Synthesis and biological evaluation of dimeric cinnamaldehydes as potent antitumor agents

It has been reported that 2-hydroxycinnamaldehyde and 2-benzoyl-oxycinnamaldehyde inhibited the activity of farnesyl protein transferase, angiogenesis, cell-cell adhesion, and tumor growth in vivo model. In order to improve its anti-tumor activity, dimeric cinnamaldehydes have been synthesized based on 2-hydroxycinnamaldehyde. The synthesized compounds strongly inhibited the growth of human colon tumor cells with GI50 values of 0.6-10 microM. Especially, 2-piperazine derivative blocked in vivo growth of human colon tumor xenograft in nude mice at 10 mg/kg. It was found that their anti-tumor effects induce apoptosis and cell cycle arrest at G2/M phase by the compounds. It was confirmed by detection of apoptosis markers such as activated caspase-3 and cleaved PARP, and cell cycle analysis. The dimeric compounds also inhibited Cdc25B phosphatase which is essential for preinitiating G2/M transition and S phase progression.     

The farnesyl transferase inhibitor (FTI) SCH66336 (lonafarnib) inhibits Rheb farnesylation and mTOR signaling. Role in FTI enhancement of taxane and tamoxifen anti-tumor activity

Lonafarnib (SCH66336) is a farnesyl transferase inhibitor (FTI) that inhibits the post-translational lipid modification of H-Ras and other farnesylated proteins. K- and N-Ras are also substrates of farnesyl transferase; however, upon treatment with FTIs, they are alternatively prenylated by geranylgeranyl transferase-1. Despite the failure to abrogate prenylation of K- and N-Ras, growth of many tumors in preclinical models is inhibited by FTIs. This suggests that the anti-proliferative action of FTIs is dependent on blocking the farnesylation of other proteins. Rheb (Ras homologue enriched in brain) is a farnesylated small GTPase that positively regulates mTOR (mammalian target of rapamycin) signaling. We found that Rheb and Rheb2 mRNA were elevated in various tumor cell lines relative to normal cells. Peptides derived from the carboxyl termini of human Rheb and Rheb2 are in vitro substrates for farnesyl transferase but not geranylgeranyl transferase-1. Rheb prenylation in cell culture was completely inhibited by SCH66336, indicating a lack of alternative prenylation. SCH66336 treatment also inhibited the phosphorylation of S6 ribosomal protein, a downstream target of Rheb and mTOR signaling. SCH66336 did not inhibit S6 phosphorylation in cells expressing Rheb-CSVL, a mutant construct of Rheb designed to be geranylgeranylated. Importantly, expression of Rheb-CSVL also abrogated SCH66336 enhancement of tamoxifen- and docetaxel-induced apoptosis in MCF-7 breast cancer cells and ES-2 ovarian cancer cells, respectively. Further, inhibition of Rheb signaling by rapamycin treatment, small interfering RNA, or dominant negative Rheb enhanced tamoxifen- and docetaxel-induced apoptosis, similar to FTI treatment. These studies demonstrated that Rheb is modified by farnesylation, is not a substrate for alternative prenylation, and plays a role in SCH66336 enhancement of the anti-tumor response to other chemotherapeutics.     

Anti-tumor activity of the farnesyl-protein transferase inhibitors arteminolides, isolated from Artemisa

Members of the Artemisia genus are important medicinal plants found throughout the world. Arteminolides A-D (1-4), isolated from the aerial parts of Artemisia, have an inhibitory activity on farnesyl-protein transferase (FPTase; EC 2.5.1.29) in in vitro assay. This study was carried out with the purpose of validating anti-tumor effects of the compounds in human tumor cells and mouse xenograft model. The arteminolides inhibited tumor cell growth in a dose-dependent manner. Furthermore, arteminolide C (3) blocked in vivo growth of human colon and lung tumor xenograft without the loss of body weight in nude mice.     

