Potent Inhibitors Of Cancer Cell Growth Research Articles

Synthesis and Structure-Activity Relationship Studies of C(13)-Desmethylene-(-)-Zampanolide Analogs.

We describe the synthesis and biochemical and cellular profiling of five partially reduced or demethylated analogs of the marine macrolide (-)-zampanolide (ZMP). These analogs were derived from 13-desmethylene-(-)-zampanolide (DM-ZMP), which is an equally potent cancer cell growth inhibitor as ZMP. Key steps in the synthesis of all compounds were the formation of the dioxabicyclo[15.3.1]heneicosane core by an intramolecular HWE reaction (67%-95% yield) and a stereoselective aza-aldol reaction with an (S)-BINOL-derived sorbamide transfer complex, to establish the C(20) stereocenter (24%-71% yield). As the sole exception, for the 5-desmethyl macrocycle, ring-closure relied on macrolactonization; however, elaboration of the macrocyclization product into the corresponding zampanolide analog was unsuccessful. Compared to DM-ZMP, all modifications led to reduced cellular activity and lowered microtubule-binding affinity, albeit to a different extent. For compounds incorporating the reactive enone moiety of ZMP, IC50's for cancer cell growth inhibition varied between 5 nM and 133 nM, compared to 1 nM to 12 nM for DM-ZMP. Reduction of the enone double bond led to a several hundred-fold loss in growth inhibition. The cellular potency of 2,3-dihydro-13-desmethylene zampanolide, as the most potent analog identified, remained within a 9-fold range of that of DM-ZMP.

Abstract 1652: A novel reversible inhibitor of XPO1 with potent efficacy in multiple preclinical mouse models

Abstract Exportin 1 (XPO1/CRM1) is a key nuclear transport receptor (karyopherin) responsible for the export of different cargo proteins out of the cell’s nucleus into the cytoplasm. Its correct function is essential for cellular homeostasis, however normal XPO1 function is often disrupted in malignant cells. XPO1 is overexpressed in solid and hematological tumors and higher XPO1 expression is often associated with poorer prognosis. XPO1-regulated cargo proteins include tumor suppressor proteins and cell cycle regulators that can be involved in tumorigenesis. For example, aberrant XPO1 function may lead to cytoplasmic mislocalization of tumor suppressor proteins which results in their functional inactivation and hence may cause tumorigenesis. Inhibition of XPO1 function will restore their proper subcellular localization and function and cause tumor regression. Although XPO1 has a central role in cellular homeostasis, it is a good target for cancer therapy, as illustrated by the clinical success of the selective inhibitor of nuclear export (SINE) selinexor. Selinexor is the first and currently the only XPO1 inhibitor clinically approved. It is applied for the treatment of patients with multiple myeloma after at least one prior treatment, and for the treatment of diffuse large B cell lymphoma. Selinexor covalently binds to XPO1. The second generation SINE eltanexor is also a covalent XPO1 inhibitor but has only minimal brain penetration and consequently lower toxicity in preclinical studies. Here, we describe a novel chemical class of reversible XPO1 inhibitors with high brain penetration but with good tolerability allowing frequent dosing in preclinical models. The lead compound, FR-027, potently inhibits XPO1 function (EC50 69 ± 10 nM) and shows potent cancer cell growth inhibition in vitro of both hematological and solid cancer cell lines (EC50 50-950 nM). FR-027 is a reversible inhibitor of XPO1 and unlike many other XPO1 inhibitors it does not induce XPO1 protein degradation; this may contribute to an increased tolerability. Indeed, while it shows high brain penetration, FR-027 allows frequent dosing in mice with good tolerability (body weight). It is orally bioavailable and demonstrates strong anti-leukemic efficacy in an aggressive MOLT-4 xenograft model. Importantly, it shows potent efficacy in both an orthotopic U87 MG brain tumor xenograft model and a metastatic syngeneic ID8-fLuc ovarian cancer model with significant survival benefit as monotherapy. Altogether, these results demonstrate that FR-027 is a novel, reversible XPO1 inhibitor with important molecular and pharmacological characteristics that warrant further clinical development. Citation Format: Janne Van Hauwenhuyse, Felien Reniers, Leentje Persoons, Sam Noppen, Eline Boel, Els Vanstreels, Ann Vankerckhoven, Bert Kwanten, An Coosemans, Guy Van den Mooter, Wim Dehaen, Dirk Daelemans. A novel reversible inhibitor of XPO1 with potent efficacy in multiple preclinical mouse models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1652.

Visible-Light-Promoted Selenylative Spirocyclization of Indolyl-ynones toward the Formation of 3-Selenospiroindolenine Anticancer Agents.

