DNA damage and cell cycle arrest induced by 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203, NSC 703786) is attenuated in aryl hydrocarbon receptor deficient MCF-7 cells

Oxindole-benzothiazole hybrids as CDK2 inhibitors and anticancer agents: design, synthesis and biological evaluation

In the current study, molecular hybridization between the oxindole core and benzothiazole system through an acetohydrazide moiety was accomplished for the design of a new series of oxindole-benzothiazole hybrids 9a-r targeting CDK2 for cancer therapy. The afforded hybrids displayed promising growth inhibitory activity on NCI cancer cell lines at 10 µM. Compound 9o displayed mean GI% = 55.91%. Based on the potent activity of 9o, it was further assessed for its cytotoxic activity at five dose level and it demonstrated GI50 reaching 2.02 µM. Analysis of the cell cycle of the prostate cancer cell line DU145 after treatment with 9o confirmed its ability to arrest its cell cycle at the G1 phase. Moreover, 9o proved its ability to potentiate the apoptosis and necrosis of the same cell line. Furthermore, the oxindole-benzothiazole hybrids 9b, 9f and 9o showed IC50 = 0.70, 0.20 and 0.21 µM, respectively on CDK2. Besides, molecular docking simulation of the synthesized oxindole-benzothiazole hybrid 9o proved the expected binding mode which involves the accommodation of the oxindole moiety in the ATP binding pocket where it is involved in hydrogen bonding and hydrophobic interactions with the essential amino acids in the hinge region while the benzothiazole moiety is oriented toward the solvent region. Investigation of the physicochemical properties of the hybrids 9a-r highlights their acceptable ADME properties that can be somewhat developed for the discovery of new anticancer agents.

Synthesis, cytotoxicity and 99mTc-MIBI tumor cell uptake evaluation of 2-phenylbenzothiazole tagged triazole derivatives

Aim: The extensive utilization of 2-phenylbenzothiazole due to their wide array of biological activities, particularly in cancer therapy, has caused great attention to explore more potent derivatives.Materials & methods: We report the synthesis of 2-phenylbenzothiazole tagged 1,2,3-triaozle (8) through Cu(I)-catalyzed cycloaddition of alkyne side chain with aryl-substituted azides.Results: The in vitro experiments, using MTT and 99mTc-MIBI cell uptake methods, demonstrated the remarkable anticancer activity of these compounds against A549, SKOV3 and MCF7 cell lines.Conclusion: Compounds 8b, 8f and 8i possessed high cytotoxic activity as compared with doxorubicin. Compound 8g has a similar inhibitory effect on the proliferation of breast cancer cells as doxorubicin. In silico study indicated that compound 8 would be a good lead for the development of new potent anticancer agents.

An epigenetic memory at the CYP1A gene in cancer-resistant, pollution-adapted killifish

Human exposure to polycyclic aromatic hydrocarbons (PAH) is a significant and growing public health problem. Frequent, high dose exposures are likely to increase due to a warming climate and increased frequency of large-scale wildfires. Here, we characterize an epigenetic memory at the cytochrome P450 1A (CYP1A) gene in a population of wild Fundulus heteroclitus that has adapted to chronic, extreme PAH pollution. In wild-type fish, CYP1A is highly induced by PAH. In PAH-tolerant fish, CYP1A induction is blunted. Since CYP1A metabolically activates PAH, this memory protects these fish from PAH-mediated cancer. However, PAH-tolerant fish reared in clean water recover CYP1A inducibility, indicating that blunted induction is a non-genetic memory of prior exposure. To explore this possibility, we bred depurated wild fish from PAH-sensitive and - tolerant populations, manually fertilized exposure-naïve embryos, and challenged them with PAH. We observed epigenetic control of the reversible memory of generational PAH stress in F1 PAH-tolerant embryos. Specifically, we observed a bivalent domain in the CYP1A promoter enhancer comprising both activating and repressive histone post-translational modifications. Activating modifications, relative to repressive ones, showed greater increases in response to PAH in sensitive embryos, relative to tolerant, consistent with greater gene activation. Also, PAH-tolerant adult fish showed persistent induction of CYP1A long after exposure cessation, which is consistent with defective CYP1A shutoff and recovery to baseline. Since CYP1A expression is inversely correlated with cancer risk, these results indicate that PAH-tolerant fish have epigenetic protection against PAH-induced cancer in early life that degrades in response to continuous gene activation.

Repurposing screen identifies novel candidates for broad-spectrum coronavirus antivirals and druggable host targets

Libraries composed of licensed drugs represent a vast repertoire of molecules modulating physiological processes in humans, providing unique opportunities for the discovery of host-targeting antivirals. We screened the Repurposing, Focused Rescue, and Accelerated Medchem (ReFRAME) repurposing library with approximately 12,000 molecules for broad-spectrum coronavirus antivirals and discovered 134 compounds inhibiting an alphacoronavirus and mapping to 58 molecular target categories. Dominant targets included the 5-hydroxytryptamine receptor, the dopamine receptor, and cyclin-dependent kinases. Gene knock-out of the drugs' host targets including cathepsin B and L (CTSB/L; VBY-825), the aryl hydrocarbon receptor (AHR; Phortress), the farnesyl-diphosphate farnesyltransferase 1 (FDFT1; P-3622), and the kelch-like ECH-associated protein 1 (KEAP1; Omaveloxolone), significantly modulated HCoV-229E infection, providing evidence that these compounds inhibited the virus through acting on their respective host targets. Counter-screening of all 134 primary compound candidates with SARS-CoV-2 and validation in primary cells identified Phortress, an AHR activating ligand, P-3622-targeting FDFT1, and Omaveloxolone, which activates the NFE2-like bZIP transcription factor 2 (NFE2L2) by liberating it from its endogenous inhibitor KEAP1, as antiviral candidates for both an Alpha- and a Betacoronavirus. This study provides an overview of HCoV-229E repurposing candidates and reveals novel potentially druggable viral host dependency factors hijacked by diverse coronaviruses.

Triumphs and challenges in exploiting poly(ADP-ribose) polymerase inhibition to combat triple-negative breast cancer

Poly(ADP-ribose) polymerase 1 (PARP1) regulates a myriad of DNA repair mechanisms to preserve genomic integrity following DNA damage. PARP inhibitors (PARPi) confer synthetic lethality in malignancies with a deficiency in the homologous recombination (HR) pathway. Patients with triple-negative breast cancer (TNBC) fail to respond to most targeted therapies because their tumors lack expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Certain patients with TNBC harbor mutations in HR mediators such as breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2), enabling them to respond to PARPi. PARPi exploits the synthetic lethality of BRCA-mutant cells. However, de novo and acquired PARPi resistance frequently ensue. In this review, we discuss the roles of PARP in mediating DNA repair processes in breast epithelial cells, mechanisms of PARPi resistance in TNBC, and recent advances in the development of agents designed to overcome PARPi resistance in TNBC.

