Lack of correlation between immunoglobulin and T cell receptor gene rearrangements and TdT expression in acute myeloid leukaemia

Terminal deoxynucleotidyl transferase expression in acute myelogenous leukemia and myelodysplasia as determined by flow cytometry

The significance of terminal deoxynucleotidyl transferase (TdT) expression in acute myelogenous leukemia (AML) remains controversial. Therefore, we studied TdT expression by flow cytometry in 120 previously untreated patients with AML or myelodysplastic syndrome (MDS) to determine the distribution of TdT-positive blasts and the intensity of TdT expression and to seek clinically significant associations. TdT expression measured by flow cytometry (flow TdT%) was heterogeneous, ranging from 0.1% to 87% (median, 8.5%), and 74 patients (62%) had at least 5% TdT-positive blasts. TdT positivity was associated with the M0 or M1 subtype and with expression of CD34 and CD7. No significant correlation was found between TdT expression and type of cytogenetic abnormality or rearrangement of immunoglobulin or T-cell receptor genes. Remission lasted longer in patients with a flow TdT% < 5 than in patients with a flow TdT% > 5 (median, 95 weeks vs 55 weeks, p = 0.02); however, complete remission rates did not differ when patients were classified by initial flow TdT%. Survival was slightly better for patients with flow TdT% less than 5%. Among patients with a flow TdT% > 5%, those with a higher TdT intensity survived longer than those with a lower intensity. These data suggest that quantitative TdT measurement may contribute to prognostic estimate in AML patients.

Prognostic significance of immunoglobulin and T cell receptor gene rearrangements in patients with acute myeloid leukemia: Taiwan experience

We investigated the prognostic significance of lymphoid antigen receptor gene rearrangement in patients with newly diagnosed acute myeloid leukemia (AML). Thirty-nine patients were included in the study. Clonal gene rearrangement of immunoglobulin heavy chain (IgH) and T cell receptor beta chain (TCRbeta) was found in leukemic cells in 11 (28.2%) and 10 (25.6%) patients, respectively. Five (12.8%) had both IgH and TCRbeta gene rearrangements. Three of the seven (42.9%) B-lymphoid marker-positive and eight of the 32 (25%) B-lymphoid marker-negative patients had clonal IgH gene rearrangements. Five of the 11 (45.5%) T-lymphoid marker-positive and 5 of the 28 (17.9%) T-lymphoid marker-negative patients had clonal TCRbeta gene rearrangements. All patients were treated with similar regimens. The complete remission rate (62.5% vs 65.2%, p=1.000) and median survival (13 vs 14 months, p=0.366) were similar in patients with and without clonal IgH or TCRbeta gene rearrangements. In conclusion, while clonal rearrangements of IgH or TCRbeta genes were found in AML patients, they did not appear to effect the prognosis.

TCR delta gene rearrangements in acute myeloid leukemia with T-lymphoid antigen expression

In this review we present our data concerning T-cell receptor (TCR) delta gene rearrangements in acute myeloid leukemia with coexpression of T-lymphoid features (CD2/CD4/CD7; Ly+ AML). We found a correlation between TCR delta gene rearrangements and coexpression of these T-lymphoid features. Ten of 66 Ly+ AML and only one of 44 AML cases without this coexpression exhibited TCR delta gene rearrangements (p = .028). In contrast, no correlation was observed between terminal deoxynucleotidyl transferase (TdT) expression and the occurrence of TCR delta gene rearrangements in AML. Rearrangements were found in two of 25 AML with and seven of 71 AML cases without TdT expression. Interestingly, nucleotide sequencing of junctional sites revealed up to 36 N-nucleotides in cases without or with only weak TdT expression indicating downregulation of TdT expression after the TCR rearrangement took place. Complete V delta 1J delta 1 and incomplete D delta 2J delta 1 gene rearrangements were observed most frequently in Ly+ AML. These recombination patterns were similar to patterns observed in acute T-lymphoblastic leukemia with coexpression of myeloid features (My+ T-ALL) suggesting transformation of a common myeloid/T-lymphoid progenitor cell in these cases.

