Identification of new halogen-containing 2,4-diphenyl indenopyridin-5-one derivative as a boosting agent for the anticancer responses of clinically available topoisomerase inhibitors.

Based on previous reports on the significance of halogen moieties and the indenopyridin-5-one skeleton, we designed and synthesized a novel series of halogen (F-, Cl-, Br-, CF3- and OCF3-)-containing 2,4-diphenyl indenopyridin-5-ones and their corresponding -5-ols. Unlike indenopyridin-5-ols, most of the prepared indenopyridin-5-ones with Cl-, Br-, and CF3- groups at the 2-phenyl ring conferred a strong dual topoisomerase I/IIα inhibitory effect. Among the series, para-bromophenyl substituted compound 9 exhibited the most potent topoisomerase inhibition and antiproliferative effects, which showed dependency upon the topoisomerase gene expression level of diverse cancer cells. In particular, as a DNA minor groove-binding non-intercalative topoisomerase I/IIα catalytic inhibitor, compound 9 synergistically promoted the anticancer efficacy of clinically applied topoisomerase I/IIα poisons both in vitro and in vivo, having the great advantage of alleviating poison-related toxicities.

Discovery of a 2,4-diphenyl-5,6-dihydrobenzo(h)quinolin-8-amine derivative as a novel DNA intercalating topoisomerase IIα poison.

Several anticancer agents have been developed and innovative approaches have been made toward cancer type-specific medicines for cancer treatment. As a continuous effort to develop potential chemotherapeutic agents, a novel series of 2,4-diphenyl-5,6-dihydrobenzo(h)quinolin-8-amines containing amino groups, hydroxyphenyl and fluorine functionalities were designed and synthesized. The compounds were evaluated for topo IIα inhibitory and cytotoxicity against HCT15, and HeLa human cancer cell lines. Among synthesized thirty compounds, the majority exhibited strong topo IIα inhibition and anti-proliferation against HCT15 colorectal adenocarcinoma cell line. The structure-activity relationship study revealed that compounds with -CF3 and -OCF3 substituents at 4- position and 3' or 4'-hydroxyphenyl at 2-position attached to the central pyridine ring displayed potent topo IIα and anti-proliferative activity in colorectal and cervix cancer cell line. In vitro studies provided the evidence that compounds 16, 19, 22, and 28 possess excellent topo IIα inhibition and antiproliferative activity. For a better understanding, topo IIα cleavage complex, EtBr displacement, KI quenching assays and molecular docking of compound 19 was performed and the results revealed the mode of action as a DNA intercalative topo IIα poison inhibitor. The results obtained from this study provide insight into the DNA binding mechanism of 2,4-diphenyl-5,6-dihydrobenzo(h)quinolin-8-amines and alteration in topo IIα inhibitory and antiproliferative activity with modifications in the rigid structure.

Targeting the Nuclear Receptor-Binding SET Domain Family of Histone Lysine Methyltransferases for Cancer Therapy: Recent Progress and Perspectives.

Nuclear receptor-binding SET domain (NSD) proteins are a class of histone lysine methyltransferases (HKMTases) that are amplified, mutated, translocated, or overexpressed in various types of cancers. Several campaigns to develop NSD inhibitors for cancer treatment have begun following recent advances in knowledge of NSD1, NSD2, and NSD3 structures and functions as well as the U.S. FDA approval of the first HKMTase inhibitor (tazemetostat, an EZH2 inhibitor) to treat follicular lymphoma and epithelioid sarcoma. This perspective highlights recent findings on the structures of catalytic su(var), enhancer-of-zeste, trithorax (SET) domains and other functional domains of NSD methyltransferases. In addition, recent progress and efforts to discover NSD-specific small molecule inhibitors against cancer-targeting catalytic SET domains, plant homeodomains, and proline-tryptophan-tryptophan-proline domains are summarized.

An orally available inverse agonist of estrogen-related receptor gamma showed expanded efficacy for the radioiodine therapy of poorly differentiated thyroid cancer.

