伴3′RARα亚显微缺失的急性早幼粒细胞白血病一例

One case of acute promyelocytic leukemia with 3＇ RARα submicroscopic deletion

目的 报道1例伴RAR仪3＇-末端（3’RARd）亚显微缺失的M3r亚型急性早幼粒细胞白血病（APL）病例及其形态学、细胞遗传学、分子遗传学和分子生物学的研究结果。方法骨髓细胞直接法和短期培养法制备染色体，应用反带技术进行核型分析；分别用CEPX／Yα-卫星DNA探针、LSIPML—RARα双色双融合探针和LSIRAROL双色断裂点分离探针进行荧光原位杂交（FISH）分析；实时定量反转录聚合酶链反应（RT—PCR）方法检测PML-RARα融合基因转录本；多重巢式RT．PCR技术检测急性白血病29种染色体畸变所形成的融合基因，包括PML—RARα，PLZF—RARα和NPM—RARα融合基因转录本。结果反带分析显示核型为45，X，-Y[6]／46，XY[8]，CEPX／Y探针FISH进一步证实了Y染色体丢失；RARd双色断裂点分离探针FISH分析显示1个RAROt等位基因的整个3’-末端缺失；通过细胞遗传学、FISH以及RT—PCR等方法检测，排除PML—RARd、PLZF—RAROt、NPM—RARd、NuMA—RARd和STAT5B—RARd重排。结论识别APL中一种新的RARα基因重排类型（3’RARα[亚显微缺失而无X—RARα融合），RARα双色断裂点分离探针FISH分析是明确该异常的有效手段，其分子学结果有待进一步阐明．

Objective To report a rare case of M3r subtype of acute promyelocytic leukemia （APL） with 3＇-end of RARer （3＇RARer） submicroscopic deletion, and the characters of morphologic, cytogenetie, molecular genetic and molecular biology studies. Methods Chromosomes of bone marrow （BM） cells were prepared with direct method and short-term culture method, and R-banding technique was used for karyotypic analysis. Fluorescence in situ hybridization （FISH） assays were performed on fixed BM cells using the following specific DNA probes： CEP X/Y alpha satellite DNA probe, LSI PML-RARα dual-color dual-fusion and LSI RARer dual-color break apart probes. A quantitative real-time reverse-transcription polymerase chain reaction （RT-PCR） was performed to detect the PML-RARα transcript. A multiplex nested RT-PCR was also performed, which may simultaneously detect the fusion genes derived from 29 chromosomal aberrations in acute leukemia including PML-RARa, PIZF-RARα and NPM-RARα fusion transcripts. Results R-banding analysis revealed a karyotype of 45,X,-Y[6]/46,XY[8], FISH using CEP X/Y probe further confirmed Y-chromosome loss. FISH analysis with RARer dual-color break apart probe demonstrated a deletion of the entire 3＇-end of one allele of RARa gene. Cytogenetic, FISH and RT-PCR analyses showed no PML-RARα, PLZF-RARα, NPM-RARα, NuMA-RARα and STAT5b-RARα rearrangements. Conclusion A new RARα rearrangement involving 3＇RARα submicroscopic deletion in APL without X-RARα fusion has been identified. FISH analysis with RARα dual-color break apart probe is a useful method for characterization of this abnormality, but its molecular consequences remain to be elucidated.