR), and DNA sequencing in a patient who had undergone treatment for breast cancer. A 40-yr-old woman developed acute leukemia 15 months after undergoing 6 cycles of adjuvant chemotherapy (doxorubicin 60 mg/m2 and cyclophosphamide 600 mg/m2), radiation therapy (dose, 5,900 cGy), and anticancer endocrine therapy with tamoxifen. The complete blood cell counts and bone marrow examination showed increased blasts and the blasts showed B lineage immunophenotype (positive for CD19, CD34, and cytoplasmic CD79a). Cytogenetic analysis revealed the karyotype 47,XX,+X,t(11;19)(q23;p13.3)[4]/46,XX[16]. FISH analyses, multiplex RT-PCR, and DNA sequencing confirmed the MLL-MLLT1 gene rearrangement. The patient underwent induction chemotherapy with fractionated cyclophosphamide, vincristine, doxorubicin, and dexamethasone (Hyper-CVAD) and achieved complete remission. Subsequently, she underwent consolidation chemotherapy, but died of brain ischemia in the pons and the region of the middle cerebral artery. To our knowledge, this is the first case report of t-ALL with t(11;19)(q23;p13.3) and the MLL-MLLT1 gene rearrangement.
PMCID: PMC3111038  PMID: 21239865
MLL gene rearrangement; Secondary leukemia; Therapy-related ALL; Breast cancer
6.  Spectra of Chromosomal Aberrations in 325 Leukemia Patients and Implications for the Development of New Molecular Detection Systems 
Journal of Korean Medical Science  2011;26(7):886-892.
This study investigated the spectrum of chromosomal abnormalities in 325 leukemia patients and developed optimal profiles of leukemic fusion genes for multiplex RT-PCR. We prospectively analyzed blood and bone marrow specimens of patients with acute leukemia. Twenty types of chromosomal abnormalities were detected in 42% from all patients by commercially available multiplex RT-PCR for detecting 28 fusion genes and in 35% by cytogenetic analysis including FISH analysis. The most common cytogenetic aberrations in acute myeloid leukemia patients was PML/PARA, followed by AML1/MGT8 and MLL1, and in acute lymphoid leukemia patients was BCR/ABL, followed by TEL/AML1 and MLL1 gene rearrangement. Among the negative results for multiplex RT-PCR, clinically significant t(3;3)(q21;q26.2), t(8;14)(q24;q32) and i(17)(q10) were detected by conventional cytogenetics. The spectrum and frequency of chromosomal abnormalities in our leukemia patients are differed from previous studies, and may offer optimal profiles of leukemic fusion genes for the development of new molecular detection systems.
PMCID: PMC3124718  PMID: 21738341
Leukemia; Chromosomal Abnormalities; Molecular Detection System
7.  Routine use of microarray-based gene expression profiling to identify patients with low cytogenetic risk acute myeloid leukemia: accurate results can be obtained even with suboptimal samples 
Gene expression profiling has shown its ability to identify with high accuracy low cytogenetic risk acute myeloid leukemia such as acute promyelocytic leukemia and leukemias with t(8;21) or inv(16). The aim of this gene expression profiling study was to evaluate to what extent suboptimal samples with low leukemic blast load (range, 2-59%) and/or poor quality control criteria could also be correctly identified.
Specific signatures were first defined so that all 71 acute promyelocytic leukemia, leukemia with t(8;21) or inv(16)-AML as well as cytogenetically normal acute myeloid leukemia samples with at least 60% blasts and good quality control criteria were correctly classified (training set). The classifiers were then evaluated for their ability to assign to the expected class 111 samples considered as suboptimal because of a low leukemic blast load (n = 101) and/or poor quality control criteria (n = 10) (test set).
With 10-marker classifiers, all training set samples as well as 97 of the 101 test samples with a low blast load, and all 10 samples with poor quality control criteria were correctly classified. Regarding test set samples, the overall error rate of the class prediction was below 4 percent, even though the leukemic blast load was as low as 2%. Sensitivity, specificity, negative and positive predictive values of the class assignments ranged from 91% to 100%. Of note, for acute promyelocytic leukemia and leukemias with t(8;21) or inv(16), the confidence level of the class assignment was influenced by the leukemic blast load.
Gene expression profiling and a supervised method requiring 10-marker classifiers enable the identification of favorable cytogenetic risk acute myeloid leukemia even when samples contain low leukemic blast loads or display poor quality control criterion.
PMCID: PMC3284426  PMID: 22289410
8.  A Leukemic Stem Cell Gene Expression Signature is Associated with Clinical Outcomes in Acute Myeloid Leukemia 
In many cancers, specific subpopulations of cells appear to be uniquely capable of initiating and maintaining tumors. The strongest support for this cancer stem cell model comes from transplantation assays in immune-deficient mice, which indicate that human acute myeloid leukemia (AML) is driven by self-renewing leukemia stem cells (LSC). This model has significant implications for the development of novel therapies, but its clinical relevance has yet to be determined.
To identify a leukemic stem cell gene expression signature and test its association with clinical outcomes in AML.
Design, Setting, and Patients
Global gene expression (microarray) profiles of LSC-enriched subpopulations from primary AML and normal patient samples were analyzed. Patient samples were obtained at Stanford University Medical Center between April 2005 and July 2007. Validation datasets of global transcriptional profiles of AML tumors from four independent cohorts totaling 1047 patients were analyzed retrospectively.
