Synthesis, cytotoxicity, and DNA topoisomerase II inhibitory activity of benzofuroquinolinediones

Benzofuroquinolinediones (7c and 7d) were synthesized by base-catalyzed condensation of dichloroquinolinediones with phenolic derivatives. Their dialkylaminoalkoxy derivatives (8i-8p) were prepared by reaction with various dialkylaminoalkyl chlorides. The cytotoxicity of the synthesized compounds was evaluated against eight types of human cancer cell lines, and their topoisomerase II inhibition was assessed. In general, the cytotoxicity of benzofuroquinolinediones (8i-8p) was similar or superior to that of doxorubicin and showed more potent inhibitory activity than naphthofurandiones (8a-8h). Also, most of the compounds exhibited excellent topoisomerase II inhibitory activity at a concentration of 5 microM and two compounds, 8d and 8i, showed IC50 values of 1.19 and 0.68 microM, respectively, and were much more potent than etoposide (IC50=78.4 microM), but similar to doxorubicin (IC50=2.67 microM). However their inhibitory activity on topoisomerase I was lower, and 8d and 8i showed IC50 values of 42.0 and 64.3 microM, respectively.     

Synthesis and antiproliferative activity of benzyl and phenethyl analogs of makaluvamines

Analogs of marine alkaloid, makaluvamine, bearing substituted benzyl and substituted phenethyl side chains have been synthesized and their antiproliferative activities have been evaluated. 4-Methyl, 4-chloro, and 4-fluoro substituted benzyl analogs possessed pronounced antiproliferative effects on the breast cancer cell line, MCF-7 at IC(50) values of 2.3 microM, 1.8 microM, and 2.8 microM, respectively. 4-Methyl, 4-chloro, and 3,4-methylenedioxy derivatives showed the best activity against MCF-7 among the phenethyl analogs with IC(50) values of 2.3 microM, 2.8 microM, and 2.4muM, respectively. In general, methoxy substitutions resulted in slight loss in activity in both benzyl and phenethyl series. Benzyl, 4-fluorobenzyl, 3,4-dimethoxyphenethyl, and 3,4-methylenedioxyphenethyl analogs were tested by NCI in their 60 cell lines in vitro human cancer cell screen. All four compounds showed excellent inhibition against several tested cancer cell lines. Benzyl and 4-fluorobenzyl analogs were relatively more active than 3,4-dimethoxy phenethyl and 3,4-methylenedioxy phenethyl analogs. In NCI assays, the best LogGI(50) values were shown by the fluorobenzyl analog against the renal cancer cell line RXF-393 (<-8.0M) and dimethoxy phenethyl analog against the CNS cancer cell line, SF-268 (<-8.0M). The best LogLC(50) value was shown by the fluorobenzyl analog against the breast cancer cell line MCF-7 (-6.01 M).     

Antitumor dinuclear platinum(II) complexes derived from a novel chiral ligand

A new chiral ligand, 2-(((1R,2R)-2-aminocyclohexyl)amino)acetic acid (HL), was designed and synthesized to prepare a series of novel dinuclear platinum(II) complexes with dicarboxylates or sulfate as bridges. The evaluation of these metal complexes in vitro cytotoxicity against human HCT-116, MCF-7 and HepG-2 cell lines were made. All compounds showed antitumor activity to HCT-116 and MCF-7. Particularly, compounds M3 and M5 not only exhibited better activity than carboplatin against MCF-7 and HepG-2, but also showed very close activity to oxaliplatin against HCT-116.     

