A Benzenesulfonamide-Based Mitochondrial Uncoupler Induces Endoplasmic Reticulum Stress and Immunogenic Cell Death in Epithelial Ovarian Cancer

Epithelial ovarian cancer (EOC) is the leading cause of death from gynecologic malignancies and requires new therapeutic strategies to improve clinical outcomes. EOC metastasizes in the abdominal cavity through dissemination in the peritoneal fluid and ascites, efficiently adapt to the nutrient-deprived microenvironment, and resist current chemotherapeutic agents. Accumulating evidence suggests that mitochondrial oxidative phosphorylation is critical for the adaptation of EOC cells to this otherwise hostile microenvironment. Although chemical mitochondrial uncouplers can impair mitochondrial functions and thereby target multiple, essential pathways for cancer cell proliferation, traditional mitochondria uncouplers often cause toxicity that precludes their clinical application. In this study, we demonstrated that a mitochondrial uncoupler, specifically 2,5-dichloro-N-(4-nitronaphthalen-1-yl)benzenesulfonamide, hereinafter named Y3, was an antineoplastic agent in ovarian cancer models. Y3 treatment activated AMP-activated protein kinase and resulted in the activation of endoplasmic reticulum stress sensors as well as growth inhibition and apoptosis in ovarian cancer cells in vitro Y3 was well tolerated in vivo and effectively suppressed tumor progression in three mouse models of EOC, and Y3 also induced immunogenic cell death of cancer cells that involved the release of damage-associated molecular patterns and the activation of antitumor adaptive immune responses. These findings suggest that mitochondrial uncouplers hold promise in developing new anticancer therapies that delay tumor progression and protect patients with ovarian cancer against relapse.

Potent Synergistic Effect on C-Myc-Driven Colorectal Cancers Using a Novel Indole-Substituted Quinoline with a Plk1 Inhibitor

Developing effective treatments for colorectal cancers through combinations of small-molecule approaches and immunotherapies present intriguing possibilities for managing these otherwise intractable cancers. During a broad-based, screening effort against multiple colorectal cancer cell lines, we identified indole-substituted quinolines (ISQ), such as N7,N7 -dimethyl-3-(1-methyl-1H-indol-3-yl)quinoline-2,7-diamine (ISQ-1), as potent in vitro inhibitors of several cancer cell lines. We found that ISQ-1 inhibited Wnt signaling, a main driver in the pathway governing colorectal cancer development, and ISQ-1 also activated adenosine monophosphate kinase (AMPK), a cellular energy-homeostasis master regulator. We explored the effect of ISQs on cell metabolism. Seahorse assays measuring oxygen consumption rate (OCR) indicated that ISQ-1 inhibited complex I (i.e., NADH ubiquinone oxidoreductase) in the mitochondrial, electron transport chain (ETC). In addition, ISQ-1 treatment showed remarkable synergistic depletion of oncogenic c-Myc protein level in vitro and induced strong tumor remission in vivo when administered together with BI2536, a polo-like kinase-1 (Plk1) inhibitor. These studies point toward the potential value of dual drug therapies targeting the ETC and Plk-1 for the treatment of c-Myc-driven cancers.

Amino-Substituted 3-Aryl- and 3-Heteroarylquinolines as Potential Antileishmanial Agents

Leishmaniasis, a disease caused by protozoa of the Leishmania species, afflicts roughly 12 million individuals worldwide. Most existing drugs for leishmaniasis are toxic, expensive, difficult to administer, and subject to drug resistance. We report a new class of antileishmanial leads, the 3-arylquinolines, that potently block proliferation of the intramacrophage amastigote form of Leishmania parasites with good selectivity relative to the host macrophages. Early lead 34 was rapidly acting and possessed good potency against L. mexicana (EC50 = 120 nM), 30-fold selectivity for the parasite relative to the macrophage (EC50 = 3.7 μM), and also blocked proliferation of Leishmania donovani parasites resistant to antimonial drugs. Finally, another early lead, 27, which exhibited reasonable in vivo tolerability, impaired disease progression during the dosing period in a murine model of cutaneous leishmaniasis. These results suggest that the arylquinolines provide a fruitful departure point for the development of new antileishmanial drugs.

