Jee Sun Yang

Histone deacetylase inhibitor KBH-A42 inhibits cytokine production in RAW 264.7 macrophage cells and in vivo endotoxemia model

In light of the anti-inflammatory properties of histone deacetylase (HDAC) inhibitors, such as suberoylanilide hydroxamic acid (SAHA) and trichostatin A (TSA), we examined a new HDAC inhibitor KBH-A42 for its anti-inflammatory activities. KBH-A42 showed noteworthy anti-inflammatory properties in vitro via suppression of the production of TNF-α, a proinflammatory cytokine, and nitric oxide (NO), a proinflammatory effector molecule, in LPS-stimulated RAW264.7 cells and peritoneal macrophages. It also inhibited TNF-α production in vivo as demonstrated in a LPS-induced mouse endotoxemia model. The levels of TNF-α, IL-1β, IL-6 and iNOS mRNAs determined by RT-PCR propose that the inhibition of these pro-inflammatory mediators by KBH-A42 resulted from inhibiting expression of these genes. However, the EMSA study to see the effect of KBH-A42 on the binding of NF-κB, a transcription factor, to a specific DNA sequence showed that the binding of NF-κB to DNA was not changed regardless of increasing the concentration of KBH-A42 in the presence and absence of LPS stimulation. Interestingly, DNA binding of another transcription factor AP-1 dose-dependently increased by KBH-A42. KBH-A42 differentially regulated the phosphorylation of MAP kinases. While the phosphprylation of ERK1/2 and SAPK/JNK was not affected by KBH-A42, the phosphorylation of p38 decreased by KBH-A42. These results showed that KBH-A42 inhibits production of proinflammatory cytokines in macrophages by decreasing their mRNA levels, and p38 kinase is involved in the KBH-A42-mediated inhibition.

Chemical inhibition of prometastatic lysyl-tRNA synthetase–laminin receptor interaction

Lysyl-tRNA synthetase (KRS), a protein synthesis enzyme in the cytosol, relocates to the plasma membrane after a laminin signal and stabilizes a 67-kDa laminin receptor (67LR) that is implicated in cancer metastasis; however, its potential as an antimetastatic therapeutic target has not been explored. We found that the small compound BC-K-YH16899, which binds KRS, impinged on the interaction of KRS with 67LR and suppressed metastasis in three different mouse models. The compound inhibited the KRS-67LR interaction in two ways. First, it directly blocked the association between KRS and 67LR. Second, it suppressed the dynamic movement of the N-terminal extension of KRS and reduced membrane localization of KRS. However, it did not affect the catalytic activity of KRS. Our results suggest that specific modulation of a cancer-related KRS-67LR interaction may offer a way to control metastasis while avoiding the toxicities associated with inhibition of the normal functions of KRS.

Property-based optimization of hydroxamate-based γ-lactam HDAC inhibitors to improve their metabolic stability and pharmacokinetic profiles.

Hydroxamate-based HDAC inhibitors have promising anticancer activities but metabolic instability and poor pharmacokinetics leading to poor in vivo results. QSAR and PK studies of HDAC inhibitors showed that a γ-lactam core and a modified cap group, including halo, alkyl, and alkoxy groups with various carbon chain linkers, improved HDAC inhibition and metabolic stability. The biological properties of the γ-lactam HDAC inhibitors were evaluated; the compound designated 8f had potent anticancer activity and high oral bioavailability.

Discovery of thienopyrimidine-based FLT3 inhibitors from the structural modification of known IKKβ inhibitors

Inactivation of the NF-κB signaling pathway by inhibition of IKKβ is a well-known approach to treat inflammatory diseases such as rheumatoid arthritis and cancer. Thienopyrimidine-based analogues were designed through modification of the known IKKβ inhibitor, SPC-839, and then biologically evaluated. The resulting analogues had good inhibitory activity against both nitric oxide and TNF-α, which are well-known inflammatory responses generated by activated NF-κB. However, no inhibitory activity against IKKβ was observed with these compounds. The thienopyrimidine-based analogues were subsequently screened for a target kinase, and FLT3, which is a potential target for acute myeloid leukemia (AML), was identified. Thienopyrimidine-based FLT3 inhibitors showed good inhibition profiles against FLT3 under 1μM. Overall, these compounds represent a promising family of inhibitors for future development of a treatment for AML.

A novel antitumor piperazine alkyl compound causes apoptosis by inducing RhoB expression via ROS-mediated c-Abl/p38 MAPK signaling

PurposeWe investigated the action mechanism of a novel anticancer compound, KR28 (1-allyl-4-dodecanoyl-1-ethyl-piperazin-1-ium; bromide), to induce apoptosis of human prostate carcinoma PC-3 cells.MethodsTo explore an apoptotic signaling of KR28, we used ROS assay, SRB assay, flow cytometry analysis, reporter assay, xenograft assay, Western blotting, and RT-PCR analysis.ResultsThe growth inhibitory action of KR28 is cell line specific, impeding the growth of prostate carcinoma PC-3 and stomach carcinoma NUGC-3 cells. KR28 showed strong antitumor activity in PC-3 mouse xenograft model. KR28 increased ROS production, leading to nuclear c-Abl expression, which in turn activated p38 mitogen-activated protein kinase (MAPK) to enhance the expression of RhoB, an apoptosis inducer. The KR28-induced apoptosis was abrogated by the ROS scavenger N-acetylcysteine and by knockdown of c-Abl, p38 MAPK, or ATF2. Moreover, the p300 binding site and two CCAAT boxes in the RhoB promoter appear to be involved in ROS-mediated RhoB expression in the presence of KR28.ConclusionThe antitumor agent KR28 induces apoptosis of PC-3 cells by ROS-mediated RhoB expression via c-Abl upregulation and activation of p38 MAPK/ATF-2.

