α-Tomatine inhibits growth and induces apoptosis in HL-60 human myeloid leukemia cells.

α­Tomatine is a glycoalkaloid that occurs naturally in tomatoes (Lycopersicon esculentum). In the present study, the effects of α­tomatine on human myeloid leukemia HL­60 cells were investigated. Treatment of HL­60 cells with α­tomatine resulted in growth inhibition and apoptosis in a concentration­dependent manner. Tomatidine, the aglycone of tomatine had little effect on the growth and apoptosis of HL­60 cells. Growth inhibition and apoptosis induced by α­tomatine in HL­60 cells was partially abrogated by addition of cholesterol indicating that interactions between α­tomatine and cell membrane­associated cholesterol may be important in mediating the effect of α­tomatine. Activation of nuclear factor­κB by the phorbol ester, 12­O­tetradecanoylphorbol­13­acetate failed to prevent apoptosis in HL­60 cells treated with α­tomatine. In animal experiments, it was found that treatment of mice with α­tomatine inhibited the growth of HL­60 xenografts in vivo. Results from the present study indicated that α­tomatine may have useful anti­leukemia activities.

Anticancer activity of Acanthopanax trifoliatus (L) Merr extracts is associated with inhibition of NF-kB activity and decreased Erk1/2 and Akt phosphorylation.

Acanthopanax trifoliatus (L) Merr (AT) is commonly used as an herbal medicine and edible plant in some areas of China and other Asian countries. AT is thought to have anticancer effects, but potential mechanisms remain unknown. To assess the anticancer properties of AT, we exposed prostate cancer cells to AT extracts and assessed cell proliferation and signaling pathways. An ethanol extract of AT was suspended in water followed by sequential extraction with petroleum ether, ethyl acetate and n-butanol. PC-3 cells were treated with different concentrations of each extract and cell viability was determined by the MTT and trypan blue exclusion assays. The ethyl acetate extract of the ethanol extract had a stronger inhibitory effect on growth and a stronger stimulatory effect on apoptosis than any of the other extracts. Mechanistic studies demonstrated that the ethyl acetate extract suppressed the transcriptional activity of NF-kB, increased the level of caspase-3, and decreased the levels of phospho-Erk1/2 and phospho-Akt. This is the first report on the anticancer activity of AT in cultured human prostate cancer cells. The results suggest that AT can provide a plant-based medicine for the treatment or prevention of prostate cancer.

Potent inhibitory effect of δ-tocopherol on prostate cancer cells cultured in vitro and grown as xenograft tumors in vivo.

In the present study, the effects of δ-tocopherol (δ-T) on growth and apoptosis of human prostate cancer cells were determined and compared with that of α-tocopherol (α-T), a commonly used form of vitamin E. Treatment of human prostate cancer cells with δ-T resulted in strong growth inhibition and apoptosis stimulation, while the effects of α-T were modest. The strong effects of δ-T on the cells were associated with suppression of androgen receptor (AR) activity and decreased level of prostate specific antigen (PSA) that is a downstream target of the AR signaling. In the in vivo study, we found that δ-T had a more potent inhibitory effect on the formation and growth of prostate xenograft tumors than that of α-T. Moreover, δ-T inhibited proliferation and stimulated apoptosis in the tumors. The present study identified δ-T as a better form of vitamin E than α-T for future clinical studies of prostate cancer prevention.

Nrf2 null enhances UVB-induced skin inflammation and extracellular matrix damages.

Nrf2 plays a critical role in defending against oxidative stress and inflammation. We previously reported that Nrf2 confers protection against ultraviolet-B (UVB)-induced inflammation, sunburn reaction, and is involved in sulforaphane-mediated photo-protective effects in the skin. In this study, we aimed to demonstrate the protective role of Nrf2 against inflammation-mediated extracellular matrix (ECM) damage induced by UVB irradiation. Ear biopsy weights were significantly increased in both Nrf2 wild-type (Nrf2 WT) and knockout (Nrf2 KO) mice one week after UVB irradiation. However, these weights increased more significantly in KO mice compared to WT mice, suggesting a greater inflammatory response in KO mice. In addition, we analyzed the protein expression of numerous markers, including macrophage inflammatory protein-2 (MIP-2), pro-matrix metalloproteinase-9 (MMP-9), and p53. p53, a regulator of DNA repair, was overexpressed in Nrf2 KO mice, indicating that the absence of Nrf2 led to more sustained DNA damage. There was also more substantial ECM degradation and increased inflammation in UVB-irradiated Nrf2 KO mice compared to UVB-irradiated WT mice. Furthermore, the protective effects of Nrf2 in response to UVB irradiation were mediated by increased HO-1 protein expression. Collectively, our results show that Nrf2 plays a key role in protecting against UVB irradiation and that the photo-protective effect of Nrf2 is closely related to the inhibition of ECM degradation and inflammation.

