Retinoic acid syndrome in patients following the treatment of acute promyelocytic leukemia with all-trans retinoic acid.

BACKGROUND: Retinoic acid syndrome (RAS) is a potentially lethal complication during all-trans retinoic acid (ATRA) treatment of acute promyelocytic leukemia (APL). The incidence and risk factors have been shown to vary in different series. In this study we want to establish the incidence of RAS in our hospital and try to elucidate factors that increase its risk. METHODS: We retrospectively analyzed 102 patients diagnosed with APL between August 1993 and December 2007 at Chang Gung Memorial Hospital, Taiwan. All patients received ATRA as an induction regimen with or without conventional chemotherapy. RESULTS: Eight of the 102 patients (7.8%) experienced RAS which developed after a median of 9 days (range: 2 to 23 days) of ATRA treatment. Respiratory distress and fever were the most common presentations, occurring in 7 of 8 patients (87.5%). Age, gender, morphological or molecular subtypes, an initial white blood cell (WBC) count of more than 10 x 10(9)/L and concurrent chemotherapy did not statistically attribute to the occurrence of RAS. One patient developed RAS manifesting with pulmonary hemorrhage but experienced a complete recovery after administration of high-dose dexamethasone. The RAS-related mortality was 12.5% (1 out of 8 patients). CONCLUSION: The incidence of RAS in this study was similar to those of other series with ATRA and concurrent chemotherapy. Age, gender, morphological or molecular subtypes, an initial leukocyte count of more than 10 x 10(9)/L or the presence of concurrent chemotherapy is not significantly associated with the occurrence of the RAS.

Analysis of acute leukemias with MLL/ENL fusion transcripts: identification of two novel breakpoints in ENL.

t(11;19)(q23;p13.3); is one of the common chromosomal translocations in acute leukemias involving MLL rearrangements. This translocation generates MLL/ENL fusion transcripts. In a study of acute leukemias, 148 patients were identified to have MLL rearrangements by Southern blot analysis. Reverse transcriptase-polymerase chain reaction (RT-PCR) assay, using primer sets covering the 2 previously described breakpoints at exons 2 and 7 of ENL detected 11 samples harboring MLL/ENL. complementary DNA panhandle PCR further identified 4 additional cases with novel breakpoints in ENL at exon 4 or 6. Sequencing analysis showed that all novel fusion transcripts were in-frame. The conventional cytogenetic analysis failed to detect t(11;19) in 6 of 13 cases. Of 15 patients with MLL/ENL, 7 had precursor B-cell acute lymphoblastic leukemia, 4 had T-cell acute lymphoblastic leukemia, and 4 had acute myeloid leukemia. The present study showed that PCR-based techniques are more sensitive than conventional karyotyping for detecting MLL/ENL fusions and an extra antisense primer at exon 6 of ENL should be included in RT-PCR assay to ensure complete detection of all MLL/ENL fusion transcripts.

Recombinant urate oxidase (rasburicase) for the prevention and treatment of tumor lysis syndrome in patients with hematologic malignancies.

In this multicenter, nonrandomized, open-label clinical trial conducted from July 2003 to July 2004, recombinant urate oxidase (rasburicase) was administered to patients at risk for tumor lysis syndrome before or during the initiation of chemotherapy. Forty-five patients were enrolled, including 18 children (10 with acute lymphoblastic leukemia, 6 with high-grade lymphoma, and 2 with acute myeloid leukemia) and 27 adults (8 with acute lymphoblastic leukemia, 4 with high-grade lymphoma, 9 with multiple myeloma, and 6 with acute myeloid leukemia). The age ranged from 3 to 98 years, with a median age of 7 years in children and 59.3 years in adults. There were 14 males and 4 females in the pediatric group and 18 males and 9 females in the adult group. Rasburicase 0.2 mg/kg was administered intravenously once a day for 2-6 days, for a median of 3 days in children and of 4 days in adults. After 3 days of treatment, the median uric acid levels in the 18 children decreased from 10.5 mg/dl (range 8-18.6) to 0.5 mg/dl (range 0.0-1.7). Similarly, in the 27 adults, the median levels decreased from 10.8 mg/dl (range 8-24.4) to 0.5 mg/dl (range 0.0-1.6). No significant changes were observed in serum potassium, calcium, and phosphorus concentrations. None of the patients required dialysis for acute renal failure. Rasburicase was very well tolerated, with only 1 adult having grade 1 vomiting. We conclude that rasburicase is safe and highly effective for preventing the complications of tumor lysis syndrome in patients with hematologic malignancies.

Characterization of a myeloid tyrosine phosphatase, Lyp, and its role in the Bcr-Abl signal transduction pathway.

The Bcr-Abl protein-tyrosine kinase is implicated in the development of chronic myeloid leukemia. The potential role of protein-tyrosine phosphatase in the regulation of Bcr-Abl signaling was explored. First, expression patterns of tyrosine phosphatases in leukemic cell lines were investigated using degenerate primers for reverse transcription-PCR followed by cloning and sequencing of the cDNA. Distinct patterns of distribution of phosphatase were found in erythroid and myeloid leukemic cell lines. Whereas some phosphatases were ubiquitously expressed, others were limited to specific cell types. Surprisingly, a previously cloned "lymphocyte-specific" phosphatase, Lyp, was frequently detected in a number of myeloid cell lines as well as normal granulocytes and monocytes. Lyp was localized to the cytosol, and overexpression of Lyp caused reduction in the phosphorylation levels of multiple proteins in KCL22 chronic myeloid leukemia blast cells including Cbl, Bcr-Abl, Erk1/2, and CrkL. Co-expression of Lyp and Bcr-Abl in Cos-7 cells resulted in decreased levels of Bcr-Abl, Grb2, and Myc. Overexpression of Lyp markedly suppressed anchorage-independent clonal growth of KCL22 cells. Taken together, the data suggest that Lyp may play an antagonistic role in signaling by the Bcr-Abl fusion protein.