The Role of the Aryl Hydrocarbon Receptor (AhR) and Its Ligands in Breast Cancer

Breast cancer is a complex disease which is defined by numerous cellular and molecular markers that can be used to develop more targeted and successful therapies. The aryl hydrocarbon receptor (AhR) is overexpressed in many breast tumor sub-types, including estrogen receptor -positive (ER+) tumors; however, the prognostic value of the AhR for breast cancer patient survival is not consistent between studies. Moreover, the functional role of the AhR in various breast cancer cell lines is also variable and exhibits both tumor promoter- and tumor suppressor- like activity and the AhR is expressed in both ER-positive and ER-negative cells/tumors. There is strong evidence demonstrating inhibitory AhR-Rα crosstalk where various AhR ligands induce ER degradation. It has also been reported that different structural classes of AhR ligands, including halogenated aromatics, polynuclear aromatics, synthetic drugs and other pharmaceuticals, health promoting phytochemical-derived natural products and endogenous AhR-active compounds inhibit one or more of breast cancer cell proliferation, survival, migration/invasion, and metastasis. AhR-dependent mechanisms for the inhibition of breast cancer by AhR agonists are variable and include the downregulation of multiple genes/gene products such as CXCR4, MMPs, CXCL12, SOX4 and the modulation of microRNA levels. Some AhR ligands, such as aminoflavone, have been investigated in clinical trials for their anticancer activity against breast cancer. In contrast, several publications have reported that AhR agonists and antagonists enhance and inhibit mammary carcinogenesis, respectively, and differences between the anticancer activities of AhR agonists in breast cancer may be due in part to cell context and ligand structure. However, there are reports showing that the same AhR ligand in the same breast cancer cell line gives opposite results. These differences need to be resolved in order to further develop and take advantage of promising agents that inhibit mammary carcinogenesis by targeting the AhR.

Aryl Hydrocarbon Receptor: From Homeostasis to Tumor Progression

Transcription factor aryl hydrocarbon receptor (AHR) has emerged as one of the main regulators involved both in different homeostatic cell functions and tumor progression. Being a member of the family of basic-helix-loop-helix (bHLH) transcriptional regulators, this intracellular receptor has become a key member in differentiation, pluripotency, chromatin dynamics and cell reprogramming processes, with plenty of new targets identified in the last decade. Besides this role in tissue homeostasis, one enthralling feature of AHR is its capacity of acting as an oncogene or tumor suppressor depending on the specific organ, tissue and cell type. Together with its well-known modulation of cell adhesion and migration in a cell-type specific manner in epithelial-mesenchymal transition (EMT), this duality has also contributed to the arise of its clinical interest, highlighting a new potential as therapeutic tool, diagnosis and prognosis marker. Therefore, a deregulation of AHR-controlled pathways may have a causal role in contributing to physiological and homeostatic failures, tumor progression and dissemination. With that firmly in mind, this review will address the remarkable capability of AHR to exert a different function influenced by the phenotype of the target cell and its potential consequences.

Amino alcohol acrylonitriles as broad spectrum and tumour selective cytotoxic agents

We have identified specific dichlorophenylacrylonitriles as lead compounds in the development of novel anticancer compounds, notably, (Z)-N-(4-(2-cyano-2-(3,4-dichlorophenyl)vinyl)phenyl)acetamide (1) and ANI-7 (2). Herein we specifically probe the SAR associated with the terminal aromatic ring and associated cytoxicity in a broad range of human cancer cell lines. Synthesis of three focused libraries revealed a poor tolerance for electron withdrawing and donating moieties (Library A). A clear preference for hydrophobic substituents on a terminal piperazine moiety (Library B) with good levels of broad spectrum cytotoxicity, e.g. 13a (GI50 2.5-6.0 μM), as did the introduction of a methylene spacer with 13i (4-CH3PhCH2; GI50 1.5-4.5 μM). Removal of the aromatic moiety and installation of simple hydrophobic groups (Library C), in particular an adamantyl moiety, afforded highly active broad spectrum cytotoxic agents with GI50 values ranging from 1.7 μM (14k; 1-adamantyl) to 5.6 μM (14i; pyrrolidine). Within these libraries we note lung cancer selectivity, relative to normal cells, of 13h (fluoro substituted acrylonitrile, GI50 1.6 μM, 9.3-fold selective); the colorectal selectivity of 14h (methylpiperidine analogue, GI50 0.36 μM, 6.9-fold selective) and the breast cancer selectivity of 13f (nitrile substituted acrylonitrile, GI50 2.3-6.0 μM, up to 20-fold selective). The latter was confirmed as a novel AhR ligand and a CYP1A1 activating compound, that likely induces cell death following bioactivation; a phenomenon previously described in breast cancer cell populations.

Molecular modeling approaches to address drug-metabolizing enzymes (DMEs) mediated chemoresistance: a review

Resistance against clinically approved anticancer drugs is the main roadblock in cancer treatment. Drug metabolizing enzymes (DMEs) that are capable of metabolizing a variety of xenobiotic get overexpressed in malignant cells, therefore, catalyzing drug inactivation. As evident from the literature reports, the levels of DMEs increase in cancer cells that ultimately lead to drug inactivation followed by drug resistance. To puzzle out this issue, several strategies inclusive of analog designing, prodrug designing, and inhibitor designing have been forged. On that front, the implementation of computational tools can be considered a fascinating approach to address the problem of chemoresistance. Various research groups have adopted different molecular modeling tools for the investigation of DMEs mediated toxicity problems. However, the utilization of these in-silico tools in maneuvering the DME mediated chemoresistance is least considered and yet to be explored. These tools can be employed in the designing of such chemotherapeutic agents that are devoid of the resistance problem. The current review canvasses various molecular modeling approaches that can be implemented to address this issue. Special focus was laid on the development of specific inhibitors of DMEs. Additionally, the strategies to bypass the DMEs mediated drug metabolism were also contemplated in this report that includes analogs and pro-drugs designing. Different strategies discussed in the review will be beneficial in designing novel chemotherapeutic agents that depreciate the resistance problem.