Analysis of farnesyl transferase activity during hormone-induced maturation of Xenopus laevis oocytes

Preincubation of Xenopus laevis oocytes with insulin or insulin-like growth factor 1 (IGF-1) resulted in inhibition of farnesyl transferase (FTase) activity measured both in vivo (after microinjection of tritiated farnesyl pyrophosphate and Ras-CVIM into oocytes) and in extracts using a filtration assay. FTase activity measured in oocyte extracts was inhibited 55% after a 20 min treatment of oocytes with 1 microM insulin or 10 nM IGF-1. The apparent IC(50) for inhibition of oocyte FTase by IGF-1 is 0.3 nM. The observed decrease in FTase activity was apparently not due to translocation of enzyme from cytosol to membrane, since activities measured both in soluble extracts and resuspended crude pellets displayed comparable levels of inhibition following hormone treatment. Using a hexapeptide (TKCVIM) as substrate, FTase activity was also inhibited 65% when oocytes were pretreated with 10 nM IGF-1. Two FTase inhibitors [(alpha-hydroxyfarnesyl) phosphonic acid (HFPA) and chaetomellic acid A (CA)] effectively inhibited Xenopus oocyte FTase by 80-90% when added to assay mixtures (IC(50) values of 338 +/- 96 nM HFPA and 232 +/- 80 nM CA) or after incubation of oocytes in drug before preparation of soluble extracts for assay (IC(50) values of 7 +/- 6 nM HFPA and 328 +/- 128 nM CA). The farnesyl transferase inhibitors were observed to slow the time course of oocyte maturation but did not block the IGF-1-induced maturation response. J. Exp. Zool. 286:193-203, 2000.Copyright 2000 Wiley-Liss, Inc.     

Anti-inflammatory flavonoids and pterocarpanoid from Crotalaria pallida and C. assamica

One new isoflavone, 5,7,4'-trihydroxy-2'-methoxyisoflavone (3) and seven, and four known compounds were isolated from the barks of Crotalaria pallida and the seeds of C. assamica, respectively. The known compounds, apigenin (1) and 2'-hydroxygenistein (2), isolated from C. pallida, showed significant concentration-dependent inhibitory effects on the release of beta-glucuronidase and lysozyme from rat neutrophils in response to formyl-Met-Leu-Phe/cytochalasin B (fMLP/CB) with IC(50) values of 2.8+/-0.1 and 17.7+/-1.9, and 5.9+/-1.4 and 9.7+/-3.5 microM, respectively. The known compounds, daidzein (4) and 2'-hydroxydaidzein (6), isolated from C. pallida, inhibited of the release of lysozyme and beta-glucuronidase from rat neutrophils in response to fMLP/CB with IC(50) values of 26.3+/-5.5 and 13.7+/-2.6 microM, respectively. Compounds 1 and 4 also showed significant concentration-dependent inhibitory effects on superoxide anion generation in rat neutrophils stimulated with fMLP/CB with IC(50) values of 3.4+/-0.3 and 25.1+/-5.0 microM, respectively. Compounds 1 and 5, previously isolated from C. pallida, showed the inhibition of NO production in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages and LPS/interferon-gamma (IFN-gamma)-stimulated N9 microglial cells with IC(50) values of 10.7+/-0.1 and 13.9+/-1.1 microM, respectively. Flavonoids, suppressed chemical mediators in inflammatory cells, may have value in treatment and prevention of central and peripheral inflammatory diseases associated with excess production of chemical mediators.     

Lipid peroxidation, cyclooxygenase enzyme and tumor cell proliferation inhibitory compounds in Cornus kousa fruits

