CG0006, a novel histone deacetylase inhibitor, induces breast cancer cell death via histone-acetylation and chaperone-disrupting pathways independent of ER status.

We previously reported that CG0006, a novel hydroxamate-based pan-histone deacetylase inhibitor (HDACI), suppresses the growth of human cancer cells. Here, we tested the ability of CG0006 to inhibit breast cancer cell proliferation in relation to estrogen receptor (ER) status, and examined changes in the expression of cell-cycle regulatory proteins. CG0006 effects on the proliferation of multiple human cancer cell lines were tested using MTT and MTS assays. Changes in estrogen-signaling proteins and cell-cycle regulatory proteins were examined by western blotting and quantitative RT-PCR, and cell-cycle effects were tested using flow cytometry. CG0006 increased histone H3 and H4 acetylation, up-regulated p21 protein, and promoted cell-cycle arrest, inducing G(2)/M-phase accumulation in ER-positive MCF7 cells, and G(1)- and G(2)/M-phase accumulation in ER-negative MDA-MB-231 cells. In both cell types, CG0006 treatment (1 µM) reduced the levels of the estrogen-signaling proteins ERα and cyclin D1, and promoted massive degradation of cell-cycle regulatory proteins. CG0006 down-regulated the histone deacetylase HDAC6 at the protein level in association with a subsequent increase in Hsp90 and α-tubulin acetylation. HDAC6 depletion using small interfering RNA produced a protein-degradation phenotype similar to that of CG0006 treatment. These findings suggest that CG0006 inhibits breast cancer cell growth by two different pathways: a histone acetylation-dependent pathway, and a non-epigenetic pathway that disrupts chaperone function.

In vitro chemosensitivity of gastric adenocarcinomas to histone deacetylase inhibitors, compared to established drugs.

BACKGROUND/AIMS: This study was performed to determine the efficacy of histone deacetylase inhibitors in gastric cancer, together with other established regimens. METHODOLOGY: The chemosensitivities of 93 gastric cancer patients to established drugs, and three histone deacetylase inhibitors (SAHA, PXD101, and a novel candidate, CG-2) were evaluated using the histoculture drug response assay. RESULTS: Tumor growth inhibition rates were the highest with cisplatin, followed by PXD101, taxol, docetaxel, and TS-1, in descending order. The response rates were 41.9-68.8%, and 37.6-47.3%, respectively, at an inhibition rate cutoff value of 30%. Synergistic activity was evident with most combinations of established drugs and histone deacetylase inhibitors. Diffuse- or mixed-type carcinomas on Lauren classification were closely associated with increased chemosensitivity to TS-1 (p = 0.044). Node-positive and "other than tubular type" tumors on WHO classification were chemosensitive to cisplatin (p = 0.011 and 0.014, respectively). CG-2 chemosensitivity was markedly associated with low preoperative CA724 level (< or = 4 U/ml) (p = 0.046). CONCLUSIONS: This in vitro chemosensitivity assay validates the comparable chemo-response of gastric cancers to histone deacetylase inhibitors and established drugs, indicating considerable therapeutic efficacy of these agents. Additionally, a number of clinicopathological parameters are significantly associated with specific regimens.

Novel histone deacetylase inhibitors CG05 and CG06 effectively reactivate latently infected HIV-1.

Histone deacetylase plays an important role in HIV latency. Novel histone deacetylase inhibitors, CG05 and CG06, were evaluated for their roles in HIV latency using ACH2 cells. Both inhibitors were highly efficient in reactivation of provirus and exerted lesser toxicity compared with other known histone deacetylase inhibitors. Histone acetylation increased when proviruses were reactivated by the compounds. These new inhibitors may contribute to the reduction of the HIV reservoir when used in conjunction with highly active antiretroviral therapy.

Design, synthesis, and evaluation of 2-aryl-7-(3',4'-dialkoxyphenyl)-pyrazolo[1,5-a]pyrimidines as novel PDE-4 inhibitors.

Described herein is design, synthesis, and biological evaluation of novel series of 2-aryl-7-(3',4'-dialkoxyphenyl)-pyrazolo[1,5-a]pyrimidines acting as inhibitors of type 4 phosphodiesterase (PDE4) which is known as a good target for the treatment of asthma and COPD. For this purpose, structure optimization was conducted with the aid of structure-based drug design using the known X-ray crystallography. Also, biological effects of these compounds on the target enzyme were evaluated by using in vitro assays, leading to the potent and selective PDE-4 inhibitor (IC(50)<10nM).

A novel histone deacetylase inhibitor, CG0006, induces cell death through both extrinsic and intrinsic apoptotic pathways.

