Anticancer and superoxide scavenging activities of p-alkylaminophenols having various length alkyl chains

A series of p-alkylaminophenols including 3, p-butylaminophenol; 4, p-hexylaminophenol; 5, p-octylaminophenol; and 6, N-(p-methoxybenzyl)aminophenol were synthesized based on the structure of fenretinide, N-(4-hydroxyphenyl)retinamide (1). This latter agent is a synthetic amide of all-trans-retinoic acid (RA), which is a cancer chemopreventive and antiproliferative agent. It was found that elongation of the alkyl chain length in these compounds increased antioxidative activity and inhibition of lipid peroxidation. These findings led us to investigate whether antiproliferative activity against cancer cells was effected by the length of alkyl chains linked to the aminophenol residue. All p-alkylaminophenols inhibited growth of HL60 and HL60R cells in a dose-dependent manners. The HL60R line is a resistant clone against RA. Growth of various cancer cell lines (HL60, HL60R, MCF-7, MCF-7/Adr(R), HepG2, and DU-145) was suppressed by p-alkylaminophenols in a fashion dependent on the aminophenol alkyl chain length (5>4>3>p-methylaminophenol (2)), with 5 being the most potent inhibitor of cell growth against HL60R, MCF-7/Adr(R), and DU-145 cells among p-alkylaminophenols tested, including 1. In particular, with the exception of compound 2, antiproliferative activity against DU-145 cells by these p-alkylaminophenols was greater than by 1. In HL60 cells, growth inhibition was associated with apoptosis. On the other hand, elongation of the alkyl chain length reduced superoxide trapping capability (2>3>4>5) in contrast to the effects on inhibition of lipid peroxidation. These results indicate that anticancer activity of p-alkylaminophenols correlated with the inhibitory activity of lipid peroxidation, but not with the superoxide scavenging activity.     

Biological activity of p-methylaminophenol,an essential structural component of N-(4-hydroxyphenyl)retinamide,fenretinide

Fenretinide, N-(4-hydroxyphenyl)retinamide (4-HPR), is a synthetic amide of all-trans-retinoic acid (RA), which inhibits cell growth, induces apoptosis, and is an antioxidant, and cancer chemopreventive and antiproliferative agent. These findings led us to investigate which structural component of 4-HPR contributes to these potent activities. Our approach was to examine 4-aminophenol (4-AP), p-methylaminophenol (p-MAP), and p-acetaminophen (p-AAP). It was found that vitamin E, 4-AP and p-MAP scavenge alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radicals in a 1:2 ratio, in contrast to 4-HPR and p-AAP, for which 1:1 and 1:0.5 ratios were observed relative to DPPH radicals. However, RA was inactive. Lipid peroxidation in rat liver microsomes was reduced by compounds (RA > p-MAP = 4-HPR > 4-AP) in a dose-dependent manner, while p-AAP was inactive. In addition, both p-MAP and 4-HPR are potent inhibitors of cell growth and inducers of apoptosis in HL60 cells. p-MAP exhibits the same level of antiproliferative activity as 4-HPR against HL60R cells, which are a resistant clone against RA, and it inhibits the growth of various cancer cell lines (MCF-7, MCF-7/Adr(R), HepG2, and DU-145) to an extent greater than 4-AP and p-AAP, but is less potent than 4-HPR. Thus, although the antioxidant activity of p-MAP is more potent than that of 4-HPR, p-MAP is less potent than 4-HPR in anticancer activity. These results suggest that both the anticancer and antioxidative activities shown by 4-HPR are due to the structure of p-MAP. The retinoyl residue or long alkyl chain substituent attached to an aminophenol may be significant for anticancer properties.     

