title: Targeted delivery of doxorubicin through conjugation with EGF receptor-binding peptide overcomes drug resistance in human colon cancer cells.
abstract: OBJECTIVE
  Induction of multidrug resistance by doxorubicin (DOX), together with non-specific toxicities, has restricted DOX-based chemotherapy. Recently, we demonstrated that DOX conjugated with an EGF receptor-binding peptide (DOX-EBP) had enhanced anticancer efficacy and reduced systemic toxicity when targeting EGF receptor-overexpressing tumours. Here we investigated whether DOX-EBP is able to overcome drug resistance and the underlying molecular mechanisms.
  
  
  METHODS
  DOX-resistant SW480/DOX cells were derived from non-resistant SW480 cells by stepwise exposure to increasing concentrations of DOX, and P-glycoprotein overexpression induced by DOX was confirmed by Western blotting. Cytotoxicity and intracellular distribution of drugs were evaluated by MTT assay and fluorescence microscopy respectively. EGF receptor-mediated endocytosis was determined in EGF receptor and endocytosis inhibition assays. Drug accumulation in tumour cells and murine xenografts was determined by HPLC.
  
  
  RESULTS
  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 prevented by inhibitors of both EGF receptors and endocytosis, suggesting EGF receptors mediate endocytotic uptake. Tumour accumulation of DOX-EBP was significantly higher than free DOX in mice, and the levels of DOX-EBP were similar in DOX-resistant and non-resistant tumour tissues. Importantly, DOX-EBP, but not free DOX, was effective at inhibiting solid tumour growth and increased survival rate in both sensitive and resistant models.
  
  
  CONCLUSIONS
  DOX-EBP can overcome DOX resistance of tumour cells and increase in vivo antitumour efficacy. Therefore, it has the potential to be a potent therapeutic agent for treating drug-resistant cancers.
authors.affiliation: Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education, School of Pharmaceutical Sciences, Wuhan University, Wuhan, China.
authors.forename: Shibin
authors.initials: S
authors.lastname: Ai
authors.forename: Tao
authors.initials: T
authors.lastname: Jia
authors.forename: Weilun
authors.initials: W
authors.lastname: Ai
authors.forename: Jianli
authors.initials: J
authors.lastname: Duan
authors.forename: Yongmei
authors.initials: Y
authors.lastname: Liu
authors.forename: Jing
authors.initials: J
authors.lastname: Chen
authors.forename: Xin
authors.initials: X
authors.lastname: Liu
authors.forename: Fan
authors.initials: F
authors.lastname: Yang
authors.forename: Yuan
authors.initials: Y
authors.lastname: Tian
authors.forename: Zebo
authors.initials: Z
authors.lastname: Huang
mesh_terms: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000737:chemistry / Q000494:pharmacology*; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D004317:Doxorubicin / Q000737:chemistry / Q000494:pharmacology*; D016503:Drug Delivery Systems; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004705:Endocytosis; D066246:ErbB Receptors / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D009368:Neoplasm Transplantation; D009842:Oligopeptides / Q000737:chemistry*; D014183:Transplantation, Heterologous
chemical_list: D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D009842:Oligopeptides; D004317:Doxorubicin; D066246:ErbB Receptors