Veterinary Clinical Sciences, University of Minnesota, Minneapolis, MN, USA.
Int J Cancer. 2013 Oct 15;133(8):1936-44. doi: 10.1002/ijc.28187. Epub 2013 Apr 25.
Targeted toxins have the potential to overcome intrinsic or acquired resistance of cancer cells to conventional cytotoxic agents. Here, we hypothesized that EGFuPA-toxin, a bispecific ligand-targeted toxin (BLT) consisting of a deimmunized Pseudomonas exotoxin (PE) conjugated to epidermal growth factor and urokinase, would efficiently target and kill cells derived from canine hemangiosarcoma (HSA), a highly chemotherapy resistant tumor, as well as cultured hemangiospheres, used as a surrogate for cancer stem cells (CSC). EGFuPA-toxin showed cytotoxicity in four HSA cell lines (Emma, Frog, DD-1 and SB) at a concentration of ≤100 nM, and the cytotoxicity was dependent on specific ligand-receptor interactions. Monospecific targeted toxins also killed these chemoresistant cells; in this case, a "threshold" level of EGFR expression appeared to be required to make cells sensitive to the monospecific EGF-toxin, but not to the monospecific uPA-toxin. The IC₅₀ of CSCs was higher by approximately two orders of magnitude as compared to non-CSCs, but these cells were still sensitive to EGFuPA-toxin at nanomolar (i.e., pharmacologically relevant) concentrations, and when targeted by EGFuPA-toxin, resulted in death of the entire cell population. Taken together, our results support the use of these toxins to treat chemoresistant tumors such as sarcomas, including those that conform to the CSC model. Our results also support the use of companion animals with cancer for further translational development of these cytotoxic molecules.
靶向毒素有可能克服癌细胞对传统细胞毒药物的固有或获得性耐药。在这里，我们假设 EGFuPA-毒素是一种双特异性配体靶向毒素（BLT），由与表皮生长因子和尿激酶偶联的去免疫假单胞菌外毒素（PE）组成，将有效地靶向和杀死源自犬血管肉瘤（HSA）的细胞，HSA 是一种高度化疗耐药的肿瘤，以及用作癌症干细胞（CSC）替代物的培养的血管球体。EGFuPA-毒素在四种 HSA 细胞系（Emma、Frog、DD-1 和 SB）中的浓度≤100 nM 时表现出细胞毒性，并且细胞毒性依赖于特异性配体-受体相互作用。单特异性靶向毒素也能杀死这些化疗耐药细胞；在这种情况下，似乎需要 EGFR 表达的“阈值”水平使细胞对单特异性 EGF-毒素敏感，但对单特异性 uPA-毒素不敏感。与非 CSCs 相比，CSC 的 IC₅₀ 高约两个数量级，但这些细胞在纳摩尔（即药理学相关）浓度下仍对 EGFuPA-毒素敏感，并且当被 EGFuPA-毒素靶向时，会导致整个细胞群体死亡。总之，我们的结果支持使用这些毒素治疗化学耐药肿瘤，如肉瘤，包括符合 CSC 模型的肿瘤。我们的结果还支持使用患有癌症的伴侣动物进一步开发这些细胞毒性分子。