Main Outcome Measures
Identification of genes discriminating LSC-enriched from other subpopulations in AML tumors; association of the LSC-specific genes with overall, event-free, and relapse-free survival, and with therapeutic response.
Expression levels of 52 genes distinguished LSC-enriched from other subpopulations in cell-sorted AML samples. An LSC score summarizing expression of these genes in bulk primary AML tumor samples was defined and found to be associated with clinical outcomes in four independent patient cohorts. High LSC scores were associated with worse overall (OS), event-free (EFS), and relapse-free (RFS) survival, among patients with either a normal karyotype (NKAML), or with chromosomal abnormalities. For the largest cohort of patients with NKAML (n=163), the LSC score was significantly associated with OS as a continuous variable (hazard ratios [HR] 1.15, 95% Confidence Interval [CI] 1.08-1.22, log-likelihood p<0.001). When patients were split into high and low LSC score groups, the absolute risk of death by 3 years was 57% (95% CI 43-67%) for the low LSC score group, versus 78% (95% CI 66-86%) in the high LSC score group (HR 1.9, 95% CI 1.3-2.7, log-rank p=0.002). In another cohort with available data on EFS for 70 patients with NKAML, the risk of an event by 3 years was 48% (95% CI 27-63%) in the low LSC score group vs. 81% (95% CI 60-91%) in the high LSC score group (HR 2.4, 95% CI 1.3-4.5, log-rank p=0.006). The LSC score was associated with poorer outcomes, independently of known prognostic factors including age, FLT3 or NPM1 mutations, and cytogenetic risk group, and added to their prognostic value. For OS in three cohorts that included patients with cytogenetic abnormalities, the HRs of the continuous LSC score in multivariate Cox regression with FLT3/NPM1 status, age, and cytogenetic risk group were respectively HR 1.07 (95%CI 1.01-1.13), p=0.02; HR 1.10 (95% CI 1.03-1.17), p=0.005; and HR 1.17 (95% CI 1.05-1.30), p=0.005.
High expression of a leukemic stem cell gene expression signature is independently associated with adverse outcomes in AML.
PMCID: PMC4089862  PMID: 21177505
9.  Use of whole genome sequencing to diagnose a cryptic fusion oncogene 
Whole genome sequencing (WGS) is becoming increasingly available for research purposes, but it has not yet been routinely used for clinical diagnosis.
To determine whether whole genome sequencing can identify cryptic, actionable mutations in a clinically relevant time frame.
Design, Setting, and Patient
We were referred a difficult diagnostic case of acute promyelocytic leukemia with no pathogenic X-RARA fusion identified by routine metaphase cytogenetics or interphase FISH. The patient was enrolled in an IRB approved protocol, with consent specifically tailored to the implications of whole genome sequencing. The protocol employs a ‘movable firewall,’ which maintains patient anonymity within the entire research team, but allows the research team to communicate medically relevant information to the treating physician.
Main Outcome Measure
Clinical relevance of whole genome sequencing and time to communicate validated results to the treating physician.
Massively parallel paired-end sequencing allowed us to identify a cytogenetically cryptic event: 77 kilobases from chromosome 15 was inserted en bloc into the second intron of the RARA gene on chromosome 17, resulting in a classic bcr3 PML-RARA fusion gene. RT-PCR subsequently validated the expression of the fusion transcript. Novel FISH probes identified two additional cases of t(15;17)-negative acute promyelocytic leukemia that had cytogenetically invisible insertions. Whole genome sequencing and validation were completed in seven weeks, and changed the treatment plan for the patient.
Whole genome sequencing can identify cytogenetically invisible oncogenes in a clinically relevant timeframe.
PMCID: PMC3156695  PMID: 21505136
10.  Gene dosage as a relevant mechanism contributing to the determination of ovarian function in Turner syndrome 
What is the burden of X chromosome mosaicism in the occurrence of spontaneous menarche (SM) in Turner syndrome (TS)?
SM was significantly associated with X chromosome mosaicism in the TS patients; a mosaicism with around 10% euploid cell line may predict spontaneous pubertal development when determined by molecular-cytogenetic techniques on uncultivated tissues.
Spontaneous puberty can be observed in a minority of patients with TS, more frequently, but not exclusively, in those with a high level of 46,XX/45,X mosaicism at standard karyotype. The genetic mechanisms contributing to ovarian function in TS patients are still not determined. However, submicroscopic X-linked and autosomal copy number variations (CNVs) have recently emerged as an important genetic risk category for premature ovarian insufficiency and may be involved in modulating the TS ovarian phenotype.
A group of 40 patients with a diagnosis of TS at conventional karyotyping participated in the study; 6 patients had SM and 34 patients had primary amenorrhoea (PA). All clinical data and the patients’ DNA samples were collected over the years at a single paediatric clinic.
The patients' samples were used to perform both genetic (Copy Number Assay) and molecular-cytogenetic (array-CGH and iFISH, interphase-FISH) analyses in order to evaluate the X chromosome mosaicism rate and to detect possible rare CNVs of genes with a known or predicted role in female fertility.