Critical role of p53 upregulated modulator of apoptosis in benzyl isothiocyanate-induced apoptotic cell death

Benzyl isothiocyanate (BITC), a constituent of edible cruciferous vegetables, decreases viability of cancer cells by causing apoptosis but the mechanism of cell death is not fully understood. The present study was undertaken to determine the role of Bcl-2 family proteins in BITC-induced apoptosis using MDA-MB-231 (breast), MCF-7 (breast), and HCT-116 (colon) human cancer cells. The B-cell lymphoma 2 interacting mediator of cell death (Bim) protein was dispensable for proapoptotic response to BITC in MCF-7 and MDA-MB-231 cells as judged by RNA interference studies. Instead, the BITC-treated MCF-7 and MDA-MB-231 cells exhibited upregulation of p53 upregulated modulator of apoptosis (PUMA) protein. The BITC-mediated induction of PUMA was relatively more pronounced in MCF-7 cells due to the presence of wild-type p53 compared with MDA-MB-231 with mutant p53. The BITC-induced apoptosis was partially but significantly attenuated by RNA interference of PUMA in MCF-7 cells. The PUMA knockout variant of HCT-116 cells exhibited significant resistance towards BITC-induced apoptosis compared with wild-type HCT-116 cells. Attenuation of BITC-induced apoptosis in PUMA knockout HCT-116 cells was accompanied by enhanced G2/M phase cell cycle arrest due to induction of p21 and down regulation of cyclin-dependent kinase 1 protein. The BITC treatment caused a decrease in protein levels of Bcl-xL (MCF-7 and MDA-MB-231 cells) and Bcl-2 (MCF-7 cells). Ectopic expression of Bcl-xL in MCF-7 and MDA-MB-231 cells and that of Bcl-2 in MCF-7 cells conferred protection against proapoptotic response to BITC. Interestingly, the BITC-treated MDA-MB-231 cells exhibited induction of Bcl-2 protein expression, and RNA interference of Bcl-2 in this cell line resulted in augmentation of BITC-induced apoptosis. The BITC-mediated inhibition of MDA-MB-231 xenograft growth in vivo was associated with the induction of PUMA protein in the tumor. In conclusion, the results of the present study indicate that Bim-independent apoptosis by BITC in cancer cells is mediated by PUMA.     

Synthesis, characterization, molecular docking and cytotoxic activity of novel plumbagin hydrazones against breast cancer cells

Novel plumbagin hydrazonates were prepared, structurally characterized and evaluated for anti-proliferative activity against estrogen receptor-positive MCF-7 and triple negative MDA-MB-231 and MDA-MB-468 breast cancer cell lines which exhibited superior inhibitory activity than parent plumbagin compound. Molecular docking studies indicated that hydroxyl groups on plumbagin and hydrazonate side chain favor additional hydrogen bonding interactions with amino acid residues in p50-subunit of NF-κB protein and these compounds inhibited NF-κB expression which may be responsible for the enhanced anti-proliferative activity. These compounds were found to be more effective against triple negative breast cancer cells and might serve as a starting point for building future strategies against triple negative breast cancers which are known for their increased drug resistance and poor prognosis of breast cancer patients.     

Cytotoxicity of aporphines in human colon cancer cell lines HCT-116 and Caco-2: an SAR study

A series of synthetic aporphine derivatives structurally related to domesticine and nantenine (ring A, N6 and ring C truncated analogs), was evaluated in MTS cytotoxicity assays against the human colon cancer cell lines, HCT-116 and Caco-2. In general, the C1 position of ring A is tolerant of alkoxy substituents as well as a benzoyl ester functionality. Other modifications evaluated resulted in a decrease in cytotoxic activity. The most potent compounds identified had IC₅₀ values in the range 23-38 μM, comparable to the known cytotoxic agent, etoposide.     

Synthesis and evaluation of heteroaromatic 6,7-diaryl-2,3,8,8a-tetrahydroindolizin-5(1H)-ones for cytotoxicity against the HCT-116 colon cancer cell line

A heteroaromatic 6,7-diaryl-2,3,8,8a-tetrahydroindolizin-5(1H)-one analog library was prepared and tested for cytotoxic properties against the HCT-116 colon cancer cell line, thus providing additional information pertaining to structure-activity relationships for this class of compounds. The most active of the new analogs proved to be the C6 2-thiophene and 3-thiophene analogs with IC(50) values of 0.27 microM and 0.60 microM, respectively.     

