Purpose

The development of diagnostic and therapeutic agents utilizing small peptides (e.g., bombesin (BBN)) to target the overexpression of the gastrin-releasing peptide receptor (GRPR) in cancers has been widely investigated. Herein, we examine the capabilities of BBN-modified HPMA copolymers to target the GRPR.

Methods

Four positive, four negative, and two zwitterionic BBN HPMA copolymer conjugates of varying peptide content and charge were synthesized. In vitro and in vivo studies were conducted in a GRPR-overexpressing prostate cancer cell line (PC-3) and a normal CF-1 mouse model, respectively.

Results

Cellular uptake of the conjugates were found to be charge and BBN density dependent. The positively-charged conjugates illustrated a direct relationship between the extent of cellular internalization, ranging from 0.7 to 20%, and BBN-incorporation density. The negative and zwitterionic conjugates showed low PC-3 uptake values. Blocking studies confirmed the GRPR-targeting effect of the positively-charged constructs. In vivo studies of the positively-charged copolymers resulted in rapid blood clearance by the mononuclear phagocyte system (MPS)-associated tissues (e.g., liver and spleen).

Conclusion

Positively-charged BBN-HPMA copolymer conjugates demonstrated good GRPR-targeting and internalization in vitro. However, the impact of peptide density and charge on in vivo MPS recognition are parameters that must be optimized in future agent development.

中文翻译：

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靶向胃泌素释放肽受体的HPMA共聚物在前列腺癌中的体外评估和生物分布研究

目的

已经广泛研究了利用小肽（例如，蛙皮素（BBN））靶向靶向胃泌素释放肽受体（GRPR）的过表达的诊断和治疗剂在癌症中的发展。在本文中，我们研究了BBN改性HPMA共聚物靶向GRPR的能力。

方法

合成了四种具有不同肽含量和电荷的两性正离子，四种负离子和两种两性离子BBN HPMA共聚物共轭物。分别在过表达GRPR的前列腺癌细胞系（PC-3）和正常CF-1小鼠模型中进行了体外和体内研究。

结果

发现结合物的细胞摄取是电荷和BBN密度依赖性的。带正电荷的结合物说明细胞内在化程度（介于0.7％至20％）与BBN掺入密度之间存在直接关系。负性和两性离子共轭物显示出低的PC-3摄取值。阻断研究证实了带正电荷的构建体的GRPR靶向作用。对带正电荷的共聚物进行的体内研究导致单核吞噬细胞系统（MPS）相关组织（例如，肝脏和脾脏）快速清除血液。

结论

带正电的BBN-HPMA共聚物共轭物在体外表现出良好的GRPR靶向和内在化。但是，肽密度和电荷对体内MPS识别的影响是在将来的药物开发中必须优化的参数。