Isothiocyanates and freeze-dried strawberries as inhibitors of esophageal cancer

A group of arylalkyl isothiocyanates were tested for their abilities to inh ibit tumorigenicity and DNA methylation induced by the esophageal-specific carcinogen, N-nitrosomethylbenzylamine (NMBA) in the F344 rat esophagus. Ph enylpropyl isothiocyanate (PPITC) was more potent than either phenylethyl i sothiocyanate (PEITC) or benzyl isothiocyanate (BITC). Phenylbutyl isothioc yanate (PBITC), however, had a lesser inhibitory effect on esophageal tumor igenesis, and phenylhexyl isothiocyanate (PHITC) actually enhanced esophage al tumorigenesis. Thus, the two- and three-carbon isothiocyanates were more effective inhibitors of NMBA-esophageal carcinogenesis than the longer cha in isothiocyanates. The effects of the isothiocyanates on tumorigenesis wer e well correlated as to their effects on DNA adduct formation. The most lik ely mechanism of inhibition of tumorigenesis by these isothiocyanates is vi a inhibition of the cytochrome P450 enzymes responsible for the metabolic a ctivation of NMBA in rat esophagus. A freeze-dried strawberry preparation w as also evaluated for its ability to inhibit NMBA-esophageal tumorigenesis. It proved to be an effective inhibitor, although not as potent as either P EITC or PPITC. The inhibitory effect of the berries could not be attributed solely to the content of the chemopreventive agent, ellagic acid, in the b erries.