Kyu-Yeon Jun

Synthesis, biological evaluation, and molecular docking study of 3-(3′-heteroatom substituted-2′-hydroxy-1′-propyloxy) xanthone analogues as novel topoisomerase IIα catalytic inhibitor

Epoxide ring-opened xanthone derivatives were synthesized and tested for their topoisomerase inhibitory activity and cytotoxicity. Most of the compounds showed topo IIα specific inhibitory activity. To clarify the mechanism of action of these compounds, the most potent compound (compound 14) of the synthesized analogues was further studied by testing its ATPase inhibitory activity and through molecular docking experiments. The results showed that the topo IIα inhibitory activity of compound 14 was inversely proportional to ATP concentration. In the ATPase inhibitory test, ATP hydrolysis was reduced less efficiently by compound 14 (28.5±4.6%) than novobiocin (60.4±8.1%). Molecular docking study revealed compound 14 to have a stable binding pattern to the ATP-binding domain of human topo II.

A series of novel terpyridine-skeleton molecule derivants inhibit tumor growth and metastasis by targeting topoisomerases.

A series of novel terpyridine-skeleton molecules containing conformational rigidity, 14 containing benzo[4,5]furo[3,2-b]pyridine core and 15 comprising chromeno[4,3-b]pyridine core, were synthesized, and their biological activities were evaluated. 3-(4-Phenylbenzo[4,5]furo[3,2-b]pyridin-2-yl)phenol (8) was determined to be a nonintercalative topo I and II dual catalytic inhibitor and 3-(4-phenylchromeno[4,3-b]pyridine-2-yl)phenol (22) was determined to be a nonintercalative topo IIα specific catalytic inhibitor by various assays. These two catalytic inhibitors induced apoptosis in addition to G1 arrest in T47D human breast cancer cells with much less DNA toxicity than etoposide. Compounds 8 and 22 significantly inhibited tumor growth in HCT15 subcutaneously implanted xenografted mice. The modification of compounds 8 and 22 with the introduction of a methoxy instead of a hydroxy group enhanced endogenous topo inhibitory activity, metabolic stability in diverse types of liver microsomes and improved pharmacokinetic parameters in rat plasma such as augmentation of bioavailability (41.3% and 33.2% for 2-(3-methoxyphenyl)-4-phenylbenzofuro[3,2-b]pyridine (8-M) and 3-(4-phenylchromeno[4,3-b]pyridine-2-yl)methoxybenzene (22-M), respectively).

Mutations in SOHLH1 Gene Associate with Nonobstructive Azoospermia

In a previous study, we found SOHLH1 (spermatogenesis and oogenesis‐specific basic helix‐loop‐helix 1) as the first testis‐specific basic helix‐loop‐helix transcription factor essential for spermatogonial differentiation. SOHLH1 therefore represents an excellent candidate gene for testicular failure such as nonobstructive azoospermia (NOA). We analyzed whether there were mutations in the SOHLH1 gene in 96 Korean patients with NOA. The sequence analysis discovered three novel variations: one intronic variant (c.346−1G>A), and two nonsynonymous exonic variants (c.91T>C and c.529C>A) with known single nucleotide polymorphisms (SNPs), which included six intronic variants, two synonymous, and two nonsynonymous variants. We examined the consequences of mutations in SOHLH1 using in vivo and in vitro assays. Analysis of transcripts from minigenes carrying the c.346−1G>A revealed that splicing site variation leads to the partial deletion at a cryptic splicing site within exon 4. This deletion results in SOHLH1 with a truncated bHLH domain. Transient transfection assay showed that the SOHLH1 mutant with the truncated domain disrupted the transcriptional activity of KIT promoter, whereas two missense mutations harboring either p.Arg37Gln or p.Pro269Ser did not have a significant effect on its transactivation. Our findings indicate that a splice‐acceptor site mutation that probably causes a nonfunctional SOHLH1 protein results in nonobstructive azoospermia by the lack of normal spermatogenesis. Hum Mutat 31:788–793, 2010.

