Cytogenetic Abnormalities and Molecular Markers of Acute Lymphoblastic Leukemia

Cytogenetic studies in patients from India with T-acute lymphoblastic leukemia

Cytogenetic analysis was performed in 30 patients with T cell acute lymphoblastic leukemia (11 adults, 19 children) at initial presentation and analysis was also repeated in clinical and hematological remission in 15 patients. At initial presentation, chromosomal abnormalities were detected in 27 cases (90%) and hypodiploidy was detected in 19 patients (63.3%), followed by pseudodiploidy in six patients (20%) and hyperdiploidy in two patients (6.6%). Other karyotypic abnormalities detected were deletion 6q (40%), deletion 11 q (16.6%), deletion 7q (10%), abnormalities of chromosome 9 in (13.3%) and translocation t(11;14)(p13;q11) in 6.6% and der(12)t(12;?)(p13;?) in (3.3%). In complete remission, nine out of 15 cases (60%) showed chromosomal aberrations. Original abnormalities were detected in two cases (13.3%) and new abnormalities were detected in seven cases (46.6%).

Regional cancer cytogenetics: a report on 1,143 diagnostic cases

The results of studies from a regional cancer cytogenetics diagnostic service are reported. In a 10-year period, 1,143 marrow samples from patients with newly diagnosed leukemia and myelodysplastic syndrome were referred. Successful studies were completed on 992 cases (87%). Among all referred cases, the rates of detection of cytogenetically abnormal clones were 95% for chronic myelogenous leukemia (CML), 54% for acute lymphoblastic leukemia (ALL), 51% for acute myeloid leukemia (ANLL), and 43% for myelodysplastic syndrome (MDS). Of 169 cases of CML studied, 90.5% bore the standard Philadelphia chromosome (Ph), 3.55% had an unusual Ph, and 5.33% were Ph-negative. Among the 59 cases of cytogenetically abnormal MDS, common abnormalities observed were trisomy 8 and changes resulting in loss of material from the long arm of chromosomes 5 and 7, and 20q-. Of the 168 abnormal ANLL, there was a strikingly non-random pattern of aneuploidy, with monosomy 7 and trisomy 8 predominating. Common structural changes observed were changes resulting in loss of material from the long arm of chromosomes 5 and 7, trisomy 8, rearrangements of 11q23, t(15;17), t(8;21), rearrangements of 12q13 and 3q, inversion 16, trisomy 11, Ph, trisomy 21, t(6;9) and t(1;22). The differences between adult and pediatric findings were minor, with the exception of chromosome 5 abnormalities, which were common among adults with ANLL but rare in the pediatric cases. There were 273 ALLs with abnormal cytogenetic findings. There was preferential gain of chromosomes 21, X, 14, 6, 4, 18, 17, and 10 (in decreasing order of frequency) in leukemic clones. Of the 193 ALLs with structural changes, many fell into-well-defined categories with established correlations to FAB subtypes. Common changes in ALL were rearrangements of 9p, 12p, 6q, TCR loci, 11q23, Ig loci, and 8q24, and duplication of 1q, Ph, i(17q), t(1;19), i(9q) and dic(9;12). The detailed documentation of the cytogenetic findings in this relatively large, single-institution study will likely facilitate the further characterization of rare, primary cytogenetic changes associated with leukemias and MDS. From a managed health care perspective, regional cancer cytogenetic services may be cost-effective alternatives to single-institution laboratories.

Genetic changes: relevance for diagnosis and detection of minimal residual disease in acute lymphoblastic leukaemia

Cure can now be achieved in a proportion of patients with ALL. However, relapse and eventual treatment failure occur in many cases receiving identical treatment, presumably as a result of failure to eradicate MRD. While for many years marrow morphology has been the standard by which leukaemic remission has been assessed, more sensitive techniques have been developed for detection of MRD including immunophenotypic analysis, and as discussed in this chapter, methods which detect leukemia-associated clonal genetic changes at the karyotypic and genomic levels. Table 10 lists the applicability and sensitivity of various markers used in MRD analysis in ALL. It is apparent that of the karyotypic and molecular approaches described, only PCR-based strategies for detection of either leukaemia-specific translocations or clonal Ag receptor rearrangements are reliably applicable to a high proportion of both B- and T-ALL at sufficiently high sensitivity. Initial clinical studies of patients undergoing therapy for ALL using a variety of PCR-based methods suggest that in some cases a persistent or increasing level of residual disease may be predictive for clinical relapse, although a number of technical factors and the phenomena of oligo-clonality and clonal evolution may limit the usefulness of this analysis in a few instances. From current available data it appears that in order to define the potential predictive value of PCR detection of MRD a large number of patients will need to be prospectively assessed over several years at multiple time points during and after therapy, preferably using more than one semi-quantitative PCR approach. In addition to reliable prediction of clinical relapse allowing appropriate individual treatment modification, progress in the molecular detection of MRD in ALL is also likely to be of benefit in the assessment of the efficacy of autograft purging and the evaluation of new therapeutic strategies such as the use of biological response modifiers to eliminate a low tumour burden.

A complex translocation, t(4;11;13)(q21;q23;q12-14), in a case of infantile acute lymphoblastic leukemia

Cytogenetic analysis provides valuable prognostic information in children diagnosed with hematologic malignancies. While the t(4;11)(q21;q23) has frequently been reported in patients with acute lymphoblastic leukemia, the additional involvement of chromosome 13 to form a three-way translocation has not been described previously. We report a case of acute lymphoblastic leukemia in a 5-month old infant with a complex t(4;11;13)(q21;q23;q12-14).

Prognostic significance of karyotype analysis in children with acute lymphoblastic leukemia

Chromosome studies, using bone marrow samples of 26 pretreated children (below 15 years of age) with Acute Lymphoblastic Leukemia were carried out to explore the potentialities of applying chromosomal findings as a prognostic indicator in these patients. Abnormal karyotype was identified in 15 patients (57.6 per cent). The chromosomes frequently involved in non-random numerical abnormalities were Nos. 8, 18 and 21. Structural chromosome changes observed consisted of deletion 6q- and translocation t (4;11). After karyotype analysis, patients were grouped into subsets on the basis of the karyotype pattern observed. They were followed up to evaluate their prognosis and survival period. Patients showing hyperdiploid clone with greater than 51 chromosomes had the best prognosis. Patients with normal karyotype and patients with deletion of the long arm of chromosome 6 showed intermediate prognosis whereas patients showing t (4;11), trisomy 8, trisomy 18, trisomy 21, and hypodiploid karyotype were associated with worst prognosis. Thus, karyotype analysis before treatment helps to classify ALL patients as poor, intermediate and good prognosis groups and on this basis therapy can be designed accordingly.