Synthesis and biological evaluation of novel aliphatic amido-quaternary ammonium salts for anticancer chemotherapy: Part II

We synthesized novel aliphatic amido-quaternary ammonium salts in an effort to discover anticancer agents that increase Ras homolog gene family, member B, (RhoB) levels. These compounds exert anti-proliferative activities against several human cancer cell types. Seventeen compounds, varying in aliphatic carbon chain length and N-substituents, were synthesized and their biological activities were evaluated. Of these 17 compounds, compound 3i emerged as the most promising anticancer compound by promoting apoptosis through the RhoB mediated pathway. Potent biological activities observed for these novel aliphatic amido-quaternary ammonium salt analogues support their potential as anticancer, chemotherapeutic agents.

Synthesis and biological evaluation of novel thieno(2,3-d)pyrimidine- based FLT3 inhibitors as anti-leukemic agents

The most common mutations in acute myeloid leukemia (AML) are those that cause the activation of FMS-like tyrosine kinase 3 (FLT3). Therefore, FLT3 is regarded as a potential target for the treatment of AML. A novel series of thieno[2,3-d]pyrimidine-based analogs was designed and synthesized as FLT3 inhibitors. All synthesized compounds were assayed for the tyrosine kinase activity of FLT3 and growth inhibitory activity in four human leukemia cell lines (THP1, MV4-11, K562, and HL-60). Among these compounds, compound 17a, which possesses relatively short and simple substituents at the C6 position of thieno[2,3-d]pyrimidine, emerged as the most promising anti-leukemic agent. Compound 17a exhibited potent inhibition of FLT3-positive leukemic cell growth and of the FLT3 D835Y kinase; such inhibition is required for the successful treatment of AML. The data supports the further investigation of this class of compounds as potential anti-leukemic agents.

Discovery of Pyridone‐Based Histone Deacetylase Inhibitors: Approaches for Metabolic Stability

Histone deacetylases (HDACs) are important enzymes in epigenetic regulation and are therapeutic targets for cancer. Most zinc‐dependent HDACs induce proliferation, dedifferentiation, and anti‐apoptotic effects in cancer cells. We designed and synthesized a new series of pyridone‐based HDAC inhibitors that have a pyridone ring in the core structure and a conjugated system with an olefin connecting the hydroxamic acid moiety. Consequently, most of the selected pyridone‐based HDAC inhibitors showed similar or higher inhibition profiles in addition to remarkable metabolic stability against hydrolysis relative to the corresponding lactam‐based HDAC inhibitors. Furthermore, the selectivity of the novel pyridine‐based compounds was evaluated across all of the HDAC isoforms. One of these compounds, (E)‐N‐hydroxy‐3‐{1‐[3‐(naphthalen‐2‐yl)propyl]‐2‐oxo‐1,2‐dihydropyridin‐3‐yl}acrylamide, exhibited the highest level of HDAC inhibition (IC50=0.07 μM), highly selective inhibition of class I HDAC1 and class II HDAC6 enzymes, metabolic stability in mouse liver microsomal studies, and effective growth inhibition of various cancer cell lines. Docking studies indicated that a long alkyl linker and bulky hydrophobic cap groups affect in vitro activities. Overall, the findings reported herein regarding pyridone‐based HDAC inhibitors can be used to guide future research efforts to develop new and effective anticancer therapeutics.

Small-molecule binding of the axin RGS domain promotes β-catenin and Ras degradation.

Both the Wnt/β-catenin and Ras pathways are aberrantly activated in most human colorectal cancers (CRCs) and interact cooperatively in tumor promotion. Inhibition of these signaling may therefore be an ideal strategy for treating CRC. We identified KY1220, a compound that destabilizes both β-catenin and Ras, via targeting the Wnt/β-catenin pathway, and synthesized its derivative KYA1797K. KYA1797K bound directly to the regulators of G-protein signaling domain of axin, initiating β-catenin and Ras degradation through enhancement of the β-catenin destruction complex activating GSK3β. KYA1797K effectively suppressed the growth of CRCs harboring APC and KRAS mutations, as shown by various in vitro studies and by in vivo studies using xenograft and transgenic mouse models of tumors induced by APC and KRAS mutations. Destabilization of both β-catenin and Ras via targeting axin is a potential therapeutic strategy for treatment of CRC and other type cancers activated Wnt/β-catenin and Ras pathways.

Structural modifications at the 6-position of thieno[2,3-d]pyrimidines and their effects on potency at FLT3 for treatment of acute myeloid leukemia.

Fms-like tyrosine kinase 3 (FLT3) is a well-known and important target for the treatment of acute myeloid leukemia (AML). A series of thieno[2,3-d]pyrimidine derivatives from a modification at the 6-position were synthesized to identify effective FLT3 inhibitors. Although compounds 1 and 2 emerged as promising FLT3 inhibitors among the synthesized compounds, both compounds exhibited poor metabolic stability in human and rat liver microsomes. Hence, further optimization was required for the discovery of FLT3 inhibitors, with a focus on improving metabolic stability. Compound 16d, which had structural modifications of the methyl group at the 5-position and the 4-(2-methylaminoethoxy) phenyl group at the 6-position, exhibited good inhibitory activity against FLT3 and showed effective antiproliferative activity against four leukemia cell lines, including MV4-11. Moreover, compound 16d displayed enhanced metabolic stability. The results of this study indicated that 16d could be a promising compound for further optimization and development as a potent FLT3 inhibitor.