All TS patients showed variable percentages of the 46,XX lineage, but these percentages were higher in the SM group (P < 0.01). A mosaicism around 10% for the euploid cell line may predict spontaneous pubertal development when determined by molecular-cytogenetic techniques performed in uncultivated tissues. A few CNVs involving autosomal and X-linked ovary-related loci were identified by array-CGH analysis and confirmed by real-time quantitative PCR, including a BMP15 gene duplication at Xp11.22, a deletion interrupting the PAPPA gene at 9q33.1, and an intragenic duplication involving the PDE8A gene at 15q25.3.
This is a pilot study on a relatively small sample size and confirmation in larger TS cohorts may be required. The ovarian tissue could not be studied in any patients and in a subgroup of patients, the mosaicism was estimated in tissues of different embryonic origin.
The combined determination of X chromosome mosaicism by molecular and molecular-cytogenetic techniques may become useful for the prediction of SM in TS. The detection of CNVs in both X-linked and autosomal ovary-related genes further suggests gene dosage as a relevant mechanism contributing to the ovarian phenotype of TS patients. These CNVs may pinpoint novel candidates relevant to female fertility and generate further insights into the mechanisms contributing to ovarian function.
This study was funded by Telethon Foundation (grant no: GGP09126 to L.P.), the Italian Ministry of the University and Research (grant number: 2006065999 to P.F.) and a Ministry of Health grant ‘Ricerca Corrente’ to IRCCS Istituto Auxologico Italiano (grant number: 08C704-2006). The authors have no conflict of interest to declare.
PMCID: PMC3896225  PMID: 24324027
Turner syndrome; ovary; BMP15; X chromosome; copy number variations
11.  Clinical significance of cytogenetic aberrations in bone marrow of patients with diffuse large B-cell lymphoma: prognostic significance and relevance to histologic involvement 
Although knowledge of the genetics of diffuse large B-cell lymphoma (DLBCL) has been increasing, little is known about the characteristics and prognostic significance of cytogenetic abnormalities and the clinical utility of cytogenetic studies performed on bone marrow (BM) specimens. To investigate the significance of isolated cytogenetic aberrations in the absence of histologic BM involvement, we assessed the implication of cytogenetic staging and prognostic stratification by a retrospective multicenter analysis of newly diagnosed DLBCL patients.
We analyzed cytogenetic and clinical data from 1585 DLBCL patients whose BM aspirates had been subjected to conventional karyotyping for staging. If available, interphase fluorescence in situ hybridization (FISH) data were also collected from patients.
Histologic BM involvement were found in 259/1585 (16.3%) patients and chromosomal abnormalities were detected in 192 (12.1%) patients (54 patients with single abnormalities and 138 patients with 2 or more abnormalities). Isolated cytogenetic aberrations (2 or more abnormalities) without histologic involvement were found in 21 patients (1.3%). Two or more cytogenetic abnormalities were associated with inferior overall survival (OS) compared with a normal karyotype or single abnormality in both patients with histologic BM involvement (5-year OS, 16.5% vs. 52.7%; P < 0.001) and those without BM involvement (31.8% vs. 66.5%; P < 0.001). This result demonstrated that BM cytogenetic results have a significant prognostic impact that is independent of BM histology. The following abnormalities were most frequently observed: rearrangements involving 14q32, 19q13, 19p13, 1p, 3q27, and 8q24; del(6q); dup(1q); and trisomy 18. In univariate analysis, several specific abnormalities including abnormalities at 16q22-q24, 6p21-p25, 12q22-q24, and -17 were associated with poor prognosis. Multivariate analyses performed for patients who had either chromosomal abnormalities or histologic BM involvement, revealed IPI high risk, ≥ 2 cytogenetic abnormalities, and several specific chromosomal abnormalities, including abnormalities at 19p13, 12q22-q24, 8q24, and 19q13 were significantly associated with a worse prognosis.
We suggest that isolated cytogenetic aberrations can be regarded as BM involvement and cytogenetic evaluation of BM improves staging accuracy along with prognostic information for DLBCL patients.
PMCID: PMC3851800  PMID: 24220305
Diffuse large B-cell lymphoma; Cytogenetics; Chromosomal abnormalities; Bone marrow involvement; Prognosis
12.  The Origin and Nature of Tightly Clustered BTG1 Deletions in Precursor B-Cell Acute Lymphoblastic Leukemia Support a Model of Multiclonal Evolution 
PLoS Genetics  2012;8(2):e1002533.
Recurrent submicroscopic deletions in genes affecting key cellular pathways are a hallmark of pediatric acute lymphoblastic leukemia (ALL). To gain more insight into the mechanism underlying these deletions, we have studied the occurrence and nature of abnormalities in one of these genes, the B-cell translocation gene 1 (BTG1), in a large cohort of pediatric ALL cases. BTG1 was found to be exclusively affected by genomic deletions, which were detected in 65 out of 722 B-cell precursor ALL (BCP-ALL) patient samples (9%), but not in 109 T-ALL cases. Eight different deletion sizes were identified, which all clustered at the telomeric site in a hotspot region within the second (and last) exon of the BTG1 gene, resulting in the expression of truncated BTG1 read-through transcripts. The presence of V(D)J recombination signal sequences at both sites of virtually all deletions strongly suggests illegitimate RAG1/RAG2-mediated recombination as the responsible mechanism. Moreover, high levels of histone H3 lysine 4 trimethylation (H3K4me3), which is known to tether the RAG enzyme complex to DNA, were found within the BTG1 gene body in BCP-ALL cells, but not T-ALL cells. BTG1 deletions were rarely found in hyperdiploid BCP-ALLs, but were predominant in other cytogenetic subgroups, including the ETV6-RUNX1 and BCR-ABL1 positive BCP-ALL subgroups. Through sensitive PCR-based screening, we identified multiple additional BTG1 deletions at the subclonal level in BCP-ALL, with equal cytogenetic distribution which, in some cases, grew out into the major clone at relapse. Taken together, our results indicate that BTG1 deletions may act as “drivers” of leukemogenesis in specific BCP-ALL subgroups, in which they can arise independently in multiple subclones at sites that are prone to aberrant RAG1/RAG2-mediated recombination events. These findings provide further evidence for a complex and multiclonal evolution of ALL.