Synthesis of some new benzoxazole derivatives and investigation of their anticancer activities

Phortress is an anticancer prodrug, which has active metabolite (5F-203) being potent agonist of the aryl hydrocarbon receptor (AhR). The 5F-203 switches on cytochrome P450 CYP1A1 gene expression and thus exhibits anticancer activity. In this study, it is aimed to obtain new phortress analogues by bioisosteric replacement of benzothiazole core in the structure to benzoxazole ring system. Synthesis of compounds (3a-3p) were performed according to literature methods. Their structures were elucidated by IR, ¹H NMR, ¹³C NMR, 2D-NMR and HRMS spectroscopic methods. Cytotoxicity (MTT), inhibition of DNA synthesis and flow cytometric analysis assays were applied to determine anticancer activity of the compounds on colon (HT-29), breast (MCF7), lung (A549), liver (HepG2) and brain (C6) carcinoma cell types. When compared reference agent doxorubicin, compounds 3m and 3n displayed very attractive anticancer effect against carcinogenic cell lines. Due to structural similarity to phortress, biotransformation studies for 3m and 3n were examined by LCMS-IT-TOF system and probable metabolites of these compounds were determined. Induction potential of these compounds on CYP1A1/2 enzymes was also investigated to clarify possible mechanism of action. Interaction modes between CYP1A1 enzyme and compound 3n or its some metabolites were investigated by docking studies. In conclusion, findings of these study indicate that compounds 3m and 3n possess significant anticancer activity, probably with the same mechanism of action to Phortress.

Design, synthesis and evaluation of benzothiazole derivatives as multifunctional agents

Oxidative stress is the product or aetiology of various multifactorial diseases; on the other hand, the development of multifunctional compounds is a recognized strategy for the control of complex diseases. To this end, a series of benzothiazole derivatives was synthesized and evaluated for their multifunctional effectiveness as antioxidant, sunscreen (filter), antifungal and antiproliferative agents. Compounds were easily synthesized via condensation reaction between 2-aminothiophenols and different benzaldehydes. SAR study, particularly in position 2 and 6 of benzothiazoles, led to the identification of 4g and 4k as very interesting potential compounds for the design of multifunctional drugs. In particular, compound 4g is the best blocker of hERG potassium channels expressed in HEK 293 cells exhibiting 60.32% inhibition with IC₅₀ = 4.79 μM.

POCl3 Mediated Syntheses, Pharmacological Evaluation and Molecular Docking Studies of Some Novel Benzofused Thiazole Derivatives as a Potential Antioxidant and Anti-inflammatory Agents

Background:

The present research work is focused on the development of alternative antioxidant and anti-inflammatory agents. The review of the literature reveals that many benzofused thiazole analogues have been used as lead molecules for the design and development of therapeutic agent, including anticancer, anti-inflammatory, antioxidant and antiviral. The synthesized benzofused thiazole derivatives are evaluated for in vitro antioxidant, anti-inflammatory activities and molecular docking study. Thus, the present research work aims to synthesize benzofused thiazole derivatives and to test their antioxidant and antiinflammatory activities.

Objective:

To design and synthesize an alternative antioxidant and anti-inflammatory agents.

Methods:

The substituted benzofused thiazoles 3a-g were prepared by cyclocondensation reaction of appropriate carboxylic acid with 2-aminothiophenol in POCl3 and heated for about 2-3 h to offer benzofused thiazole derivatives 3a-g. All the newly synthesized compounds were in vitro screened for their anti-inflammatory and antioxidant activities by using a known literature method.

Results:

At the outset, the study of in vitro indicated that the compounds code 3c, 3d and 3e possessed distinct anti-inflammatory activity as compared to a standard reference. All the tested compounds show potential antioxidant activity against one or more reactive (H2O2, DPPH, SO and NO) radical scavenging species. Additionally, docking simulation is further performed to the position of compounds 3d & 3e into the anti-inflammatory active site to determine the probable binding model.

Conclusion:

New anti-inflammatory and antioxidant agents were needed; it has been proved that benzofused thiazole derivatives were 3c, 3d and 3e constituted as an interesting template for the evaluation of new anti-inflammatory agents and an antioxidant’s work also may provide an interesting template for further development.

Amino Alcohol Acrylonitriles as Activators of the Aryl Hydrocarbon Receptor Pathway: An Unexpected MTT Phenotypic Screening Outcome

Lead (Z)-N-(4-(2-cyano-2-(3,4-dichlorophenyl)vinyl)phenyl)acetamide, 1 showed MCF-7 GI₅₀ =30 nM and 400-fold selective c.f. MCF10A (normal breast tissue). Acetamide moiety modification (13 a-g) to introduce additional hydrophobicity was favoured with MCF-7 breast cancer cell activity enhanced at 1.3 nM. Other analogues were potent against the HT29 colon cancer cell line at 23 nM. Textbook SAR data was observed in the MCF-7 cell line, in an MTT assay, via the ortho (17 a), meta (17 b) and para (13 f). The amino alcohol -OH moiety was pivotal, but no stereochemical preference noted. But, these data did not fit our homology modelling expectations. Aberrant MTT ((3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) screening results and metabolic interference confirmed by sulforhodamine B (SRB) screening. Interfering analogues resulted in 120 and 80-fold CYP1A1 and CYP1A2 amplification, with no upregulation of SULT1A1. This is consistent with activation of the AhR pathway. Piperidine per-deuteration reduced metabolic inactivation. 3-OH / 4-OH piperidine analogues showed differential MTT and SRB activity supporting MTT assay metabolic inactivation. Data supports piperidine 3-OH, but not the 4-OH, as a CYP substrate. This family of β-amino alcohol substituted 3,4-dichlorophenylacetonitriles show broad activity modulated via the AhR pathway. By SRB analysis the most potent analogue was 23 b, (Z)-3-(4-(3-(4-phenylpiperidin-1-yl)-2-hydroxypropoxy)phenyl)-2-(3,4-dichlorophenyl)-acrylonitrile.

Design, synthesis, and molecular docking of novel 2-arylbenzothiazole multiangiokinase inhibitors targeting breast cancer

A novel series of 2-arylbenzothiazoles 9, 10, and 12 were designed and synthesized as VEGFR-2/FGFR-1/PDGFR-β multiangiokinase inhibitors targeting breast cancer. Structural elongation of the known 2-phenylbenzothiazole scaffold (type I protein kinase inhibitor [PKI]), was carried out to afford series of type II PKIs 9, 10, and 12. Compounds 9d, 9f, 9i, and 9k exhibited potent multikinase inhibitory activity with IC₅₀ values of 0.19, 0.18, 0.17, and 0.13 μM, respectively, against VEGFR-2; IC₅₀ values of 0.28, 0.37, 0.19, and 0.27 μM, respectively, against FGFR-1; and IC₅₀ values of 0.07, 0.04, 0.08, and 0.14 μM, respectively, against PDGFR-β. Moreover, the synthesized benzothiazoles demonstrated promising cytotoxic activity against the MCF-7 cell line. The most potent benzothiazoles 9d and 9i exhibited IC₅₀ values of 7.83 and 6.58 μM, respectively, on the MCF-7 cell line in comparison to sorafenib (III), which showed IC₅₀  = 4.33 μM. Additionally, 9d and 9i showed VEGFR-2 inhibitory activity in MCF-7 cells of 81% and 83% when compared with sorafenib (III), which showed 88% inhibition. Molecular docking of the designed compounds in the VEGFR-2 and FGFR-1 active sites showed the accommodation of the 2-phenylbenzothiazole moiety, as reported, in the hinge region of the receptor tyrosine kinase (RTK)-binding site, while the amide moiety is involved in hydrogen bond interactions with the key amino acids in the gate area; this in turn directs the aryl group to the hydrophobic allosteric back pocket of the RTKs in a type II-like binding mode. The synthesized benzothiazoles showed satisfactory ADME properties for further optimization in drug discovery.