Histone deacetylase inhibitors (HDACIs) are potent anticancer drugs, and suberoylanilide hydroxamic acid is used for the treatment of cutaneous T-cell lymphoma patients. We synthesized a novel hydroxamate-based HDACI, CG0006, and assessed its antiproliferative effects on the NCI-60 cancer cell panel and cell lines from liver and stomach cancers that are common in Korea. Micromolar levels of CG0006 induced cell death in several breast, central nervous system, colon, hematopoietic, lung, melanoma, ovarian, prostatic, renal, and stomach cancer cell lines. We further analyzed cell death mechanisms activated by CG0006 in HCT116 (colon cancer) and K562 (leukemia) cells. First, to test the activity of CG0006, we analyzed acetylation of substrates of HDACs and effect on gene expression. CG0006 increased acetylation of histone 3, histone 4, and tubulin in a time-dependent and dose-dependent manner in both HCT116 and K562 cells. Moreover, CG0006 increased the mRNA level of p21 and decreased that of Bcl-xl efficiently in HCT116 cells. Cell cycle analysis showed G2-M arrest, and increased apoptosis in populations of HCT116 and K562 cells treated with CG0006. Western blot analysis showed that CG0006 increased levels of p21 in HCT116 cells and of p21 and p27 in K562 cells. In addition, CG0006 activated caspase-9, caspase-3, and caspase-8. These results indicate that CG0006 induces death in HCT116 and K562 cells through both intrinsic and extrinsic apoptotic pathways. The HDACI CG0006 may be a potent anticancer drug for solid tumors and leukemia.

Design and synthesis of 7-hydroxy-1H-benzoimidazole derivatives as novel inhibitors of glycogen synthase kinase-3beta.

A hydroxy functional group was introduced as the hydrogen bond donor and acceptor at the hinge region of protein kinase in order to develop novel ATP-competitive inhibitors. Several derivatives of 7-hydroxyl-1H-benzoimidazole were designed as inhibitors of glycogen synthase kinase-3beta with the help of ab initio calculations and a docking study. Enzymatic assay and an X-ray complex study showed that these designed compounds were highly potent ATP-competitive inhibitors.

Structural chemoproteomics and drug discovery.

Our laboratories have developed several technologies to accelerate drug discovery process on the basis of structural chemoproteomics. They include SPS technology for the efficient determination of protein structures, SCP technology for the rapid lead generation and SDF technology for the productive lead optimization. Using these technologies, we could determine many 3D structures of target proteins bound with biologically active chemicals including the structure of phosphodiesterase 5/Viagra complex and obtain highly potent compounds in animal models of obesity, diabetes, cancer and inflammation. In this paper, we will discuss concepts and applications of structural chemoproteomics for drug discovery.

Structural basis for the selective inhibition of JNK1 by the scaffolding protein JIP1 and SP600125.

The c-jun N-terminal kinase (JNK) signaling pathway is regulated by JNK-interacting protein-1 (JIP1), which is a scaffolding protein assembling the components of the JNK cascade. Overexpression of JIP1 deactivates the JNK pathway selectively by cytoplasmic retention of JNK and thereby inhibits gene expression mediated by JNK, which occurs in the nucleus. Here, we report the crystal structure of human JNK1 complexed with pepJIP1, the peptide fragment of JIP1, revealing its selectivity for JNK1 over other MAPKs and the allosteric inhibition mechanism. The van der Waals contacts by the three residues (Pro157, Leu160, and Leu162) of pepJIP1 and the hydrogen bonding between Glu329 of JNK1 and Arg156 of pepJIP1 are critical for the selective binding. Binding of the peptide also induces a hinge motion between the N- and C-terminal domains of JNK1 and distorts the ATP-binding cleft, reducing the affinity of the kinase for ATP. In addition, we also determined the ternary complex structure of pepJIP1-bound JNK1 complexed with SP600125, an ATP-competitive inhibitor of JNK, providing the basis for the JNK specificity of the compound.

Structure of the catalytic domain of human phosphodiesterase 5 with bound drug molecules.

Phosphodiesterases (PDEs) are a superfamily of enzymes that degrade the intracellular second messengers cyclic AMP and cyclic GMP. As essential regulators of cyclic nucleotide signalling with diverse physiological functions, PDEs are drug targets for the treatment of various diseases, including heart failure, depression, asthma, inflammation and erectile dysfunction. Of the 12 PDE gene families, cGMP-specific PDE5 carries out the principal cGMP-hydrolysing activity in human corpus cavernosum tissue. It is well known as the target of sildenafil citrate (Viagra) and other similar drugs for the treatment of erectile dysfunction. Despite the pressing need to develop selective PDE inhibitors as therapeutic drugs, only the cAMP-specific PDE4 structures are currently available. Here we present the three-dimensional structures of the catalytic domain (residues 537-860) of human PDE5 complexed with the three drug molecules sildenafil, tadalafil (Cialis) and vardenafil (Levitra). These structures will provide opportunities to design potent and selective PDE inhibitors with improved pharmacological profiles.