Cross-resistance of an amsacrine-resistant human leukemia line to topoisomerase II reactive DNA intercalating agents. Evidence for two topoisomerase II directed drug actions.

HL-60/AMSA is a human leukemia cell line that is 50-100-fold more resistant than its drug-sensitive HL-60 parent line to the cytotoxic actions of the DNA intercalator amsacrine (m-AMSA). HL-60/AMSA topoisomerase II is also resistant to the inhibitory actions of m-AMSA. HL-60/AMSA cells and topoisomerase II are cross-resistant to anthracycline and ellipticine intercalators but relatively sensitive to the nonintercalating topoisomerase II reactive epipodophyllotoxin etoposide. We now demonstrate that HL-60/AMSA and its topoisomerase II are cross-resistant to the DNA intercalators mitoxantrone and amonafide, thus strongly indicating that HL-60/AMSA and its topoisomerase II are resistant to topoisomerase II reactive intercalators but not to nonintercalators. At high concentrations, mitoxantrone and amonafide were also found to inhibit their own, m-AMSA's, and etoposide's abilities to stabilize topoisomerase II-DNA complexes. This appears to be due to the ability of these concentrations of mitoxantrone and amonafide to inhibit topoisomerase II mediated DNA strand passage at a point in the topoisomerization cycle prior to the acquisition of the enzyme-DNA configuration that yields DNA cleavage and topoisomerase II-DNA cross-links. In addition, amonafide can inhibit the cytotoxic actions of m-AMSA and etoposide. Taken together, these results suggest that the cytotoxicity of m-AMSA and etoposide is initiated primarily by the stabilization of the topoisomerase II-DNA complex. Other topoisomerase II reactive drugs may inhibit the enzyme at other steps in the topoisomerization cycle, particularly at elevated concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Design,synthesis, and biological evaluation of novel 1-oxo-1,2,3,4-tetrahydropyrazino[1,2-a]indole-3-carboxamide analogs in MCF-7 and MDA-MB-468 breast cancer cell lines

A series of novel 1-oxo-1,2,3,4-tetrahydropyrazino[1,2-a]indole-3-carboxamide analogs were designed and synthesized for developing pyrazinoindolone scaffolds as anti-breast cancer agents. Compounds 1h and 1i, having a furan-2-yl-methylamide and benzylamide group, respectively, exhibited more potent cytotoxicity in MDA-MB-468 triple-negative breast cancer (TNBC) cells than compounds possessing aliphatic groups. Compounds 2a and 2b, as (R)-enantiomers of 1h and 1i, also had inhibitory activity against MDA-MB-468 cells. Moreover, analogs (3a–b and 3d–e) bearing a benzyl group at the N-2 position showed more potent activity than gefitinib, as a potent EFGR-TK inhibitor. Especially, compound 3a exhibited selective cytotoxic activity against MDA-MB-468 cells; it also had a synergistic effect in combination with gefitinib against MDA-MB-468 cells. In addition, we confirmed that compounds 3a and 3d inhibit phosphorylation of Akt in MDA-MB-468 cells using western blot analysis. Therefore, these 1-oxo-1,2,3,4-tetrahydropyrazino[1,2-a]indole-3-carboxamide analogs may be helpful for investigating new anti-TNBC agents.     

Oleanane-type triterpenoids from Panax stipuleanatus and their anticancer activities

