['Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among females owing.', 'This study aimed to construct a kind of PEG-coated irinotecan cationic liposomes for investigating its efficacy and mechanism of action in the treatment of breast cancer in preclinical models.', 'Evaluations were performed on the MDA-MB231 breast cancer cells, the xenografted MDA-MB231 cancer cells in Female nude mice and Sprague-Dawley (SD) rat. The liposomes were characterized through assays of cytotoxicity, intracellular uptake, nuclei morphology, antitumor activities, pharmacokinetics and tissue distribution.', 'The zeta potential of PEG-coated irinotecan cationic liposomes was approximately 23 mV. The PEG-coated irinotecan cationic liposomes were approximately 66nm in diameter, significantly increased the intracellular uptake of irinotecan, and showed strong inhibitory effect on MDA-MB231 breast cancer cells. A significant antitumor efficacy in the xenografted MDA-MB231 breast cancer cells in nude mice was evidenced by intravenous administration of PEG-coated irinotecan cationic liposomes. PEG-coated irinotecan cationic liposomes also improved the irinotecan blood circulation time and showed an enhanced drug concentration in tumor.'] Do pEG-coated irinotecan cationic liposomes improve the therapeutic efficacy of breast cancer in animals?