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Targeted delivery of doxorubicin through conjugation with EGF receptor-binding peptide overcomes drug resistance in human colon cancer cells.
Ai S, Jia T, Ai W, Duan J, Liu Y, Chen J, Liu X, Yang F, Tian Y, Huang Z., Br J Pharmacol. 2012 Nov 12. doi: 10.1111/bph.12055. [Epub ahead of print]

Induction of multidrug resistance by doxorubicin (DOX), together with non-specific toxicities, has restrained DOX-based chemotherapy. We have recently conjugated DOX with EGFR-binding peptide EBP, and demonstrated the enhanced anticancer efficacy and reduced systemic toxicity of DOX-EBP conjugate by targeting EGFR-overexpressing tumours. Here we investigated whether DOX-EBP was capable of overcoming drug resistance and the underlying molecular mechanisms.
DOX-resistant SW480/DOX cells were derived from non-resistant SW480 cells by stepwise exposure to increased DOX, and P-glycoprotein overexpression induced by DOX was confirmed by Western blotting. Cytocidal capacity and intracellular distribution of drugs were evaluated by MTT assay and fluorescence microscopy, respectively. EGFR-mediated endocytosis was tested by EGFR and endocytosis inhibition assays. Drug accumulation in tumour cells and murine xenografts was determined by HPLC.
The cytotoxicity and accumulation of DOX-EBP in SW480/DOX cells were almost the same as in SW480 cells, but those of free DOX were reduced. DOX-EBP accumulation was inhibited by both EGFR and endocytosis inhibitors, suggesting an EGFR-mediated endocytotic uptake. Tumour accumulation of DOX-EBP was significantly higher than free DOX in mice, and DOX-EBP remained at similar levels in DOX-resistant and non-resistant tumour tissues. Importantly, DOX-EBP, but not free DOX, was effective to inhibit solid tumour growth and increase survival rate of both sensitive and resistant models.
DOX-EBP is capable of overcoming DOX resistance of tumour cells and increasing in vivo antitumour efficacy and therefore may serve as a potent therapeutic agent for the treatment of resistant cancers.
© 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.