Effect of conjugated linoleic acid, μ-calpain inhibitor, on pathogenesis of Alzheimer's disease.

μ-Calpain is a calcium-dependent cysteine protease, which is activated by μM concentration of calcium in vitro. Disrupted intracellular calcium homeostasis leads to hyper-activation of μ-calpain. Hyper-activated μ-calpain enhances the accumulation of β-amyloid peptide by increasing the expression level of β-secretase (BACE1) and induces hyper-phosphorylation of tau along with the formation of neurofibrillary tangle by mediating p35 cleavage into p25, both of which are the major mechanisms of neurodegeneration in Alzheimers disease (AD). Hence, inhibition of μ-calpain activity is very important in the treatment and prevention of AD. In this study, conjugated linoleic acid (CLA), an eighteen-carbon unsaturated fatty acid, was discovered as a μ-calpain-specific inhibitor. CLA showed neuroprotective effects against neurotoxins such as H2O2 and Aβ1-42 in SH-SY5Y cells, and inhibited Aβ oligomerization/fibrillation and Aβ-induced Zona Occludens-1 degradation. In addition, CLA decreased the levels of proapoptotic proteins, p35 conversion to p25 and tau phosphorylation. These findings implicate CLA as a new core structure for selective μ-calpain inhibitors with neuroprotective effects. CLA should be further evaluated for its potential use as an AD therapeutic agent.

Identification of 3-Acetyl-2-aminoquinolin-4-one as a Novel, Nonpeptidic Scaffold for Specific Calpain Inhibitory Activity

A series of 3-acetyl-2-aminoquinolin-4-one derivatives selected from the Korean Chemical Bank were screened for calpain inhibitory activity by using a high-throughput fluorimetric calpain assay. We identified a potent and selective mu-calpain inhibitor, compound 17, whose specificity and efficacy for mu-calpain inhibition was better than MDL28170. Docking studies revealed that the efficacy of its inhibitory effect on calpain depended on the size and charge properties of the substitutions on the phenylamino ring.

Hydroxylated 2,4-diphenyl indenopyridine derivatives as a selective non-intercalative topoisomerase IIα catalytic inhibitor.

For the development of novel anticancer agents, we designed and synthesized hydroxylated 2,4-diphenyl indenopyridines, and evaluated their topoisomerase inhibitory activity as well as their antiproliferative activities against several human cancer cell lines. The structure-activity relationship study showed that indenopyridines with hydroxyl group at meta or para positions of 2- or 4-phenyl ring displayed selective and significant topoisomerase IIα (topo IIα) inhibitory activity and potent antiproliferative activity. Positive correlation between topo IIα inhibition and antiproliferative activity was observed for compounds 15, 16, 18-20, 22, 23, 25 and 26. The mode of action of compound 16 was further evaluated to be a non-intercalative topo IIα catalytic inhibitor.

Synthesis, antitumor activity, and structure-activity relationship study of trihydroxylated 2,4,6-triphenyl pyridines as potent and selective topoisomerase II inhibitors.

A series of eighteen trihydroxylated 2,4,6-triphenyl pyridines were designed and synthesized which contain hydroxyl groups at ortho, meta or para position of each phenyl rings attached to the central pyridine. They were evaluated for topoisomerase I and II inhibitory activity, and cytotoxicity against several human cancer cell lines for the development of novel anticancer agents. Most of the compounds exhibited strong and selective topoisomerase II inhibitory activity compared to the positive control, etoposide, and also displayed significant cytotoxicity in low micromolar range. Trihydroxylated 2,4,6-triphenyl pyridines were more potent than mono- and di-hydroxylated 2,4,6-triphenyl pyridines, which have been previously studied in our research group. Positive correlation between topoisomerase II inhibitory activity and cytotoxicity was observed for the most compounds. Molecular docking study shows qualitatively consistent with the results of biological assays.