A metal-free and efficient visible-light-induced spirocyclization of indolyl-ynones with diselenides at room temperature under air atmosphere to prepare 3-selenospiroindolenines in moderate to good yields has been developed. The resulting products were tested for in vitro anticancer activity by MTT assay, and compounds 3 c and 3 e showed potent cancer cell-growth inhibition activities.

The Clinically Used Iron Chelator Deferasirox Is an Inhibitor of Epigenetic JumonjiC Domain-Containing Histone Demethylases.

Fe(II)- and 2-oxoglutarate (2OG)-dependent JumonjiC domain-containing histone demethylases (JmjC KDMs) are "epigenetic eraser" enzymes involved in the regulation of gene expression and are emerging drug targets in oncology. We screened a set of clinically used iron chelators and report that they potently inhibit JMJD2A (KDM4A) in vitro. Mode of action investigations revealed that one compound, deferasirox, is a bona fide active site-binding inhibitor as shown by kinetic and spectroscopic studies. Synthesis of derivatives with improved cell permeability resulted in significant upregulation of histone trimethylation and potent cancer cell growth inhibition. Deferasirox was also found to inhibit human 2OG-dependent hypoxia inducible factor prolyl hydroxylase activity. Therapeutic effects of clinically used deferasirox may thus involve transcriptional regulation through 2OG oxygenase inhibition. Deferasirox might provide a useful starting point for the development of novel anticancer drugs targeting 2OG oxygenases and a valuable tool compound for investigations of KDM function.

Inhibition of SF3b1 by pladienolide B evokes cycle arrest, apoptosis induction and p73 splicing in human cervical carcinoma cells

Pladienolide B is a potent cancer cell growth inhibitor that targets the SF3b1 subunit of the spliceosome. There is considerable interest in the compound as a tool to study SF3b1 function in cancer. However, so far little information is available on the molecular mechanism of SF3b1 eliciting apoptosis in cancer cells. Here, we investigated the molecular mechanism of SF3b1 eliciting apoptosis in human cervical carcinoma cells. We demonstrated that inhibition of SF3b1 by pladienolide B inhibited proliferation of HeLa cells at low nanomolar concentrations in a dose- and time-dependent manner. It also induced G2/M phase arrest and significant rise of apoptotic cells. Moreover, it is indicated that inhibition of SF3b1 by pladienolide B induced Tap73/ΔNp73 expression and consequently down-regulated Bax/Bcl-2 ratio, cytochrome c release and caspase-3 expression. Thus, our results showed that SF3b1 plays a pivotal role in cycle arrest, apoptosis induction, and p73 splicing in human cervical carcinoma cells, suggesting that SF3b1 could be used as a potential candidate for cervical cancer therapy.

Metal-free visible-light induced cyclization/substitution cascade reaction of alkyne-tethered cyclohexadienones and diselenides: access to 5-hydroxy-3-selenyl-4a,8a-dihydro-2H-chromen-6(5H)-ones

A simple and efficient Se-radical triggered cyclization/substitution cascade reaction of alkyne-tethered cyclohexadienones to the product of 3 has been developed. The compounds 3e and 3q showed potent cancer cell-growth inhibition activities.

Copper-Catalyzed Decarboxylative/Click Cascade Reaction: Regioselective Assembly of 5-Selenotriazole Anticancer Agents.

A simple and efficient Cu-catalyzed decarboxylative/click reaction for the preparation of 1,4-disubstituted 5-arylselanyl-1,2,3-triazoles from propiolic acids, diselenides, and azides has been developed. The mechanistic study revealed that the intermolecular AAC reaction of an alkynyl selenium intermediate occurred. The resulting multisubstituted 5-seleno-1,2,3-triazoles were tested for in vitro anticancer activity by MTT assay, and compounds 4f, 4h, and 4p showed potent cancer cell-growth inhibition activities.

Antineoplastic Agents. 606. The Betulastatins.

The medicinal potential of the plant pentacyclic triterpene betulin has generated long-term interest focused on various SAR research avenues. The present approach was based on producing further analogues (chimeras) arising from a studied modification of betulin bonded to the Dov-Val-Dil-Dap unit of the powerful anticancer drug dolastatin 10, which provided betulastatins 1 (7b), 2 (11b), 3 (16b), and 4 (18b). Betulastatin 1, 2, and 4 exhibited modest levels of cancer cell growth inhibition against six cancer cell lines. Betulastatin 3 proved to be the most potent cancer cell growth inhibitor (GI50 0.01 μg/mL) and seems worthy of further development, as the presumed mixture of anticancer mechanisms of action may prove to be useful.

