Protection by the alkyllysophospholipid, 1-octadecyl-2-methoxy-rac-glycero-3-phosphocholine, but not by the retinoid etretinate against leukemia development in DMBA-treated Long-Evans rats

The antileukemic potency of the alkyllysophospholipid, 1-octadecyl-2-methoxy-rac-glycero-3-phosphocholine (Et-18-OCH3) and of the retinoid etretinate was examined alone and in combination in 7,12-dimethylbenz-anthracene(DMBA)-induced Long-Evans (LE) rats. Lifelong administration of Et-18-OCH3 at a dose of 20 mg/kg per day slightly but significantly reduced the incidence of leukemias and thereby significantly prolonged the life span of animals. The best effect was seen when treatment started at day 58 of life, i.e. 1 day after the third of 4 DMBA injections (P = 0.0001). Administration of etretinate, however, at a dose of 5 mg/kg did not show any efficacy against leukemia development. The combination of both agents reduced the incidence of mammary neoplasias only (P = 0.04).