Inhibition of human tumor colony formation by the new alkyl lysophospholipid ilmofosine

The cytostatic-cytotoxic effect of the new thioether alkyl lysophospholipid analogue Ilmofosine (1-hexadecylthio-2-methoxymethyl-rac-glycero-3-phosphocholine, BM 41.440) on colony formation of 30 different spontaneous human tumors was investigated in vitro with the use of a methylcellulose monolayer assay. Twenty-five neoplasms were sensitive to Ilmofosine within the concentration range tested (0-16 micrograms/ml). The most susceptible tumors were 2 colon carcinomas, 2 squamous cell carcinomas and 1 small-cell carcinoma of the lungs, 2 myosarcomas, 2 ovarian carcinomas, 1 gallbladder carcinoma, and 1 pleural mesothelioma with 50% colony formation inhibition doses ranging from 1.5 to 4.0 micrograms/ml. Due to the sensitivity criteria of the U.S. National Cancer Institute (greater than or equal to 70% inhibition of colony formation at 10 micrograms/ml), 15 of 30 tumors tested have to be considered as susceptible to Ilmofosine.