DiGiuseppe Joseph A, Fuller Sheila G, Borowitz Michael J
Department of Pathology and Laboratory Medicine, Hartford Hospital, Connecticut 06102-5037, USA.
Cytometry B Clin Cytom. 2009 Mar;76(2):150-5. doi: 10.1002/cyto.b.20440.
The persistence of minimal residual disease (MRD) following therapy is an established prognostic factor in precursor B-cell acute lymphoblastic leukemia (pB-ALL). Detection of MRD in pB-ALL by flow cytometric immunophenotyping requires demonstration of abnormal antigen expression in leukemic B-cell precursors relative to that of normal B-cell precursors. The gene encoding CD49f (integrin alpha-6) is one of several whose overexpression in pB-ALL at diagnosis has been associated with the subsequent detection of MRD. However, whether CD49f might be a useful reagent in the immunophenotypic detection of MRD in pB-ALL has not been evaluated.
We evaluated CD49f expression by 4-color flow cytometry in normal B-cell precursors, and in a series of cases of pB-ALL, both at diagnosis and at intervals following the initiation of therapy.
In 10 control marrow samples, CD49f was undetectable or extremely dim in all but a minor subset of normal CD19+ B-lineage cells, whereas in 11 of 15 cases (73%) of pB-ALL, CD49f was moderate or bright at diagnosis, and persisted or became brighter after initiation of therapy. MRD detected using CD49f corresponded precisely with that obtained using a standard panel of antibodies, and permitted the detection of leukemic populations comprising as little as 0.02% of cells. Of the four pB-ALL cases in which CD49f was undetectable or dim at diagnosis, MRD was detected in two; in one of these, CD49f expression was substantially increased in the leukemic cells that persisted following initiation of therapy.
CD49f is commonly overexpressed in p-B-ALL, and represents a potentially useful marker for the immunophenotypic detection of MRD.
治疗后微小残留病（MRD）的持续存在是前体B细胞急性淋巴细胞白血病（pB-ALL）中已确定的预后因素。通过流式细胞术免疫表型分析检测pB-ALL中的MRD需要证明白血病B细胞前体相对于正常B细胞前体存在异常抗原表达。编码CD49f（整合素α-6）的基因是诊断时在pB-ALL中过表达且与随后MRD检测相关的几个基因之一。然而，CD49f是否可能成为pB-ALL中MRD免疫表型检测的有用试剂尚未得到评估。
我们通过四色流式细胞术评估正常B细胞前体以及一系列pB-ALL病例在诊断时和开始治疗后的不同时间点的CD49f表达。
在10份对照骨髓样本中，除了一小部分正常CD19+B谱系细胞外，所有细胞中CD49f均无法检测到或极其微弱，而在15例pB-ALL病例中的11例（73%）中，CD49f在诊断时为中度或明亮表达，并且在开始治疗后持续存在或变得更亮。使用CD49f检测到的MRD与使用标准抗体组合获得的结果精确对应，并且能够检测到仅占细胞总数0.02%的白血病细胞群。在诊断时CD49f无法检测到或微弱的4例pB-ALL病例中，有2例检测到了MRD；其中1例中，开始治疗后持续存在的白血病细胞中CD49f表达大幅增加。
CD49f在p-B-ALL中通常过表达，是MRD免疫表型检测的一个潜在有用标志物。
