The synthesis and in vitro evaluation of four mesoporphyrin IX-peptide conjugates designed to target EGFR, over-expressed in colorectal and other cancers, are reported. Two peptides with known affinity for EGFR, LARLLT (1) and GYHWYGYTPQNVI (2), were conjugated to mesoporphyrin IX (MPIX, 3) via one or both the propionic side chains, directly (4, 5) or with a triethylene glycol spacer (7, 8). The conjugates were characterized using NMR, MS, CD, SPR, UV-vis and fluorescence spectroscopies. Energy minimization and molecular dynamics suggest different conformations for the conjugates. SPR studies show that conjugate 4, bearing two LARLLT with no PEG spacers, has the greatest affinity for binding to EGFR, followed by conjugate 7with two PEG and two LARLLT sequences. Molecular modeling and docking studies suggest that both conjugates 4 and 7 can bind to monomer and dimer EGFR in open and closed conformations. The cytotoxicity and cellular targeting ability of the conjugates were investigated in human HEp2 cells over-expressing EGFR. All conjugates showed low dark- and photo-toxicities. The cellular uptake was highest for conjugates 4 and 8 and lowest for 7 bearing two LARLLT linked via PEG groups, likely due to decreased hydrophobicity. Among the conjugates investigated, 4 is the most efficient EGFR-targeting agent, and therefore the most promising for the detection of cancers that over-express EGFR.

中文翻译：

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使用中卟啉 IX-肽缀合物靶向表皮生长因子受体

报道了四种中卟啉 IX 肽缀合物的合成和体外评估，这些缀合物旨在靶向在结直肠癌和其他癌症中过度表达的 EGFR。两种对 EGFR 具有已知亲和力的肽 LARLLT (1) 和 GYHWYGYTPQNVI (2) 通过一个或两个丙酸侧链直接 (4, 5) 或通过三甘醇间隔基与中卟啉 IX (MPIX, 3) 缀合（ 7、8）。使用 NMR、MS、CD、SPR、UV-vis 和荧光光谱对缀合物进行表征。能量最小化和分子动力学表明缀合物具有不同的构象。SPR 研究表明，带有两个不带 PEG 间隔基的 LARLLT 的缀合物 4 与 EGFR 的结合亲和力最大，其次是带有两个 PEG 和两个 LARLLT 序列的缀合物 7。分子建模和对接研究表明，缀合物 4 和 7 都可以以开放和闭合构象结合单体和二聚体 EGFR。在过表达 EGFR 的人 HEp2 细胞中研究了缀合物的细胞毒性和细胞靶向能力。所有缀合物均表现出较低的暗毒性和光毒性。结合物 4 和 8 的细胞摄取最高，而带有通过 PEG 基团连接的两个 LARLT 的 7 的细胞摄取最低，可能是由于疏水性降低。在所研究的缀合物中，4 是最有效的 EGFR 靶向剂，因此最有希望用于检测过度表达 EGFR 的癌症。