Curcumin analogues with high activity for inhibiting human prostate cancer cell growth and androgen receptor activation.

The androgen receptor (AR) has a critical role in prostate cancer development and progression. Several curcumin analogues (A10, B10, C10, E10 and F10) with different linker groups were investigated for their effects in human prostate cancer CWR­22Rv1 and LNCaP cell lines. The ability of these compounds to inhibit testosterone (TT)­ or dihydrotestosterone (DHT)­induced AR activity was determined by an AR­linked luciferase assay and by TT­ or DHT­induced expression of prostate specific antigen. Compounds F10 and E10 had stronger inhibitory effects on the growth of cultured CWR­22Rv1 and LNCaP cell lines, and they also had enhanced stimulatory effects on apoptosis compared with curcumin and other curcumin analogues (A10, B10, C10) in CWR­22Rv1 cells. E10 and F10 were more potent inhibitors of AR activity than curcumin, A10 and B10. The higher activities of E10 and F10 may be correlated with a heteroatom linker. The results indicate that one of the potential mechanisms for the anticancer effect of the curcumin analogues was inhibition of AR pathways in human prostate cancer cells.

Combination of Lipitor and Celebrex inhibits prostate cancer VCaP cells in vitro and in vivo.

BACKGROUND/AIM: Lipitor is a cholesterol-lowering drug and Celebrex is a Cyclooxygenase-2 inhibitor. We investigated the effects of Lipitor and Celebrex on human prostate cancer VCaP cells cultured in vitro and grown as orthotopic xenograft tumors in SCID mice. MATERIALS AND METHODS: Apoptosis was measured by morphological assessment and caspase-3 assay. Nuclear factor-kappa B (NF-κB) activation was determined by luciferase reporter assay. B-cell lymphoma-2 (Bcl2) was measured by western blotting and immunohistochemistry. Orthotopic prostate tumors were monitored by the IVIS imaging system. RESULTS: the combination of Lipitor and Celebrex had stronger effects on the growth and apoptosis of VCaP cells than did either drug alone. The combination more potently inhibited activation of NFκB and expression of Bcl2 than either drug alone. The growth of orthotopic VCaP prostate tumors was strongly inhibited by treatment with the drug combination. CONCLUSION: Administration of Lipitor and Celebrex in combination may be an effective strategy for inhibiting the growth of prostate cancer.

Effects of curcumin analogues for inhibiting human prostate cancer cells and the growth of human PC-3 prostate xenografts in immunodeficient mice.

Four curcumin analogues ((2E,6E)-2,6-bis(thiophen-3-methylene) cyclohexanone (AS), (2E,5E)-2,5-bis(thiophen-3-methylene) cyclopentanone (BS), (3E,5E)-3,5-bis(thiophen-3-methylene)-tetrahydropyran-4-one (ES) and (3E,5E)-3,5-bis(thiophen-3-methylene)-tetrahydrothiopyran-4-one (FS) as shown in Fig. 1) with different linker groups were investigated for their effects in human prostate cancer CWR-22Rv1 and PC-3 cells. Compounds FS and ES had stronger inhibitory effects than curcumin, AS and BS on the growth of cultured CWR-22Rv1 and PC-3 cells, as well as on the androgen receptor (AR) and nuclear factor kappa B (NF-κB) activity. The strong activities of ES and FS may be correlated with a heteroatom linker. In animal studies, severe combined immunodeficient (SCID) mice were injected subcutaneously (s.c.) with PC-3 cells in Matrigel. After 4 to 6 weeks, mice with PC-3 tumors (about 0.6 cm wide and 0.6 cm long) received daily intraperitoneal (i.p.) injections of vehicle, ES and FS (10 µg/g body weight) for 31 d. FS had a potent effect in inhibiting the growth and progression of PC-3 tumors. Our results indicate that FS may be useful for inhibiting human prostate tumors growth.