One newly (1) and 10 known oleanane-type triterpenoids (2-11) were isolated from the methanol extract of Panax stipuleanatus rhizomes. Based on their spectroscopic data, these compounds were identified as spinasaponin A methyl ester (1), pesudoginsenoside RP(1) methyl ester (2), spinasaponin A 28-O-glucoside (3), pseudoginsenoside RT(1) methyl ester (4), pseudoginsenoside RT(1) (5), stipuleanoside R(2) methyl ester (6), stipuleanoside R(2) (7), araloside A methyl ester (8), 3-O-β-D-glucopyranosyl (1→3)-β-D-glucuronopyranoside-28-O-β-D-glucopyranosyl oleanolic acid methyl ester (9), 3-O-β-D-xylopyranosyl (1→2)-β-D-glucopyranosyl-28-O-β-D-glucopyranosyl oleanolic acid (10), and chikusetsusaponin IVa (11). When the cytotoxic activities of the isolated compounds were evaluated, compound 1 exhibited significant cytotoxic activity with IC(50) values of 4.44 and 0.63 μM against HL-60 (leukemia) and HCT-116 (colon cancer) cell lines, respectively. Compound 2 showed potent cytotoxicity with an IC(50) of 6.50 μM against HCT-116, whereas it was less cytotoxic against HL-60 (IC(50)=41.45 μM). After HL-60 and HCT-116 were treated with compounds 1 and 2, increased production of apoptotic bodies was observed. Furthermore, compounds 1 and 2 in HCT-116 cells activated intrinsic and extrinsic apoptosis pathways by upregulating DR-5 and Bax, downregulating Bcl-2, activating caspase-9, and cleaving poly-ADP-ribose polymerase (PARP). We also observed the activation of ERK1/2 MAPK by both compounds in the HCT-116 cells. Together, compounds 1 and 2 might induce intrinsic and extrinsic apoptosis pathways through the activation of the ERK1/2 MAPK pathway in HCT-116 colon cancer cells. Structure-activity relationship analysis indicated that a carboxyl group at position-28 is potentially responsible for the cytotoxic effects.     

Solid phase combinatorial synthesis of benzothiazoles and evaluation of topoisomerase II inhibitory activity

To investigate one possible mechanism of action of the cytotoxic activity of benzothiazoles, we synthesized 2-(substituted-phenyl)benzothiazoles and evaluated their ability to inhibit topoisomerase II activities. Solid phase combinatorial method using trityl resin was employed and benzothiazole derivatives with various substitution on 2'-, 3'-, or 4'-position of phenyl group were obtained in ca. 30 mg scale (7-96% yield). Most of the compounds synthesized exhibited topoisomerase II inhibitory activity at 100 microM. 2-(3-Amino-4-methylphenyl)benzothiazole showed high activity (IC(50) = 71.7 microM), comparable to etoposide (IC(50) = 78.4 microM).     

HIV-1 Tat peptide immunoconjugates differentially sensitize breast cancer cells to selected antiproliferative agents that induce the cyclin-dependent kinase inhibitor p21WAF-1/CIP-1

In this study, we evaluated the ability of anti-p21 antibodies conjugated to 17-mer peptides [GRKKRRQRRRPPQGYGC] harboring the membrane-translocating and nuclear import sequences [underlined] of HIV-1 tat protein to inhibit the cyclin-dependent kinase inhibitor, p21(WAF-1/Cip-1) (p21) and differentially sensitize MDA-MB-468 and MCF-7 human breast cancer (BC) cells to the antiproliferative effects of treatments that induce or do not induce p21. BC cells were treated with increasing concentrations of epidermal growth factor (EGF; 0.5-10 nM), the topoisomerase I inhibitor, camptothecin (CPT; 0.1-4 muM), or increasing doses of gamma-radiation (2-20 Gy). Western blot was used to evaluate p21 expression. The effect of treatment on cell cycle distribution was studied. Growth inhibition was measured by the WST-1 assay. Expression of p21 was increased in MDA-MB-468 cells treated with EGF or CPT but not by gamma-irradiation. MCF-7 cells exhibited p21 upregulation following exposure to CPT and gamma-radiation but not EGF. EGF caused cell cycle arrest in G(1) phase for MDA-MB-468 cells. CPT caused G(1)-phase arrest in MDA-MB-468 cells and prolonged S phase in MCF-7 cells. gamma-Radiation caused an increase in cells in G(2)/M phase for MDA-MB-468 and MCF-7. MDA-MB-468 cells were growth-inhibited by EGF, CPT, and gamma-radiation. MCF-7 cells were growth-stimulated by EGF and inhibited by CPT and gamma-radiation. Combining EGF with tat-anti-p21 immunoconjugates (ICs) amplified the growth-inhibitory effect on MDA-MB-468 cells 1.2-fold to 2.3-fold, but had no effect on the growth stimulation of MCF-7 cells by EGF. Tat-anti-p21 ICs sensitized MCF-7 cells 1.4-fold to gamma-radiation but had no effect on the growth of gamma-irradiated MDA-MB-468 cells. Tat-anti-p21 ICs sensitized both MDA-MB-468 and MCF-7 cells 1.7-fold to CPT. We conclude that tat-anti-p21 ICs are promising sensitizers for cytotoxic cancer therapies and that their sensitization is dependent on treatment-related p21 expression. This general approach could potentially be extended to other growth-regulatory molecules that are associated with tumor growth and progression.     

