We describe a patient with chronic myelogenous leukemia (CML), in whom the DNA breakpoint in the BCR-ABL fusion gene was determined to result in a rare e13a3 (b2a3) transcript. The breakpoint in BCR was intron 13, which was 30 bp downstream from exon 13, and the breakpoint in ABL was intron 2, and was 46 bp downstream from exon a2. This case conforms to the mechanism of DNA breakage occurring within ABL intron 2, but not at 5 0 to ABL exon a2. With our review of this case and the literature, it seems that CML with the BCR-a3 fusion product is associated with a low proportion of circulating immature cells, mild or lack of splenomegaly, slow progressiveness, rather resistance to IFN-a, and good response to imatinib mesylate. This is the first report of BCR-a3-type CML in which the exact DNA breakpoint was identified and located between exons a2 and a3 of the ABL gene. Am. J. Hematol. 74:268-272, 2003. INTRODUCTIONThe hallmark of chronic myelogenous leukemia (CML) is the chimeric BCR-ABL fusion gene, which is usually formed as a result of the t(9;22) translocation (Philadelphia chromosome, Ph). Most BCR-ABL fusion transcripts are e13a2 (b2a2), e14a2 (b3a2), and less commonly, e1a2, e19a2 [1]. CML with an atypical hybrid transcript, in which BCR sequences are fused to ABL exon a3 rather than exon a2, is very rare, and its characteristics are poorly understood [2][3][4][5][6][7][8][9][10][11]. Until now, the position of the DNA breakpoint in the ABL gene with BCR-a3-type CML has been reported in only three cases. ABL exon a2 encodes 58 amino acids, the last 17 of which form part of a stretch of 50 amino acids of Src homology 3 (SH3) domain of the ABL protein.The SH3 is believed to negatively regulate the kinase domain (SH1). Thus, in theory, deletion of ABL exon a2 should result in increased tyrosine kinase activity and, therefore, increased transforming activity. However, recent data suggest that SH3 does not necessarily contribute to aggressive phenotype. Details of the clinical phenotype of CML with this type of transcript are unclear because of its very low incidence.Here, we report a case of CML with the e13a3 transcript and the DNA breakpoints in the BCR and ABL genes. This case was rather resistant to interferon a (IFN-a) and showed rapid response to imatinib mesylate (imatinib). This is the first report of the exact DNA breakpoint in the ABL gene determined by nucleotide sequencing in BCR-a3-type CML.

Increased plasma levels of total bile acids serve as a diagnostic clue to the presence of portosystemic shunts in neonates with hypergalactosaemia.

Summary. CD34++ cells from 45 patients with myelodysplastic syndrome (MDS) and MDS‐acute myeloid leukaemia (MDS‐AML) were observed by flow cytometry for the expression of granulocyte colony‐stimulating factor receptor (G‐CSFR). Ten patients had a significantly reduced expression of G‐CSFR. Late stages of disease showed a higher proportion of either high or low G‐CSFR expression than earlier stages. In MDS refractory anaemia (RA), G‐CSFR was inversely related to CD33 expression. Most patients (9/10) with low G‐CSFR expression had neutropenia of the peripheral blood. Neutropenia was less common in the normal group, but also occurred in the high expression group. No neutrophil response was observed following G‐CSF administration to MDS‐AML patients (6/6) with low G‐CSFR expression. In the high expression group, patients (3/3) showed a response to G‐CSF while, in the normal group (1/2), the response was minor. In the normal‐ or high‐receptor‐expressing groups, the receptors were functionally active in terms of apoptosis but not proliferation and clonogenic growth, although no clear correlation to receptor expression was observed. The G‐CSFR signal transduction pathway in the normal and high group was not deficient of messenger RNA for either janus kinases (Jaks) or signal transducers and activators of transcription (Stats). These findings suggest that the lowered expression of G‐CSFR may cause neutropenia in MDS and MDS‐AML patients and, therefore, may partially explain the neutropenia in myelodysplastic patients.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is an interferon (IFN)-induced molecule with apoptotic activity. We examined gene mutations in the death domains of TRAIL receptor 1 (TRAIL-R1) and TRAIL receptor 2 (TRAIL-R2), and in the TRAIL gene promoter in 46 chronic myelogenous leukemia (CML) patients. In 23 of the 46 patients, all the coding regions of TRAIL-R2 were also examined. However, no mutation or loss of heterozygosity was found. Furthermore, no mutation in the death domains of TRAIL-R1 and TRAIL-R2 genes, which causes amino acid change, was found in 18 myelodysplastic syndrome (MDS) patients. Ribonuclease protection assay (RPA) and real-time quantitative polymerase chain reaction using polymorphonuclear neutrophils of five new CML patients showed that the TRAIL mRNA expression was very low before in vitro IFN-α stimulation and markedly upregulated after IFN-α stimulation. FAS mRNA was also upregulated with IFN-α stimulation but the fold induction was far lower than that of TRAIL mRNA. In addition, RPA revealed that the ratio of (TRAIL-R1 plus TRAIL-R2) to TRAIL-R3 was also increased after IFN-α stimulation. Taken together, gene mutations of TRAIL-R1, TRAIL-R2 are infrequent in patients with CML and MDS. Andso is the TRAIL promoter for CML. These mutations seem unrelated to tumorigenesis, disease progression, and response to IFN-α therapy in CML. A markedly high induction of TRAIL mRNA by IFN-α may have some relevance to IFN-α action in CML patients.

In order to investigate the mechanism of interferon-alpha (IFNalpha) action in the treatment of chronic myelogenous leukemia (CML), we examined surface expressions of both type I interferon receptor 1 (IFNAR1) and 2 (IFNAR2) subunits on CD34-positive cells in bone marrow (BM) in a total of 57 CML patients. Initial cell-surface IFNAR2 expression at diagnosis assessed by flow cytometry widely distributed but showed overall significantly higher expression in CML patients when compared with normal controls. In 15 fresh patients who subsequently received IFNalpha therapy, IFNAR2 expression at diagnosis was significantly higher in cytogenetic good responders than in poor responders. Down-regulation of IFNAR2 expression during IFNalpha therapy was observed only in good responders but not in poor responders. In addition to protein level, both initial high IFNAR2c mRNA expression level and its down-regulation during IFNalpha therapy, in purified CD34-positive cells, were also observed only in good responders. In contrast to IFNAR2, cell-surface IFNAR1 expression was generally lower than IFNAR2, and correlation between either the pretreatment level or down-regulation of IFNAR1 and clinical response was not evident. With in vitro IFNalpha stimulation, CD34-positive cells showed down-regulations of cell-surface IFNAR2, and IFNAR1 to a lesser extent, in one good-responder patient, but not in one poor-responder patient. Serum soluble interferon receptor (sIFNR) was higher in untreated CML patients than in normal controls, without any correlation with clinical response to IFNalpha. Thus, the pretreatment protein and mRNA expression levels of IFNAR2 and their down-regulations during IFNalpha therapy correlate well with IFNalpha response in CML patients.