Rosenblum M G, Cheung L, Kim S K, Mujoo K, Donato N J, Murray J L
Department of Clinical Immunology and Biological Therapy, Houston, TX 77030, USA.
Cancer Immunol Immunother. 1996 Feb;42(2):115-21. doi: 10.1007/s002620050260.
The development of cellular resistance to immunotoxins has been demonstrated in a variety of models and can involve a number of mechanisms. For the present study, an immunotoxin was utilized composed of an anti-melanoma antibody ZME-018 recognizing a 240-kDa surface glycoprotein (gp 240) and the plant toxin gelonin. Human melanoma cells (A375-M) were grown in the presence of increasing amounts of ZME-gelonin and a clonal variant (A-375-ZR) was developed that was 100-fold resistant to ZME-gelonin compared to parental cells. Scatchard analysis showed that the A375-M parental cells had 260 X 10(3) ZME-gelonin-binding sites/cell with relatively low affinity (5 nM). In contrast, resistant A375-ZR cells demonstrated a reduced number of low-affinity sites (160 x 10(3)/cel1), but showed a small number (47 x 10(3)) of higher-affinity sites (0.8 nM). Internalization rates and degradation rates of 125I-labeled ZME-gelonin were identical in both the parental and resistant cells. A375-ZR cells were found to be more resistant to vincristine and doxorubicin than were parental cells. Both cell lines were almost equally sensitive to native gelonin, 5-fluorouracil (5-FU), cisplatin. melphalan, carmustine, interferon gamma (IFNgamma) and IFNalpha. In addition. both cell lines were equally sensitive to another gelonin antibody conjugate that binds to cell-surface, GD2 (antibody 14G2A). However, resistant cells were twice as sensitive to the cytotoxic effects of etoposide than were parental cells. Finally, a variety of agents were tested in combination with ZME-gelonin against A375-ZR cells in an attempt to identify agents to augment immunotoxin cytotoxic effects against resistant cells. The agents 5-FU, cisplatin, IFNgamma, IFNalpha, and etoposide were the most effective in augmenting the cytotoxicity of ZME-gelonin against resistant cells. These studies suggest that development of resistance to one immunotoxin does not cause development of cross-resistance to other gelonin immunotoxins. Further, specific biological response modifiers and chemotherapeutic agents may be effective in augmenting the effectiveness of immunotoxins and specifically targeting or reducing the emergence of immunotoxin-resistant cells.
细胞对免疫毒素产生抗性的现象已在多种模型中得到证实，其涉及多种机制。在本研究中，使用了一种免疫毒素，它由识别240 kDa表面糖蛋白（gp 240）的抗黑色素瘤抗体ZME - 018与植物毒素相思豆毒素组成。人黑色素瘤细胞（A375 - M）在不断增加的ZME - 相思豆毒素存在下培养，培养出了一个克隆变体（A - 375 - ZR），与亲代细胞相比，它对ZME - 相思豆毒素的抗性高100倍。Scatchard分析表明，A375 - M亲代细胞具有260×10³个ZME - 相思豆毒素结合位点/细胞，亲和力相对较低（5 nM）。相比之下，抗性A375 - ZR细胞低亲和力位点数量减少（160×10³/细胞），但显示出少量（47×10³）高亲和力位点（0.8 nM）。¹²⁵I标记的ZME - 相思豆毒素在亲代细胞和抗性细胞中的内化率和降解率相同。发现A375 - ZR细胞比亲代细胞对长春新碱和阿霉素更具抗性。两种细胞系对天然相思豆毒素、5 - 氟尿嘧啶（5 - FU）、顺铂、美法仑、卡莫司汀、干扰素γ（IFNγ）和干扰素α几乎同样敏感。此外，两种细胞系对另一种与细胞表面GD2结合的相思豆毒素抗体偶联物（抗体14G2A）同样敏感。然而，抗性细胞对依托泊苷的细胞毒性作用的敏感性是亲代细胞的两倍。最后，测试了多种药物与ZME - 相思豆毒素联合作用于A375 - ZR细胞，试图找出能增强免疫毒素对抗性细胞细胞毒性作用的药物。5 - FU、顺铂、IFNγ、IFNα和依托泊苷这些药物在增强ZME - 相思豆毒素对抗性细胞的细胞毒性方面最有效。这些研究表明，对一种免疫毒素产生抗性不会导致对其他相思豆毒素免疫毒素产生交叉抗性。此外，特定的生物反应调节剂和化疗药物可能有效地增强免疫毒素的有效性，并特异性地靶向或减少免疫毒素抗性细胞的出现。