Author Summary
Recent studies have alluded to the existence of a complex clonal cellular architecture in acute lymphoblastic leukemia (ALL), where multiple subclones contribute to leukemogenesis. Here, we show that in pediatric B-cell precursor ALL (BCP-ALL) monoallelic deletions in the tumor suppressor BTG1 locus, which were found to occur in 9% of the patients studied, result in truncations of the gene rather than in complete allelic losses. Using both genetic and epigenetic approaches, we show that these deletions most likely originate from illegitimate RAG recombination. Sensitive backtracking using deletion-spanning PCRs revealed that these BTG1 deletions occur in specific BCP-ALL subtypes, with frequencies higher than previously anticipated, often in one minor subclone or in multiple independent subclones within individual patients. Subclones that carry a BTG1 deletion at diagnosis can evolve into the major clone at relapse. These findings link a mechanism of tumor suppressor gene deletion to the multiclonal evolution of ALL.
PMCID: PMC3280973  PMID: 22359517
13.  Rapid Detection of Prognostically Significant Fusion Transcripts in Acute Leukemia Using Simplified Multiplex Reverse Transcription Polymerase Chain Reaction 
Journal of Korean Medical Science  2012;27(10):1155-1161.
Multiplex reverse transcription polymerase chain reaction (mRT-PCR) has recently emerged as an alternative to cytogenetics. We designed and used simplified mRT-PCR system as a molecular screen for acute leukemia. Fifteen fusion transcripts were included: BCR-ABL1, PML-RARA, ZBTB16-RARA, RUNX1-RUNX1T1, CBFB-MYH11, DEK-NUP214, TCF3-PBX1, ETV6-RUNX1, MLL-AFF1, MLL-MLLT4, MLL-MLLT3, MLL-MLLT10, MLL-ELL, MLL-MLLT1, and MLL-MLLT6. A total of 121 diagnostic acute leukemia specimens were studied, comparing the mRT-PCR system with standard cytogenetics. Fifty-six cases (46.3%) had fusion transcripts revealed by our mRT-PCR assay. The concordance rate between mRT-PCR and cytogenetics was 91.7%. However, false negative results were found in three cases who have inv(16), t(4;11) or t(11;19)(q23;p13.1), respectively. Seven cryptic translocations including ETV6-RUNX1, MLL-MLLT3, MLL-MLLT4, and PML-RARA were detected. This mRT-PCR assay is a useful screening tool in acute leukemia because it provides rapid and reliable detection of clinically important chimeric transcripts. In addition, cryptic translocations provide additional genetic information that could be clinically useful.
PMCID: PMC3468750  PMID: 23091311
Acute Leukemia; Multiplex RT-PCR; Cytogenetics; Cryptic Translocations
14.  Three-way Translocation of MLL/MLLT3, t(1;9;11)(p34.2;p22;q23), in a Pediatric Case of Acute Myeloid Leukemia 
The chromosome band 11q23 is a common target region of chromosomal translocation in different types of leukemia, including infantile leukemia and therapy-related leukemia. The target gene at 11q23, MLL, is disrupted by the translocation and becomes fused to various translocation partners. We report a case of AML with a rare 3-way translocation involving chromosomes 1, 9, and 11: t(1;9;11)(p34.2;p22;q23). A 3-yr-old Korean girl presented with a 5-day history of fever. A diagnosis of AML was made on the basis of the morphological evaluation and immunophenotyping of bone marrow specimens. Flow cytometric immunophenotyping showed blasts positive for myeloid lineage markers and aberrant CD19 expression. Karyotypic analysis showed 46,XX,t(1;9;11)(p34.2;p22;q23) in 19 of the 20 cells analyzed. This abnormality was involved in MLL/MLLT3 rearrangement, which was confirmed by qualitative multiplex reverse transcription-PCR and interphase FISH. She achieved morphological and cytogenetic remission after 1 month of chemotherapy and remained event-free for 6 months. Four cases of t(1;9;11)(v;p22;q23) have been reported previously in a series that included cases with other 11q23 abnormalities, making it difficult to determine the distinctive clinical features associated with this abnormality. To our knowledge, this is the first description of t(1;9;11) with clinical and laboratory data, including the data for the involved genes, MLL/MLLT3.
