Acute Promyelocytic Leukemia M3: Cytomorphologic, Immunophenotypic, Cytogenetic, and Molecular Variants

Abstract

Acute promyelocytic leukemia (APL) M3 is an acute myeloid leukemia (AML) subtype characterized by proliferation of malignant promyelocytes with mature myeloid immunophenotype and the translocation t(15;17)(q22;q11), which results in the fusion of retinoic acid receptor-alpha (RARalpha) gene on chromosome 17 and the gene PML on chromosome 15. There are three M3 morphologic variants: the typical hypergranular form and the microgranular and basophilic variants. Although most leukemic cells in M3 patients express t(15;17), other cytogenetic abnormalities have also been reported. Also, there are three molecular variants of the PML/RARalpha transcript (bcr1, bcr2, bcr3). Blasts had typical hypergranular appearance (13 patients) with a mature myeloid immunophenotype (HLA-DR(-),CD13(+), and/or CD33(+)) (10 patients) in the majority of patients with M3 followed in this study. The typical translocation [t(15;17)(q22;q11)] was detected by cytogenetic analysis in 5 M3 patients, but PML/RARalpha was positive in 13 out of 15 patients, as assessed by RT-PCR (8 patients with bcr1 and 5 with bcr3 subtype). Cytogenetic diversity was found in three patients (1 with t(17;17), 1 with +8, and 1 with add (7)(q22); -7; +8). According to many studies, leukemic cell heterogeneity in APL influences the clinical outcome of disease. The analysis of certain leukemic cell characteristics on the clinical outcome in our study revealed that patients with bcr3 had shorter medians of first remission and survival in comparison to patients with the bcr1 isoform of PML/RARalpha. Also, the clinical relapse of disease in 4 APL patients with reverted PML/RAR alpha positivity is consistent with the view that detection of PML/RARalpha by RT-RCR in patients in remission implies a poor prognosis. On the contrary, lack of detection of PML/RARalpha by RT-PCR at least three times is a sign of long remission and survival.

Late Relapses in Acute Promyelocytic Leukaemia

“…The resulting hybrid PML/RARα gene is involved in leukaemic transformation, as it encodes for a fusion protein that blocks myeloid cell differentiation at the promyelocytic stage [1]. The introduction of all- trans -retinoic acid (ATRA) as a tailored treatment of APL has markedly improved its prognosis; however, about 30% of the patients that achieve complete remission (CR) will eventually relapse [2, 3].…”

Expression patterns of specific promyelocytic/retinoic acid receptor‐α transcripts in patients with acute promyelocytic leukemia

“…Patients who expressed the bcr3 isoform appeared to have shorter disease‐free and overall survival durations, than those who expressed the bcr1 isoform (Jurcic et al. , 2001; Sucić et al. , 2002).…”

Quality Assurance Guided FISH-Analysis for Optimal Detection of AMLAssociated Chromosomal Aberrations

“…Moreover, in the present study structural cytogenetic aberrations were detected in 24/41 (58.5 %) of patients. [27] and Sucic et al [28] stressed on the point that not only t(15;17) is restricted to M3, but also practically, all M3 patients had this translocation at DNA levels even if karyotypically normal. Consistent with Grimwade and Solomon [29] and Chen et al [30] , this rearrangement is firmly established as remarkably APL associated cytogenetic abnormality classified among favorable group.…”