Analysis and identification of variant Ph chromosome translocation in patients with chronic myelogenous leukemia by conventional cytogenetics and fluorescence in situ hybridization / 中国实验血液学杂志

ABSTRACT

The objective of this study was to explore the cytogenetic profiles of variant Ph chromosome translocations (VT) in patients with chronic myelogenous leukemia (CML) and to assess the applications of fluorescence in situ hybridization (FISH) technique for analysis of CML patients with variant translocation by using dual color-single fusion signal (DC-SF) and dual color-dual fusion signal (DC-DF) probe. 42 CML patients with VT were studied by conventional cytogenetic analysis (CCA). Among them, nine and eleven cases were analyzed by DC-SF-FISH and DC-DF-FISH, respectively. The results showed that 42 out of 643 (6.5%) CML cases received CCA were found to have VT, which were composed of 18 cases of simple VT, 23 of complex VT and one of masked VT. The VT involved all over the chromosomes but No. 4 and 6. Four patterns of them appeared recurrent because each occurred in at least two cases. VT with additional chromosomal aberrations were shown in 35.7% of patients with VT (15/42). 19 of 20 patients who received FISH detection were positive for bcr/abl fusion. DC-DF-FISH analysis revealed absence of abl/bcr fusion signal in all patients but one (8.8%) with abl/bcr positive cells. However, it was not an implication of gene loss but the translocation led to part of bcr retaining on der (9q34) and other part of bcr translocating to involve another chromosome. It was unable to observe variant signal features by DC-SF-FISH analysis. In conclusion, variant Ph translocations in CML involved almost all chromosomes in a varying frequencies and ways except chromosomes 9 and 22, and some of them showed recurrent aberrations. FISH provides accurate molecular diagnosis for CML with VT, while DC-DF-FISH facilitates the assessment of variant signals.