In vivo anti-tumor effect of PEG liposomal doxorubicin (DOX) in DOX-resistant tumor-bearing mice: Involvement of cytotoxic effect on vascular endothelial cells.
We evaluated the in vivo anti-tumor effect of polyethylene glycol-modified liposomal doxorubicin (PEG liposomal DOX) in the DOX-resistant Colon-26 cancer cells (C26/DOX)-bearing mice model. IC(50) value of DOX to C26/DOX in vitro (40.0 microM) was about 250 times higher than that to control C26 (C26/control) (0.15 microM). However, in vivo anti-tumor effect of PEG liposomal DOX was similar in both C26/control- and C26/DOX-bearing mice, suggesting that the in vivo anti-tumor effect of PEG liposomal DOX was not directly reflecting the sensitivity of these tumor cells to DOX. IC(50) value (0.10 microM) of DOX to HUVEC, a model vascular endothelial cell, was similar to that of C26/control. Double immunohistochemical staining of vascular endothelial cells and apoptotic cells within the tumor tissue after intravenous administration of PEG liposomal DOX showed that the extent of co-localization of apoptotic cells with endothelial cells was significantly higher for C26/DOX tumors (60%) than C26/control ones (20%), suggesting that the apoptosis is caused preferentially for vascular endothelial cells in C26/DOX tumor. From these results, it was suggested that the cytotoxic effect of DOX on vascular endothelial cells in the tumor would be involved in the in vivo anti-tumor effect of PEG liposomal DOX in C26/DOX-bearing mice.
Department of Pharmaceutics, Faculty of Pharmaceutical Sciences, Okayama University, Okayama 700-8530, Japan.
Ken-ichi
K
Ogawara
Keita
K
Un
Ken-ichi
K
Tanaka
Kazutaka
K
Higaki
Toshikiro
T
Kimura
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000378:metabolism; D000818:Animals; D000903:Antibiotics, Antineoplastic / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D004317:Doxorubicin / Q000008:administration & dosage / Q000737:chemistry / Q000627:therapeutic use*; D004347:Drug Interactions; D019008:Drug Resistance, Neoplasm; D042783:Endothelial Cells / Q000166:cytology / Q000187:drug effects*; D006801:Humans; D020128:Inhibitory Concentration 50; D008081:Liposomes / Q000737:chemistry; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D009369:Neoplasms / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D011092:Polyethylene Glycols / Q000737:chemistry*; D016019:Survival Analysis; D014700:Verapamil / Q000494:pharmacology
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000903:Antibiotics, Antineoplastic; D008081:Liposomes; D011092:Polyethylene Glycols; D004317:Doxorubicin; D014700:Verapamil