Oncogenic RAS directs silencing of tumor suppressor genes through ordered recruitment of transcriptional repressors.

We previously identified 28 cofactors through which a RAS oncoprotein directs transcriptional silencing of Fas and other tumor suppressor genes (TSGs). Here we performed RNAi-based epistasis experiments and found that RAS-directed silencing occurs through a highly ordered pathway that is initiated by binding of ZFP354B, a sequence-specific DNA-binding protein, and culminates in recruitment of the DNA methyltransferase DNMT1. RNAi and pharmacological inhibition experiments reveal that silencing requires continuous function of RAS and its cofactors and can be rapidly reversed, which may have therapeutic implications for reactivation of silenced TSGs in RAS-positive cancers.

Structure-guided discovery of 2-aryl/pyridin-2-yl-1H-indole derivatives as potent and selective hepsin inhibitors.

Hepsin, a type II transmembrane serine protease, is upregulated in prostate cancer and known to be involved in the progression of metastasis. Here we report a structure-guided approach, which resulted in the discovery of 2-aryl/pyridin-2-yl-1H-indole derivatives as potent and selective inhibitors of hepsin. Potent and selective inhibition of hepsin by compound 8 is likely due to interactions of the amidine group at the S1 site with the cyclohexyl ring from the 2-aryl group projecting towards the S1' site and the tert-hydroxyl group interacting with His57 side-chain as revealed by X-ray crystallography. Compounds 8 and 10, showed Ki of 0.1 µM for hepsin, and exhibited inhibition of invasion and migration of hepsin-overexpressing cell line. Compounds described here could serve as useful tool reagents to investigate the role of hepsin as a potential therapeutic target in cancer.

Structure-guided discovery of 1,3,5 tri-substituted benzenes as potent and selective matriptase inhibitors exhibiting in vivo antitumor efficacy.

Matriptase is a serine protease implicated in cancer invasion and metastasis. Expression of matriptase is frequently dysregulated in human cancers and matriptase has been reported to activate latent growth factors such as hepatocyte growth factor/scatter factor, and proteases such as urokinase plasminogen activator suggesting that matriptase inhibitors could have therapeutic potential in treatment of cancer. Here we report a structure-based approach which led to the discovery of selective and potent matriptase inhibitors with benzene as central core having 1,3,5 tri-substitution pattern. X-ray crystallography of one of the potent analogs in complex with matriptase revealed strong hydrogen bonding and salt-bridge interactions in the S1 pocket, as well as strong CH-π contacts between the P2/P4 cyclohexyl and Trp215 side-chain. An additional interaction of the pendant amine at cyclohexyl with Gln175 side-chain results in substantial improvement in matriptase inhibition and selectivity against other related serine proteases. Compounds 15 and 26 showed tumor growth inhibition in a subcutaneous DU-145 prostate cancer mouse model. These compounds could be useful as tools to further explore the biology of matriptase as a drug target.