Pictet-Spengler condensations using 4-(2-aminoethyl)coumarins

Androgen-deprivation therapy (ADT) is only a palliative measure, and prostate cancer invariably recurs in a lethal, castration-resistant form (CRPC). Prostate cancer resists ADT by metabolizing weak, adrenal androgens to growth-promoting 5α-dihydrotestosterone (DHT), the preferred ligand for the androgen receptor (AR). Developing small-molecule inhibitors for the final steps in androgen metabolic pathways that utilize 17-oxidoreductases required probes that possess fluorescent groups at C-3 and intact, naturally occurring functionality at C-17. Application of the Pictet-Spengler condensation to substituted 4-(2-aminoethyl)coumarins and 5α-androstane-3-ones furnished spirocyclic, fluorescent androgens at the desired C-3 position. Condensations required the presence of activating C-7 amino or N,N-dialkylamino groups in the 4-(2-aminoethyl)coumarin component of these condensation reactions. Successful Pictet-Spengler condensation, for example, of DHT with 9-(2-aminoethyl)-2,3,6,7-tetrahydro-1H,5H,11H-pyrano[2,3-f]pyrido[3,2,1-ij]quinolin-11-one led to a spirocyclic androgen, (3R,5S,10S,13S,17S)-17-hydroxy-10,13-dimethyl-1,2,2',3',4,5,6,7,8,8',9,9',10,11,12,12',13,13',14,15,16,17-docosahydro-7'H,11'H-spiro-[cyclopenta[a]phenanthrene-3,4'-pyrido[3,2,1-ij]pyrido[4',3':4,5]pyrano[2,3-f]quinolin]-5'(1'H)-one. Computational modeling supported the surrogacy of the C-3 fluorescent DHT analog as a tool to study 17-oxidoreductases for intracrine, androgen metabolism.

An Underlying Mechanism of Dual Wnt Inhibition and AMPK Activation: Mitochondrial Uncouplers Masquerading as Wnt Inhibitors

The importance of upregulated Wnt signaling in colorectal cancers led to efforts to develop inhibitors that target β-catenin in this pathway. We now report that several "Wnt inhibitors" that allegedly target β-catenin actually function as mitochondrial proton uncouplers that independently activate AMPK and concomitantly inhibit Wnt signaling. As expected for a process in which mitochondrial uncoupling diminishes ATP production, a mitochondrial proton uncoupler, FCCP, and a glucose metabolic inhibitor, 2-DG, activated AMPK and inhibited Wnt signaling. Also consistent with these findings, a well-known "Wnt inhibitor", FH535, functioned as a proton uncoupler, and in support of this finding, the N-methylated analog, 2,5-dichloro-N-methyl-N-(2-methyl-4-nitrophenyl)benzenesulfonamide (FH535-M), was inactive as an uncoupler and Wnt inhibitor. Apart from suggesting an opportunity to develop dual Wnt inhibitors and AMPK activators, these findings provide a cautionary tale that claims for Wnt inhibition alone require scrutiny as possible mitochondrial proton uncouplers or inhibitors of the electron transport chain.

Semisynthetic aurones inhibit tubulin polymerization at the colchicine-binding site and repress PC-3 tumor xenografts in nude mice and myc-induced T-ALL in zebrafish

Structure-activity relationships (SAR) in the aurone pharmacophore identified heterocyclic variants of the (Z)-2-benzylidene-6-hydroxybenzofuran-3(2H)-one scaffold that possessed low nanomolar in vitro potency in cell proliferation assays using various cancer cell lines, in vivo potency in prostate cancer PC-3 xenograft and zebrafish models, selectivity for the colchicine-binding site on tubulin, and absence of appreciable toxicity. Among the leading, biologically active analogs were (Z)-2-((2-((1-ethyl-5-methoxy-1H-indol-3-yl)methylene)-3-oxo-2,3-dihydrobenzofuran-6-yl)oxy)acetonitrile (5a) and (Z)-6-((2,6-dichlorobenzyl)oxy)-2-(pyridin-4-ylmethylene)benzofuran-3(2H)-one (5b) that inhibited in vitro PC-3 prostate cancer cell proliferation with IC50 values below 100 nM. A xenograft study in nude mice using 10 mg/kg of 5a had no effect on mice weight, and aurone 5a did not inhibit, as desired, the human ether-à-go-go-related (hERG) potassium channel. Cell cycle arrest data, comparisons of the inhibition of cancer cell proliferation by aurones and known antineoplastic agents, and in vitro inhibition of tubulin polymerization indicated that aurone 5a disrupted tubulin dynamics. Based on molecular docking and confirmed by liquid chromatography-electrospray ionization-tandem mass spectrometry studies, aurone 5a targets the colchicine-binding site on tubulin. In addition to solid tumors, aurones 5a and 5b strongly inhibited in vitro a panel of human leukemia cancer cell lines and the in vivo myc-induced T cell acute lymphoblastic leukemia (T-ALL) in a zebrafish model.

Phenylethynyl-substituted Heterocycles Inhibit Cyclin D1 and Induce the Expression of Cyclin-dependent Kinase Inhibitor p21Wif1/Cip1 in Colorectal Cancer Cells

Fluorinated, phenylethynyl-substituted heterocycles that possessed either an N-methylamino or N,N-dimethylamino group attached to heterocycles including pyridines, indoles, 1H-indazoles, quinolines, and isoquinolines inhibited the proliferation of LS174T colon cancer cells in which the inhibition of cyclin D1 and induction of the cyclin-dependent kinase inhibitor-1 (i.e., p21^Wif1/Cip1) served as a readout for antineoplastic activity at a cellular level. On a molecular level, these agents, particularly 4-((2,6-difluorophenyl)ethynyl)-N-methylisoquinolin-1-amine and 4-((2,6-difluorophenyl)ethynyl)-N,N-dimethylisoquinolin-1-amine, bound and inhibited the catalytic subunit of methionine S-adenosyltransferase-2 (MAT2A).

