Two structurally-unrelated small molecule chemotypes, represented by compounds PAV-617 and PAV-951, with antiviral activity in cell culture against monkeypox virus (MPXV) and human immunodeficiency virus (HIV) respectively, were studied for anti-cancer efficacy. Each exhibited apparent pan-cancer cytotoxicity, reasonable pharmacokinetics, and non-toxicity in mice at active concentrations. Anti-tumor properties of each compound were validated in mouse xenografts against A549 human lung cancer. The targets of these compounds are unconventional: each binds to a different transient, energy-dependent multi-protein complex containing the protein KAP-1(TRIM28), an allosteric modulator known to broadly regulate mechanisms underlying viral and nonviral disease states including cancer. Treatment with these compounds alters the target multi-protein complexes in a manner consistent with allosteric modulation as their mechanism of action. These compounds appear to remove a block, crucial for cancer survival and progression, on the homeostatic linkage of uncontrolled cellular proliferation to apoptosis. These compounds may provide starting points for development of next-generation non-toxic, cancer therapeutics.
To validate carboxyterminal processing protease of D1 protein (CtpA) as a target for herbicide discovery, CtpA sense mRNAs were overexpressed to suppress the internal level of CtpA protein in mouseearcress plants. Using antibodies raised against recombinant CtpA protein, we demonstrated that we have generated transgenic mouseearcress plants with reduced levels of CtpA protein and plants with elevated levels of CtpA protein. Transgenic plants with severely reduced levels of CtpA protein exhibited a bleached and chlorotic phenotype and stunted growth. The mutant phenotypes were enhanced by bright illumination. However, plants with a slight reduction of CtpA protein did not exhibit the mutant phenotype and could not be distinguished from wild-type plants under normal growth conditions. Several CtpA enzyme inhibitors were shown to have herbicidal activity in planta. Interestingly, plants producing excessive amount of CtpA protein were shown to be resistant to these inhibitors. Our results suggest that CtpA is essential for plant growth and development, but a reduced amount of CtpA is sufficient to carry out its essential function. CtpA may be a good target for herbicide development, but very high levels of inhibition may be required to produce a herbicidal effect. In addition, overexpressing CtpA in target plants might provide a mechanism for producing plants resistant to the herbicide.
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