Identification of PML/RARalpha fusion gene transcripts that showed no t(15;17) with conventional karyotyping and fluorescent in situ hybridization.

Acute promyelocytic leukemia (APL) is characterized by a reciprocal translocation, t(15;17)(q22;q11-21), resulting in the fusion of the promyelocytic leukemia (PML) and retinoic acid receptor alpha (RARalpha) genes. Using conventional cytogenetic methods, these translocations are normally detected in about 70-90% of patients; most negative results are due to technical problems or cryptic variants. These masked PML/RARalpha fusions can be identified by molecular analyses, such as reverse transcriptase-polymerase chain reaction (RT-PCR) or fluorescence in situ hybridization (FISH). Approximately 5 to 10% of all APL cases reported do not show PML/RARalpha fusion transcripts, even with dual-colored FISH. We report three of 40 diagnosed APL cases that showed morphological, cytochemical, and immunophenotypic features of hypergranular APL, but did not show a PML/RARalpha fusion signal or any of its variants, on FISH. All cases were identified by RT-PCR, which was further confirmed by cDNA sequencing. Conventional karyotyping showed other clonal aberrations in these cases, but failed to show t(15;17) or any other variants or complex translocations.

Analysis and comparison of clinicohematological parameters and molecular and cytogenetic response of two Bcr/Abl fusion transcripts.

Different forms of p210 are produced by alternative splicing, namely b2a2 and b3a2. There have been many contrasting data establishing a relationship between the two Bcr/Abl transcripts and platelet counts and also response to treatment. However, the data published to date have been on a small group of patients. The aim of the present study was to determine whether there was any difference between clinical and hematological parameters at diagnosis between the two Bcr/Abl fusion transcripts in our population, and whether the two transcripts responded differently or similarly to imatinib treatment. RT-PCR was performed in 202 cases for detection of Bcr/Abl transcripts in newly diagnosed chronic myelogenous leukemia cases in one year. The two transcripts were compared and correlated with clinical, hematological and FISH data and with response to treatment. A total of 138 cases were of b3a2 and 64 were of b2a2 transcript. There was no correlation between the hematological parameters and the type of transcript. There was a significant association of blast crisis with b2a2, especially with myeloid blast crisis. When compared to FISH results, 10% of b3a2 were found to have a significant association with 5'Abl deletion as compared to 3% of b2a2. On analyzing the therapeutic response, we did not find any difference between the two transcripts. In conclusion, our findings confirm that the b3a2 type transcript is not significantly associated with thrombocytosis, that the short transcript, b2a2, occurs with acute phase, i.e., blast crisis, and that there is no difference in treatment response between the two transcripts. However, further studies are required to understand the molecular pathways involved in the Bcr/Abl mechanism.

Bone marrow morphological changes in patients of chronic myeloid leukemia treated with imatinib mesylate.

BACKGROUND: Imatinib mesylate has shown promising results in chronic myeloid leukemia (CML) in all phases. This drug is an effective treatment for patients with CML in chronic phase as it induces hematological remission in nearly all patients and cytogenetic responses in many. The bone marrow changes produced by this drug are different from the treatment modalities used earlier in CML. MATERIALS & METHODS: We studied 80 patients of CML on treatment with Imatinib at doses of 400-800 mg per day. Morphological and cytogenetic evaluation (Ph analysis) of bone marrow aspirates was done at six months of treatment. RESULT: In our study, 95% (76 out of 80) patients showed complete hematological response and 63.3% showed major cytogenetic response at the end of six months of treatment. The most commonly observed changes in the bone marrow aspirates at the end of six months of therapy were in the form of reduction in the cellularity, reduction in the M: E ratio to a mean of 2:1, presence of relative erythroid hyperplasia, normalization of megakaryocytic morphology and variable increase in the bone marrow lymphocytes. None of these changes had significant correlation with the patient's Ph status. CONCLUSION: We advise study of trephine biopsies to overcome the often-faced problem of hemodiluted aspirates in these cases and evaluation of sequential bone marrows to check the durability of these morphological changes and their correlation with the cytogenetic response with emphasis on cytogenetic changes other than Ph positivity.