Discovery of dihydroxylated 2,4-diphenyl-6-thiophen-2-yl-pyridine as a non-intercalative DNA-binding topoisomerase II-specific catalytic inhibitor

We describe our rationale for designing specific catalytic inhibitors of topoisomerase II (topo II) over topoisomerase I (topo I). Based on 3D-QSAR studies of previously published dihydroxylated 2,4-diphenyl-6-aryl pyridine derivatives, 9 novel dihydroxylated 2,4-diphenyl-6-thiophen-2-yl pyridine compounds were designed, synthesized, and their biological activities were evaluated. These compounds have 2-thienyl ring substituted on the R(3) group on the pyridine ring and they all showed excellent specificity toward topo II compared to topo I. In vitro experiments were performed for compound 13 to determine the mechanism of action for this series of compounds. Compound 13 inhibited topoisomerase II specifically by non-intercalative binding to DNA and did not stabilize enzyme-cleavable DNA complex. Compound 13 efficiently inhibited cell viability, cell migration, and induced G1 arrest. Also from 3D-QSAR studies, the results were compared with other previously published dihydroxylated 2,4-diphenyl-6-aryl pyridine derivatives to explain the structure-activity relationships.

Design and synthesis of novel 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives, and their evaluation of topoisomerase inhibitory activity and cytotoxicity.

For the development of potential anticancer agents, we designed and synthesized 30 new 2,4-diaryl-5H-indeno[1,2-b]pyridine derivatives containing aryl moiety such as furyl, thienyl, pyridyl, and phenyl at 2- and 4-position of 5H-indeno[1,2-b]pyridine. They were evaluated for topoisomerase I and II inhibitory activity, and cytotoxicity against several human cancer cell lines. Among prepared 30 compounds, 7, 8, 9, 10, 12, 14, 16, 19, 20, 22, and 23 with 2- or 3-furyl and/or 2- or 3-thienyl either at 2- or 4-position of central pyridine showed the significant or moderate topoisomerase II inhibitory activity. Compounds 7, 8, 11, 12, 13, and 22 with 2-furyl, 2-thienyl or 3-thienyl at 2-position of central pyridine showed the significant or moderate topoisomerase I inhibitory activity. Especially, compound 12 with strong topoisomerase II inhibitory activity at 100 μM and 20 μM, and moderate topoisomerase I inhibitory activity displayed strong cytotoxicity against several human cancer cell lines.

3-(3-Butylamino-2-hydroxy-propoxy)-1-hydroxy-xanthen-9-one acts as a topoisomerase IIα catalytic inhibitor with low DNA damage

As a continuous study we prepared several alkylamine (n = 3-6) and evaluated for the pharmacological activity and mode of action. In the topoisomerase IIα (topo IIα) inhibition test, compound 4 showed strongest inhibitory activity among the compounds at 10 μM. Inhibitory activities of the compounds are in the order of 4 (n = 4) > 1 (n = 3) >> 5 (n = 5) ≈ 6 (n = 6); 8 (n = 4) >> 7 (n = 3) ≈ 9 (n = 5) ≈ 10 (n = 6) where n is the number of carbon in the aliphatic side chain in ring C and compounds 7-10 have additional methoxy group in ring A compared to compounds 1, 4-6. Compound 4 showed efficient cytotoxicities against T47D (IC₅₀: 0.93 ± 0.04 μM) and HCT15 (IC50: 0.78 ± 0.01 μM) cells, which are higher than etoposide. Compound 4 was also an ATP-competitive human topo IIα catalytic inhibitor with partially blocking human topo IIα-catalyzed ATP hydrolysis and intercalating into DNA. Compound 4 induced much less DNA damage than etoposide in HCT15 human colorectal carcinoma cells. Overall, compound 4 can be a potential anticancer agent acting as topo IIα catalytic inhibitor with low DNA damage.