TRIPTYCENE ANALOGS--NOVEL BIFUNCTIONAL ANTICANCER DRUGS

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Triptycene (TT) is inactive but we synthesized new TT analogs (code names TT1 to TT16) that have antileukemic activity in the nM range in vitro. The lead compound, a TT bisquinone (TT2), not only inhibits macromolecule synthesis, induces DNA fragmentation, and decreases the growth and viability (IC50: 100 nM) of L1210 cells in vitro like the quinone antitumor drug daunomycin (DAU) but can also block the cellular transport of nucleosides, an effect which DAU cannot do. Since they have unique and highly useful dual effects on nucleoside transport and DNA cleavage, these TT analogs might be valuable to develop a novel synthetic class of bifunctional anticancer drugs effective in polychemotherapy. The major objectives are 1) to demonstrate the anticancer potential of TT2 in vivo, 2) to characterize its molecular mechanism of action, and 3) to identify more potent TT2 analogs. The specific aims are: A) To establish that water-soluble TT2 derivatives can inhibit tumor development in vivo and prolong the survival of mice challenged with ascites (L1210) or solid tumors with metastatic potential (Lewis lung carcinoma and B16F10 melanoma). B) To elucidate the molecular mechanisms by which TT2 interacts with nucleoside transport (effects on equilibrative and Na+-dependent transporters, bidirectional fluxes of purines and pyrimidines, competition with nucleoside transport probes), DNA (binding, intercalation, strand breakage and crosslinks, topoisomerase activities), and tumor cells (drug uptake/retention/catabolism, cell cycle analysis, caspase-8 and -3 activation, apoptosis, potentiation of antimetabolite action, and effectiveness in P-glycoprotein-positive and -negative multidrug-resistant (MDR) cells). C) To synthesize new TT2 analogs and screen them in vitro to clarify structure-activity relationships for drug uptake, nucleoside transport/DNA synthesis, DNA fragmentation, and cell growth/viability. Because inhibition of nucleoside transport is unusual among DNA-damaging quinone antitumor drugs, the use of bifunctional TT2 analogs with antileukemic activity in the nM range in vitro might provide a considerable advantage in polychemotherapy to potentiate the action of antimetabolites and sensitize MDR tumor cells.