Zheng Shichun, Ma Xiaomei, Zhang Luoping, Gunn Laura, Smith Martyn T, Wiemels Joseph L, Leung Kenneth, Buffler Patricia A, Wiencke John K
Laboratory for Molecular Epidemiology, Department of Epidemiology and Biostatistics, University of California at San Francisco, San Francisco, CA 94143-0560, USA.
Cancer Res. 2004 Mar 15;64(6):2000-6. doi: 10.1158/0008-5472.can-03-2387.
The human FHIT (fragile histidine triad) gene is a putative tumor suppressor gene located at chromosome region 3p14.2. Previous studies have shown that loss of heterozygosity, homozygous deletions, and abnormal expression of the FHIT gene are involved in several types of human malignancies. A CpG island is present in the 5' promoter region of the FHIT gene, and methylation in this region correlates with loss of FHIT expression. To test whether aberrant methylation of the FHIT gene may play a role in pediatric leukemia, we assessed the FHIT methylation status of 10 leukemia cell lines and 190 incident population-based cases of childhood acute lymphocytic and myeloid leukemias using methylation-specific PCR. Conventional and fluorescence in situ hybridization cytogenetic data were also collected to examine aneuploidy, t(12, 21), and other chromosomal rearrangements. Four of 10 leukemia cell lines (40%) and 52 of 190 (27.4%) bone marrows from childhood leukemia patients demonstrated hypermethylation of the promoter region of FHIT. Gene expression analyses and 5-aza-2'-deoxycytidine treatment showed that promoter hypermethylation correlated with FHIT inactivation. Among primary leukemias, hypermethylation of FHIT was strongly correlated with acute lymphoblastic leukemia (ALL) histology (P = 0.008), high hyperdiploid (P < 0.0001), and translocation-negative (P < 0.0001) categories. Hyperdiploid B-cell ALLs were 23-fold more likely to be FHIT methylated compared with B-cell ALL harboring TEL-AML translocations. FHIT methylation was associated with high WBC counts at diagnosis, a known prognostic indicator. These results suggest that hypermethylation of the promoter region CpG island of the FHIT gene is a common event and may play an important role in the etiology and pathophysiology of specific cytogenetic subtypes of childhood ALL.
人类FHIT（脆性组氨酸三联体）基因是一个推定的肿瘤抑制基因，位于染色体3p14.2区域。先前的研究表明，FHIT基因的杂合性缺失、纯合性缺失及异常表达与多种人类恶性肿瘤有关。FHIT基因的5'启动子区域存在一个CpG岛，该区域的甲基化与FHIT表达缺失相关。为了检测FHIT基因的异常甲基化是否在儿童白血病中起作用，我们使用甲基化特异性PCR评估了10个白血病细胞系以及190例基于人群的儿童急性淋巴细胞白血病和髓细胞白血病新发病例的FHIT甲基化状态。还收集了常规和荧光原位杂交细胞遗传学数据，以检测非整倍体、t(12, 21)及其他染色体重排情况。10个白血病细胞系中有4个（40%）以及190例儿童白血病患者的骨髓样本中有52个（27.4%）显示FHIT启动子区域发生高甲基化。基因表达分析和5-氮杂-2'-脱氧胞苷处理表明，启动子高甲基化与FHIT失活相关。在原发性白血病中，FHIT高甲基化与急性淋巴细胞白血病（ALL）组织学类型（P = 0.008）、高超二倍体（P < 0.0001）及无易位（P < 0.0001）类别密切相关。与携带TEL-AML易位的B细胞ALL相比，超二倍体B细胞ALL发生FHIT甲基化的可能性高23倍。FHIT甲基化与诊断时的高白细胞计数相关，高白细胞计数是一个已知的预后指标。这些结果表明，FHIT基因启动子区域CpG岛的高甲基化是一个常见事件，可能在儿童ALL特定细胞遗传学亚型的病因学和病理生理学中起重要作用。