Estrogen-related receptor gamma (ERRγ) is the NR3B subgroup of associated transcription factors. In this report, a new generation of a potent and selective ERRγ inverse agonist (25) with good biocompatibility was proposed. We also explored the potential of the newly developed compound 25 in the PDTC model to expand the original indications from ATC. In addition, an X-ray crystallographic study of the ligand and ERRγ co-complex showed that 25 completely binds to the target protein (PDB 6KNR). Its medicinal chemistry, including a distinctive structural study to in vivo results, denotes that 25 may be directed towards the development of a pivotal treatment for ERRγ-related cancers.

Discovery and Biological Evaluations of Halogenated 2,4-Diphenyl Indeno[1,2-b]pyridinol Derivatives as Potent Topoisomerase IIα-Targeted Chemotherapeutic Agents for Breast Cancer.

With the aim of developing new effective topoisomerase IIα-targeted anticancer agents, we synthesized a series of hydroxy- and halogenated 2,4-diphenyl indeno[1,2-b]pyridinols using a microwave-assisted single step synthetic method and investigated structure-activity relationships. The majority of compounds with chlorophenyl group at 2-position and phenol group at the 4-position of indeno[1,2-b]pyridinols exhibited potent antiproliferative activity and topoisomerase IIα-selective inhibition. Of the 172 compounds tested, 89 showed highly potent and selective topoisomerase IIα inhibition and antiproliferative activity in the nanomolar range against human T47D breast (2.6 nM) cancer cell lines. In addition, mechanistic studies revealed compound 89 is a nonintercalative topoisomerase II poison, and in vitro studies showed it had promising cytotoxic effects in diverse breast cancer cell lines and was particularly effective at inducing apoptosis in T47D cells. Furthermore, in vivo administration of compound 89 had significant antitumor effects in orthotopic mouse model of breast cancer.

Synthesis and biological evaluation of pyridine-linked indanone derivatives: Potential agents for inflammatory bowel disease.

A series of pyridine-linked indanone derivatives were designed and synthesized to discover new small molecules for the treatment of inflammatory bowel disease (IBD). Compounds 5b and 5d exhibited strongest inhibitory activity against TNF-α-induced monocyte adhesion to colon epithelial cells (an in vitro model of colitis). In TNBS (2,4,6-trinitrobenzenesulfonic acid)-induced rat colitis model, oral administration of the compounds 5b and 5d ameliorated colitis with significant recovery in altered expressions of E-cadherin, TNF-α and IL-1ß expressions, indicating 5b and 5d as potential agents for therapeutics development against IBD.

Synthesis and SAR study of new hydroxy and chloro-substituted 2,4-diphenyl 5H-chromeno[4,3-b]pyridines as selective topoisomerase IIα-targeting anticancer agents.

As part of our effort to develop potential topoisomerase IIα (topo IIα) targeting anticancer agents, we systematically designed a new series of hydroxy and chloro-substituted 2,4-diphenyl 5H-chromeno[4,3-b]pyridines. Total eighteen compounds were synthesized and tested for their ability to inhibit the function of topo I and IIα, and proliferation of human breast (T47D), colorectal (HCT15), and cervix (HeLa) cancer cells. Except compound 11, all of the tested compounds displayed selective topo IIα inhibitory activity. Compounds 8-18, 22, 24, and 25 showed excellent topo IIα inhibitory activity than a positive control, etoposide. Most of the compounds appeared to be superior to reference compounds in their antiproliferative activity. Structure-activity relationship (SAR) study has shown that it is better to place the hydroxyphenyl group at the 4-position of the central pyridine for superior topo IIα inhibition and antiproliferative activity. Similarly, the 3'-, or 4'-hydroxyphenyl substitution at the 2- and 4-positon of pyridine ring is important for better activity than 2'-substitution.

2-Chlorophenyl-substituted benzofuro[3,2-b]pyridines with enhanced topoisomerase inhibitory activity: The role of the chlorine substituent.

A new series of 2-chloropheny-substituted benzofuro[3,2-b]pyridines were designed, synthesized, and evaluated for topoisomerase I and II inhibition and antiproliferative activity. Compounds 17-19, 23, 24, 26, and 27 exhibited excellent topo II inhibitory activity. A systematic structure-activity relationship study revealed the important role of chlorine substitution in the strong topoisomerase inhibitory activity.