Antioxidant and anticancer activities of novel p-alkylaminophenols and p-acylaminophenols (aminophenol analogues)

Novel compounds were designed based on fenretinide, N-(4-hydroxyphenyl)retinamide (2), which is a synthetic amide of all-trans-retinoic acid (1) that is a potent antioxidant and anticancer agent. Our recent findings indicated that antioxidant and anticancer activities were due to p-methylaminophenol moiety (8) in 2, and that p-octylaminophenol (7), which has an elongated alkyl chain, was more potent than 8. This finding lets us to investigate whether compounds containing alkyl or acyl chains linked to an aminophenol residue as long as 2 and 1, would show activities greater than 2. For this purpose, we prepared p-dodecanoylaminophenol (3), p-decanoylaminophenol (4), p-dodecylaminophenol (5), and p-decylaminophenol (6). The p-alkylaminophenols, 5 and 6, exhibited superoxide scavenging activities, but not p-acylaminophenols, 3 and 4. Elongation of the alkyl chain length reduced superoxide trapping capability (8>7>6>5). In contrast, lipid peroxidation in rat liver microsomes was reduced by 5 and 6 in dose-dependent manner. Compounds 3 and 4 were poor lipid peroxidation inhibitors, being approximately 400- to 1300-fold lower than 5 and 6. In addition, all compounds inhibited cell growth of human leukemia cell lines, HL60 and HL60R, in dose-dependent manners (5>6>3=4). The HL60R cell line is resistant against 1. Growth of both cell lines was suppressed by 5 and 6 in a fashion dependent on the length of the aminophenol alkyl chain, but not by 3 and 4. These results indicate that 5, a potent anticancer agent greater than 2, may potentially have clinical utility, and that its anticancer activity is correlated with inhibitory potency against lipid peroxidation, but not with superoxide scavenging activity.     

Growth inhibition and mechanism of action of p-dodecylaminophenol against refractory human pancreatic cancer and cholangiocarcinoma

Pancreatic cancer and cholangiocarcinoma are aggressive and drug-resistant refractory cancers. Based on N-(4-hydroxyphenyl)retinamide (3), a synthetic amide of all-trans-retinoic acid (RA), p-dodecylaminophenol (1) was developed to be an effective anticancer agent without key side-effects of these agents. Compound 1 suppresses cell growth of pancreatic cancer (MIA Paca2) and cholangiocarcinoma (HuCCT1), potentially by inhibiting ras expression and signaling through ERK pathways in MIA Paca2 cells and both ERK and Akt pathways in HuCCT1 cells. Compound 1 inhibits proliferation of these cells to a greater extent than either RA or 3. Compound 1 may represent a potent and useful anti-cancer drug for use against pancreatic cancer and cholangiocarcinoma that lacks their key side-effects.     

Semisynthesis and in vitro anticancer activities of andrographolide analogues

The plant Andrographis paniculata found throughout Southeast Asia contains Andrographolide 1, a diterpenoid lactone, which has antitumour activities against in vitro and in vivo breast cancer models. In the present study, we report on the synthesis of andrographolide derivatives, 3,19-isopropylideneandrographolide (2), 14-acetyl-3,19-isopropylideneandrographolide (3) and 14-acetylandrographolide (4), and their in vitro antitumour activities against a 2-cell line panel consisting of MCF-7 (breast cancer cell line) and HCT-116 (colon cancer cell line). Compounds 2 and 4 were also screened at the US National Cancer Institute (NCI) for their activities against a panel of 60 human cancer cell lines derived from nine cancer types. Compound 2 was found to be selective towards leukaemia and colon cancer cells, and compound 4 was selective towards leukaemia, ovarian and renal cancer cells at all the dose-response parameters. Compounds 2 and 4 showed non-specific phase of the cell cycle arrest in MCF-7 cells treated at different intervals with different concentrations. NCI's COMPARE and SOM mechanistic analyses indicated that the anticancer activities of these new class of compounds were not similar to that of standard anticancer agents, suggesting novel mechanism(s) of action.     

