The Design And Synthetic Studies Of Inducible DNA Cross-linking Agents: Bis-catechol Derivatives And Their High Selective Suppression Of Melanoma Cells

Because of the important role that the DNA plays in transferring genetic information, the research of antitumor drugs targeting DNA have always been one of the most attractive areas in durg design. Many anticancer drugs are involved in DNA cross-linking mechanism. They are able to cross-link DNA duplex with covalent bond and inhibit the release of the DNA duplex so that it cannot finish self-replication and the expression of genetic information, which will finally lead cells to death. Inducible DNA cross-linking agents is a novel strategy to increase the selectivity greatly of the drugs.In this thesis, a series of bis(catechol) quaternary ammonium derivatives were designed and synthesized. We investigated their ability of cross-linking DNA which induced by NaIO4 and tyrosinase. For Tyrosinase is highly expressed in malignant tumors, we provide a possible chemotherapy for melanoma by using bis(catechol) quaternary ammonium derivatives that have notable cell selectivity in the tyrosinase-efficient melanoma cells. In summary, the main ideas of this thesis were as follows:1. The DNA- DNA cross-linking ability of the tweleve bis(catechol) quaternary ammonium derivatives was investigated by denatured alkaline agarose gel electrophoresis. The 2,3-dihydroxy derivatives have good cross-linking results which induced by NaIO4 but the 3,4-dihydroxy derivatives not. When the compounds were induced by tyrosinase, the interstrand cross-linking was more efficacious for the 3,4-dihydroxy derivatives than for the 2,3-dihydroxy derivatives. And the 3,4-dihydroxy derivative with diphenol core (10f) is the most efficient crosslink agent. Then, we found that the o-quinone is key intermediate in the process by using the nucleophile 3-methyl-2-benzothiazolinone hydrazone (MBTH) in the tyrosinase assay and we proposed the mechanism of cross-linking DNA. 2. Their cytotoxicities to B16F1, Hela and CHO cells were tested by MTT assays. The specific and potent abilities to kill the tyrosinase-efficient melanoma cells have caught our interest in exploring the relationship between their abilities of cross-linking DNA and their selective cytotoxicities to cells. Through an integrated approach including intracellular imaging for detecting the dihydroxy phenol groups, alkaline comet assay andγ-H2AX immunofluorescence assay the speculation was confirmed. The bis(catechol) quaternary ammonium derivatives showed notable cell selectivity because they displayed cytotoxicities after being oxidized by tyrosinase and were able to efficiently target the DNA in the tyrosinase-efficient melanoma cells, where it forms both alkylated and cross-linked species.