Notes: Dysregulation of the NF-kB pathway has been associated with the formation of a wide variety of tumors and other cancers, as well as diseases, including chronic inflammation and immunodeficiency. Because of the association of constitutive NF-kB regulation and tumors, inhibition of the NF-kB pathway by small molecule antagonists was thought to be a means of reversing or halting the growth and spread of tumors. The authors screened compounds from a database (the NCGC Pharmaceutical Collection or NPC) of small molecule compounds: 52% of the compounds have been approved for human or animal use by the FDA, 22% were drugs approved for use in Europe, and another 25% either drugs approved in other countries or compounds that have been tested in clinical trials. The database served as a source from which to rapidly and efficiently identify already approved drugs that inhibited NF-kB. They used a quantitative high-throughput screening format. To identify small molecules that could inhibit the NF-kB pathway, the compounds were initially screened using a cell-based NF-kB lactamase reporter gene assay, with TNFalpha and MG132 as positive controls. (TNFalpha induced NF-kB coupled beta-lactamase activity, while MG132 blocked TNFalpha induction NF-kB-coupled beta-lactamase activity.) After several rounds of screening, 20 compounds were further studied for their NF-kB inhibition, with NF-kB luc2P HEK293 cells. After a concordance rate of 95% between the luciferase and beta-lactamase tests, compounds were additionally examined for their ability to affect caspase 3/7 activity, for the ability to disrupt the electrochemical gradient across the mitochondrial membrane in relation to cellular apoptosis, as well as tests of the inhibitors on cancer cell viability and affects on LDH release, an indicator of cell necrosis.
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