title: Targeting acute hypoxic cancer cells by doxorubicin-immunoliposomes directed by monoclonal antibodies specific to RON receptor tyrosine kinase.
abstract: OBJECTIVE
  Hypoxia contributes to acquired drug resistance in various cancer cells. The underlying mechanism is cellular insensitivity regulated by hypoxia-inducible factors (HIF), which impairs drug uptake, transport, and metabolism. The current study determines anti-RON antibody-directed cytotoxicity of doxorubicin (Dox)-immunoliposomes (IL) in hypoxic colon cancer cells.
  
  
  METHODS
  Cells were cultured under hypoxia (1% O(2), 5% CO(2), and 96% N(2)) for 24 h. Dox-loaded IL were formulated followed by post-insertion of monoclonal antibody Zt/g4 specific to RON. Western blotting was used to detect HIF-1α and RON expression. Cellular uptake of Zt/g4-conjugated IL was determined by confocal and internalization assays. Cell viability was assessed by the MTT assay.
  
  
  RESULTS
  RON and HIF-1α expression were observed in hypoxic colon HCT116 and SW620 cells. Resistance to Dox-induced cytotoxicity was acquired in hypoxic cells with increased IC(50) values. However, acquired resistance was attenuated by Zt/g4-directed Dox-IL, which displays increased cytotoxic activities. IL binding and uptake revealed that hypoxic RON expression is functional, which mediates high levels of Zt/g4-Dox-IL binding and cytoplasmic internalization. Zt/g4-Dox-IL is effective in killing hypoxic HCT116 and SW620 cells with reduced IC(50) values compared to Dox and pegylated-liposomal Dox. These effects were dependent on hypoxic RON expression. HCC1937 cells with diminished RON expression under hypoxia were insensitive to Zt/g4-Dox-IL-induced cytotoxic effect.
  
  
  CONCLUSIONS
  RON expressed by hypoxic colon cancer cells is thus a potential targeting molecule for delivery of chemotherapeutics. The ability of anti-RON mAb to direct Dox-IL cytotoxicity could be developed for attenuating hypoxia-acquired drug resistance in various cancer cells.
authors.affiliation: Center for Cancer Biology and Therapeutics, Department of Biomedical Sciences, School of Pharmacy, Texas Tech University Health Sciences Center, 1406 Coulter Street, Suite 1117, Amarillo, TX 79106, USA.
authors.forename: Sunny
authors.initials: S
authors.lastname: Guin
authors.forename: Qi
authors.initials: Q
authors.lastname: Ma
authors.forename: Snehal
authors.initials: S
authors.lastname: Padhye
authors.forename: Yong-Qing
authors.initials: YQ
authors.lastname: Zhou
authors.forename: Hang-Ping
authors.initials: HP
authors.lastname: Yao
authors.forename: Ming-Hai
authors.initials: MH
authors.lastname: Wang
mesh_terms: D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage / Q000494:pharmacology* / Q000633:toxicity; D000911:Antibodies, Monoclonal; D001943:Breast Neoplasms; D015687:Cell Hypoxia; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms; D004305:Dose-Response Relationship, Drug; D004317:Doxorubicin / Q000008:administration & dosage / Q000494:pharmacology* / Q000633:toxicity; D019008:Drug Resistance, Neoplasm; D005260:Female; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D008081:Liposomes; D020794:Receptor Protein-Tyrosine Kinases / Q000096:biosynthesis / Q000276:immunology*; D013997:Time Factors
chemical_list: D000903:Antibiotics, Antineoplastic; D000911:Antibodies, Monoclonal; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008081:Liposomes; D004317:Doxorubicin; C080835:RON protein; D020794:Receptor Protein-Tyrosine Kinases