PMCID: PMC3116001  PMID: 21474990
Genetic translocation; Human MLL-MLLT3 fusion protein; Chromosome aberrations; Acute myeloid leukemia
15.  Cytogenetic & molecular analyses in adult chronic myelogenous leukaemia patients in north India 
Background & objectives:
Chronic myelogenous leukaemia (CML) is the commonest leukaemia in Asia. There is a paucity data on cytogenetic and molecular analyses of Indian CML patients. This apparently reflects the low availability of cytogenetic and molecular techniques in our country. This study aimed to document various types of BCR-ABL fusion transcripts in different phases of CML and to compare the Ph chromosome positivity/negativity vis-a-vis BCR-ABL fusion transcripts in adult CML patients.
Between June 2004 and February 2009, 208 patients were diagnosed as CML in chronic phase (CP), accelerated phase (AP) and blast crisis (BC), according to standard criteria. Cytogenetic and molecular genetic analyses were performed in all patients. Various types of BCR-ABL hybrid transcripts were compared with phases of CML and cytogenetic abnormalities.
Among 208 CML patients, b3a2 BCR-ABL transcripts were most commonly detected (66.82%) followed by b2a2 (28.84%), b3a2 + b2a2 (3.36%), b3a2 + e19a2 (0.48%) and b2a2 + e19a2 (0.48%). b3a2 transcripts were more frequently detected than b2a2 transcripts, in the whole group of 208 as well as in 183 CML-CP patients (P<0.0001). Ph chromosome was positive in 135 of 139 patients with b3a2 transcripts and 56 of 60 patients with b2a2 transcripts, difference not being significant. Additional cytogenetic abnormalities detected in 3.8 per cent patients in CML-CP and 44 per cent patients in CML-AP/BC, did not show predilection for any BCR-ABL transcript type.
Interpretation & conclusions:
This study documents higher Ph positivity (96.15%) by cytogenetic analysis among CML patients, as confirmed by qualitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis in a large patient group from north India. Both the techniques contribute towards understanding the disease biology, and have important implications for diagnosis and management of CML patients.
PMCID: PMC3307183  PMID: 22382182
BCR-ABL fusion transcripts; chronic myelogenous leukaemia; cytogenetic analysis; polymerase chain reaction; reverse transcriptase
16.  Cytogenetic profile of Indian patients with de novo myelodysplastic syndromes 
Background & objectives:
Myelodysplastic syndrome (MDS) is a clonal haematopoietic stem cell disorder characterized by ineffective haematopoiesis and leukaemia progression. Cytogenetic analysis has proven to be a mandatory part of the diagnosis of MDS as well as a major indicator for predicting clinical course and outcome. Studies on cytogenetics of MDS are reported mostly from the West and only a few are available from Asian countries. We report herein cytogenetic studies on 40 Indian patients with primary MDS to find out the occurrence and type of chromosome abnormalities and recurring defects.
Cytogenetic analysis was done using GTG banding and karyotyped according to the International System for Human Cytogenetic Nomenclature (ISCN).
Of the 40 patients, 19 patients (47.5%) showed clonal karyotypic abnormalities with distribution as follows: 3 of 15 (20%) of refractory anaemia (RA), 4 of 7 (57%) of refractory anaemia with excess blasts-1 (RAEB-1), 4 of 6 (67%) of refractory anaemia with excess blasts 2 (RAEB-2), 2 of 3 (67%) of refractory anaemia with ring sideroblasts (RARS), 2 of 4 (50%) of refractory cytopenia with multilineage dysplasia (RCMD), none (0%) RCMD-ringed sideroblasts (RCMD-RS) and 4 patients with 5q syndrome. The frequent abnormalities observed in our study were -7, 5q-and trisomy 8.
Interpretation & conclusions:
Two rare chromosomal abnormalities (6q-, 3q-) were found with unknown prognostic significance. Hence, cytogenetic analysis may be incorporated in the routine diagnosis of MDS since there are racial differences in clinical pictures and the molecular events.
PMCID: PMC3237242  PMID: 22089606
AML; chromosomal abnormalities; cytogenetics; myelodysplastic syndromes
17.  Coexisting with Clonal Evolution and BCR-ABL Mutant in CML Patients Treated with Second-generation Tyrosine Kinase Inhibitors Predict the Discrepancy of in vitro Drug Sensitivity 
Second-generation tyrosine kinase inhibitors (second TKIs) such as nilotinib and dasatinib control the activity of most ABL kinase domain mutations observed in patients with imatinib resistance. Although in vitro data show that both agents can inhibit all mutations except T315I, some discrepancies have been observed in a small subset of mutation clones. Cytogenetic clonal evolution is the important resistance mechanism of chronic myeloid leukemia (CML). Accordingly, we observed the clinical significance of coexisting with clonal evolution and BCR-ABL mutant in CML patients treated with second TKIs.
Materials and Methods
We monitored BCR-ABL transcript kinetics, interrelationship of clones expressing non-mutated and mutant transcripts and clonal aberrations within Philadelphia (Ph) positive and negative clones, respectively, in eight patients with CML receiving dasatinib or nilotinib for 3~41 months.
Clinical responses were correlated with in vitro sensitivity of the BCR-ABL mutants to the second TKIs in four patients. Four patients showed resistance to the second TKIs as compared to in vitro observations; three of them developed chromosomal abnormalities in the Ph chromosome positive or negative metaphases. Another patient lost the original mutation but acquired a more resistant new mutation and became resistant to the second TKI.
