Chen J, Zhou J H, Ball E D
Division of Hematology/Bone Marrow Transplantation, University of Pittsburgh Medical Center and Pittsburgh Cancer Institute, Pittsburgh, Pennsylvania 15213, USA.
Clin Cancer Res. 1995 Nov;1(11):1319-25.
Immunotherapy using bispecific antibodies (BsAb) to direct immune effector cells toward target tumor cells has been shown to be effective in a number of studies. Several immune trigger molecules have been characterized. Among them, FcgammaRI appears to play an important role in antibody-dependent cellular cytotoxicity. It is expressed mainly on monocytes, macrophages, and neutrophils under certain clinical situations. The expression of FcgammaRI can be regulated by a variety of cytokines, primarily by IFN-gamma. Recent studies have shown that granulocyte-colony-stimulating factor (G-CSF) and granulocyte-macrophage-colony stimulating factor (GM-CSF) can increase the number of the FcgammaRI-positive monocytes, increase the expression of FcgammaRI on circulating neutrophils after in vivo infusion, and greatly enhance the cytotoxic activity of circulating neutrophils. CD33 is a glycoprotein expressed on the cell surface of mature monocytes, myeloid progenitor cells, and myeloid leukemic blasts, but not on the earliest hematopoietic progenitor cells and other normal tissues. Herein, we report the construction of a BsAb, 251 x 22, by conjugating an anti-CD33 mAb (mAb 251) to an anti-FcgammaRI mAb (mAb 22). The BsAb 251 x 22 is capable of enhancing the cytotoxicity of several leukemia cell lines by cytokine-activated monocytes. Our data also show that G-CSF- and GM-CSF-stimulated monocytes can mediate cytotoxicity of target leukemia cells comparable to that of IFN-gamma-stimulated monocytes. The expression of FcgammaRI on monocytes after 24-h in vitro incubation with G-CSF and GM-CSF was increased, although not significantly. Prolonged incubation of monocytes with G-CSF for 48 h significantly increased the FcgammaRI expression. Because humanized anti-CD33 and anti-FcgammaRI mAb are available, and because GM-CSF and G-CSF have been used widely for patients after chemotherapy to stimulate the recovery of myeloid hematopoiesis, additional clinical development of this project is feasible. A BsAb comprised of humanized anti-CD33 and anti-FcgammaRI could have clinical application in the treatment of myeloid leukemia, especially in the management of minimal residual disease.
在多项研究中已表明，使用双特异性抗体（BsAb）引导免疫效应细胞靶向肿瘤细胞的免疫疗法是有效的。几种免疫触发分子已得到表征。其中，FcγRI似乎在抗体依赖性细胞毒性中起重要作用。在某些临床情况下，它主要在单核细胞、巨噬细胞和中性粒细胞上表达。FcγRI的表达可受多种细胞因子调节，主要是受IFN-γ调节。最近的研究表明，粒细胞集落刺激因子（G-CSF）和粒细胞巨噬细胞集落刺激因子（GM-CSF）可增加FcγRI阳性单核细胞的数量，在体内输注后增加循环中性粒细胞上FcγRI的表达，并大大增强循环中性粒细胞的细胞毒性活性。CD33是一种糖蛋白，在成熟单核细胞、髓系祖细胞和髓系白血病母细胞的细胞表面表达，但在最早的造血祖细胞和其他正常组织上不表达。在此，我们报告了一种双特异性抗体251×22的构建，它是通过将抗CD33单克隆抗体（单克隆抗体251）与抗FcγRI单克隆抗体（单克隆抗体22）偶联而成。双特异性抗体251×22能够增强细胞因子激活的单核细胞对几种白血病细胞系的细胞毒性。我们的数据还表明，G-CSF和GM-CSF刺激的单核细胞介导的对靶白血病细胞的细胞毒性与IFN-γ刺激的单核细胞相当。在体外与G-CSF和GM-CSF孵育24小时后，单核细胞上FcγRI的表达增加，尽管不显著。单核细胞与G-CSF长时间孵育48小时可显著增加FcγRI的表达。由于有可利用的人源化抗CD33和抗FcγRI单克隆抗体，并且由于GM-CSF和G-CSF已广泛用于化疗后的患者以刺激髓系造血恢复，因此该项目的进一步临床开发是可行的。一种由人源化抗CD33和抗FcγRI组成的双特异性抗体可能在髓系白血病的治疗中，特别是在微小残留病的管理中具有临床应用价值。