The aryl hydrocarbon receptor (AhR) as a breast cancer drug target

Breast cancer is the most common cancer in women, with more than 1.7 million diagnoses worldwide per annum. Metastatic breast cancer remains incurable, and the presence of triple-negative phenotypes makes targeted treatment impossible. The aryl hydrocarbon receptor (AhR), most commonly associated with the metabolism of xenobiotic ligands, has emerged as a promising biological target for the treatment of this deadly disease. Ligands for the AhR can be classed as exogenous or endogenous and may have agonistic or antagonistic activity. It has been well reported that agonistic ligands may have potent and selective growth inhibition activity in a number of oncogenic cell lines, and one (aminoflavone) has progressed to phase I clinical trials for breast cancer sufferers. In this study, we examine the current state of the literature in this area and elucidate the promising advances that are being made in hijacking the cytosolic-to-nuclear pathway of the AhR for the possible future treatment of breast cancer.

Putative tumor suppressor cytoglobin promotes aryl hydrocarbon receptor ligand-mediated triple negative breast cancer cell death

Nearly 40 000 women die annually from breast cancer in the United States. Clinically available targeted breast cancer therapy is largely ineffective in triple negative breast cancer (TNBC), characterized by tumors that lack expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (Her2). TNBC is associated with a poor prognosis. Previous reports show that aryl hydrocarbon receptor (AhR) partial agonist 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203) selectively inhibits the growth of breast cancer cells, including those of the TNBC subtype. We previously demonstrated that 5F 203 induced the expression of putative tumor suppressor gene cytoglobin (CYGB) in breast cancer cells. In the current study, we determined that 5F 203 induces apoptosis and caspase-3 activation in MDA-MB-468 TNBC cells and in T47D ER+ PR + Her2 - breast cancer cells. We also show that caspases and CYGB promote 5F 203-mediated apoptosis in MDA-MB-468 cells. 5F 203 induced lysosomal membrane permeabilization (LMP) and cathepsin B release in MDA-MB-468 and T47D cells. In addition, silencing CYGB attenuated the ability of 5F 203 to induce caspase-3/-7 activation, proapoptotic gene expression, LMP, and cathepsin B release in MDA-MB-468 cells. Moreover, 5F 203 induced CYGB protein expression, proapoptotic protein expression, and caspase-3 cleavage in MDA-MB-468 cells and in MDA-MB-468 xenograft tumors grown orthotopically in athymic mice. These data provide a basis for the development of AhR ligands with the potential to restore CYGB expression as a novel strategy to treat TNBC.

Iodine mediated oxidative cross-coupling of unprotected anilines and heteroarylation of benzothiazoles with 2-methylquinoline

Iodine-promoted oxidative C-H/C-H cross-coupling of unprotected anilines and 2-methylquinoline to furnish C4-carbonylated aniline (4-aminophenyl)(quinoline-2-yl) methanones in moderate to good yields has been demonstrated. This work provides the first site-selective approach for the synthesis of free amino groups containing methanones including unprecedented C-H functionalization rather than the N-H functionalization of unprotected anilines via the Kornblum oxidation of 2-methylquinoline. Furthermore, we noticed that the incorporation of KOH under standard conditions provides 2-heteroarylbenzothiazoles from benzothiazoles and 2-methylquinoline in good to excellent yields. These transformations do not require any transition metals or peroxides and tolerate various functional groups such as methoxy, hydroxy, bromo, chloro and nitro groups. Moreover, a plausible mechanistic pathway is proposed.

Furanoflavones pongapin and lanceolatin B blocks the cell cycle and induce senescence in CYP1A1-overexpressing breast cancer cells

Expression of cytochrome P450-1A1 (CYP1A1) is suppressed under physiologic conditions but is induced (a) by polycyclic aromatic hydrocarbons (PAHs) which can be metabolized by CYP1A1 to carcinogens, and (b) in majority of breast cancers. Hence, phytochemicals or dietary flavonoids, if identified as CYP1A1 inhibitors, may help in preventing PAH-mediated carcinogenesis and breast cancer. Herein, we have investigated the cancer chemopreventive potential of a flavonoid-rich Indian medicinal plant, Pongamia pinnata (L.) Pierre. Methanolic extract of its seeds inhibits CYP1A1 in CYP1A1-overexpressing normal human HEK293 cells, with IC₅₀ of 0.6 µg/mL. Its secondary metabolites, the furanoflavonoids pongapin/lanceolatin B, inhibit CYP1A1 with IC₅₀ of 20 nM. Although the furanochalcone pongamol inhibits CYP1A1 with IC₅₀ of only 4.4 µM, a semisynthetic pyrazole-derivative P5b, has ∼10-fold improved potency (IC₅₀, 0.49 μM). Pongapin/lanceolatin B and the methanolic extract of P. pinnata seeds protect CYP1A1-overexpressing HEK293 cells from B[a]P-mediated toxicity. Remarkably, they also block the cell cycle of CYP1A1-overexpressing MCF-7 breast cancer cells, at the G₀-G₁ phase, repress cyclin D1 levels and induce cellular-senescence. Molecular modeling studies demonstrate the interaction pattern of pongapin/lanceolatin B with CYP1A1. The results strongly indicate the potential of methanolic seed-extract and pongapin/lanceolatin B for further development as cancer chemopreventive agents.

Benzothiazole analogs as potential anti-TB agents: computational input and molecular dynamics

Biotin is very important for the survival of Mycobacterium tuberculosis. 7,8-Diamino pelargonic acid aminotransaminase (DAPA) is a transaminase enzyme involved in the biosynthesis of biotin. The benzothiazole title compounds were investigated for their in vitro anti-tubercular activity against two tubercular strains: H37Rv (ATCC 25,177) and MDR-MTB (multidrug-resistant M. tuberculosis, resistant to isoniazid, rifampicin, and ethambutol) by an agar incorporation method. The possible binding mode and predicted affinity were computed using a molecular docking study. Among the synthesized compounds in the series, the title compound {2-(benzo[d]thiazol-2-yl-methoxy)-5-fluorophenyl}-(4-chlorophenyl)-methanone was found to exhibit significant activity with minimum inhibitory concentrations of 1 μg/mL and 2 μg/mL against H37Rv and MDR-MTB, respectively; this compound showed the highest binding affinity (-24.75 kcal/mol) as well.