Cytogenetic clonal evolution is an independent poor prognostic factor in CML, which could explain the onset of mechanisms for second TKIs resistance to ABL kinase domain mutations. The results indicate that an additional evaluation of chromosomal abnormalities is warranted when BCR-ABL mutants are more resistant than indicated by in vitro data.
PMCID: PMC2848746  PMID: 20369050
CML; Dasatinib; Nilotinib; Clonal evolution; BCR-ABL mutation
18.  Comprehensive chronic lymphocytic leukemia diagnostics by combined multiplex ligation dependent probe amplification (MLPA) and interphase fluorescence in situ hybridization (iFISH) 
Molecular Cytogenetics  2014;7(1):79.
Banding-karyotyping and metaphase-directed-fluorescence-in-situhybridization (FISH) may be hampered by low mitotic index in leukemia. Interphase FISH (iFISH) is a way out here, however, testing many probes at the same time is protracted and expensive. Here multiplex-ligation-dependent-probe-amplification (MLPA) was used retrospectively in chronic lymphocytic leukemia (CLL) samples initially studied by banding cytogenetics and iFISH. Detection rates of iFISH and MLPA were compared and thus a cost-efficient scheme for routine diagnostics is proposed.
Banding cytogenetics was done successfully in 67/85 samples. DNA was extracted from all 85 CLL samples. A commercially available MLPA probe set directed against 37 loci prone to be affected in hematological malignancies was applied. Besides, routine iFISH was done by commercially available probes for following regions: 11q22.3, 12p11.2-q11.1, 13q14.3, 13q34, 14q32.33 and 17p13.1. MLPA results were substantiated by iFISH using corresponding locus-specific probes.
Aberrations were detected in 67 of 85 samples (~79%) applying banding cytogenetics, iFISH and MLPA. A maximum of 8 aberrations was detected per sample; however, one aberration per sample was found most frequently. Overall 163 aberrations were identified. 15 of those (~9%) were exclusively detected by banding cytogenetics, 95 were found by MLPA (~58%) and 100 (~61%) by routine iFISH. MLPA was not able to distinguish reliably between mono- and biallelic del(13)(q14.3q14.3), which could be easily identified as well as quantified by routine iFISH. Also iFISH was superior to MLPA in samples with low tumor cell load. On the other hand MLPA detected additional aberrations in 22 samples, two of them being without any findings after routine iFISH.
Both MLPA and routine iFISH have comparable detection rates for aberrations being typically present in CLL. As MLPA can detect also rare chromosomal aberrations it should be used as an initial test if routine cytogenetics is not possible or non-informative. Still iFISH should be used additionally to distinguish mono- from biallelic deletions and also to determine rate of mosaicism for 13q14.2 to 13q14.3. In case MLPA is negative the corresponding CLL samples should be tested at least by iFISH using the standard probe set to.
Electronic supplementary material
The online version of this article (doi:10.1186/s13039-014-0079-2) contains supplementary material, which is available to authorized users.
PMCID: PMC4247644  PMID: 25435911
Chronic lymphocytic leukemia (CLL); Chromosomal aberrations; Multiplex ligation-dependent probe amplification (MLPA); Fluorescence in situ hybridization (FISH)
19.  Cytogenetic Findings of Patients with Acute Lymphoblastic Leukemia in Fars Province 
Background: Acute lymphoblastic leukemia (ALL) is the sixth most common malignancy in Iran. Cytogenetic analysis of leukemic blasts plays an important role in classification and prognosis in ALL patients. The purpose of this study was to define the frequency of chromosomal abnormalities of ALL patients in adults and children in Fars province, Iran.
Methods: In this cross-sectional study, we evaluated karyotype results of bone marrow specimens in 168 Iranian patients with ALL (154 B-ALL and 14 T-ALL) in Fars Province using the conventional cytogenetic G-banding method.
Results: The frequency of cytogenetic abnormalities, including numerical and/or structural changes, was 61.7% and 53.8% in the B-ALL and T-ALL patients, respectively. Hyperdiploidy was the most common (32%) cytogenetic abnormality. Among structural abnormalities, the most common was t(9;22) in 11% of the patients. The children showed a higher incidence of hyperdiploidy and lower incidence of t(9;22) than adults (P<0.05). We found a lower incidence of recurrent abnormalities such as 11q23, t(1;19), and t(12;21) than those reported in previous studies.
Conclusion: Normal karyotype was more frequent in our study. The frequencies of some cytogenetic abnormalities such as hyperdiploidy and t(9;22) in our study were comparable to those reported in the literature. The results of this study in Fars Province can be used as baseline information for treatment decision and research purposes in ALL patients. We recommend the use of advanced molecular techniques in the future to better elucidate cryptic cytogenetic abnormalities.
PMCID: PMC3838981  PMID: 24293783
Acute lymphoblastic leukemia; Cytogenetic analysis; Chromosomal abnormalities; Incidence; Iran
20.  Frequency of 11q23/MLL gene rearrangement in Egyptian childhood acute myeloblastic leukemia: Biologic and clinical significance 
South Asian Journal of Cancer  2014;3(4):206-208.
Molecular cytogenetic abnormalities involving 11q23 are among the most common cytogenetic abnormalities in acute myeloid leukemia (AML) patients.