A triple combination of atorvastatin, celecoxib and tipifarnib strongly inhibits pancreatic cancer cells and xenograft pancreatic tumors.

Because K-Ras mutation and cyclooxygenase-2 (COX-2) overexpression are hallmarks of majority of pancreatic cancer patients, an approach to inhibit the progression and growth of pancreatic cancer using the simultaneous administration of agents that inhibit the function of both targets, should be considered. In the present study, we assessed the effects of atorvastatin (Lipitor), celecoxib (Celebrex) and tipifarnib (Zarnestra) on the growth of human pancreatic cancer. In the in vitro studies, we found that treatment of human pancreatic tumor cells with a combination of atorvastatin, celecoxib and tipifarnib had a stronger inhibitory effect on growth and a stronger stimulatory effect on apoptosis than each drug alone or for any combination of two drugs. We also found that treatment of Panc-1 cells with a combination of all three drugs strongly decreased the levels of phosphorylated Erk1/2 and Akt. In an animal model of xenograft tumors in severe combined immunodeficient (SCID) mice, we found that daily i.p. injections of a combination of atorvastatin, celecoxib and tipifarnib had a stronger inhibitory effect on the growth of the tumors in mice than each drug alone or for any combination of two drugs. The results of our study indicate that a combination of atorvastatin, celecoxib and tipifarnib may be an effective strategy for the treatment of pancreatic cancer.

Requirement and epigenetics reprogramming of Nrf2 in suppression of tumor promoter TPA-induced mouse skin cell transformation by sulforaphane.

Nrf2 is a transcription factor that plays critical roles in regulating the expression of cellular defensive antioxidants and detoxification enzymes. However, the role of Nrf2 and Nrf2's epigenetics reprogramming in skin tumor transformation is unknown. In this study, we investigated the inhibitory role and epigenetics of Nrf2 on tumor transformation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in mouse skin epidermal JB6 (JB6 P+) cells and the anticancer effect of sulforaphane (SFN), an isothiocyanate found in cruciferous vegetables. After five days of treatment, SFN significantly inhibited TPA-induced JB6 cellular transformation and SFN enhanced the nuclear translocation of Nrf2 and increased the mRNA and protein levels of the Nrf2 target genes HO-1, NQO1 and UGT1A1. Knockdown of Nrf2 attenuated the induction of Nrf2, HO-1 and NQO1 by SFN, enhanced TPA-induced colony formation and dampened the inhibitory effect of SFN on TPA-induced JB6 transformation. Epigenetics investigation using bisulfite genomic sequencing showed that SFN decreased the methylation ratio of the first 15 CpGs of the Nrf2 gene promoter, which was corroborated by increased Nrf2 mRNA expression. Furthermore, SFN strongly reduced the protein expression of DNA methyltransferases (DNMT1, DNMT3a and DNMT3b). SFN also inhibited the total histone deacetylase (HDAC) activity and decreased the protein expression of HDAC1, HDAC2, HDAC3 and HDAC4. Collectively, these results suggest that the anti-cancer effect of SFN against TPA-induced neoplastic transformation of mouse skin could involve the epigenetic reprogramming of anti-cancer genes such as Nrf2, leading to the epigenetic reactivation of Nrf2 and the subsequent induction of downstream target genes involved in cellular protection.

Inverse relationship between p53 and phospho-Chk1 (Ser317) protein expression in UVB-induced skin tumors in SKH-1 mice.

