In vivo antitumor activity of Larrea divaricata C.: comparison of two routes of administration

We have previously demonstrated that an aqueous extract from Larrea divaricata has an antiproliferative activity on T lymphoma (BW 5147) cells in culture. Moreover the extract has in vivo antitumor activity when it was administered to a pregnant rat which had a spontaneous mammary tumor. In this work, the effect of an extract of Larrea divaricata on a mammary carcinoma chemically induced with N-nitrosomethylurea in females rats was studied. The extract was administered at a dose of 250 mg/kg three times each week by two different routes, subcutaneous (s.c.) and intratumoral (i.t.). The antitumor activity of the extract was evaluated by the survival time and the percentage of tumors that decreased, remained static or increased. From tumors treated via i.t. with the extract, 7 decreased (58%), 4 remained static (33%), and 1 increased (8%); whereas from tumors treated via s.c. with the extract, 10 decreased (12%), 59 remained static (75%) and 9 increased (11%); The total number of control tumors was 80, none of them showed regression, 12 remained static (15%) and 68 increased (85%). The survival time of treated animals using both routes (s.c. and i.t.) was significantly greater (p < 0.05) than the saline-treated rats (control): extract 70 +/- 19 days, n: 32; saline (control) 38 +/- 22 days, n: 20. We conclude that the aqueous extract of this plant has an in vivo antitumor activity with the intratumor route being most effective in induction of tumor regression.