Pagliaro L C, Liu B, Munker R, Andreeff M, Freireich E J, Scheinberg D A, Rosenblum M G
Division of Medicine, The University of Texas M.D. Anderson Cancer Center, Houston 77030, USA.
Clin Cancer Res. 1998 Aug;4(8):1971-6.
The recently characterized immunotoxin HuM195-gelonin consists of a humanized anti-CD33 monoclonal antibody conjugated to the single-chain plant toxin gelonin. Binding of the immunotoxin to hematopoietic cells that express the CD33 differentiation antigen has been demonstrated and results in cytotoxicity due to ribosomal inactivation by gelonin. Blast cells from most patients with acute myelogenous leukemia express CD33, whereas normal stem cells necessary for maintenance of hematopoiesis do not. We asked whether an immunoconjugate using recombinant gelonin rather than plant gelonin is toxic to acute myelogenous leukemia (AML) cell lines and primary AML blasts obtained from patients and exposed to the immunotoxin in vitro. The CD33pos cell lines HL60, OCI/AML2, and OCI/ AML5 showed decreased proliferation when exposed to immunotoxin for 24-72 h. The CD33neg cell line OCI/AML3 was relatively resistant to HuM195, and all cell lines were resistant to equimolar concentrations of unconjugated antibody and gelonin. Primary blast cultures from seven patients with AML had CD33 detectable on 75.7-99.8% of cells by flow cytometry, and all showed dose-dependent decreases in clonogenic cell survival during 24-h incubation with the immunotoxin. Cells selected for low CD33 expression by cell sorting or by prolonged incubation with immunotoxin could reexpress CD33 at baseline levels and remained sensitive to immunotoxin. We conclude that humanized M195 conjugated to recombinant gelonin has antileukemic activity and should be considered for clinical testing in Phase I trials.
最近鉴定的免疫毒素HuM195-去甲氧基鬼臼毒素由与单链植物毒素去甲氧基鬼臼毒素偶联的人源化抗CD33单克隆抗体组成。免疫毒素与表达CD33分化抗原的造血细胞的结合已得到证实，并且由于去甲氧基鬼臼毒素使核糖体失活而导致细胞毒性。大多数急性髓性白血病患者的原始细胞表达CD33，而维持造血所需的正常干细胞则不表达。我们询问使用重组去甲氧基鬼臼毒素而非植物去甲氧基鬼臼毒素的免疫偶联物对急性髓性白血病（AML）细胞系以及从患者获得并在体外暴露于免疫毒素的原发性AML原始细胞是否有毒性。当暴露于免疫毒素24至72小时时，CD33阳性细胞系HL60、OCI/AML2和OCI/AML5的增殖减少。CD33阴性细胞系OCI/AML3对HuM195相对耐药，并且所有细胞系对等摩尔浓度的未偶联抗体和去甲氧基鬼臼毒素均耐药。通过流式细胞术检测，来自7例AML患者的原发性原始细胞培养物中，75.7%至99.8%的细胞可检测到CD33，并且在与免疫毒素孵育24小时期间，所有细胞均显示克隆形成细胞存活率呈剂量依赖性下降。通过细胞分选或与免疫毒素长时间孵育选择的低CD33表达细胞可将CD33重新表达至基线水平，并对免疫毒素保持敏感。我们得出结论，与重组去甲氧基鬼臼毒素偶联的人源化M195具有抗白血病活性，应考虑在I期试验中进行临床试验。