Indomethacin derivatives as tubulin stabilizers to inhibit cancer cell proliferation

Cyclooxygenase (COX) inhibitor Indomethacin analogs exhibited more potent cancer cell growth inhibition and apoptosis inducing activities than the parental compound. The anti-proliferative mechanism investigation of the analogs revealed that they inhibited tubulin polymerization at high concentrations whereas enhanced polymerization at low concentrations. The two opposite activities might antagonize each other and impaired the anti-proliferative activity of the derivatives eventually. In this study, we further performed lead optimization based on the structure activity relationship (SAR) generated. One of the new Indomethacin derivatives compound 11 {2-(4-(benzyloxy)phenyl)-N-(1-(4-bromobenzoyl)-3-(2-((2-(dimethylamino)ethyl)amino)-2-oxoethyl)-2-methyl-1H-indol-5-yl)acetamide} inhibited the proliferation of a panel of cancer cell lines with IC50s at the sub-micromole levels. Further study revealed that the compound only enhanced tubulin polymerization and was a tubulin stabilizer.

Synthesis of novel 5-[(1,2,3-triazol-4-yl)methyl]-1-methyl-3H-pyridazino[4,5-b]indol-4-one derivatives by click reaction and exploration of their anticancer activity

A series of pyridazino[4,5-b]indole derivatives containing alkyl-, benzyl- and phenacyl-substituted 1,2,3-triazolylmethyl units was synthesized using click chemistry approach. All 30 compounds of the series were screened in vitro against four cancer cell lines, viz. breast cancer cells MDA-MB-231 and MCF 7, human primary glioblastoma U-87 and human neuroblastoma IMR-32 cell lines. Most of the compounds exhibited potent cancer cell growth inhibition activity at very low micromolar concentrations. The IC50 value of compounds 7v and 7x against human neuroblastoma IMR-32 cell line is 0.07 and 0.04 µM, respectively. Among the tested compounds, ten compounds showed IC50 value less than 1 µM against MDA-MB-231 cells, whereas against IMR-32 cells, nine compounds and, against U-87 cells, six compounds showed similar inhibition activity. Further, these molecules exhibited prominent binding affinity and docking scores in the molecular simulation study with the target enzyme PI3 kinase. This paper illustrates the synthesis of new fused indole–pyridazinone derivatives containing substituted 1,2,3-triazoles via click chemistry approach. Most of the compounds exhibited potent cancer cell growth inhibition activity at very low micromolar concentrations.

The Cephalostatins. 23. Conversion of Hecogenin to a Steroidal 1,6-Dioxaspiro[5.5]nonane Analogue for Cephalostatin 11.

Cephalostatin 1 (1) has proved to be a remarkably potent cancer cell growth inhibitor. Since this steroidal alkaloid constituent of the marine worm Cephalodiscus gilchristi possesses a complex structure, providing preclinical supplies by total synthesis continues to be challenging. Therefore, syntheses of less complex structural modifications of this important pyrazine have also received substantial attention. Herein are summarized the synthesis of [5.5]spiroketal 5, a simplified right-side steroidal unit of 1, in seven steps from hecogenin acetate (11) with an overall yield of 4.6%. Consistent with other SAR studies, such reduction in structural complexity compared to 1 led to loss of cancer cell growth inhibitory activity against the P388 lymphocytic leukemia cell line.

Coherence between Cellular Responses and in Vitro Splicing Inhibition for the Anti-tumor Drug Pladienolide B and Its Analogs

Pladienolide B (PB) is a potent cancer cell growth inhibitor that targets the SF3B1 subunit of the spliceosome. There is considerable interest in the compound as a potential chemotherapeutic, as well as a tool to study SF3B1 function in splicing and cancer development. The molecular structure of PB, a bacterial natural product, contains a 12-member macrolide ring with an extended epoxide-containing side chain. Using a novel concise enantioselective synthesis, we created a series of PB structural analogs and the structurally related compound herboxidiene. We show that two methyl groups in the PB side chain, as well as a feature of the macrolide ring shared with herboxidiene, are required for splicing inhibition in vitro. Unexpectedly, we find that the epoxy group contributes only modestly to PB potency and is not absolutely necessary for activity. The orientations of at least two chiral centers off the macrolide ring have no effect on PB activity. Importantly, the ability of analogs to inhibit splicing in vitro directly correlated with their effects in a series of cellular assays. Those effects likely arise from inhibition of some, but not all, endogenous splicing events in cells, as previously reported for the structurally distinct SF3B1 inhibitor spliceostatin A. Together, our data support the idea that the impact of PB on cells is derived from its ability to impair the function of SF3B1 in splicing and also demonstrate that simplification of the PB scaffold is feasible.

