Effects of free and liposome-encapsulated taxol on two brain tumors xenografted into nude mice.

Free taxol and liposome-encapsulated taxol were compared for their antitumoral activities on two human brain tumors serially grafted into female athymic mice in the scapular region. In the first experiment, a human glioblastoma (15th and 16th passages) was studied. In the second experiment, a fast growing human gliosarcoma (19th passage) was used. Free taxol and liposomal taxol were administered intraperitoneally, at the same dose; 12.5 mg/kg (i.e. 1/15 of the evaluated LD 50 value). In the first experiment, the treatment was performed for four consecutive days, with four courses separated by three rest periods of three days in between. Both free taxol and encapsulated taxol produced a statistically significant delay in tumor growth, and at the end of the experiment some total tumor regressions were obtained. However, liposomes were observed to be more effective in their action on the two consecutive passages of the glioblastoma, giving a marked increase of the number of total tumor regressions. In the second experiment another schedule of treatment was chosen because of the fast growth pattern of the xenografted human gliosarcoma: free taxol and liposome-encapsulated taxol were administered for five consecutive days and three courses of treatment were performed with two rest periods of two days. The two forms of taxol had a significant inhibitory effect on gliosarcoma tumor growth; as before encapsulation in liposomes was found to increase the anti-tumoral activity of taxol, although, in this case no tumor regression was observed.