Synthesis, anticancer and antioxidant activities of some novel N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives

A series of N-(benzo[d]oxazol-2-yl)-2-(7- or 5-substituted-2-oxoindolin-3-ylidene) hydrazinecarboxamide derivatives were synthesized by treating N-(benzoxazol-2-yl)hydrazinecarboxamide with different isatin derivatives. The newly synthesized compounds were characterized on the basis of spectral analyses. All the synthesized derivatives (Va-l) were screened for anticancer and antioxidant activities. The results showed the anticancer activity of test compounds against HeLa, IMR-32 and MCF-7 cancer cell lines using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. All the synthetic compounds produced a dose-dependant inhibition of growth of the cells. The IC(50) values of some compounds were comparable with standard anticancer agent, cisplatin. All the title compounds effectively scavenged the free radical, α,α-diphenyl-β-picryl hydrazyl. The test compounds having substitution with different halides (electron withdrawing groups) at C5 position showed more potent anticancer and antioxidant activities than those at C7 position. These results indicate that C5-substituted derivatives may be useful for developing antioxidant agents that play a protective role in many pathological conditions such as cancer, diabetes and so on.     

Two New Norlignans and a New Lignanamide from Peperomia tetraphylla

Two new cyclobutane-type norlignans, methyl rel-(1R,2S,3S)-2-(7-methoxy-1,3-benzodioxol-5-yl)-3-(2,4,5-trimethoxyphenyl)cyclobutanecarboxylate (1), and methyl rel-(1R,2R,3S)-2-(7-methoxy-1,3-benzodioxol-5-yl)-3-(2,4,5-trimethoxyphenyl)cyclobutanecarboxylate (2), and a new lignanamide, 3-hydroxy-N-[2-(4-hydroxyphenyl)ethyl]-α-[4-(2-{N-[2-(4-hydroxyphenyl)ethyl]carbamoyl}ethenyl)-3-methoxyphenoxy]-4-methoxycinnamamide 4,8″-ether (3), along with five known amides, 4-8, were obtained from the whole plant of Peperomia tetraphylla. Their structures were elucidated mainly by the analysis of NMR and MS data. The new compounds 1-3 and the known compound 4 were tested for their cytotoxic activities against the HepG2 (human hepatocarcinoma), A549 (human lung cancer), and HeLa (human cervical cancer) cell lines. Compound 4 showed significant cytotoxicity against HepG2 cell lines with an IC(50) value of 9.4 ± 1.0?μM.     

Design, synthesis and anticancer activity of novel dihydrobenzofuro[4,5-b][1,8]naphthyridin-6-one derivatives

On the basis of the chemical structures of psorospermin with a xanthone template and acronycine derivatives with an acridone template, rac-1 and rac-2 constructed on an 1,2-dihydrobenzofuro[4,5-b][1,8]naphthyridin-6(11H)-one scaffold were designed and synthesized as potential anticancer agents. Their anticancer activities were evaluated against five human cancer cell lines. Rac-2 showed similar anticancer activity to doxorubicin and rac-1 exhibited even higher anticancer activity against LNCaP (IC(50)=0.14 μM), DU145 (IC(50)=0.15 μM), PC3 (IC(50)=0.30 μM) and MCF-7 (IC(50)=0.26 μM) cancer lines than doxorubicin and rac-2. Also, rac-1 revealed very potent anticancer activity (IC(50)=0.15 μM) against MCF-7/ADR cell (doxorubicin-resistant breast cancer cell) lines and induced G2/M phase arrest of the cell cycle in MCF-7/ADR cells.     

Synthesis and biological evaluation of halogenated phenoxychalcones and their corresponding pyrazolines as cytotoxic agents in human breast cancer

Novel halogenated phenoxychalcones 2a–f and their corresponding N-acetylpyrazolines 3a–f were synthesised and evaluated for their anticancer activities against breast cancer cell line (MCF-7) and normal breast cell line (MCF-10a), compared with staurosporine. All compounds showed moderate to good cytotoxic activity when compared to control. Compound 2c was the most active, with IC₅₀ = 1.52 µM and selectivity index = 15.24. Also, chalcone 2f showed significant cytotoxic activity with IC₅₀ = 1.87 µM and selectivity index = 11.03. Compound 2c decreased both total mitogen activated protein kinase (p38α MAPK) and phosphorylated enzyme in MCF-7 cells, suggesting its ability to decrease cell proliferation and survival. It also showed the ability to induce ROS in MCF-7 treated cells. Compound 2c exhibited apoptotic behaviour in MCF-7 cells due to cell accumulation in G2/M phase and elevation in late apoptosis 57.78-fold more than control. Docking studies showed that compounds 2c and 2f interact with p38alpha MAPK active sites.     