Discovery and structure-activity relationship studies of 2-benzylidene-2,3-dihydro-1H-inden-1-one and benzofuran-3(2H)-one derivatives as a novel class of potential therapeutics for inflammatory bowel disease.

To develop effective therapeutics for inflammatory bowel disease (IBD), 2-benzylidene-2,3-dihydro-1H-inden-1-one and benzofuran-3(2H)-one derivatives, were designed and synthesized and their structure-activity relationships (SAR) were investigated. Compounds 7, 25, 26, 32, 39, 41, 52, 54, and 55 showed potent inhibitory effect (>70%) on the TNF-α-induced adhesion of monocytes to colon epithelial cells, which is one of the hallmark events leading to IBD. Such inhibitory activity of the compounds correlated with their suppressive activities against the TNF-α-induced production of ROS; ICAM-1 and MCP-1 expression, critical molecules involved in monocyte-epithelial adhesion; and NF-κB transcriptional activity. In addition, compounds 41 and 55 significantly suppressed the lipopolysaccharide (LPS)-induced expression of the TNF-α gene, with compound 55 showing better efficacy. This inhibition of TNF-α expression by compounds 41 and 55 corresponded to their additional inhibitory activity against AP-1 transcriptional activity, which is another transcription factor required for high level TNF-α expression. The strong inhibitory activity of compound 55 against an in vivo colitis model was confirmed by its dose-dependent inhibitory activity in a rat model of 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis, demonstrating compound 55 as a new potential candidate for the development of therapeutics against IBD.

Rational design, synthesis, and evaluation of novel 2,4-Chloro- and Hydroxy-Substituted diphenyl Benzofuro[3,2-b]Pyridines: Non-intercalative catalytic topoisomerase I and II dual inhibitor.

Novel series of conformationally constrained 2,4-chloro- and hydroxy-substituted diphenyl benzofuro[3,2-b]pyridines were rationally designed and synthesized. Their biological activities were evaluated for topoisomerase I and II inhibitory activity, and antiproliferative activity against several human cancer cell lines for the development of novel anticancer agents. Most of the compounds with phenol moiety at 4-position of central pyridine exhibited significant dual topoisomerase I and II inhibitory activities, and strong antiproliferative activity in low micromolar range. Structure activity relationship study suggested that phenol moiety at 4-position of the central pyridine regardless of chlorophenyl moiety at 2-position of the central pyridine has an important role in dual topoisomerase inhibitory activity as well as antiproliferative activity. For investigation of mode of action for compound 14 which displayed the most strong dual topoisomerase I and II inhibitory activity and antiproliferative activity against HCT15 cell, we performed cleavable complex assay, band depletion assay, comet assay, and competitive EtBr displacement assay. Compound 14 functioned as non-intercalative catalytic topo I and II dual inhibitor. In addition, compound 14 induced apoptosis in HCT15 cells through increase of Bax, decrease of Bcl-2 and increase of PARP cleavage.

Novel 2-aryl-4-(4'-hydroxyphenyl)-5H-indeno[1,2-b]pyridines as potent DNA non-intercalative topoisomerase catalytic inhibitors.

On the basis of previous reports on the importance of thienyl, furyl or phenol group substitution on 5H-indeno[1,2-b]pyridine skeleton, a new series of rigid 2-aryl-4-(4'-hydroxyphenyl)-5H-indeno[1,2-b]pyridine derivatives were systematically designed and synthesized. Topoisomerase inhibitory activity and antiproliferative activity of all the synthesized compounds were determined using human colorectal (HCT15), breast (T47D), prostate (DU145) and cervix (HeLa) cancer cells. Compounds 9, 10, 12, 13, 15, 16, 18 and 19 with thienyl or furyl moiety at the 2-position and hydroxyl group at the meta or para positions of 4-phenyl ring displayed strong to moderate topoisomerase IIα (topo IIα) inhibitory activity and significant antiproliferative activity. The evaluation of compound 16 to determine its mechanism of action was performed with topo IIα-DNA cleavable complex, topo IIα-mediated ATPase assay, DNA unwinding and in vitro and ex vivo topo IIα relaxation assay. Compound 16 functioned as a DNA non-intercalative topo IIα catalytic inhibitor with better potency than etoposide in T47D breast cancer cells. Molecular docking study revealed that compound 16 cannot intercalate into regularly stacked base-pairs of DNA duplex but can interact or intercalate to topo IIα-bound DNA.