Discovery of novel osthole derivatives as potential anti-breast cancer treatment

Osthole, an ingredient of Traditional Chinese Medicine (TCM) from natural product Cnidium monnieri (L.) Cusson, was used as a lead compound for structural modification. A series of osthole derivatives bearing aryl substituents at 3-position of coumarin, has been prepared and evaluated for their growth inhibitory activity against human breast cancer cell lines MCF-7 and MDA-MB-231. Interestingly, some derivatives exhibited good inhibition, among them compound 8e was found to be the most potent compound with IC(50) values of 0.24 μM, 0.31 μM against MCF-7 and MDA-MB-231, respectively, which was improved more than 100-folds compared with its parent compound osthole.     

Synthesis of miltirone analogues as inhibitors of Cdc25 phosphatases

Miltirone analogues were synthesized and evaluated for inhibitory activity against Cdc25 and PTP1B. Most of the compounds demonstrated potent Cdc25 inhibitory activity, and several exhibited higher selectivity for Cdc25 than for PTP1B. In a cytotoxic assay, most of the compounds displayed cytotoxicity against the tumor cell lines A549 and HCT-116, producing IC(50) values in the micromolar range.     

Synthesis and antitumor evaluation of a novel series of triaminotriazine derivatives

A series of triaminotriazine derivatives (compounds 5a-f, 6a-x, and 7a-g) was designed, synthesized, and evaluated for their inhibition activities to colorectal cancer (CRC) cell lines (HCT-116 and HT-29). Most of the synthesized compounds demonstrated moderate anti-proliferatory effects on both HCT-116 and HT-29 cell lines at the concentration of 10 microM. The inhibitory activities against HCT-116 and HT-29 cell lines were discussed to develop the structure-activity relationships of this new series. Compounds 6l and 6o exhibited prominent inhibition activities toward HCT-116, with IC50s of 0.76 and 0.92 microM, respectively. The in vivo antitumor studies and pharmacokinetics of compound 6l showed that it might be a promising new hit for further development of antitumor agents.     

Synthesis of 1-/2-substituted-[1,2,3]triazolo[4,5-g]phthalazine-4,9-diones and evaluation of their cytotoxicity and topoisomerase II inhibition

Studies on antitumor heterocyclic quinones containing nitrogens revealed that the number and position of nitrogens on the heterocyclic ring have significance on cytotoxicity of quinones. In our continuous effort to find more cytotoxic quinone compounds, we designed triazolophthalazine analogues in order to introduce more nitrogens on the heterocyclic quinones. 1-/2-Substituted-[1,2,3]triazolo[4,5-g]phthalazine-4,9-diones were synthesized by 1,3-dipolar addition of phthalazine-5,8-dione and 4-methoxybenzyl azide by modification of previously reported method. The cytotoxicity of the synthesized compounds was evaluated by a SRB (sulforhodamine B) assay against nine types of human cancer cell lines and inhibition against topoisomerase II (Topo II) of them was assessed by a decatenation assay. Most of the synthesized compounds showed considerably higher cytotoxicity than that of doxorubicin. Also, topoisomerase II inhibitory activity of the tested compounds was higher than that of etoposide and IC(50) values of the compounds were 19.4-64.5 microM.     