Modulation of CYP1A1 metabolism: From adverse health effects to chemoprevention and therapeutic options

The human cytochrome P450 (CYP) 1A1 gene encodes a monooxygenase that metabolizes multiple exogenous and endogenous substrates. CYP1A1 has become infamous for its oxidative metabolism of benzo[a]pyrene and related polycyclic aromatic hydrocarbons, converting these chemicals into very potent human carcinogens. CYP1A1 expression is mainly controlled by the aryl hydrocarbon receptor (AHR), a transcription factor whose activation is induced by binding of persistent organic pollutants, including polycyclic aromatic hydrocarbons and dioxins. Accordingly, induction of CYP1A1 expression and activity serves as a biomarker of AHR activation and associated xenobiotic metabolism as well as toxicity in diverse animal species and humans. Determination of CYP1A1 activity is integrated into modern toxicological concepts and testing guidelines, emphasizing the tremendous importance of this enzyme for risk assessment and regulation of chemicals. Further, CYP1A1 serves as a molecular target for chemoprevention of chemical carcinogenesis, although present literature is controversial on whether its inhibition or induction exerts beneficial effects. Regarding therapeutic applications, first anti-cancer prodrugs are available, which require a metabolic activation by CYP1A1, and thus enable a specific elimination of CYP1A1-positive tumors. However, the application range of these drugs may be limited due to the frequently observed downregulation of CYP1A1 in various human cancers, probably leading to a reduced metabolism of endogenous AHR ligands and a sustained activation of AHR and associated tumor-promoting responses. We here summarize the current knowledge on CYP1A1 as a key player in the metabolism of exogenous and endogenous substrates and as a promising target molecule for prevention and treatment of human malignancies.

MALDI imaging reveals NCOA7 as a potential biomarker in oral squamous cell carcinoma arising from oral submucous fibrosis

Oral squamous cell carcinoma (OSCC) ranks among the most common cancer worldwide, and is associated with severe morbidity and high mortality. Oral submucous fibrosis (OSF), characterized by fibrosis of the mucosa of the upper digestive tract, is a pre-malignant lesion, but the molecular mechanisms underlying this malignant transformation remains to be elucidated. In this study, matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS)-based proteomic strategy was employed to profile the differentially expressed peptides/proteins between OSCC tissues and the corresponding adjacent non-cancerous OSF tissues. Sixty-five unique peptide peaks and nine proteins were identified with altered expression levels. Of them, expression of NCOA7 was found to be up-regulated in OSCC tissues by immunohistochemistry staining and western blotting, and correlated with a pan of clinicopathologic parameters, including lesion site, tumor differentiation status and lymph node metastasis. Further, we show that overexpression of NCOA7 promotes OSCC cell proliferation in either in vitro or in vivo models. Mechanistic study demonstrates that NCOA7 induces OSCC cell proliferation probably by activating aryl hydrocarbon receptor (AHR). The present study suggests that NCOA7 is a potential biomarker for early diagnosis of OSF malignant transformation, and leads to a better understanding of the molecular mechanisms responsible for OSCC development.

Synthesis and biological evaluation of triazole and isoxazole-tagged benzothiazole/benzoxazole derivatives as potent cytotoxic agents

Cancer is a major health problem and the most upsetting disease in humans, leading to death in both developed and developing countries.

(Z)-2-(3,4-Dichlorophenyl)-3-(1H-Pyrrol-2-yl)Acrylonitrile Exhibits Selective Antitumor Activity in Breast Cancer Cell Lines via the Aryl Hydrocarbon Receptor Pathway

We have previously reported the synthesis and breast cancer selectivity of (Z)-2-(3,4-dichlorophenyl)-3-(1H-pyrrol-2-yl)acrylonitrile (ANI-7) in cancer cell lines. To further evaluate the selectivity of ANI-7, we have expanded upon the initial cell line panel to now include the breast cancer cell lines (MCF7, MCF7/VP16, BT474, T47D, ZR-75-1, SKBR3, MDA-MB-468, BT20, MDA-MB-231); normal breast cells (MCF-10A); and cell lines derived from colon (HT29), ovarian (A2780), lung (H460), skin (A431), neuronal (BE2C), glial (U87, SJG2), and pancreatic (MIA) cancers. We now show that ANI-7 is up to 263-fold more potent at inhibiting the growth of breast cancer cell lines (MCF7, MCF7/VP16, BT474, T47D, ZR-75-1, SKBR3, MDA-MB-468) than normal breast cells (MCF-10A) or cell lines derived from other tumor types. Measures of growth inhibition, cell cycle analysis, morphologic assessment, Western blotting, receptor binding, gene expression, small interfering RNA technology, reporter activity, and enzyme inhibition assays were exploited to define the mechanism of action of ANI-7. In this work, we report that ANI-7 mediates its effects via the activation of the aryl hydrocarbon receptor (AhR) pathway and the subsequent induction of CYP1-metabolizing mono-oxygenases. The metabolic conversion of ANI-7 induces DNA damage, checkpoint activation, S-phase cell cycle arrest, and cell death in sensitive breast cancer cell lines. Basal expression of AhR, the AhR nuclear translocator, and the CYP1 family members do not predict for sensitivity; however, inherent expression of the phase II-metabolizing enzyme sulfur transferase 1A1 does. For the first time, we identify (Z)-2-(3,4-dichlorophenyl)-3-(1H-pyrrol-2-yl)acrylonitrile as a new AhR ligand.

In Vitro Antitumor Effects of AHR Ligands Aminoflavone (AFP 464) and Benzothiazole (5F 203) in Human Renal Carcinoma Cells

We investigated activity and mechanism of action of two AhR ligand antitumor agents, AFP 464 and 5F 203 on human renal cancer cells, specifically examining their effects on cell cycle progression, apoptosis, and migration. TK-10, SN12C, Caki-1, and ACHN human renal cancer cell lines were treated with AFP 464 and 5F 203. We evaluated cytotoxicity by MTS assays, cell cycle arrest, and apoptosis by flow cytometry and corroborated a mechanism of action involving AhR signal transduction activation. Changes in migration properties by wound healing assays were investigated: 5F 203-sensitive cells show decreased migration after treatment, therefore, we measured c-Met phosphorylation by Western blot in these cells. A 5F 203 induced a decrease in cell viability which was more marked than AFP 464. This cytotoxicity was reduced after treatment with the AhR inhibitor α-NF for both compounds indicating AhR signaling activation plays a role in the mechanism of action. A 5F 203 is sequestered by TK-10 cells and induces CYP1A1 expression; 5F 203 potently inhibited migration of TK-10, Caki-1, and SN12C cells, and inhibited c-Met receptor phosphorylation in TK-10 cells. AhR ligand antitumor agents AFP 464 and 5F 203 represent potential new candidates for the treatment of renal cancer. A 5F 203 only inhibited migration of sensitive cells and c-Met receptor phosphorylation in TK-10 cells. c-Met receptor signal transduction is important in migration and metastasis. Therefore, we consider that 5F 203 offers potential for the treatment of metastatic renal carcinoma. J. Cell. Biochem. 118: 4526-4535, 2017. © 2017 Wiley Periodicals, Inc.