The genus Cornus is well known for its medicinal properties. Bioassay-guided isolation and characterization of C. kousa fruits afforded kaempferol 3-O-rhamnoside (1), myricetin 3-O-rhamnoside (2), kaempferol 3-O-glucoside (3), cornin (4) and stenophyllin (5) in addition to ursolic acid and beta-sitosterol. These compounds are isolated for the first time from C. kousa. Compounds 1-5 inhibited Fe(2+) catalyzed lipid peroxidation by 63%, 57%, 61%, 53%, and 51%, at 23, 22, 23, 129, and 108 microM, respectively. Similarly, they inhibited COX-1 and -2 enzymes activities by 24% and 47%, 40% and 37%, 20% and 37%, 52% and 63%, and 48% and 55% respectively, at 231, 215, 226, 258, and 217 microM, respectively. At 129 microM, compound 4 displayed growth inhibition of HCT-116 (colon), MCF-7 (breast), NCI-H460 (lung), SF-268 (central nervous system CNS), and AGS (stomach) human tumor cell lines by 31%, 29%, 40%, 9%, and 28%, respectively. Similarly, compound 5 inhibited the growth of colon, breast, lung, CNS, and stomach tumor cell lines by 0%, 27%, 35%, 16%, and 27%, respectively, at 108 microM.     

Farnesyl transferase inhibitors block the farnesylation of CENP-E and CENP-F and alter the association of CENP-E with the microtubules

Human tumor cell lines that are sensitive to the effects of farnesyl transferase inhibitors accumulate in G(2) --> M (except for cells with an activated Ha-ras that accumulate in G(1)). A search for CAAX box proteins from Swiss-Prot revealed more than 300 peptides. Of these, the centromeric proteins CENP-E and CENP-F are preferentially expressed during mitosis and are implicated as mediators of the G(2) --> M checkpoint. Experiments performed here show that peptides from the COOH-terminal CAAX box of CENP-E and CENP-F are substrates for farnesyl transferase but not geranylgeranyl transferase-I. Although both proteins are prenylated in the human tumor cell line DLD-1, their prenylation is completely inhibited by the farnesyl transferase inhibitor, SCH 66336. Immunohistochemical data with the lung carcinoma cell line, A549, showed that preventing the farnesylation of CENP-E and CENP-F by treatment with the farnesyl transferase inhibitor SCH 66336 does not affect their localization to the kinetochores. However, the presence of farnesyl transferase inhibitors alters the association between CENP-E and the microtubules. Our results imply that the inhibition of CENP-E farnesylation results in the alteration of the microtubule-centromere interaction during mitosis and results in the accumulation of cells prior to metaphase.     

Stereoselective biotransformation of timosaponin A-III by Saccharomyces cerevisiae

Bioconversion of timosaponin A-III (TA-III), one of the major steroidal saponins isolated from the rhizomes of Anemarrhenae asphodeloides Bunge (Liliaceae), was investigated in Saccharomyces cerevisiae. Five bioconversion products, denoted compounds 2-6, were obtained. Biotransformation metabolite 2 was a stereoisomer of TAIII with a specific isotype F-ring and beta-ranged CH3-21, which rarely occurs in nature. The structure of 2 was elucidated by extensive spectroscopic analysis (H-H COSY, HSQC, HMBC), as well as by high-resolution mass spectral analysis. The growth inhibitory activity of compounds 1-6 was assayed against four human cancer cell lines, HepG2, H-1299, HT-29, and HCT-116. Compounds 1 and 2 obviously inhibited the growth of the four types of cancer cells with IC50 values being less than 19 micrometer. A structure-activity relationship is discussed, and the spirostane-ring F in compounds 1 and 2 appears to be the critical bioactive moiety for the cell growth inhibitory property.     

Dietary organic isothiocyanates are cytotoxic in human breast cancer MCF-7 and mammary epithelial MCF-12A cell lines

