Polito Letizia, Mercatelli Daniele, Bortolotti Massimo, Maiello Stefania, Djemil Alice, Battelli Maria Giulia, Bolognesi Andrea
Department of Experimental, Diagnostic and Specialty Medicine-DIMES, General Pathology Section, Alma Mater Studiorum-University of Bologna, Via S. Giacomo 14, 40126 Bologna, Italy.
Toxins (Basel). 2017 May 30;9(6):182. doi: 10.3390/toxins9060182.
Immunotoxins (ITs) are hybrid proteins combining the binding specificity of antibodies with the cytocidal properties of toxins. They represent a promising approach to lymphoma therapy. The cytotoxicity of two immunotoxins obtained by chemical conjugation of the plant toxin saporin-S6 with the anti-CD20 chimeric antibody rituximab and the anti-CD22 murine antibody OM124 were evaluated on the CD20-/CD22-positive cell line Raji. Both ITs showed strong cytotoxicity for Raji cells, but the anti-CD22 IT was two logs more efficient in killing, probably because of its faster internalization. The anti-CD22 IT gave slower but greater caspase activation than the anti-CD20 IT. The cytotoxic effect of both immunotoxins can be partially prevented by either the pan-caspase inhibitor Z-VAD or the necroptosis inhibitor necrostatin-1. Oxidative stress seems to be involved in the cell killing activity of anti-CD20 IT, as demonstrated by the protective role of the H₂O₂ scavenger catalase, but not in that of anti-CD22 IT. Moreover, the IT toxicity can be augmented by the contemporary administration of other chemotherapeutic drugs, such as PS-341, MG-132, and fludarabine. These results contribute to the understanding of the immunotoxin mechanism of action that is required for their clinical use, either alone or in combination with other drugs.
免疫毒素（ITs）是一种融合蛋白，它将抗体的结合特异性与毒素的杀细胞特性结合在一起。它们代表了一种有前景的淋巴瘤治疗方法。通过将植物毒素皂草素 - S6与抗CD20嵌合抗体利妥昔单抗以及抗CD22鼠源抗体OM124化学偶联获得的两种免疫毒素，在CD20⁺/CD22⁺阳性细胞系Raji上评估了其细胞毒性。两种免疫毒素对Raji细胞均表现出强烈的细胞毒性，但抗CD22免疫毒素在杀伤效率上高两个对数级，这可能是因为其内化速度更快。与抗CD20免疫毒素相比，抗CD22免疫毒素诱导的半胱天冬酶激活较慢但程度更高。泛半胱天冬酶抑制剂Z - VAD或坏死性凋亡抑制剂坏死抑制因子 - 1均可部分阻断两种免疫毒素的细胞毒性作用。氧化应激似乎参与了抗CD20免疫毒素的细胞杀伤活性，这一点由过氧化氢清除剂过氧化氢酶的保护作用得以证明，但抗CD22免疫毒素则不然。此外，同时给予其他化疗药物，如PS - 341、MG - 132和氟达拉滨，可增强免疫毒素的毒性。这些结果有助于理解免疫毒素的作用机制，这对于其单独或与其他药物联合用于临床是必要的。
