ABSTRACT
There are two major forms of the BCR/ABL fusion gene, involving ABL exon 2, but including different exons of BCR gene. The transcripts b2a2 or b3a2 code for a p210 protein. Another fusion gene leads to the expression of an e1a2 transcript, which codes for a p190 protein. Another, less common fusion gene is c3a2[e19a2], which encodes a p230 protein. The incidence of one or the other rearrangement in chronic myeloid leukaemia (CML) patients varies in different reported series. This study was designed to determine the frequency of coexpresion of the p210, p190 and p230 transcripts in 250 Mexican patients with CML. We performed nested and multiplex reverse transcriptase polymerase chain reaction (RT-PCR) on bone marrow samples from adult patients and found that all cases were positive for some type of BCR/ABL rearrangement. In 226 (90.4%) patients it was p210, while the remaining 9.6% showed coexpression or one of the transcripts of p190/p210/p230. In 7% of patients with p210 expression there are both isoforms (b3a2/b2a2), presumably the result of alternative splicing. The rate of coexpression of the p190/p210 transcripts was 5%, which is much lower than in other reports. This may be due to the technical factors. These patients had high platelet counts, marked splenomegaly and chromosomal abnormalities in addition to Ph'. Other types of coexpression seen were p210/p230 and p190/p210/p230, in patients with high-risk clinical factors. Our study confirms the occurrence of coexpression of different BCR/ABL transcripts, although the rate (9.6%) was much lower than has been reported in other populations. This may reflect either the sensitivity of the detection techniques used or the possibility of genetic differences between the populations studied. Coexpression may be due to alternative splicing or to phenotypic variation, with clinical courses different from classical CML.
Subject(s)
Fusion Proteins, bcr-abl/genetics , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/genetics , Adolescent , Adult , Aged , Cytogenetic Analysis , Exons , Female , Gene Rearrangement , Genetic Variation , Humans , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/epidemiology , Leukemia, Myelogenous, Chronic, BCR-ABL Positive/pathology , Male , Mexico/epidemiology , Middle Aged , Phenotype , Protein Isoforms/analysis , Protein Isoforms/genetics , RNA, Messenger/analysis , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
OBJECTIVE: To evaluate if human recombinant interferon alpha (IFN) combined with chemotherapy is able to suppress the Philadelphia chromosome clone in patients with chronic myeloid leukemia (CML). MATERIAL AND METHODS: The cytogenetic evolution in 53 patients with CML in chronic phase de novo was studied. They received one of three treatment schemes: a) induction of remission with daunorubicin, vincristine, cytosine arabinose and prednisone (DOAP) and maintenance with IFN (n = 12); b) induction with busulfan (BUS) or hydroxyurea (HYDX) and maintenance with IFN (n = 26); c) induction with DOAP and maintenance with BUS (n = 15). RESULTS: The remission was seen two to six months after the start of treatment: 10 had complete remission, six a partial one, 14 a minor remission and 23 none. The 16 with complete or partial response received treatment with IFN. None of the 15 cases maintained with BUS had complete or partial response. The proportion of cases with complete response (3/12) was slightly lower in patients treated with intensive chemotherapy (BUS/HIDX/IFN) than in those receiving conventional treatment (7/26). CONCLUSIONS: Our results showed that: a) IFN in combination with chemotherapy induced partial or complete response in 30% of our cases; and b) intensive chemotherapy combined with IFN was not superior in terms of a cytogenetic response to treatment with monodrugs (BUS/HIDX) and IFN.
