Key Lab of Transplant Engineering and Immunology, Ministry of Health, West China Hospital, Sichuan University, Chengdu 610041, China.
Acta Pharmacol Sin. 2011 Jan;32(1):79-88. doi: 10.1038/aps.2010.162. Epub 2010 Dec 6.
To investigate whether the conjugation of magainin II (MG2), an antimicrobial peptides (AMPs), to the tumor-homing peptide bombesin could enhance its cytotoxicity in tumor cells.
A magainin II-bombesin conjugate (MG2B) was constructed by attaching magainin II (MG2) to bombesin at its N-terminus. The peptides were synthesized using Fmoc-chemistry. The in vitro cytotoxicity of the peptide in cancer cells was quantitatively determined using the CCK-8 cell counting kit. Moreover, the in vivo antitumor effect of the peptide was determined in tumor xenograft models.
The IC(50) of MG2B for cancer cells (10-15 μmol/L) was at least 10 times lower than the IC(50) of unconjugated MG2 (125 μmol/L). Moreover, the binding affinity of MG2B for cancer cells was higher than that of unconjugated MG2. In contrast, conjugation to a bombesin analog lacking the receptor-binding domain failed to increase the cytotoxicity of MG2, suggesting that bombesin conjugation enhances the cytotoxicity of MG2 in cancer cells through improved binding. Indeed, MG2B selectively induced cell death in cancer cells in vitro with the IC(50) ranging from 10 to 15 μmol/L, which was about 6-10 times lower than the IC(50) for normal cells. MG2B (20 mg/kg per day, intratumorally injected for 5 d) also exhibited antitumor effects in mice bearing MCF-7 tumor grafts. The mean weights of tumor grafts in MG2B- and PBS-treated mice were 0.21±0.05 g and 0.59±0.12 g, respectively.
The results suggest that conjugation of AMPs to bombesin might be an alternative approach for targeted cancer therapy.
研究抗菌肽（AMPs）蛙皮素（Bombesin）与抗菌肽（AMPs）蛙皮素（Bombesin）的缀合是否能增强其在肿瘤细胞中的细胞毒性。
通过将抗菌肽（MG2）连接到蛙皮素（Bombesin）的 N 端，构建了抗菌肽（MG2）-蛙皮素（Bombesin）缀合物（MG2B）。肽采用 Fmoc-化学法合成。使用 CCK-8 细胞计数试剂盒定量测定肽在癌细胞中的体外细胞毒性。此外，还在肿瘤异种移植模型中测定了肽的体内抗肿瘤作用。
MG2B 对癌细胞的 IC50（10-15μmol/L）至少比未缀合的 MG2 的 IC50（125μmol/L）低 10 倍。此外，MG2B 与癌细胞的结合亲和力高于未缀合的 MG2。相反，与缺乏受体结合域的蛙皮素类似物缀合未能提高 MG2 的细胞毒性，这表明通过提高结合，蛙皮素缀合增强了 MG2 在癌细胞中的细胞毒性。事实上，MG2B 选择性地诱导体外癌细胞死亡，IC50 范围为 10-15μmol/L，约为正常细胞 IC50 的 6-10 倍。MG2B（每天 20mg/kg，瘤内注射 5 天）也在携带 MCF-7 肿瘤移植物的小鼠中表现出抗肿瘤作用。MG2B 和 PBS 处理的小鼠的肿瘤移植物的平均重量分别为 0.21±0.05g 和 0.59±0.12g。
结果表明，将 AMP 与蛙皮素缀合可能是一种靶向癌症治疗的替代方法。
