Utility of RARa Fluorescence In Situ Hybridization for Follow-up in Acute Promyelocytic Leukemia: Comparison with PML/RARa Fluorescence In Situ Hybridization / 대한임상병리학회지

BACKGROUND: The most noted rearrangement identified in acute promyelocytic leukemia (APL) involves the PML and RARa genes, which results in the formation of the PML/RARa gene fusion. In the fluorescence in situ hybridization (FISH) for PML/RARa, the two signals may coincidentally overlap in normal nuclei. We investigated whether a new RARa rearrangement probe could discriminate the false-positive fusion signal of the PML/RARa translocation probe. METHODS: A total of 51 cases, which showed the results from 1% to the borderline level by PML/ RARa FISH, were re-tested with the RARa rearrangement probe. Also, we compared the RARa FISH with the PML/RARa FISH on 16 patients with newly diagnosed APL and performed the RARa FISH on 20 bone marrow specimens without hematologic malignancies in order to set up the cut-off value. RESULTS: The cut-off for the RARa FISH was determined as 1.02%. For patients with newly diagnosed APL, the PML/RARa FISH showed positive signals in 95.3+/-6.5% of the cells and RARa FISH showed positive signals in 97.0+/-7.0% (r=0.83). Of a total of 41 cases consisting of hematological disorders other than APL, five cases showed results equal to or greater than 5% with PML/RARa FISH and one case showed a positive result with RARa FISH. Of 10 follow-up APL cases, seven cases showed results equal to or greater than 5% with the PML/RARa FISH and four cases showed positive results with the RARa FISH. CONCLUSIONS: The cut-off value for the RARa FISH is 1.02% and we consider RARa FISH as the proper method for follow-up of APL.

Why Should FISH Be Done in Patients with Acute Leukemias to Detect MLL Translocation? / 대한임상병리학회지

BACKGROUND: Translocations involving the MLL gene on the long arm of chromosome 11 (11q23) are frequently observed in acute leukemia. The detection of this genetic change has a unique significance due to its implication for poor prognosis. The aim of this study was to determine the utility of fluorescence in situ hybridization (FISH) method in detecting the MLL translocation. METHODS: We applied both conventional cytogenetic analysis (CC) and MLL FISH on 289 consecutive Korean patients (children and adults) with acute leukemia and analyzed the data, placing an emphasis on the discrepancies in the results. RESULTS: Twenty-two of 289 patients (7.6%) had the 11q23/MLL translocation. In 9 cases of 22 (41%), only FISH detected the translocation. In 8 among 22 patients, a total of 19 follow-up examinations were performed, of which FISH detected a significant level of leukemia cells harboring the MLL translocation in 5 (26%) without cytogenetic evidence. Besides the MLL translocation, FISH detected submicroscopic amplification, partial deletion of the MLL gene, and trisomy 11 in 12 cases without cytogenetic evidence. CONCLUSIONS: These results demonstrate that up to 41% of the MLL translocations at initial workups and 26% during follow-up were detected by FISH without cytogenetic evidence. Thus, we recommend that MLL FISH should be performed in the diagnosis and monitoring of acute leukemia in combination with CC.

The incidence of ABL Deletion on Derivative 9 Chromosome in Chronic Myelogenous Leukemia by Interphase Fluorescence In Situ Hybridization and its Association with Progression to Blast Crisis / 대한임상병리학회지

BACKGROUND: Philadelphia(Ph) chromosome is found in about 95 percent of chronic myelogenous leukemia(CML) patients. Ph chromosome results from a reciprocal translocation between the long arms of chromosomes 9 and 22, and the fusion gene, BCR-ABL contribute to oncogenesis. Three to five years after first diagnosis, CML progresses to the blast crisis, and is accompanied by secondary cytogenetic changes in about 85% of cases. In this study, we investigated the incidence of ABL deletion of derivative 9 chromosome in CML and evaluated the association between this deletion and progression to the blast crisis by interphase fluorescence in situ hybridization(FISH). METHOD: The subjects included in this study were a consecutive series of 58 patients who were diagnosed as CML at Seoul National University Hospital between January 1997 and April 2000. On 90 archival bone marrow aspirate samples from these 58 CML patients, interphase FISH was performed with a commercially available probe. RESULTS: The ABL deletion of derivative 9 chromosome was detected in 17(29.3%) of 58 patients with CML. Eighteen of 58 patients progressed to blast crisis in this period. ABL deletion was found in 7 of 18 patients with blast crisis, and not in 11 remainders. The mean duration from the diagnosis to blast crisis was 37.1 months in 7 patients with the ABL deletion, while the mean duration was 74.2 months in 11 patients without the ABL deletion. The mean duration from the diagnosis to blast crisis in patients with ABL deletion was significantly shorter than in patients without ABL deletion(P=0.043). CONCLUSIONS: We found that 29.3% of patients with CML had the ABL deletion on derivative 9 chromosome. In these patients, the time taken for evolution to blast crisis was significantly shorter than that of the patients without ABL deletion.