Identification of leads for antiproliferative activity on MDA-MB-435 human breast cancer cells through pharmacophore and CYP1A1-mediated metabolism

CYP1A1 is a potential target for anticancer drug development due to its overexpression in certain cancer cells and role in cancer progression. To identify new leads for CYP1A1 mediated anticancer action, we attempted ligand based pharmacophore mapping, virtual screening of databases, molecular docking, MetaSite based filtering, and molecular dynamics simulations. Initial computational and in vitro screening identified 11 compounds from which we identified two lead compounds, ZINC33468944 and ZINC32101539, showed potential antitumor activity on MDA-MB-435 cell lines (GI50 < 0.1 μM) and CYP1A1 inhibition of 0.13 and 0.3 μM, respectively. Furthermore, the lead compounds were evaluated for CYP1A1 mediated metabolism, showing N-hydroxylated metabolites, which have potential of DNA adduct formation and cause cancerous cell death. Analysis of molecular dynamics simulations provided important guidelines for the further modification of the lead compounds. Hence, we claim the lead molecules for further development in anticancer drug discovery.

Differential Effects of Glycyrrhiza Species on Genotoxic Estrogen Metabolism: Licochalcone A Downregulates P450 1B1, whereas Isoliquiritigenin Stimulates It

Estrogen chemical carcinogenesis involves 4-hydroxylation of estrone/estradiol (E1/E2) by P450 1B1, generating catechol and quinone genotoxic metabolites that cause DNA mutations and initiate/promote breast cancer. Inflammation enhances this effect by upregulating P450 1B1. The present study tested the three authenticated medicinal species of licorice [Glycyrrhiza glabra (GG), G. uralensis (GU), and G. inflata (GI)] used by women as dietary supplements for their anti-inflammatory activities and their ability to modulate estrogen metabolism. The pure compounds, liquiritigenin (LigF), its chalcone isomer isoliquiritigenin (LigC), and the GI-specific licochalcone A (LicA) were also tested. The licorice extracts and compounds were evaluated for anti-inflammatory activity by measuring inhibition of iNOS activity in macrophage cells: GI ≫ GG > GU and LigC ≅ LicA ≫ LigF. The Michael acceptor chalcone, LicA, is likely responsible for the anti-inflammatory activity of GI. A sensitive LC-MS/MS assay was employed to quantify estrogen metabolism by measuring 2-MeOE1 as nontoxic and 4-MeOE1 as genotoxic biomarkers in the nontumorigenic human mammary epithelial cell line, MCF-10A. GG, GU, and LigC increased 4-MeOE1, whereas GI and LicA inhibited 2- and 4-MeOE1 levels. GG, GU (5 μg/mL), and LigC (1 μM) also enhanced P450 1B1 expression and activities, which was further increased by inflammatory cytokines (TNF-α and IFN-γ). LicA (1, 10 μM) decreased cytokine- and TCDD-induced P450 1B1 gene expression and TCDD-induced xenobiotic response element luciferase reporter (IC50 = 12.3 μM), suggesting an antagonistic effect on the aryl hydrocarbon receptor, which regulates P450 1B1. Similarly, GI (5 μg/mL) reduced cytokine- and TCDD-induced P450 1B1 gene expression. Collectively, these data suggest that, of the three licorice species that are used in botanical supplements, GI represents the most promising chemopreventive licorice extract for women's health. Additionally, the differential effects of the Glycyrrhiza species on estrogen metabolism emphasize the importance of standardization of botanical supplements to species-specific bioactive compounds.

Aryl Hydrocarbon Receptor Ligand 5F 203 Induces Oxidative Stress That Triggers DNA Damage in Human Breast Cancer Cells

Breast tumors often show profound sensitivity to exogenous oxidative stress. Investigational agent 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203) induces aryl hydrocarbon receptor (AhR)-mediated DNA damage in certain breast cancer cells. Since AhR agonists often elevate intracellular oxidative stress, we hypothesize that 5F 203 increases reactive oxygen species (ROS) to induce DNA damage, which thwarts breast cancer cell growth. We found that 5F 203 induced single-strand break formation. 5F 203 enhanced oxidative DNA damage that was specific to breast cancer cells sensitive to its cytotoxic actions, as it did not increase oxidative DNA damage or ROS formation in nontumorigenic MCF-10A breast epithelial cells. In contrast, AhR agonist and procarcinogen benzo[a]pyrene and its metabolite, 1,6-benzo[a]pyrene quinone, induced oxidative DNA damage and ROS formation, respectively, in MCF-10A cells. In sensitive breast cancer cells, 5F 203 activated ROS-responsive kinases: c-Jun-N-terminal kinase (JNK) and p38 mitogen activated protein kinase (p38). AhR antagonists (alpha-naphthoflavone, CH223191) or antioxidants (N-acetyl-l-cysteine, EUK-134) attenuated 5F 203-mediated JNK and p38 activation, depending on the cell type. Pharmacological inhibition of AhR, JNK, or p38 attenuated 5F 203-mediated increases in intracellular ROS, apoptosis, and single-strand break formation. 5F 203 induced the expression of cytoglobin, an oxidative stress-responsive gene and a putative tumor suppressor, which was diminished with AhR, JNK, or p38 inhibition. Additionally, 5F 203-mediated increases in ROS production and cytoglobin were suppressed in AHR100 cells (AhR ligand-unresponsive MCF-7 breast cancer cells). Our data demonstrate 5F 203 induces ROS-mediated DNA damage at least in part via AhR, JNK, or p38 activation and modulates the expression of oxidative stress-responsive genes such as cytoglobin to confer its anticancer action.

Isostructural Re(i)/99mTc(i) tricarbonyl complexes for cancer theranostics

Novel cysteamine-based (N,S,O)-chelators were successfully applied in the synthesis of isostructural M(i) (M = Re, ^99mTc) tricarbonyl complexes for cancer theranostics.

