Aspartate‐modified doxorubicin on its N ‐terminal increases drug accumulation in LAT 1 ‐overexpressing tumors

• Published in: Cancer science 2015-06, Vol.106 (6), p.747-756
• Main Authors: Wu, Weidang, Dong, Yan, Gao, Jing, Gong, Min, Zhang, Xing, Kong, Weiling, Li, Yazhuo, Zeng, Yong, Si, Duanyun, Wei, Zihong, Ci, Xiaoyan, Jiang, Lixin, Li, Wei, Li, Quansheng, Yi, Xiulin, Liu, Changxiao
• Format: Article
• Language: English
• ISSN: 1347-9032; 1349-7006
• DOI: 10.1111/cas.12672

L‐type amino acid transporter 1 ( LAT 1), overexpressed on the membrane of various tumor cells, is a potential target for tumor‐targeting therapy. This study aimed to develop a LAT 1 ‐mediated chemotherapeutic agent. We screened doxorubicin modified by seven different large neutral amino acids. The aspartate‐modified doxorubicin (Asp‐ DOX ) showed the highest affinity (Km = 41.423 μmol/L) to LAT 1. Aspartate was attached to the N ‐terminal of DOX by the amide bond with a free carboxyl and a free amino group on the α‐carbon atom of the Asp residue. The product Asp‐ DOX was characterized by HPLC / MS . In vitro , Asp‐ DOX exerted stronger inhibition on the cancer cells overexpressing LAT 1 and the uptake of Asp‐ DOX was approximately 3.5‐fold higher than that of DOX in HepG2 cells. Pharmacokinetic data also showed that Asp‐ DOX was expressed over a longer circulation time ( t 1/2  = 49.14 min) in the blood compared to DOX alone ( t 1/2  = 15.12 min). In HepG2 and HCT 116 tumor‐bearing mice, Asp‐ DOX achieved 3.1‐fold and 6.4‐fold accumulation of drugs in tumor tissue, respectively, than those of the unmodified DOX . More importantly, treatment of tumor‐bearing mice with Asp‐ DOX showed a significantly stronger inhibition of tumor growth than mice treated with free DOX in HepG2 tumor models. Furthermore, after Asp modification, Asp‐ DOX avoided MDR mediated by P‐glycoprotein. These results suggested that the Asp‐ DOX modified drug may provide a new treatment strategy for tumors that overexpress LAT 1 and MDR 1 .