Organic isothiocyanates (ITCs) are dietary components present in cruciferous vegetables. The purpose of this investigation was to examine the cytotoxicity of 1-naphthyl isothiocyanate (NITC), benzyl isothiocyanate (BITC), beta-phenethyl isothiocyanate (PEITC), and sulforaphane in human breast cancer MCF-7 and human mammary epithelium MCF-12A cell lines, as well as in a second human epithelial cell line, human kidney HK-2 cells. The cytotoxicity of NITC, BITC, PEITC, and sulforaphane, as well as the cytotoxicity of the chemotherapeutic agents daunomycin (DNM) and vinblastine (VBL), were examined in MCF-7/sensitive (wt), MCF-7/Adr (which overexpresses P-glycoprotein), MCF-12A, and HK-2 cells. Cell growth was determined by a sulforhodamine B assay. The IC50 values for DNM and VBL in MCF-7/Adr cells were 7.12 +/- 0.42 microM and 0.106 +/- 0.004 microM (mean +/- SE) following a 48-hr exposure; IC50 values for BITC, PEITC, NITC, and sulforaphane were 5.95 +/- 0.10, 7.32 +/- 0.25, 77.9 +/- 8.03, and 13.7 +/- 0.82 microM, respectively, with similar values obtained in MCF-7/wt cells. Corresponding values for BITC, PEITC, NITC, and sulforaphane in MCF-12A cells were 8.07 +/- 0.29, 7.71 +/- 0.07, 33.6 +/- 1.69, and 40.5 +/- 1.25 microM, respectively. BITC and PEITC can inhibit the growth of human breast cancer cells as well as human mammary epithelium cells at concentrations similar to those of the chemotherapeutic drug DNM. Sulforaphane and NITC exhibited higher IC50 values. The effect of these ITCs on cell growth may contribute to the cancer chemopreventive properties of ITCs by suppressing the growth of preclinical tumors, and may indicate a potential use of these compounds as chemotherapeutic agents in cancer treatment.     

Inhibition of intrinsic protein tyrosine kinase activity of EGF-receptor kinase complex from human breast cancer cells by the marine sponge metabolite (+)-aeroplysinin-1

1. (+)-Aeroplysinin-1, a naturally occurring tyrosine metabolite from the marine sponge Verongia aerophoba, was found to inhibit the phosphorylation of lipocortin-like proteins by a highly purified preparation of the epidermal growth factor (EGF) receptor-tyrosine protein kinase complex from MCF-7 breast carcinoma cells. 2. (+)-Aeroplysinin-1 blocked the EGF-dependent proliferation of both MCF-7 and ZR-75-1 human breast cancer cells and inhibited the ligand-induced endocytosis of the EGF receptor in vitro. 3. Treatment with aeroplysinin-1 in the concentration range at 0.25-0.5 microM resulted in a time- and dose-dependent total tumor cell death in vitro. 4. At a 10-fold higher concentration the compound did not reveal any cytostatic activity in normal human fibroblasts. 5. From these data we conclude that (+)-aeroplysinin-1 represents a compound which displays a strong anti-tumor effect on EGF-dependent tumor cell lines.     

Synthesis, crystal structure and biological activities of copper(II) complexes with chelating bidentate 2-substituted benzimidazole ligands

A series of Cu(II) coordination compounds with benzimidazole-derived bidentate chelating ligands have been prepared and characterized by X-ray crystallography. The 2-(4,5-dihydro-1H-imidazol-2-yl)-1H-benzimidazole CuCl2 complex 8 showed very potent superoxide dismutase (Cu,Zn-SOD) activity in vitro with IC50 of 0.09 microM, comparable to those described in the literature for best low molecular weight CuZnSOD mimics. Cytotoxicity studies with seven different human tumor cell lines in vitro showed that the most active 2-(4,5-dihydro-1H-imidazol-2-yl)-5-nitro-1H-benzimidazole CuCl2 complex 10 inhibited the growth of cancer cells with IC50 between 4.76 and 10.84 microM.     

Protein tyrosine phosphatase 1B inhibitors from Morus root bark

An organic layer prepared from the Chinese crude drug 'Sang-Bai-Pi' (Morus root bark) was studied in order to identify the inhibitory compounds for protein tyrosine phosphatase 1B (PTP1B). Bioassay-guided fractionation resulted in the isolation of sanggenon C (1), sanggenon G (2), mulberrofuran C (3) and kuwanon L (4) as PTP1B inhibitors, along with moracin O (5) and moracin P (6). Compounds 1-4 inhibited PTP1B with IC(50) values ranging from 1.6+/-0.3 microM to 16.9+/-1.1 microM.     