2-(4-Hydroxy-3-methoxyphenyl)-benzothiazole suppresses tumor progression and metastatic potential of breast cancer cells by inducing ubiquitin ligase CHIP

Breast cancer is the most common malignancy among women and has poor survival and high recurrence rates for aggressive metastatic disease. Notably, triple-negative breast cancer (TNBC) is a highly aggressive cancer and there is no preferred agent for TNBC therapy. In this study, we show that a novel agent, 2-(4-hydroxy-3-methoxyphenyl)-benzothiazole (YL-109), has ability to inhibit breast cancer cell growth and invasiveness in vitro and in vivo. In addition, YL-109 repressed the sphere-forming ability and the expression of stem cell markers in MDA-MB-231 mammosphere cultures. YL-109 increased the expression of carboxyl terminus of Hsp70-interacting protein (CHIP), which suppresses tumorigenic and metastatic potential of breast cancer cells by inhibiting the oncogenic pathway. YL-109 induced CHIP transcription because of the recruitment of the aryl hydrocarbon receptor (AhR) to upstream of CHIP gene in MDA-MB-231 cells. Consistently, the antitumor effects of YL-109 were depressed by CHIP or AhR knockdown in MDA-MB-231 cells. Taken together, our findings indicate that a novel agent YL-109 inhibits cell growth and metastatic potential by inducing CHIP expression through AhR signaling and reduces cancer stem cell properties in MDA-MB-231 cells. It suggests that YL-109 is a potential candidate for breast cancer therapy.

Molecular dynamics simulation studies for DNA sequence recognition by reactive metabolites of anticancer compounds

The discovery of novel anticancer molecules 5F-203 (NSC703786) and 5-aminoflavone (5-AMF, NSC686288) has addressed the issues of toxicity and reduced efficacy by targeting over expressed Cytochrome P450 1A1 (CYP1A1) in cancer cells. CYP1A1 metabolizes these compounds into their reactive metabolites, which are proven to mediate their anticancer effect through DNA adduct formation. However, the drug metabolite-DNA binding has not been explored so far. Hence, understanding the binding characteristics and molecular recognition for drug metabolites with DNA is of practical and fundamental interest. The present study is aimed to model binding preference shown by reactive metabolites of 5F-203 and 5-AMF with DNA in forming DNA adducts. To perform this, three different DNA crystal structures covering sequence diversity were selected, and 12 DNA-reactive metabolite complexes were generated. Molecular dynamics simulations for all complexes were performed using AMBER 11 software after development of protocol for DNA-reactive metabolite system. Furthermore, the MM-PBSA/GBSA energy calculation, per-nucleotide energy decomposition, and Molecular Electrostatic Surface Potential analysis were performed. The results obtained from present study clearly indicate that minor groove in DNA is preferable for binding of reactive metabolites of anticancer compounds. The binding preferences shown by reactive metabolites were also governed by specific nucleotide sequence and distribution of electrostatic charges in major and minor groove of DNA structure. Overall, our study provides useful insights into the initial step of mechanism of reactive metabolite binding to the DNA and the guidelines for designing of sequence specific DNA interacting anticancer agents.

Isoxazole derivatives of 6-fluoro-N-(6-methoxybenzo[d]thiazol-2-yl)benzo[d]thiazol-2-amine and N-(pyrimidin-2-yl)benzo[d]thiazol-2-amine: regulation of cell cycle and apoptosis by p53 activation via mitochondrial-dependent pathways

The compounds depicted were shown to induce DNA damage and activate p53, which in turn activates Bax and decreases Bcl2 levels. This resulted in apoptosis in Colo205 cells.

Synthesis and anticancer potential of benzothiazole linked phenylpyridopyrimidinones and their diones as mitochondrial apoptotic inducers

A series of benzothiazole linked phenylpyridopyrimidinones (8a-g) and their diones (9a-g) have been designed, synthesized and evaluated for their anticancer activity. Among the series one of the conjugate 8b showed significant cytotoxicity against human cervical cancer cell line ME-180 with IC50 value of 4.01μM. This compound was tested on the cell cycle perturbations and DNA damage. Flow cytometry analysis revealed that the compound 8b showed drastic cell cycle perturbations due to concentration dependent increase in the sub-G0 phase in ME-180 cell line. DNA fragmentation and Hoechst staining reveals that this compound induced cell death by apoptosis. Further caspase-3 and loss of mitochondrial membrane potential suggested that the compound induces cell death by apoptosis.

Chemistry of ring-substituted 4-(benzothiazol-2-yl)phenylnitrenium ions from antitumor 2-(4-aminophenyl)benzothiazoles

Ring-substituted derivatives of 2-(4-aminophenyl)benzothiazole, 1a, 1b-g, are under development as antitumor agents. One derivative, 1f, has reached phase 1 clinical trials as the prodrug 2f, Phortress (NSC 710305). These amines are activated by CYP450 1A1, apparently into hydroxylamines 8a-g that are likely metabolized into esters that ionize into nitrenium ions responsible for cellular damage. Previously we showed that 9a, the acetic acid ester of 8a, generates the long-lived (530 ns) nitrenium ion 11a by hydrolysis or photolysis in water. In this study, azide trapping shows that 9b-g generate 11b-g via rate-limiting N-O heterolysis. Ion lifetimes, estimated from azide/solvent selectivities, range from 250 to 1150 ns with identical lifetimes for 11a and 11f. Differences in biological activity of the amines are likely not due to differences in the chemistry of the cations but to differences in metabolic activation/deactivation of individual amines. Unlike the nitrenium ions, lifetimes of the esters are strongly dependent on the 3'-Me substituent. Esters containing 3'-Me (9b, 9f, 9g) have lifetimes of 5-10 s compared to 400-800 s for esters without 3'-Me (9a, 9c, 9d, 9e). This restricts 3'-Me esters to cells/tissues in which activation occurs, concentrating their effects in tumor cells if metabolism is restricted to those cells.

CYP1A1 regulates breast cancer proliferation and survival

Cytochrome P450-1A1 (CYP1A1) is an extrahepatic phase I metabolizing enzyme whose expression is suppressed under physiologic conditions but can be induced by substrates via the aryl hydrocarbon receptor (AhR). Recent studies have shown that the majority of breast cancer tumors constitutively express CYP1A1. These findings led us to test the hypothesis that CYP1A1 promotes breast cancer progression by evaluating the effects of CYP1A1 knockdown on the proliferation and survival of the MCF7 and MDA-MB-231 lines. Independently of estrogen receptor status, CYP1A1 knockdown decreased colony formation, decreased cell proliferation, blocked the cell cycle at G0-G1 associated with reduction of cyclin D1, and increased apoptosis associated with reduction of survivin. CYP1A1 knockdown markedly increased phosphorylation of AMP-activated protein kinase (AMPK) and decreased phosphorylation of AKT, extracellular signal-regulated kinases 1 and 2 (ERK1/2), and 70-kDa ribosomal protein S6 kinase (P70S6K). AMPK inhibition by compound C partially abrogated the proapoptotic effects of CYP1A1 knockdown, suggesting that effects of CYP1A1 knockdown are mediated in part through AMPK signaling. Consistent with CYP1A1 knockdown, pharmacologic reduction of CYP1A1 levels by the phytopolyphenol carnosol also correlated with impaired proliferation and induced AMPK phosphorylation. These results indicate that reduction of basal CYP1A1 expression is critical for inhibition of proliferation, which is not affected by α-naphthoflavone-mediated inhibition of CYP1A1 activity nor modulated by AhR silencing. This study supports the notion that CYP1A1 promotes breast cancer proliferation and survival, at least in part, through suppression of AMPK signaling and that reduction of CYP1A1 levels is a potential strategy for breast cancer therapeutics.

