Influence of the alkyllysophospholipid ET-18-OCH3 on methylnitrosourea-induced rat mammary carcinomas.

This study describes the efficacy of the alkyllysophospholipid 1-octadecyl-2-methoxy-Sn-racglycero-3-phosphocholine (ET-18-OCH3) in inhibiting the growth of methylnitrosourea-induced mammary carcinomas in Sprague-Dawley rats. In experiment A 2 X 10 mg/kg Et-18-OCH3 were administered daily for 10 weeks prior to manifestation of mammary carcinomas which resulted in a significant inhibition of median tumor number and median tumor volume per rat. Treatment of established tumors (experiment B) with 6 and 60 mg/kg ET-18-OCH3 daily for 3 weeks effected a stagnation in tumor growth for the higher dosage only with 90% tumor inhibition in comparison to untreated controls; at the same time, however, clear toxic effects were seen, thus indicating a narrow therapeutic index of ET-18-OCH3 in single-drug therapy. Combination of ET-18-OCH3 with compounds possessing a different toxicity spectrum is suggested.