Discovery of novel quinoline-based analogues of combretastatin A-4 as tubulin polymerisation inhibitors with apoptosis inducing activity and potent anticancer effect

A new series of quinoline derivatives of combretastatin A-4 have been designed, synthesised and demonstrated as tubulin polymerisation inhibitors. These novel compounds showed significant antiproliferative activities, among them, 12c exhibited the most potent inhibitory activity against different cancer cell lines (MCF-7, HL-60, HCT-116 and HeLa) with IC₅₀ ranging from 0.010 to 0.042 µM, and with selectivity profile against MCF-10A non-cancer cells. Further mechanistic studies suggest that 12c can inhibit tubulin polymerisation and cell migration, leading to G₂/M phase arrest. Besides, 12c induces apoptosis via a mitochondrial-dependant apoptosis pathway and caused reactive oxygen stress generation in MCF-7 cells. These results provide guidance for further rational development of potent tubulin polymerisation inhibitors for the treatment of cancer.

Highlights

• A novel series of quinoline derivatives of combretastatin A-4 have been designed and synthesised.
• Compound 12c showed significant antiproliferative activities against different cancer cell lines.
• Compound 12c effectively inhibited tubulin polymerisation and competed with [³H] colchicine in binding to tubulin.
• Compound 12c arrested the cell cycle at G₂/M phase, effectively inducing apoptosis and inhibition of cell migration.

     

Synthesis, biological evaluation, and molecular docking studies of N-((1,3-diphenyl-1H-pyrazol-4-yl)methyl)aniline derivatives as novel anticancer agents

A series of N-((1,3-diphenyl-1H-pyrazol-4-yl)methyl)aniline derivatives (5a-8d) have been designed and synthesized, and their biological activities were also evaluated as potential antitumor and cyclin dependent kinase 2 (CDK2) inhibitors. Among all the compounds, compound 5a displayed the most potent CDK2/cyclin E inhibitory activity in vitro, with an IC(50) of 0.98±0.06μM. Antitumor assays indicated that compound 5a owned high antiproliferative activity against MCF-7 and B16-F10 cancer cell lines with IC(50) values of 1.88±0.11 and 2.12±0.15μM, respectively. Docking simulation was performed to insert compound 5a into the crystal structure of CDK2 at active site to determine the probable binding model. Based on the preliminary results, compound 5a with potent inhibitory activity in tumor growth may be a potential anticancer agent.     

Microwell bioreactor system for cell-based high throughput proliferation and cytotoxicity assays

Cell-based high throughput proliferation and cytotoxicity assays are increasingly used in drug screening and bioprocess development. However, online monitoring of cell proliferation, pH, and dissolved oxygen (DO) has been a challenge in 3D cell-based assays. In this work, a 40-microwell bioreactor (40-MBR) system was developed from a 384-well plate for real-time, noninvasive monitoring of pH, DO, and cell proliferation in 3D microenvironments. Chinese hamster ovary (CHO) and MCF-07 breast cancer cells cultured in 40-MBR confirmed that the 40-MBR was capable of simultaneously monitoring DO and cell proliferation based on culture fluorescence and pH by measuring the absorbance of phenol red. Cytotoxicity studies of sodium butyrate on CHO cells demonstrated that 40-MBR with dynamic background fluorescence correction gave more reliable and highly reproducible growth kinetic data compared to conventional multiwells with static background correction. Furthermore, the dosage effects of two new anticancer drug candidates, 5,7-dihydroxy-2-(4-hydroxyphenyl)-8-[(E)-2-phenylethenyl]-3,4-dihydro-2H-1-benzopyran-4-one (DH-8P-DB) and 5,7-dihydroxy-2-(4-hydroxyphenyl)-6-[(E)-2-phenylethenyl]-3,4-dihydro-2H-1-benzopyran-4-one (DH-6P-DB), on HT-29 colon cancer cells were assessed using the 40-MBR, and the results indicated that DH-6P-DB would be a more potent drug in treating colon cancer than DH-8P-DB. These studies demonstrated that 40-MBR could serve as a high throughput platform for screening potential cancer drugs in early-stage drug discovery.     