Aim of the work:
we aimed to evaluate the frequency of MLL/AF9 fusion gene in de novo AML patients, its impact on clinical features, and its prognostic significance.
Patients and Methods:
Twenty-eight children patients with AML and 20 healthy controls were subjected to complete clinical examination and laboratory investigations including, complete hemogram and bone marrow (BM) examination. Diagnosis was based on FAB morphologic and immunophenotypic criteria. Detection of (MLL/AF9) fusion gene was assessed by dual color fluorescent in situ hybridization (FISH). Follow-up were carried out clinically and by blast count in BM, and response to therapy to detect the outcome of the disease.
The incidence of MLL-fusion gene MLL/AF9 in AML cases was about (6/28) (21%). Four patients with MLL/AF9 fusion gene were newly diagnosed, two cases were at relapse and no patient at remission showed positivity. As regard the clinical outcome, five out of six MLL positive cases died, three of them during induction and two during relapse. The FAB AML subtypes with MLL/AF9 fusion were one M2, three M4, and two M5.
MLL-fusion gene MLL/AF9 was found in about 21% of studied AML patients when assessed by FISH technique and this is of high clinical relevance as most of these abnormalities have been associated with poor prognosis.
PMCID: PMC4236697  PMID: 25422805
Acute myelobastic leukemia; 11q23/MLL gene; Dual color FISH
21.  Chronic lymphocytic leukemia-associated chromosomal abnormalities and miRNA deregulation 
Video abstract
Chronic lymphocytic leukemia is the most common leukemia in adults. By cytogenetic investigations major subgroups of the disease can be identified that reflect different routes of tumor development. Of these chromosomal deviations, trisomy 12 and deletions of parts of either the long arm of chromosome 13, the long arm of chromosome 11, or the short arm of chromosome 17 are most commonly detected. In some of these aberrations the molecular target has been identified as eg, ataxia telangiectasia mutated (ATM) in case of deletions of chromosomal region 11q22~23 and the genes encoding microRNAs miR-15a/16-1 as likely targets of deletions of chromosomal band 13q14.3. Of note, these aberrations do not characterize independent subgroups but often coexist within the metaphases of one tumor. Generally, complex aberrations are associated with a worse prognosis than simple karyotypic alterations. Due to smaller sizes of the missing segment the detection of recurrent deletions is not always possible by means of classical cytogenetics but requires more advanced techniques as in particular fluorescence in situ hybridization (FISH). Nevertheless, at this time it is not recommended to replace classical cytogenetics by FISH because this would miss additional information given by complex or secondary karyotypic alterations. However, the results of cytogenetic analyses allow the stratification of prognostic and predictive groups of the disease. Of these, the group characterized by deletions involving TP53 is clinically most relevant. In the future refined methods as eg, array-based comparative genomic hybridization will supplement the existing techniques to characterize CLL.
PMCID: PMC3681189  PMID: 23776377
chronic lymphocytic leukemia; chromosomal abnormality; miRNA deregulation
22.  A Phase 2 Trial of Ponatinib in Philadelphia Chromosome–Positive Leukemias 
The New England journal of medicine  2013;369(19):10.1056/NEJMoa1306494.
Ponatinib is a potent oral tyrosine kinase inhibitor of unmutated and mutated BCR-ABL, including BCR-ABL with the tyrosine kinase inhibitor–refractory threonine-to-isoleucine mutation at position 315 (T315I). We conducted a phase 2 trial of ponatinib in patients with chronic myeloid leukemia (CML) or Philadelphia chromosome–positive acute lymphoblastic leukemia (Ph-positive ALL).
We enrolled 449 heavily pretreated patients who had CML or Ph-positive ALL with resistance to or unacceptable side effects from dasatinib or nilotinib or who had the BCR-ABL T315I mutation. Ponatinib was administered at an initial dose of 45 mg once daily. The median follow-up was 15 months.
Among 267 patients with chronic-phase CML, 56% had a major cytogenetic response (51% of patients with resistance to or unacceptable side effects from dasatinib or nilotinib and 70% of patients with the T315I mutation), 46% had a complete cytogenetic response (40% and 66% in the two subgroups, respectively), and 34% had a major molecular response (27% and 56% in the two subgroups, respectively). Responses were observed regardless of the baseline BCR-ABL kinase domain mutation status and were durable; the estimated rate of a sustained major cytogenetic response of at least 12 months was 91%. No single BCR-ABL mutation conferring resistance to ponatinib was detected. Among 83 patients with accelerated-phase CML, 55% had a major hematologic response and 39% had a major cytogenetic response. Among 62 patients with blast-phase CML, 31% had a major hematologic response and 23% had a major cytogenetic response. Among 32 patients with Ph-positive ALL, 41% had a major hematologic response and 47% had a major cytogenetic response. Common adverse events were thrombocytopenia (in 37% of patients), rash (in 34%), dry skin (in 32%), and abdominal pain (in 22%). Serious arterial thrombotic events were observed in 9% of patients; these events were considered to be treatment-related in 3%. A total of 12% of patients discontinued treatment because of an adverse event.
Ponatinib had significant antileukemic activity across categories of disease stage and mutation status. (Funded by Ariad Pharmaceuticals and others; PACE number, NCT01207440.)