Antitumor agents. Part 3: synthesis and cytotoxicity of new trans-stilbene benzenesulfonamide derivatives

A new series of trans-stilbene benzenesulfonamide derivatives were designed and synthesized as potential antitumor agents. These new compounds were evaluated in the National Cancer Institute's 60 human tumor cell line in vitro screen. Compounds 9-13 were cytotoxic against several cell lines. Notably, two compounds, 9 and 12, demonstrated selective cytotoxic activity against BT-549 breast cancer (GI(50)=0.205 microM) and HT-29 colon cancer (GI(50)=0.554 microM), respectively.     

Synthesis, antiproliferative, and antiplatelet activities of oxime- and methyloxime-containing flavone and isoflavone derivatives

Certain oxime- and methyloxime-containing flavone and isoflavone derivatives were synthesized and evaluated for their antiproliferative activity against three solid cancer cells, human cervical epithelioid carcinoma (HeLa), hepatocellular carcinoma (SKHep1), and oral squamous cell carcinoma (SAS), which are commonly seen in Asian countries, including Taiwan. Selective compounds were also evaluated in the full panel of 60 human tumor cell lines and their mean GI50 values were obtained. The preliminary assays indicated flavone-6-yl derivatives are the most cytotoxic while isoflavone-7-yl derivatives are the best antiplatelet agents. Among them, (E)-6-(2-methoxyiminopropoxy)-2-phenyl-4H-1-benzopyran-4-one (14), (Z)-6-(2-hydroxyimino-2-phenylethoxy)-2-phenyl-4H-1-benzopyran-4-one (18a), and (Z)-6-[2-hydroxyimino-2-(4-methoxyphenyl)ethoxy]-2-phenyl-4H-1-benzopyran-4-one (18c) are three of the best antiproliferative agents with GI50 values of 0.8, 0.7, and 0.8 microM, respectively, against the growth of SKHep1; 0.9, 0.8, and 1.0 microM, respectively, against the growth of HeLa cells. Compound 18c is not only the most cytotoxic with a mean GI50 value of 0.08 microM against the full panel of 60 human tumor cell lines but also the only flavone derivative that exhibited a GI50 value of less than 1 microM against the growth of SAS. Flow cytometric analyses revealed that growth inhibition by 18c was due to accumulation in G2/M phase arrest and followed by apoptosis.     

2'-benzoyloxycinnamaldehyde induces apoptosis in human carcinoma via reactive oxygen species

2'-hydroxycinnamaldehyde (HCA) has been shown to have inhibitory effects on farnesyl protein transferase in vitro, angiogenesis, and tumor cell growth. However, mechanism for these inhibitions remains unknown. As a derivative of HCA, BCA (2'-benzoyl-oxycinnamaldehyde) was synthesized by replacing hydroxyl group with benzoyl-oxyl group. When p53-mutated cancer cell lines (MDA-MB-231 breast cancer cell and SW620 colon cancer cell) were treated with 10 microM HCA or BCA, it induced growth arrest and apoptosis of tumor cells. Markers of apoptosis such as degradations of chromosomal DNA and poly(ADP-ribose) polymerase and activation of caspase-3 were detected after HCA or BCA treatment. BCA-induced apoptosis was blocked by pretreatment of cells with anti-oxidants, glutathione, or N-acetyl-cysteine. In addition, BCA-induced activation of caspase-3 and degradation of poly(ADP-ribose) polymerase were abolished by pretreatment of cells with the anti-oxidants. These results suggest that reactive oxygen species are major regulator of BCA-induced apoptosis. HCA or BCA-induced accumulation of reactive oxygen species was detected by using DCF-DA, an intracellular probe of oxidative stress. Furthermore, when BCA (100 mg/kg) was administrated intraperitoneally or orally into a nude mouse, it inhibited >88 or 41% of tumor growth, respectively, without any detectable weight change. These results suggest that BCA is a good drug candidate for cancer therapy.     