Synthesis and evaluation of naphthalene-based thiosemicarbazone derivatives as new anticancer agents against LNCaP prostate cancer cells

Fourteen new naphthalene-based thiosemicarbazone derivatives were designed as anticancer agents against LNCaP human prostate cancer cells and synthesized. MTT assay indicated that compounds 6, 8 and 11 exhibited inhibitory effect on LNCaP cells. Among these compounds, 4-(naphthalen-1-yl)-1-[1-(4-hydroxyphenyl)ethylidene)thiosemicarbazide (6), which caused more than 50% death on LNCaP cells, was chosen for flow cytometric analysis of apoptosis. Flow cytometric analysis pointed out that compound 6 also showed apoptotic effect on LNCaP cells. Compound 6 can be considered as a promising anticancer agent against LNCaP cells owing to its potent cytotoxic activity and apoptotic effect.     

Novel anticancer Hsp90 inhibitor disubstituted pyrazolyl 2-aminopyrimidine compound 7t induces cell cycle arrest and apoptosis via mitochondrial pathway in MCF-7 cells

Compound 7t, 4-(4-bromophenyl)-6-(1-(4-chlorophenyl)-3-(4-nitrophenyl)-1H-pyrazol-4-yl) pyrimidin-2-amine, is a proven potent anticancer agent exhibiting Hsp90 inhibition in our previous studies. Herein, we explored the apoptotic potential of compound 7t by Annexin V assay. The mechanism underlining the apoptosis process is elucidated. As a potent Hsp90 inhibitor, compound 7t would induce the mitochondrial stress leading to increased permeability of its membrane, that would subsequently initiate the apoptosis in MCF-7 cells. This was proven by increased J-monomer formation using JC-1 stain. Moreover, due to the impaired mitochondrial function, compound 7t also exaggerated the apoptosis process by ROS generation as proved by DCFDA staining. The morphological and nuclear changes in MCF-7 cells following apoptosis were identified by AO/EB and DAPI staining techniques. It also induced subG1 phase cell cycle arrest. Thus, compound 7t could serve as potential drug in the treatment regimen of breast cancer.     

Synthesis of stable benzimidazole derivatives bearing pyrazole as anticancer and EGFR receptor inhibitors

A new series of benzimidazole linked pyrazole derivatives were synthesized by cyclocondensation reaction through one-pot multicomponent reaction in absolute ethanol. All the synthesized compounds were tested for their in vitro anticancer activities on five human cancer cell lines including MCF-7, HaCaT, MDA-MB231, A549 and HepG2. EGFR receptor inhibitory activities were carried out for all the compounds. Majority of the compounds showed potent antiproliferative activity against the tested cancer cell lines. Compound 5a showed the most effective activity against the lungs cancer cell lines (IC₅₀ = 2.2 µM) and EGFR binding (IC₅₀ = 0.97 µM) affinity as compared to other members of the series. Compound 5a inhibited growth of A549 cancer cells by inducing a strong G₂/M phase arrest. In addition, same compound inhibited growth of A549 cancer cells by inducing apoptosis. In molecular docking studies compound 5a was bound to the active pocket of the EGFR (PDB 1M17) with five key hydrogen bonds and two π-π interaction with binding energies ΔG = −34.581 Kcal/mol.     