Anti-proliferative potential of triphenyl substituted pyrimidines against MDA-MB-231, HCT-116 and HT-29 cancer cell lines

A series of triphenyl substituted pyrimidines as analogous of colchicine and combretastatin A-4 was synthesized and evaluated for the antiproliferative potential. The compounds were screened against MDA-MB-231, HCT-116 and HT-29 cell lines using MTT assay. Most of the compounds displayed antiproliferative activity in low to sub micro molar concentration. Amongst the synthesized derivatives, compounds HK-2, HK-10 and HK-13 were found to be effective against all the three cancer cell lines. HK-2 exhibited IC₅₀ values of 3.39 µM, 4.78 µM and 4.23 µM, HK-10 showed IC₅₀ values of 0.81 µM, 5.89 µM, 4.96 µM and HK-13 showed IC₅₀ values 3.24 µM, 4.93 µM and 4.73 µM against MDA-MB-231, HCT-116 and HT-29 cancer cell lines, respectively. HK-10 was found to be the most potent compound in the series with IC₅₀ values of 0.81 µM against MDA-MB-231. In the cell cycle analysis, HK-2 and HK-10 showed cell arrest at G2/M phase of the cell cycle while HK-13 inhibited cell growth at the G1/G0 phase. All the three compounds showed cell death induced through apoptosis. In the docking studies, HK-2, HK-10 and HK-13 were found to fit well in the colchicine binding site of the tubulin. Some of the compounds in the current series were found to be promising against all the three cancer cell lines and may act as potent leads for further development.     

Curcumin as a DNA topoisomerase II poison

Curcumin, the major active component of the spice turmeric, is recognised as a safe compound with great potential for cancer chemoprevention and cancer therapy. It induces apoptosis, but its initiation mechanism remains poorly understood. Curcumin has been assessed on the human cancer cell lines, TK-10, MCF-7 and UACC-62, and their IC50 values were 12.16, 3.63, 4.28 microM respectively. The possibility of this compound being a topoisomerase II poison has also been studied and it was found that 50 microM of curcumin is active in a similar fashion to the antineoplastic agent etoposide. These results point to DNA damage induced by topoisomerase II poisoning as a possible mechanism by which curcumin initiates apoptosis, and increase the evidence suggesting its possible use in cancer therapy.     

Two New Eudesmane-Type Sesquiterpene from Clonostachys sp. Y6-1and Their Cytotoxic Activity

Two undescribed eudesmane-type sesquiterpenoids together with four known compounds were isolated from Clonostachys sp. Y6-1 associated. Their chemical structures were unambiguously determined by NMR, mass spectrometry, and ¹³C-NMR calculation as well as DP4+ probability analyses. The absolute configurations of compounds 1 and 2 were determined by ECD calculation and X-ray single-crystal diffraction methods. Furthermore, all isolates were evaluated for in vitro cytotoxic activities against MCF-7, HCT-116, MDA-MB-231, and SW620 cancer cells. Among them, bioactivity evaluation of compound 5 revealed that weak activity (IC₅₀=66.55±0.82 μM) against SW620.     

Synthesis and biological evaluation of histone deacetylase and DNA topoisomerase II-Targeted inhibitors

HDAC inhibitors enable histones to maintain a high degree of acetylation. The resulting looser state of chromatin DNA may increase the accessibility of DNA drug targets and consequently improve the efficiency of anticancer drugs targeting DNA, such as Topo II inhibitors. A novel class of nucleoside-SAHA derivatives has been designed and synthesized based on the synergistic antitumor effects of topoisomerase II and histone deacetylase inhibitors. Their inhibitory activities toward histone deacetylases and Topo II, and their cytotoxicities in cancer cell lines, were evaluated. Among the synthesized hybrid compounds, compound 16b showed the potent HDAC inhibitory activity at a low nanomolar level and exhibited antiproliferative activity toward cancer cell lines including MCF-7 (breast), HCT-116 (colon), and DU-145 (prostate) cancer cells at a low micromolar level. Moreover, compound 16a showed HDAC6-selectivity 20-fold over HDAC1.