An asymmetric synthesis of 1,2,4-trioxane anticancer agents via desymmetrization of peroxyquinols through a Brønsted acid catalysis cascade.

The desymmetrization of p-peroxyquinols using a Brønsted acid-catalyzed acetalization/oxa-Michael cascade was achieved in high yields and selectivities for a variety of aliphatic and aryl aldehydes. Mechanistic studies suggest that the reaction proceeds through a dynamic kinetic resolution of the peroxy hemiacetal intermediate. The resulting 1,2,4-trioxane products were derivatized and show potent cancer cell-growth inhibition.

Synthesis and biological evaluation of novel flavonols as potential anti-prostate cancer agents

A library of flavonol analogues was synthesised and evaluated as potential anticancer agents against a human prostate cancer cell line, 22rν1. Compounds 3, 8 and 11 (IC50 2.6, 3.3 and 4.0 μM respectively) showed potent cancer cell growth inhibition, comparable to the lead compound 3′,4′,5′-trimethoxyflavonol (1) (IC50 3.1 μM) and superior to the naturally occurring flavonols quercetin (16) and fisetin (22) (both >15 μM). Results indicate that the 3′,4′,5′- arrangement of either hydroxy (OH) or methoxy (OMe) residues is important for growth arrest of these cells and that the OMe analogues may be superior to their OH counterparts. Compounds 1, 3, 8 and 11 warrant further investigation as potential agents for the management of prostate cancer.

Microarray-Based Transcriptional Profiling of Renieramycin M and Jorunnamycin C, Isolated from Thai Marine Organisms

Renieramycin M and jorunnamycin C, two isoquinolinequinone compounds differing only at the C-22 ester side chain, were evaluated for their cytotoxic effects on human colon (HCT116) and breast (MDA-MB-435) cancer cell lines. These two compounds displayed potent cancer cell growth inhibition, their IC50 values reaching nanomolar order. To examine their effects on transcription, we carried out oligonucleotide microarray analysis with focus on the similarities and differences between the two compounds in terms of transcriptional profiles. We found that the down-regulation of PTPRK (protein tyrosine phosphatase receptor type K) can be considered as a biomarker responsive to the cytotoxic effects of this class of antitumor marine natural products.

Total Synthesis of (S)-(+)-Tylophorine Via Enantioselective Intramolecular Alkene Carboamination

The enantioselective synthesis of (S)-(+)-tylophorine, a potent cancer cell growth inhibitor, has been accomplished in eight steps from commercially available 3,4-dimethoxybenzyl alcohol. A copper (II)-catalyzed enantioselective intramolecular alkene carboamination was employed as the key step to construct the chiral indolizidine ring.

Antineoplastic agents. 443. Synthesis of the cancer cell growth inhibitor hydroxyphenstatin and its sodium diphosphate prodrug.

A structure-activity relationship (SAR) study of the South African willow tree (Combretum caffrum) antineoplastic constituent combretastatin A-4 (3b) led to the discovery of a potent cancer cell growth inhibitor designated phenstatin (5a). This benzophenone derivative of combretastatin A-4 showed remarkable antineoplastic activity, and the benzophenone derivative of combretastatin A-1 was therefore synthesized. The benzophenone, designated hydroxyphenstatin (6a), was synthesized by coupling of a protected bromobenzene and a benzaldehyde to give the benzhydrol with subsequent oxidation to the ketone. Hydroxyphenstatin was converted to the sodium phosphate prodrug (6e) by a dibenzyl phosphite phosphorylation and subsequent benzyl cleavage (6a --> 6d --> 6e). While hydroxyphenstatin (6a) was a potent inhibitor of tubulin polymerization with activity comparable to that of combretastatin A-1 (3a), the phosphorylated derivative (6e) was inactive.

Antineoplastic agents. 291. Isolation and synthesis of combretastatins A-4, A-5, and A-6(1a)

The antineoplastic constituents of Combretum caffrum (Eckl. and Zeyh) Kuntze (Combretaceae family), a species indigenous to South Africa, have been investigated. Subsequently we isolated a series of closely related bibenzyls, stilbenes, and phenanthrenes from C. caffrum. Some of the stilbenes proved to be potent antimitotic agents which inhibited both tubulin polymerization and the binding of colchicine to tubulin. Combretastatin A-4 has been shown to be the most potent cancer cell growth inhibitor of the series. Presently this cis-stilbene is the most effective inhibitor of colchicine binding to tubulin and the simplest natural product yet described with such potent antitubulin effects. Combretastatin A-4, A-5, and A-6 were also found to inhibit growth of Neisseria gonorrhoeae. Details of the isolation and syntheses of combretastatins A-4 (2a), A-5 (2c), and A-6 (3a) have been described.