Epigenetic and genetic mechanisms contribute to telomerase inhibition by EGCG

The ends of human chromosomes are protected from the degradation associated with cell division by 15-20 kb long segments of hexameric repeats of 5'-TTAGGG-3' termed telomeres. In normal cells telomeres lose up to 300 bp of DNA per cell division that ultimately leads to senescence; however, most cancer cells bypass this lifespan restriction through the expression of telomerase. hTERT, the catalytic subunit essential for the proper function of telomerase, has been shown to be expressed in approximately 90% of all cancers. In this study we investigated the hTERT inhibiting effects of (-)-epigallocatechin-3-gallate (EGCG), the major polyphenol found in green tea catechins, in MCF-7 breast cancers cells and HL60 promyelocytic leukemia cells. Exposure to EGCG reduced cellular proliferation and induced apoptosis in both MCF-7 and HL60 cells in vitro, although hTERT mRNA expression was decreased only in MCF-7 cells when treated with EGCG. Furthermore, down-regulation of hTERT gene expression in MCF-7 cells appeared to be largely due to epigenetic alterations. Treatment of MCF-7 cells with EGCG resulted in a time-dependent decrease in hTERT promoter methylation and ablated histone H3 Lys9 acetylation. In conjunction with demethylation, further analysis showed an increase in hTERT repressor E2F-1 binding at the promoter. From these findings, we propose that EGCG is effective in causing cell death in both MCF-7 and HL60 cancer cell lines and may work through different pathways involving both anti-oxidant effects and epigenetic modulation.     

Synthesis, molecular docking and evaluation of thiazolyl-pyrazoline derivatives as EGFR TK inhibitors and potential anticancer agents

Fourty-two thiazolyl-pyrazoline derivatives were synthesized to screen for their EGFR kinase inhibitory activity. Compound 4-(4-chlorophenyl)-2-(3-(3,4-dimethylphenyl)-5-p-tolyl-4,5-dihydro-1H-pyrazol-1-yl)thiazole (11) displayed the most potent EGFR TK inhibitory activity with IC(50) of 0.06 μM, which was comparable to the positive control. Molecular docking results indicated that compound 11 was nicely bound to the EGFR kinase. Compound 11 also showed significant antiproliferative activity against MCF-7 with IC(50) of 0.07 μM, which would be a potential anticancer agent.     

Proliferation of human breast cancer cells and anti-cancer action of doxorubicin and vinblastine are independent of PKC-alpha

Protein kinase C (PKC) has been considered for a potential target of anticancer chemotherapy. PKC-alpha has been associated with growth and metastasis of some cancer cells. However, the role of PKC-alpha in human breast cancer cell proliferation and anticancer chemotherapy remains unclear. In this study, we examined whether alterations of PKC-alpha by phorbol esters and PKC inhibitors could affect proliferation of human breast cancer MCF-7 cells and the cytotoxic effect of chemotherapeutic agents. Exposure for 24 h to doxorubicin (DOX) and vinblastine (VIN) caused a concentration-dependent reduction in proliferation of MCF-7 cells. However, these two anticancer drugs altered cellular morphology and growth pattern in distinct manners. Phorbol 12,13-dibutyrate (PDBu, 100 nM), which enhanced activities of PKC-alpha, increased cancer cell proliferation and attenuated VIN (1 microM)-induced cytotoxicity. These effects were not affected in the presence of 10 nM staurosporine. Phorbol myristate acetate (PMA, 100 nM) that completely depleted PKC-alpha also enhanced cancer cell proliferation and attenuated VIN-induced cytotoxicity. Three potent PKC inhibitors, staurosporine (10 nM), chelerythrine (5 microM) and bisindolylmaleimide-I (100 nM), had no significant effect on MCF-7 cell proliferation; staurosporine and chelerythrine, but not bisindolylmaleimide-I, attenuated VIN-induced cytotoxicity. Moreover, neither phorbol esters nor PKC inhibitors had an effect on cytotoxic effects of DOX (1 microM) on MCF-7 cell proliferation. Thus, these data suggest that MCF-7 cell proliferation or the anti-cancer action of DOX and VIN on breast cancer cells is independent of PKC-alpha.