Tumor necrosis factor-alpha (TNF-alpha) is a proinflammatory cytokine playing a part in various pathological states. Non-toxic inhibitors of TNF-alpha release are thought to be promising agents for cancer prevention. We found that the acetone fraction of the tobacco leaf surface lipid containing glucose esters and sucrose esters inhibited both TNF-alpha release from BALB/3T3 and KATO III cells induced by okadaic acid and tumor promotion by okadaic acid on mouse skin initiated with 7,12-dimethylbenz(a)anthracene (DMBA). Next, we investigated the inhibition of TNF-alpha release with synthetic disaccharide esters, such as 6,6'-di-O-alkanoyl-alpha, alpha-trehaloses (6,6'-diester-trehaloses), 4,4'-di-O-alkanoyl-alpha, alpha-trehaloses (4,4'-diester-trehaloses) and 6,6'-diamino-6,6'-dideoxy-N,N'-dialkanoyl-alpha, alpha-trehaloses (6,6'-diamide-trehaloses) bearing fatty acids of various chain lengths, and n-dodecyl-beta-D-maltoside as a disaccharide monoester. 6,6'-Diester-trehaloses and 4,4'-diester-trehaloses of C8 to C12 fatty acids, 6,6'-diamide-trehaloses of C8 to C14 fatty acids, and n-dodecyl-beta-D-maltoside all inhibited TNF-alpha release in a dose-dependent manner. The IC50 values are 7.4-14.8 microM for 6,6'-diester-trehaloses (C8 to C12), 14.6-21.6 microM 4,4'-diester-trehaloses (C8 to C12), 2.9-15.0 microM for 6,6'-diamide-trehaloses (C8 to C14) and 23 microM for dodecyl-beta-D-maltoside. Both 6,6'-di-O-octanoyl-alpha, alpha-trehalose (C8, designated as SS555) and n-dodecyl-beta-D-maltoside (C12) inhibited tumor promotion by okadaic acid on mouse skin initiated with DMBA. Percentages of tumor-bearing mice in week 15 of tumor promotion were reduced from 60.0 to 13.3 with SS555, and to 46.7 with n-dodecyl-beta-D-maltoside. Moreover, SS555 inhibited TNF-alpha gene expression mediated through inhibition of AP-1 activation, but not NF-kappa B activation. This paper reports that diester-trehaloses of C8 to C12 fatty acids and mimics of disaccharide monoesters such as n-dodecyl-beta-D-maltoside appear to be potential cancer-preventive agents of a new type.