Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892.
Department of Hematology/Oncology, University Hospital Erlangen, 91054 Erlangen, Germany.
Proc Natl Acad Sci U S A. 2018 Feb 20;115(8):E1867-E1875. doi: 10.1073/pnas.1714512115. Epub 2018 Feb 5.
Moxetumomab pasudotox (Moxe) is a chimeric protein composed of an anti-CD22 Fv fused to a portion of exotoxin A and kills CD22-expressing leukemia cells. It is very active in hairy-cell leukemia, but many children with relapsed/refractory acute lymphoblastic leukemia (ALL) either respond transiently or are initially resistant. Resistance to Moxe in cultured cells is due to low expression of diphthamide genes (DPH), but only two of six ALL blast samples from resistant patients had low DPH expression. To develop a more clinically relevant model of resistance, we treated NSG mice bearing KOPN-8 or Reh cells with Moxe. More than 99.9% of the cancer cells were killed by Moxe, but relapse occurred from discrete bone marrow sites. The resistant cells would no longer grow in cell culture and showed major chromosomal changes and changes in phenotype with greatly decreased CD22. RNA deep sequencing of resistant KOPN-8 blasts revealed global changes in gene expression, indicating dedifferentiation toward less-mature B cell precursors, and showed an up-regulation of myeloid genes. When Moxe was combined with 5-azacytidine, resistance was prevented and survival increased to over 5 months in the KOPN-8 model and greatly improved in the Reh model. We conclude that Moxe resistance in mice is due to a new mechanism that could not be observed using cultured cells and is prevented by treatment with 5-azacytidine.
Moxetumomab pasudotox（Moxe）是一种嵌合蛋白，由抗 CD22 Fv 与外毒素 A 的一部分融合而成，可杀死表达 CD22 的白血病细胞。它在毛细胞白血病中非常活跃，但许多复发/难治性急性淋巴细胞白血病（ALL）患儿要么短暂缓解，要么最初耐药。培养细胞对 Moxe 的耐药性是由于二氢叶酸基因（DPH）表达水平低，但在 6 例耐药患者的 ALL blasts 样本中只有 2 例 DPH 表达水平低。为了开发更具临床相关性的耐药模型，我们用 Moxe 治疗携带 KOPN-8 或 Reh 细胞的 NSG 小鼠。超过 99.9%的癌细胞被 Moxe 杀死，但复发发生在离散的骨髓部位。耐药细胞将不再在细胞培养中生长，并表现出主要的染色体变化和表型变化，CD22 表达大大降低。耐药 KOPN-8 blasts 的 RNA 深度测序显示基因表达的全局变化，表明向不成熟 B 细胞前体的去分化，并显示髓样基因的上调。当 Moxe 与 5-氮杂胞苷联合使用时，耐药性被预防，KOPN-8 模型中的存活率提高到 5 个月以上，在 Reh 模型中大大改善。我们得出结论，小鼠中的 Moxe 耐药性是由于一种新的机制所致，这种机制在使用培养细胞时无法观察到，并且可以通过 5-氮杂胞苷治疗来预防。