Rearrangement of the immunoglobulin heavy chain gene in juvenile chronic myeloid leukaemia

Five patients with clinical and laboratory features typical for juvenile chronic myeloid leukaemia (JCML) are presented. Rearrangement of the j joining region of the immunoglobulin heavy chain (Jh) was demonstrated in three children out of five analysed. As no Vh to DhJh nor kappa light chain rearrangements were demonstrated, it is reasonable to speculate that the transforming event of the stem cell happened at the stage when Dh to Jh rearrangement took place. As the monocytic lineage is prominent in JCML, it is suggested that the transforming event happens in a unique stem cell with intermediate differentiation towards the myelomonocytic as well as the B-lymphatic lineage. This stem cell, which is present at a certain stage of embryogenesis, disappears later. Such an early 'hybrid' cell is sometimes involved in leukaemias of early infancy, and may be the transformed cell in some cases of infantile leukaemia.

Molecular analysis of CD2 gene expression in acute myeloblastic leukemia expressing T-lineage associated surface antigens

CD2 is a surface marker of T cells and NK cells, and is not normally expressed on human myeloid cells, but is found on a significant minority of cases of acute myeloid leukemia (AML). Molecular studies were performed on bone marrow myeloblasts from two patients with CD2 surface positive AML. No abnormality of the CD2 gene was detected on Southern blot analysis. On Northern blots, CD2 mRNA of normal size was present. The CD2 gene contained a site which was unmethylated, consistent with active transcription, in a CD2 positive AML case, and in a CD2 positive T cell line, but methylated in CD2 negative AML cells. The evidence does not support the hypothesis that inappropriate surface expression of lineage markers is due to leukemia-related genetic changes, such as amplification or rearrangement, of the CD2 gene itself. Rather, the results are consistent with the hypothesis that mixed lineage leukaemia arises from rare normal bone marrow progenitors with multilineage phenotypes.

The diagnostic and prognostic value of immunophenotyping in acute leukemia

Immunophenotyping with monoclonal antibodies to leucocyte differentiation antigens has an established diagnostic role in the laboratory investigation of acute leukemia. In the vast majority of cases, a hemopoietic lineage can be confidently assigned; namely, acute myeloid leukemia (AML), or the precursor-B and precursor-T variants of acute lymphoblastic leukemia (ALL). The areas of greatest practical importance are in morphologically difficult or undifferentiated cases, and in distinguishing between the major variants of precursor-B and T-ALL. Cases with aberrant patterns of marker expression (acute mixed lineage leukemia, lineage infidelity) are frequently encountered in both ALL and AML, and can lead to diagnostic confusion. However, correlation with morphology and other clinicopathologic features, and careful consideration of the weight of phenotyping evidence almost always allows the correct lineage to be identified. The prognostic value of phenotypic information in acute leukemia is generally limited. Recognition of the major variants of ALL is still of clinical importance, but the significance of myeloid antigen positivity in ALL is controversial, and may not have prognostic value. Patterns of myeloid antigen expression in AML have limited prognostic significance, while the relationship between lymphoid antigen expression and treatment response in AML remains highly controversial. Careful evaluation of the predictive power of immunophenotype in large controlled clinical trials in acute leukemia is still required.

Ig-gene and T-cell receptor gene rearrangements in a secondary, mono-histiocytic malignancy

In 1984, a 21-year-old male was diagnosed with an acute lymphoblastic leukemia of pre-B cell type. Treatment with chemotherapy, including alkylating agents and prophylactic radiotherapy to the central nervous system, induced a complete remission. In June 1990, a biopsy from a supraclavicular node revealed a malignancy of mono-histiocytic type with erythrophagocytosis. Soon thereafter bone marrow involvement was found. No remission was achieved and the patient died in December 1990. DNA from bone marrow and lymph node obtained 1990 showed clonal rearrangements of both the immunoglobulin heavy-chain gene and the T-cell receptor gamma chain gene. This unusual case illustrates a typical secondary malignancy proven to be separate from the primary neoplasm judged by morphological appearance, immunophenotype and cytogenetic constitution. Coexistent clonal rearrangements of immunoglobulin and T-cell receptor genes have been reported in acute non-lymphoblastic leukemias and notably in cases expressing TdT, interpreted as a predominant lymphoid commitment of the tumor cells. In the present case, however, the malignant cells had a differentiated phenotype and showed erythrophagocytosis, indicating a more mature mono-histiocytic cell type. However, also CD3 expression was found by immunohistochemistry of frozen sections which might indicate a biphenotypic malignancy.