Fluoride has been used to prevent caries in the dentition, but the possible underlying mechanisms of cytotoxicity induction by this compound are still unclear. Since fluoride is known as an inhibitor of glycolytic enzymes, we investigated the possible connection between NaF-induced apoptosis and glycolysis in human promyelocytic leukemia HL-60 cells. NaF-induced apoptotic cell death is characterized by caspase activation, internucleosomal DNA fragmentation, loss of mitochondrial membrane potential, and production of apoptotic bodies. Higher activation of caspases-3 and -9, as compared with that of caspase-8, suggested the involvement of an extrinsic pathway. Utilization of glucose was nearly halted by NaF, whereas that of glutamine was rather enhanced. NaF enhanced the expression of Bad protein, but not that of Bcl-2 and Bax proteins, and reduced HIF-1alpha mRNA expression. Analysis of these data suggests a possible link between glycolysis and apoptosis.

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We examined the anti-tumor activity and structure-activity requirements of omega-hydroxy fatty acids (omega-HFAs) on the human melanoma cell line G361. The omega-hydroxystearic acid (omega-HSA) had strong growth-inhibiting and cytotoxic activity. Although omega-hydroxypalmitic acid (omega-HPA) also had growth-inhibiting and cytotoxic activity, these effects were relatively low. The effects of both these acids were dose and time dependent. Further, DNA laddering, which is an index of apoptosis, was also observed in G361 cells on treatment with these compounds. On the other hand, the omega-HFAs tested in this study, omega-hydroxymyristic acid and omega-hydroxyeicosanoic acid, had no growth-inhibiting or cytotoxic activity. Treatment for 12 h with 100 microM of omega-HPA and omega-HSA resulted in the expression of caspase-3 activity, and then increased upon 24 h, suggesting that the cell death induced by omega-HPA and omega-HSA was apoptosis. Fatty acids and dicarboxylic acids, which are analogs of omega-HFAs, had no cytotoxicity. However, fatty alcohols and diols, which have a 16- to 18-carbon chain length had weak cytotoxicity. From these results, the most effective carbon chain length is 18. Furthermore, the hydroxyl group at one end of the carbon chain and the carboxyl group at the other end seem to be required for the cytotoxic effect. At least one end of the carbon chain must have a hydroxyl group. The carbon chain length of omega-HFAs appears to be closely related to the cytotoxicity. This study revealed the potent cytotoxic actions of omega-HFAs on the human melanoma cell line G361.

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