Bis(N-amidinohydrazones) and N-(amidino)-N'-aryl-bishydrazones: New classes of antibacterial/antifungal agents

The emergence of multidrug-resistant bacterial and fungal strains poses a threat to human health that requires the design and synthesis of new classes of antimicrobial agents. We evaluated bis(N-amidinohydrazones) and N-(amidino)-N'-aryl-bishydrazones for their antibacterial and antifungal activities against panels of Gram-positive/Gram-negative bacteria as well as fungi. We investigated their potential to develop resistance against both bacteria and fungi by a multi-step resistance-selection method, explored their potential to induce the production of reactive oxygen species, and assessed their toxicity. In summary, we found that these compounds exhibited broad-spectrum antibacterial and antifungal activities against most of the tested strains with minimum inhibitory concentration (MIC) values ranging from <0.5 to >500μM against bacteria and 1.0 to >31.3μg/mL against fungi; and in most cases, they exhibited either superior or similar antimicrobial activity compared to those of the standard drugs used in the clinic. We also observed minimal emergence of drug resistance to these newly synthesized compounds by bacteria and fungi even after 15 passages, and we found weak to moderate inhibition of the human Ether-à-go-go-related gene (hERG) channel with acceptable IC₅₀ values ranging from 1.12 to 3.29μM. Overall, these studies show that bis(N-amidinohydrazones) and N-(amidino)-N'-aryl-bishydrazones are potentially promising scaffolds for the discovery of novel antibacterial and antifungal agents.

N-Aryl benzenesulfonamide inhibitors of [3H]-thymidine incorporation and β-catenin signaling in human hepatocyte-derived Huh-7 carcinoma cells

Structure-activity relationships (SAR) in 2,5-dichloro-N-(2-methyl-4-nitrophenyl)benzenesulfonamide (FH535) were examined as part of a program to identify agents that inhibit the Wnt/β-catenin signaling pathway that is frequently upregulated in hepatocellular carcinoma (HCC). FH535 was reported as an inhibitor of both β-catenin in the Wnt signaling pathway and the peroxisome proliferator-activated receptor (PPAR). A β-catenin/T-cell factor (TCF)/Lymphoid-enhancer factor (LEF)-dependent assay (i.e., luciferase-based TOPFlash assay) as well as a [(3)H]-thymidine incorporation assay were used to explore SAR modifications of FH535. Although replacing the 2,5-dichlorophenylsulfonyl substituent in FH535 with a 2,6-dihalogenation pattern generally produced more biologically active analogs than FH535, other SAR modifications led only to FH535 analogs with comparable or slightly improved activity in these two assays. The absence of a clear SAR pattern in activity suggested a multiplicity of target effectors for N-aryl benzenesulfonamides.

Fluorinated N,N-dialkylaminostilbenes repress colon cancer by targeting methionine S-adenosyltransferase 2A

Methionine S-adenosyltransferase 2A (MAT2A) is the catalytic subunit for synthesis of S-adenosylmethionine (SAM), the principal methyl donor in many biological processes. MAT2A is up-regulated in many cancers, including liver cancer and colorectal cancer (CRC) and is a potentially important drug target. We developed a family of fluorinated N,N-dialkylaminostilbene agents, called FIDAS agents, that inhibit the proliferation of CRC cells in vitro and in vivo. Using a biotinylated FIDAS analogue, we identified the catalytic subunit of MAT2A as the direct and exclusive binding target of these FIDAS agents. MAT2B, an associated regulatory subunit of MAT2A, binds indirectly to FIDAS agents through its association with MAT2A. FIDAS agents inhibited MAT2A activity in SAM synthesis, and depletion of MAT2A by shRNAs inhibited CRC cell growth. A novel FIDAS agent delivered orally repressed CRC xenografts in athymic nude mice. These findings suggest that FIDAS analogues targeting MAT2A represent a family of novel and potentially useful agents for cancer treatment.

Fluorinated N,N-dialkylaminostilbenes for Wnt pathway inhibition and colon cancer repression

Colorectal cancer (CRC) is the second leading cause of cancer-related mortality in the United States. CRC is initiated by mutations of the tumor suppressor gene, adenomatous polyposis coli (APC), or β-catenin gene. These mutations stabilize β-catenin and constitutively activate Wnt/β-catenin target genes, such as c-Myc and cyclin D1, ultimately leading to cancer. Naturally occurring stilbene derivatives, resveratrol and pterostilbene, inhibit Wnt signaling and repress CRC cell proliferation but are ineffective at concentrations less than 10 μM. To understand the structure--activity relationship within these stilbene derivatives and to develop more efficacious Wnt inhibitors than these natural products, we synthesized and evaluated a panel of fluorinated N,N-dialkylaminostilbenes. Among this panel, (E)-4-(2,6-difluorostyryl)-N,N-dimethylaniline (4r) inhibits Wnt signaling at nanomolar levels and inhibits the growth of human CRC cell xenografts in athymic nude mice at a dosage of 20 mg/kg. These fluorinated N,N-dialkylaminostilbenes appear to inhibit Wnt signaling downstream of β-catenin, probably at the transcriptional level.