Synthesis of pyrazolo[1,5-a]pyrimidine linked aminobenzothiazole conjugates as potential anticancer agents

A series of pyrazolo[1,5-a]pyrimidine linked 2-aminobenzothizole conjugates (6a-t) were synthesized and evaluated for their anticancer activity against five human cancer cell lines. Among them two compounds 6p and 6m showed significant anticancer activity with IC50 values ranging from 2.01 to 7.07 and 1.94-3.46 μM, respectively. Moreover, cell cycle arrest in G2/M and reduction in Cdk1 expression level were observed upon treatment of these compounds and they also induced caspase-3 dependent apoptosis. This was further confirmed by staining as well as DNA fragmentation analysis.

Recent advances on structural modifications of benzothiazoles and their conjugate systems as potential chemotherapeutics

INTRODUCTION

Benzothiazole scaffold comprises a bicyclic ring system and is known to exhibit a wide range of biological properties including antimicrobial and anticancer activities. Benzothiazole derivatives have long been therapeutically used for the treatment of various diseases. However, in recent years, 2-arylbenzothiazoles have emerged as an important pharmacophore in the development of antitumor agents. The promising biological profile and synthetic accessibility have been attractive in the design and development of new benzothiazoles and their conjugate systems as potential chemotherapeutics.

AREAS COVERED

This review mainly focuses on the structural modifications of benzothiazole scaffold, development of various series of benzothiazoles and their conjugates as new antitumor agents. Furthermore, heterocyclic derivatives bearing benzothiazole moiety and their in vitro as well as in vivo screening, structure-activity relationships (SAR), mechanism, pharmacokinetics, clinical use and their future therapeutic applications are discussed here.

EXPERT OPINION

A large number of benzothiazole derivatives discussed here possess potent anticancer activity and can be further developed as drug candidates. Benzothiazole conjugates could also display synergistic effect and still there is a need to use the drug combinations permitting lower dose and development of new generation of drugs. Despite encouraging results that have been observed for their response to tumor in clinical studies, full characterization of their toxicity is further required for their clinical usage as safe drugs for the treatment of cancer. We believe that this review gives a better understanding and scope for future drug design and development of benzothiazole-based compounds to implicate their use in cancer chemotherapy.

Synthesis and biological evaluation of novel triazoles and isoxazoles linked 2-phenyl benzothiazole as potential anticancer agents

A new series of isoxazoles and triazoles linked 2-phenyl benzothiazole were synthesized and evaluated for their anticancer activity. These compounds have been tested for their cytotoxicity three cancer cell lines. Among the compounds tested, compound 5d showed good cytotoxicity against Colo-205 and A549 cells in comparison to standard control PMX 610(1). Further compound 5d has been tested for its apoptotic activity and its inhibitory activity against caspase and PARP proteins. Hence this compound has the potential that it can be selected for further biological studies.

Bioactivation of fluorinated 2-aryl-benzothiazole antitumor molecules by human cytochrome P450s 1A1 and 2W1 and deactivation by cytochrome P450 2S1

Both 2-(4-amino-3-methylphenyl)-5-fluorobenzothiazole (5F 203) and 5-fluoro-2-(3,4-dimethoxyphenyl)-benzothiazole (GW 610) contain the benzothiazole pharmacophore and possess potent and selective in vitro antitumor properties. Prior studies suggested the involvement of cytochrome P450 (P450) 1A1 and 2W1-mediated bioactivation in the antitumor activities and P450 2S1-mediated deactivation of 5F 203 and GW 610. In the present study, the biotransformation pathways of 5F 203 and GW 610 by P450s 1A1, 2W1, and 2S1 were investigated, and the catalytic parameters of P450 1A1- and 2W1-catalyzed oxidation were determined in steady-state kinetic studies. The oxidations of 5F 203 catalyzed by P450s 1A1 and 2W1 yielded different products, and the formation of a hydroxylamine was observed for the first time in the latter process. Liquid chromatography-mass spectrometry (LC-MS) analysis with the synthetic hydroxylamine and also a P450 2W1/5F 203 incubation mixture indicated the formation of dGuo adduct via a putative nitrenium intermediate. P450 2W1-catalyzed oxidation of GW 610 was 5-fold more efficient than the P450 1A1-catalyzed reaction. GW 610 underwent a two-step oxidation process catalyzed by P450 1A1 or 2W1: a regiospecific O-demethylation and a further hydroxylation. Glutathione (GSH) conjugates of 5F 203 and GW 610, presumably through a quninoneimine and a 1,2-quinone intermediate, respectively, were detected. These results demonstrate that human P450s 1A1 and 2W1 mediate 5F 203 and GW 610 bioactivation to reactive intermediates and lead to GSH conjugates and a dGuo adduct, which may account for the antitumor activities of 5F 203 and GW 610 and also be involved in cell toxicity. P450 2S1 can catalyze the reduction of the hydroxylamine to the amine 5F 203 under anaerobic conditions and, to a lesser extent, under aerobic conditions, thus attenuating the anticancer activity.

Cytochrome P450 1A1-mediated anticancer drug discovery: in silico findings

INTRODUCTION

Target-specific drugs may offer fewer side/adverse effects in comparison with other anticancer agents and thus save normal healthy cells to a greater extent. The selective overexpression of cytochrome P450 1A1 (CYP1A1) in tumor cells induces the metabolism of benzothiazole and aminoflavone compounds to their reactive species, which are responsible for DNA adduct formation and cell death. This review encompasses the novelty of CYP1A1 as an anticancer drug target and explores the possible in silico strategies that would be applicable in the discovery and development of future antitumor compounds.

AREAS COVERED

This review highlights the various ligand-based and target-based in silico methodologies that were efficiently used in exploration of CYP1A1 as a novel antitumor target. These methodologies include electronic structure analysis, CoMFA studies, homology modeling, molecular docking, molecular dynamics analysis, pharmacophore mapping and quantitative structure activity relationship (QSAR) studies. It also focuses on the various approaches used in the development of the lysyl amide prodrug of 5F-203 (NSC710305) and dimethanesulfonate salt of 5-aminoflavone (NSC710464) as clinical candidates from their less potent analogues.

EXPERT OPINION

Selective overexpression of CYP1A1 in cancer cells offers tumor-specific drug design to ameliorate the current adverse effects associated with existing antitumor agents. Medicinal chemistry and in vitro driven approaches, in combination with knowledge-based drug design and by using the currently available tools of in silico methodologies, would certainly make it possible to design and develop novel anticancer compounds targeting CYP1A1.