Professor Nihon University Fujisawa-Shi, Kanagawa, Japan
Abstract: Melanoma is a malignant type of skin cancer that develops from melanocytes. Because of high risk for recurrence and lack of effective therapy, it is important to prevent the proliferation of melanoma cells in the early stage by taking functional foods. According to the Designer Foods Project conducted by the National Cancer Institute in the United States in the 1990s to find anti-carcinogenic substances, garlic was ranked in the top vegetables for the cancer prevention. The major functional components in garlic are reported to be diallyl disulfide (DADS) and diallyl trisulfide (DATS) that are produced from allyl-L-cysteine sulfoxide (ACSO) by C-S lyase when cells are damaged by cutting or crushing. However, DADS and DATS are volatile lipophilic compounds having strong garlic odor, which limits their use in food. On the other hand, as ACSO is water-soluble and odorless, it can be used in various types of food. ACSO is biosynthesized from γ-glutamyl allyl-L-cysteine sulfoxide (GACSO). We have already reported that ACSO shows various pharmacological effects in vivo such as prevention of platelet aggregation and hepatic injury. The present study aimed to examine the inhibitory effect of ACSO and GACSO on proliferation of melanoma cells by comparing the effect with their analogues such as allyl-L-cysteine (ACS), γ-glutamyl allyl-L-cysteine (GACS), methyl-L-cysteine sulfoxide (MCSO) and ethyl-L-cysteine sulfoxide (ECSO). As a result, ACSO and GACSO showed much higher preventive activity of melanoma proliferation than their analogues indicating that both allyl group and sulfoxide structure are crucial for their activity. In in-vivo experiment, melanoma cells were injected to rats subcutaneously and ACSO was orally administered daily. Daily oral administration of ACSO effectively suppressed the melanoma proliferation even in vivo.
