In vitro and in vivo evaluation of tumor targeting styrene-maleic acid copolymer-pirarubicin micelles: Survival improvement and inhibition of liver metastases.
Pirarubicin is a derivative of doxorubicin with improved intracellular uptake and reduced cardiotoxicity. We have prepared a micellar formulation of pirarubicin using styrene-maleic acid copolymer (SMA) of mean molecular weight of 1.2 kDa, which exhibits a mean diameter of 248 nm in solution. Being a macromolecule, SMA-pirarubicin micelles exhibit excellent tumor targeting capacity due to the enhanced permeability and retention (EPR) effect. Here we report the antitumor activity of SMA-pirarubicin micelles on human colon and breast cancer cell lines in vitro, and a murine liver metastasis model in vivo. Metastatic tumor microvasculature, necrosis, apoptosis, proliferation, and survival were also investigated using immunohistochemistry for Ki-67, active caspase-3, and CD34, respectively. Drug cytotoxicity in vitro was assessed using MTT (3-[4,5-dimethyl-2-thiazolyl]-2, 5-diphenyl-2H-tetrazolium bromide) assay. In vivo, SMA-pirarubicin was administered at 100, 150, or 200 mg/kg (pirarubicin equivalent). Tumor microvasculature was also assessed using scanning electron microscopy. Styrene-maleic acid copolymer (SMA)-pirarubicin micelles were toxic against human colorectal and breast cancer cells in vitro. IC(50) was at or below 1 muM, free pirarubicin equivalent. In vivo, SMA-pirarubicin at 100 mg/kg reduced tumor volume by 80% and achieved a survival rate of 93% at 40 days after tumor inoculation. Styrene-maleic acid copolymer (SMA)-pirarubicin micelles demonstrated potent antitumor activity in this liver metastases model, contributing to prolonged survival. Histological examination of tumor nodules showed significant reduction and proliferation of tumor cells (>90%). The present results suggest that investigation of the effect of multiple dosing at later time points to further improve survival is warranted.
Daruwalla
Jurstine
J
Department of Surgery, University of Melbourne, Austin Health, Melbourne, Victoria, Australia.
Nikfarjam
Mehrdad
M
Greish
Khaled
K
Malcontenti-Wilson
Cathy
C
Muralidharan
Vijayaragavan
V
Christophi
Chris
C
Maeda
Hiroshi
H
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D053148:Caspase 3 / Q000502:physiology; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D004317:Doxorubicin / Q000008:administration & dosage / Q000031:analogs & derivatives*; D006801:Humans; D008114:Liver Neoplasms, Experimental / Q000517:prevention & control* / Q000556:secondary*; D008297:Male; D008298:Maleates / Q000008:administration & dosage*; D051379:Mice; D008808:Mice, Inbred CBA; D008823:Micelles; D009336:Necrosis; D009374:Neoplasms, Experimental / Q000098:blood supply / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology; D011137:Polystyrenes / Q000008:administration & dosage*
D008298:Maleates; D008823:Micelles; D011137:Polystyrenes; C024074:styrene-maleic acid polymer; D004317:Doxorubicin; C027260:pirarubicin; D053148:Caspase 3