Cytotoxicities, cell cycle and caspase evaluations of 1,6-diaryl-3(Z)-hexen-1,5-diynes, 2-(6-aryl-3(Z)-hexen-1,5-diynyl)anilines and their derivatives

Compounds 3, 6-7, 9-10, 15-17, and 20-21 showed growth inhibition effects on a full panel of 60 human cancer cell lines, and most of the average IC50 values of the indicated analogues were from < 0.01 to 96.6 microM, in which analogues 16 and 17 revealed the highest cytotoxic activity with the cancer cell lines at 10(-7) M concentration range. During the cell cycle analysis, a moderate to high apoptotic progress induction was shown by 3, 9, 16-17, and 20 compared with the control, which 2-(6-(2-thienyl)-3(Z)-hexen-1,5-diynyl)aniline 16 showed the highest apoptotic effect. Structures 16-17 displayed a significant G2/M phase arrest in the cell growth cycle compared with other derivatives, which the proportions of the G2/M phase cells were accumulated to 71.5% and 82.6%, respectively. Moreover, the colorimetric assay of 16-17 also provided advanced evidence to the relationship between the compounds and the caspase-3 enzyme, which was one of the major promoters of apoptotic effect.     

Human ACAT-1 and -2 inhibitory activities of saucerneol B, manassantin A and B isolated from Saururus chinensis

The sesquineolignan, saucerneol B (1), and dineolignans, manassantin A (2), and manassantin B (3), were isolated from the methanol extracts of Saururus chinensis root and elucidated by their spectroscopic data analysis. Compounds 1-3 inhibited hACAT-1 and hACAT-2 with IC(50) values of 43.0 and 124.0 microM for 1, of 39.0 and 8.0 microM for 2, of 82.0 microM and only 32% inhibition at 1mM for 3, respectively. The EtOAc-soluble fraction, which contained compounds 1-3, of methanol extracts of S. chinensis exhibited strong cholesterol-lowering effect in high cholesterol-fed mice.     

Antitumor agents. Part 212. Bucidarasins A-C, three new cytotoxic clerodane diterpenes from Bucida buceras

As part of a study on antitumor agents from rainforest plants, four new clerodane diterpenes, bucidarasins A--D (1-4), were isolated from Bucida buceras. Their structures were elucidated from detailed 2D NMR analyses. Compounds 1-3 showed potent cytotoxicity against human tumor cell lines with IC(50) values of 0.5-1.9 microM. The potency was retained in drug resistant lines.     

E,E,E-1-(4-Arylamino-4-oxo-2-butenoyl)-3,5-bis(arylidene)-4-piperidones: a topographical study of some novel potent cytotoxins

A series of E,E,E-3,5-bis(arylidene)-1-(4-arylamino-4-oxo-2-butenoyl)-4-piperidones 4 (phenylidene) and 5 (4-nitrophenylidene) were prepared in order to explore the structural features of the N-acyl group which affects the cytotoxic potency. Evaluation toward human Molt 4/C8 and CEM T-lymphocytes revealed that many of the IC(50) figures were submicromolar and lower than melphalan. Marked inhibitory potencies toward murine leukemia L1210 cells were also noted. When evaluated against a panel of human tumor cell lines, three representative compounds in series 4 displayed selective toxicity to leukemia and colon cancer cell lines and were significantly more potent than the reference drug melphalan. Molecular modeling of representative compounds in both series 4 and the analogs, in which the configuration of the olefinic double bond was changed from E to Z (series 3), revealed that the torsion angles of the arylidene aryl rings and locations of the terminal arylaminocarbonyl groups may have contributed to the greater cytotoxic properties displayed in 3. Compounds 4c (3,4-dichlorophenylamino), d (4-methylphenylamino) and 5c (3,4-dichlorophenylamino), d (4-methylphenylamino) inhibited the activity of human N-myristoyltransferase by approximately 50% at concentrations of 50-100 microM. The compounds in series 4 and 5 were well tolerated in a short-term toxicity study in mice.