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Inhibition of X-Ray or Chemical Carcinogen-induced Neoplastic Transformation of C3H10T1/2 Fibroblasts by Lipopolysaccharides¹

Division of Physiology and Pathology, National Institute of Radiological Sciences, 4-9-1 Anagawa, Chiba 260 [H. S., M. Y., T. T.], and The Institute of Medical Science, The University of Tokyo, 4-6-1 Shirokanedai, Minato-ku, Tokyo 108 [S. K.] Japan

Oncogenic transformation of mouse 10T 1/2 fibroblasts induced upon exposure to X-ray or N-methyl-N'-nitro-N-nitrosoguanidine was suppressed if lipopolysaccharide (LPS) was present in the culture medium. The suppressive effect of LPS was exerted within 24 h after irradiation. Suppression was dependent on the concentration of LPS added and LPS (2 µg/ml) derived from Salmonella minnesota R595 reduced the number of transformed type III foci per dish from 0.39 to 0.15. Indomethacin (1 to 30 µM) further enhanced the effect of LPS in a dose-dependent manner.

¹ Supported by a project research grant for radiation carcinogenesis from the Science and Technology Agency.

² To whom requests for reprints should be addressed.

Received 12/26/85. Revised 4/21/86. Accepted 5/ 1/86.