Molecular characterization of Ph' + hybrid acute leukemia

Age-related patterns of immunoglobulin and T-cell receptor gene rearrangements in precursor-B-ALL: implications for detection of minimal residual disease

Detailed Southern blot and PCR analysis of Ig heavy (IGH), Ig kappa (IGK), T-cell receptor delta (TCRD), and TCR gamma (TCRG) genes were performed in 289 children with precursor-B-ALL in order to determine age-related Ig/TCR patterns and their implications for detection of minimal residual disease (MRD). Overall, IGH, IGK, TCRD, and TCRG gene rearrangements were detected in 98, 62, 90, and 58% of patients, respectively. The frequency of IGH and TCRD rearrangements was independent of rearrangements in one of the other three loci, whereas Ig kappa deleting element and TCRG rearrangements preferentially coincided. Southern blot analysis showed that oligoclonality of IGH, IGK, and TCRD was interrelated, that is, oligoclonality in one locus was related with a higher chance of oligoclonality in another locus. Combined Southern blot and PCR analysis revealed that Ig/TCR patterns were age related: children younger than 3 years or older than 10 years showed a higher prevalence of incomplete IGH rearrangements and a lower prevalence of IGK deletions, TCRG rearrangements, and TCRD rearrangements than children between 3 and 10 years. In addition, IGH oligoclonality was more frequent in the younger and older children. These age-related differences probably reflect ALL subsets with different cellular origin and differences in the duration of the preleukemic phase between the initial and final leukemogenetic hit. The more immature Ig/TCR gene rearrangement pattern in children younger than 3 years or older than 10 years resulted in relatively low numbers of potential MRD-PCR targets per patient, particularly if only monoclonal rearrangements were taken into account. These data provide insight into the immunobiological characteristics of Ig/TCR gene rearrangements in childhood precursor-B-ALL and form a useful basis for designing improved strategies for the identification and selection of MRD-PCR targets.

Minor myeloid component in Ph chromosome-positive acute lymphoblastic leukaemia: correlation with cytogenetic pattern and implication for poor response to therapy

Morphological, immunological and cytogenetic features were studied in 27 adults presenting with Ph chromosome-positive acute lymphoblastic leukaemia (ALL), in correlation with clinical outcome. Twenty patients (group 1) were diagnosed as having typical ALL according to the FAB criteria supported by immunological findings. Less than 1% blast cells with azurophilic granules were detected in all cases. Myeloid cytochemistry, i.e. peroxidase and Sudan black-B stain, was negative in all cases. A minor phenotype deviation consisting of the expression of the CD13 myeloid-associated marker was detected in two patients. In seven patients (group 2) a diagnosis of ALL with a minor myeloid component was made because of the presence of a majority of lymphoid blasts and of 5-15% blast cells with morphological cytochemical and immunological features of the myeloid lineage. Abnormal metaphases were found in 6/20 (30%) patients in group 1, compared with 7/7 (100%) patients in group 2. All patients were treated by antilymphoid regimens; however, complete remission was achieved in 17/20 (85%) patients in group 1 versus 1/7 (14.3%) patients in group 2. Median survival was 16 months, range < 1-120+ in group 1 and 9 months, range < 1-15 in group 2. It is concluded that morphological, immunological and cytogenetic studies allow for the recognition of two cytological subsets of Ph+ ALL. The presence of a minor myeloid component in otherwise typical Ph chromosome-positive ALL may be associated with a distinct cytogenetic pattern and poor responses to antilymphoid therapy.

Immunophenotype of acute lymphoblastic leukemia cells: the experience of the Italian Cooperative Group (Gimema)

The immunophenotype of 304 adult lymphoblastic leukemias (> 18 years) diagnosed on the basis of the FAB criteria was determined at the time of diagnosis using a panel of monoclonal antibodies. The series comprised cases diagnosed and immunophenotyped in 43 Italian centers (GIMEMA Cooperative Group) between April 1988 and June 1991. The immunophenotypic characterization consisted of two consecutive steps. The initial screening was based on the reactivity for TdT, HLA-Dr, CD7, CD10, CD13, CD19, CD24, CD33 and CD41. According to the results obtained, the second level of investigation assessed the positivity for intra cytoplasmic (Cy) Ig, CD1a, CD2, CD3, CD4, CD5, CD8 and CD20. Based on the hierarchical expression of the different B- and T-cell related antigens, each case was assigned to a given differentiation stage. B-lineage ALL were classified in five subgroups (B0-B4) and T-lineage ALL in four subgroups (T0-T3). Cases in which the blasts were lymphoid according to the FAB criteria, but expressed myeloid antigens in association with B- and T-lymphoid markers were defined as hybrid leukemias. As expected, CD10+ cases (B2-B3) were the most frequent within the B-lineage ALL (83.2% of cases). CyIg+ (B3) accounted for about 20% of CD10+ ALL. Twenty eight cases (13.4%) were at a pre-cALL stage (B0-B1) and of these, 8 (3.8% of the total series) were positive only for TdT and HLA-Dr (B0). Intermediate and mature thymic phenotypes (T2-T3) were predominant within the T-ALL (67.2%) groups. Five cases, were positive only for TdT and CD7 (CD5+), and classified as T0. 9.2% of cases fulfilled the definition of hybrid leukemia, largely in view of the co-expression of B-lymphoid and myeloid markers.(ABSTRACT TRUNCATED AT 250 WORDS)

Evolution of Ig- and T-cell receptor gene configuration in a Ph1+ hybrid leukemia patient

In a longitudinal study of a 32-year-old male with Ph1+ hybrid leukemia we have followed the immunophenotype and configuration of Ig- and TCR genes during the course of different chemotherapy regimens directed first against the myeloid and later against the lymphoid components of the disease. We identified changes in all parameters, interpretable as an evolution of the malignant clone resulting in a leukemic switch towards a more lymphoid character. Thus, while the expression of the myeloid antigens CD13 and CD33 decreased, that of CD10 (CALLA) and CD20 (B1) increased. Moreover, while the configuration of the Ig heavy and light chain lambda genes remained constant during the whole period of treatment, that of the Ig light chain kappa gene and TCR beta gene displayed extensive rearrangements after initiation of ALL therapy. Since this patient represents a de novo acute leukemia as evaluated by location of the translocation-breakpoint on chromosome 22, our data clearly indicate that Ig- and TCR gene rearrangements might prove a valuable addition in monitoring Ph1+ hybrid leukemias, providing guidelines for optimizing chemotherapy.