Synthesis and biological evaluation of 2-phenol-4-chlorophenyl-6-aryl pyridines as topoisomerase II inhibitors and cytotoxic agents.

A new series of 2-phenol-4-chlorophenyl-6-aryl pyridines were designed, synthesized, and evaluated for topoisomerase (topo) I and II inhibitory activities as well as cytotoxic activity against four different human cancer cell lines such as HCT15, T47D, DU145, and Hela. Most of the tested compounds exhibited stronger topo II inhibitory activity at 100µM as compared to etoposide. All the compounds, except 39, did not show topo I inhibitory activity. Interestingly, compounds that showed better topo II inhibition than etoposide have ortho- or para-chlorophenyl at 4-position of central pyridine, and none of the compounds possess meta-chlorophenyl. SAR study revealed the importance of ortho- or para-chlorophenyl at 4-position of the central pyridine for selective topo II inhibitory activity. Similarly, all compounds possessing meta- or para-hydroxyphenyl moieties showed moderate to significant cytotoxic effects. Particularly, compounds 27-37, and 39 which showed excellent cytotoxicity (IC50=0.68-1.25µM) against T47D breast cancer cells suggest the importance of meta- or para-hydroxyphenyl moiety at 2-position of the central pyridine for the design of anticancer agents with related scaffolds.

Effect of chlorine substituent on cytotoxic activities: Design and synthesis of systematically modified 2,4-diphenyl-5H-indeno[1,2-b]pyridines.

In continuation of our previous work, six hydroxylated 2,4-diphenyl-5H-indeno[1,2-b]pyridine analogs were modified by introducing one chlorine functionality at ortho, meta or para position of the 2- or 4-phenyl ring. Eighteen new chlorinated compounds were thus prepared and assessed for topoisomerase inhibitory activity and cytotoxicity against HCT15, T47D, and HeLa cancer cell lines. All of the chlorinated compounds displayed significant cytotoxic effect, revealing potent anticancer activity against T47D breast cancer cells. This functional group modification allowed us to explore the importance of chlorine group substitution for the cytotoxic properties. The information reported here provides valuable insight for further study to develop new anticancer agents using related scaffolds.

A new series of 2-phenol-4-aryl-6-chlorophenyl pyridine derivatives as dual topoisomerase I/II inhibitors: Synthesis, biological evaluation and 3D-QSAR study.

As a continuous effort to develop novel antitumor agents, a new series of forty-five 2-phenol-4-aryl-6-chlorophenyl pyridine compounds were synthesized and evaluated for cytotoxicity against four different human cancer cell lines (DU145, HCT15, T47D, and HeLa), and topoisomerase I and II inhibitory activity. Several compounds (10-15, 20, 22, 24, 28, 42, and 49) displayed strong to moderate dual topoisomerase I and II inhibitory activity at 100 µM. It was observed that hydroxyl and chlorine moiety at meta or para position of phenyl ring is favorable for dual topoisomerase inhibitory activity and cytotoxicity. Most of the compounds displayed stronger cytotoxicities than those of all positive controls against the HCT15 and T47D cell lines. For investigation of the structure-activity relationships, a 3D-QSAR analysis using the method of comparative molecular field analysis (CoMFA) was performed. The generated 3D contour maps can be used for further rational design of novel terpyridine derivatives as highly selective and potent cytotoxic agents.

Design and synthesis of conformationally constrained hydroxylated 4-phenyl-2-aryl chromenopyridines as novel and selective topoisomerase II-targeted antiproliferative agents.