PMCID: PMC3886799  PMID: 24180494
23.  Del(15q) is a recurrent “minor route” cytogenetic abnormality in the clonal evolution of chronic myelogenous leukemia 
Cancer genetics and cytogenetics  2009;192(1):18-23.
Del(15q) is known to occur in acute leukemias, but has been described rarely in chronic myelogenous leukemia (CML). We describe five cases of CML associated with del(15q). There were four men and one woman. Bone marrow aspirate smears demonstrated increased blasts in all cases at the time of del(15q) detection, showing accelerated phase in two and myeloid blast phase in three. Conventional cytogenetic analysis showed t(9;22) and del(15q), as well as other inconsistent clonal abnormalities. All patients received imatinib mesylate, four received additional chemotherapy, and two underwent allogeneic stem cell transplantation (ASCT). For the three patients who did not receive ASCT, one died, one was in persistent blast phase, and one was in clinical remission with molecular evidence of residual disease, 16, 6, and 34 months after identification of del(15q), respectively. For the two patients who underwent ASCT, one died and one was in clinical remission with molecular evidence of disease, 15 and 64 months after identification of del(15q), respectively. Our findings indicate that del(15q) is a recurrent cytogenetic abnormality that may be seen either at initial presentation of advanced disease or emerge during disease progression. Del(15q) appears to be associated with a poor prognosis in CML.
PMCID: PMC4167428  PMID: 19480932
del(15q); CML; minor route abnormality; clonal evolution
24.  Assessing karyotype precision by microarray-based comparative genomic hybridization in the myelodysplastic/myeloproliferative syndromes 
Recent genome-wide microarray-based research investigations have revealed a high frequency of submicroscopic copy number alterations (CNAs) in the myelodysplastic syndromes (MDS), suggesting microarray-based comparative genomic hybridization (aCGH) has the potential to detect new clinically relevant genomic markers in a diagnostic laboratory.
We performed an exploratory study on 30 cases of MDS, myeloproliferative neoplasia (MPN) or evolving acute myeloid leukemia (AML) (% bone marrow blasts ≤ 30%, range 0-30%, median, 8%) by aCGH, using a genome-wide bacterial artificial chromosome (BAC) microarray. The sample data were compared to corresponding cytogenetics, fluorescence in situ hybridization (FISH), and clinical-pathological findings. Previously unidentified imbalances, in particular those considered submicroscopic aberrations (< 10 Mb), were confirmed by FISH analysis. CNAs identified by aCGH were concordant with the cytogenetic/FISH results in 25/30 (83%) of the samples tested. aCGH revealed new CNAs in 14/30 (47%) patients, including 28 submicroscopic or hidden aberrations verified by FISH studies. Cryptic 344-kb RUNX1 deletions were found in three patients at time of AML transformation. Other hidden CNAs involved 3q26.2/EVI1, 5q22/APC, 5q32/TCERG1,12p13.1/EMP1, 12q21.3/KITLG, and 17q11.2/NF1. Gains of CCND2/12p13.32 were detected in two patients. aCGH failed to detect a balanced translocation (n = 1) and low-level clonality (n = 4) in five karyotypically aberrant samples, revealing clinically important assay limitations.
The detection of previously known and unknown genomic alterations suggests that aCGH has considerable promise for identification of both recurring microscopic and submicroscopic genomic imbalances that contribute to myeloid disease pathogenesis and progression. These findings suggest that development of higher-resolution microarray platforms could improve karyotyping in clinical practice.
PMCID: PMC3000833  PMID: 21078186
25.  Very Long-term Follow-Up Results of Imatinib Mesylate Therapy in Chronic Phase Chronic Myeloid Leukemia After Failure of Interferon Alpha Therapy 
Cancer  2012;118(12):3116-3122.
The long-term outcome of patients with chronic phase chronic myeloid leukemia treated with imatinib after failure of interferon alpha therapy has not been detailed.
Patients and Methods
368 patients were analyzed. Univariate and multivariate analyses for survival were conducted using standard statistical methods.
Overall, 247 patients (67%) achieved complete cytogenetic response (CCyR). Of 327 patients studied, 207(63%) achieved major molecular response (MMR), and 99 (30%) had undetectable BCR-ABL levels at some time on therapy. The estimated 10-year survival rate was 68%, progression-free survival rate 67%, and event-free survival rate 51%. By multivariate analysis, age ≥ 60 years, hemoglobin < 10g/dl, marrow basophils ≥ 5%, any peripheral blasts, and clonal evolution were independent adverse factors for survival. The estimated 7-year survival by the presence of none (n=154), 1-2 (n=190), or ≥ 3 factors (n=24) were 93%, 70%, and 25% respectively (p <0.01). Achievement of MMR, CCyR, or partial cytogenetic response at 12 months were associated with significantly better 10-year survival rate by landmark analysis (10-year survival 80-90%) vs. achieving minor cytogenetic response or complete hematologic response (10-year survival 55-65%) vs. other response (10-year survival 10%). Using landmark analysis to include imatinib response at 12 months, achievement of major cytogenetic response or better (hazard ratio 0.12; p< 0.001) and complete hematologic response or minor cytogenetic response (hazard ratio 0.36; p=0.003) were significant favorable prognostic factors.
The estimated 10-year survival rate of 68% in patients with chronic myeloid leukemia receiving imatinib after interferon failure has improved.
PMCID: PMC3370116  PMID: 22370904

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