Evaluation of Antitumor Activity of Long-Circulating and pH-Sensitive Liposomes Containing Ursolic Acid in Animal Models of Breast Tumor and Gliosarcoma.

Background Ursolic acid (UA) is a triterpene found in different plant species, possessing antitumor activity, which may be a result of its antiangiogenic effect. However, UA has low water solubility, which limits its use because the bioavailability is impaired. To overcome this inconvenience, we developed long-circulating and pH-sensitive liposomes containing ursolic acid (SpHL-UA). We investigated the antiangiogenic effect of free UA and SpHL-UA in murine brain cancer and human breast tumor models by means of determination of the relative tumor volume, dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI), and histopathological analysis. Methods The animals were treated with dimethyl sulfoxide in 0.9% (w/v) NaCl, free UA, long-circulating and pH-sensitive liposomes without drug (SpHL), or SpHL-UA. The animals were submitted to each treatment by intraperitoneal injection for 5 days. The dose of free UA or SpHL-UA was equal to 23 mg/kg. Results Tumor growth inhibition was not observed in human breast tumor-bearing animals. For murine gliosarcoma-bearing animals, a slight tumor growth inhibition was observed in the groups treated with free UA or SpHL-UA (9% and 15%, respectively). No significant change in any of the parameters evaluated by DCE-MRI for both experimental models could be observed. Nevertheless, the evaluation of the mean values of magnetic resonance parameters of human breast tumor-bearing animals showed evidence of a possible antiangiogenic effect induced by SpHL-UA. Histopathological analysis did not present significant change for any treatment. Conclusion SpHL-UA did not show antiangiogenic activity in a gliosarcoma model and seemed to induce an antiangiogenic effect in the human breast tumor model.

Antitumor effectiveness and toxicity of cisplatin-loaded long-circulating and pH-sensitive liposomes against Ehrlich ascitic tumor.

Cisplatin (CDDP) is one of the most active cytotoxic agents commonly used in the treatment of peritoneal carcinomatosis. The disadvantages of its clinical use are systemic side-effects, such as nephrotoxicity and myelotoxicity. Long-circulating and pH-sensitive liposomes containing CDDP (SpHL-CDDP) were developed by our research group aiming to promote the release of CDDP near the tumor as well as decreasing toxicity. The aim of this study was to evaluate the antitumor efficacy and toxicity of SpHL-CDDP after intraperitoneal administration in initial or disseminated tumor-bearing mice, at a dose of 12 mg/kg. The survival was monitored and blood samples were collected for biochemical and hematological analysis. Kidneys, liver and spleen were removed for histopathological examination. Tumor cells were evaluated for cellular viability and cell cycle. The survival of animals treated with SpHL-CDDP was higher than those treated with free CDDP. The cell death caused by treatment with SpHL-CDDP occurred through induction of apoptosis, with a cell cycle arrest at the G0/G1 phase. The treatment of mice presenting initial cancer with both formulations provoked a suppression of granulocytes. Mice treated with free CDDP also showed a decrease in platelet count, which suggests a high myelotoxicity. In an advanced cancer model, SpHL-CDDP treatment allowed an improvement of the immune response. Mice affected by cancer at an early stage and treated with free CDDP or SpHL-CDDP showed a lower urea/creatinine index compared with the saline control group. These findings indicate that both treatments were able to reduce the renal damage caused by peritoneal carcinomatosis. Microscopic analysis of kidneys from mice treated with SpHL-CDDP showed a discrete morphological alteration, while tubular necrosis was observed for free CDDP-treated mice. Concerning hepatotoxicity, no alteration in clinical chemistry parameters was observed. These findings reveal that SpHL-CDDP can improve the antitumor efficacy and decrease renal and bone marrow toxicity.