Targeted therapy of the highest globally incident breast cancer shall resolve the issue of off‐target toxicity concurring with augmented killing of specific diseased cells. Thus, the goal of this study was to prepare a peptide‐drug conjugate targeting elevated expression of HER2 receptors in breast cancer. Towards this, the rL‐A9 peptide was conjugated with the chemotherapeutic drug doxorubicin (DOX) through a N‐succinimidyl‐4‐(N‐maleimidomethyl) cyclohexane‐1‐carboxylate (SMCC) linker. The synthesized peptide‐drug conjugate, rL‐A9‐DOX, was characterized by mass spectrometry. Molecular docking studies, based on binding energy data, suggested a stronger interaction of rL‐A9‐DOX with the HER2 receptor in comparison to the unconjugated peptide, rL‐A9. The cytotoxic effect of the rL‐A9‐DOX conjugate was observed to be higher in HER2‐positive SKOV3 cells compared to HER2‐negative MDA‐MB‐231 cells, indicating selective cell killing. Cellular internalization of the rL‐A9‐DOX conjugate was evident from the flow cytometry analysis, where a noticeable shift in mean fluorescent intensity (MFI) was observed for the conjugate compared to the control group. This data was further validated by confocal microscopy, where the fluorescent signal ascertained nuclear accumulation of rL‐A9‐DOX. The present studies highlight the promising potential of rL‐A9‐DOX for targeted delivery of the drug into a defined group of cancer cells.

中文翻译：

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指定用于靶向递送至表达 HER2 的癌细胞的肽-药物缀合物

全球发病率最高的乳腺癌的靶向治疗将解决脱靶毒性与增强对特定病变细胞的杀伤力相伴的问题。因此，本研究的目标是制备一种针对乳腺癌中 HER2 受体表达升高的肽-药物缀合物。为此，rL-A9 肽与化疗药物阿霉素 (DOX) 通过氮‐琥珀酰亚胺基‐4‐(氮-马来酰亚胺甲基）环己烷-1-羧酸酯（SMCC）连接体。通过质谱法对合成的肽-药物缀合物 rL-A9-DOX 进行了表征。基于结合能数据的分子对接研究表明，与未结合的肽 rL-A9 相比，rL-A9-DOX 与 HER2 受体的相互作用更强。与 HER2 阴性 MDA-MB-231 细胞相比，rL-A9-DOX 缀合物在 HER2 阳性 SKOV3 细胞中的细胞毒性作用更高，表明选择性细胞杀伤作用。从流式细胞术分析中可以明显看出 rL-A9-DOX 缀合物的细胞内化，与对照组相比，观察到缀合物的平均荧光强度 (MFI) 发生显着变化。该数据通过共聚焦显微镜进一步验证，其中荧光信号确定了 rL-A9-DOX 的核积累。目前的研究强调了 rL-A9-DOX 将药物靶向输送到特定癌细胞群中的巨大潜力。