To develop novel selective topoisomerase II inhibitors, we designed and synthesized a series of conformationally constrained hydroxylated 4-phenyl-2-aryl chromenopyridines and evaluated their topoisomerase inhibitory activity and cytotoxicity against three human cancer cell lines (DU145, HCT15, and T47D) and a normal cell line (MCF10A). All of the prepared compounds displayed stronger or similar topoisomerase II inhibitory activity as well as cytotoxicity against three human cancer cell lines compared to etoposide. Compounds 10a, 10g, 11a, 11f, 11g, 12a, 12f, and 12g especially showed stronger topoisomerase II inhibitory activity as compared to etoposide at both 100 µM and 20 µM. A structure-activity relationship study revealed that hydroxyphenyl moiety at 4-position of pyridine and ortho-hydroxyphenyl or thienyl moiety at 2-position of pyridine has an important role in displaying selective topoisomerase II inhibition. The compound 12b with para-hydroxyphenyl and meta-hydroxyphenyl at 4- and 2-position of pyridine, respectively, showed the most significant cytotoxicity against all three cancer cell lines, whereas less cytotoxicity to a normal cell line as compared to adriamycin.

Modified 2,4-diaryl-5H-indeno[1,2-b]pyridines with hydroxyl and chlorine moiety: Synthesis, anticancer activity, and structure-activity relationship study.

As a part of ongoing studies in developing novel anticancer agents, a series of modified 2,4-diaryl-5H-indeno[1,2-b]pyridines were designed, and synthesized by introducing hydroxyl and chlorine moieties. They were evaluated for topoisomerase inhibitory activity and cytotoxicity against HCT15, T47D, and HeLa cancer cell lines. This modification allowed us to demonstrate structure-activity relationship (SAR) study with respect to the non-substituted 2,4-diaryl-5H-indeno[1,2-b]pyridines. Compounds (2, 3, 4, 5, 8, and 9) with meta or para hydroxyl group on 2 or 4-phenyl ring have enhanced topo I and II inhibitory activity and cytotoxicity. However, additional substitution of chlorine group on furyl or thienyl ring (11, 12, 14, 16-18) generally reduced topo I and II inhibitory activity but improved cytotoxicity. The observation of cytotoxic properties and SAR study according to the position of hydroxyl and chlorine group will provide valuable insight for further study of development of novel anticancer agents with related scaffolds.

Synthesis, topoisomerase I and II inhibitory activity, cytotoxicity, and structure-activity relationship study of 2-phenyl- or hydroxylated 2-phenyl-4-aryl-5H-indeno[1,2-b]pyridines.

A series of novel twenty-eight rigid 2-phenyl- or hydroxylated 2-phenyl-4-aryl-5H-indeno[1,2-b]pyridines were synthesized and evaluated for their topoisomerase inhibitory activity as well as their cytotoxicity against several human cancer cell lines. Generally, hydroxylated compounds (16-18, 22-25, and 29-31) containing furyl or thienyl moiety at 4-position of central pyridine exhibited strong topoisomerase I and II inhibitory activity compared to positive control, camptothecin and etoposide, respectively, in low micromolar range. Structure-activity relationship study revealed that indenopyridine compounds with hydroxyl group at 2-phenyl ring in combination with furyl or thienyl moiety at 4-position are important for topoisomerase inhibition. Compounds (22-25) which contain hydroxyl group at meta position of the 2-phenyl ring at 2-position and furanyl or thienyl substitution at 4-position of indenopyridine, showed concrete correlations between topo I and II inhibitory activity, and cytotoxicity against evaluated human cancer cell lines.

Topoisomerase I and II inhibitory activity, cytotoxicity, and structure-activity relationship study of dihydroxylated 2,6-diphenyl-4-aryl pyridines.

A new series of thirty-six dihydroxylated 2,6-diphenyl-4-aryl pyridines containing hydroxyl groups at the ortho, meta, or para position of 2- and 6-phenyl rings attached to the central pyridine were designed and synthesized. 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 with hydroxyl moiety either at the meta or para position of 2- or 6-phenyl ring in combination with thienyl or furyl group at 4-position of central pyridine displayed significant topoisomerase II inhibitory activity and cytotoxicity. Positive correlation between topoisomerase II inhibitory activity and cytotoxicity was observed for the compounds 9-11, 15-17, 19, 21-23, 28, and 41. Among all the synthesized compounds, compound 17 emerged as the most promising topoisomerase II inhibitor with significant cytotoxicity.

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).

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.