Immunohistochemical evaluation of serial stored paraffin sections from 42 keratoacanthomas and 11 squamous cell carcinomas demonstrated that skin tumors from UVB-exposed mice showed an inverse relationship (>95%) between p53 protein expression and phospho-Chk1 (Ser317), but not phospho-Chk1 (Ser345) protein expression. Tumors expressing high levels and large areas of p53 protein had no detectable phospho-Chk1 (Ser317), whereas tumors expressing high levels and large areas of phospho-Chk1 (Ser317) protein had no detectable p53. Squamous cell carcinomas that demonstrated heterogeneous p53 and phospho-Chk1 (Ser317) protein expression within the same tumor showed that areas expressing p53 were negative for phospho-Chk1 (Ser317) immunostaining while areas expressing phospho-Chk1 (Ser317) were negative for p53. Similar patterns were observed for keratoacanthomas. These findings were also observed in epidermal areas distant from tumors that demonstrated no detectable phospho-Chk1 (Ser317), but appreciable p53 protein in the basal layer. Tumors from congenic hairless p53 knockout mice had elevated levels of phospho-Chk1 (Ser317) compared to tumors from p53 wild-type SKH-1 controls. After a single exposure to UVB, normal epidermal cells from a p53 knockout mouse expressed a relatively high level of phospho-Chk1 (Ser317) whereas epidermal cells from a p53 wild-type littermate induced p53 protein and expressed a relatively low level of phospho-Chk1 (Ser317). These data illustrate the dynamic regulation of checkpoint function, suggesting that phosphorylation of Chk1 on Serine 317 is regulated by p53 status and that p53 may act as a molecular on/off switch for phosphorylation at this site.

Parametrial fat tissue from high fat diet-treated SKH-1 mice stimulates transformation of mouse epidermal JB6 cells.

Our previous studies indicated that decreasing visceral adipose tissue by surgical removal of the parametrial fat pads inhibited UVB-induced carcinogenesis in SKH-1 mice fed a high fat diet (HFD), but not a low fat diet (LFD) indicating that the parametrial fat tissue from mice fed a HFD played a role in skin carcinogenesis. OBJECTIVE: In the present study, we sought to investigate how a HFD may influence the intrinsic properties of the parametrial fat tissue to influence UVB-induced skin tumor formation. METHODS AND RESULTS: Immunohistochemical staining, adipokine array, and flow cytometry showed that parametrial fat tissue from mice fed a HFD had a higher density of macrophage-fused dead adipocytes (crown-like structures), more adipokines, and stimulated the production of more reactive oxygen species compared with parametrial fat tissue from mice fed a LFD. These differences between parametrial fat tissue from mice fed a HFD and LFD were associated with their effect on the in vitro transformation of mouse epidermal JB6 cells. Our results indicated that fat tissue filtrate (an aqueous filtrate made from the parametrial fat pad) from mice fed a HFD enhanced the conversion of JB6 cells from an epithelial-like morphology to cells with a fibroblast-like morphology to a greater extent than fat tissue filtrate from mice fed a LFD. Studies indicated that the fibroblast-like cells had decreased levels of E-cadherin, increased levels of Twist as assayed by western blot. Fat tissue filtrate made from the parametrial fat tissue of mice fed a HFD had 160% more transforming activity than that from mice fed a LFD and formed malignant mesenchymal tumors in vivo. CONCLUSION: These studies provide the first in vitro demonstration of a parametrial fat tissue-induced transformation of an epidermal cell.

Inhibition of IL-6 expression in LNCaP prostate cancer cells by a combination of atorvastatin and celecoxib.

In the present study, we investigated the effect of a combination of atorvastatin and celecoxib on the formation of interleukin (IL)-6, a cytokine that is increased during the progression of LNCaP tumors from androgen dependence to androgen independence. Culturing LNCaP cells in androgen­depleted (AD) medium increased the levels of IL-6 and survivin, and treatment of the cells in AD medium with a combination of atorvastatin and celecoxib strongly inhibited the increase in IL-6 and survivin which is one of the downstream targets of the IL-6 signaling pathway. Addition of recombinant IL-6 partially abrogated the combined effect of atorvastatin and celecoxib on apoptosis in LNCaP cells cultured in AD medium. In SCID mice, we found that the levels of IL-6 and survivin expression were increased when LNCaP tumors became androgen-independent. Treatment of the mice with atorvastatin or celecoxib alone caused decrease in the levels of IL-6 and survivin as LNCaP tumors became androgen-independent, but treatment of the mice with a combination of celecoxib and atorvastatin resulted in a much stronger inhibition in the increase in IL-6 and survivin expression. Our results indicate that decreases in IL-6 and survivin levels by atorvastatin and celecoxib administration are associated with increased apoptosis in LNCaP cells treated with this drug combination. Our in vivo studies indicate that the inhibitory effect of a combination of atorvastatin and celecoxib on the progression of androgen-dependent LNCaP xenograft tumors to androgen independence is associated with inhibition of the increase in IL-6 and survivin that occurs when androgen-dependent LNCaP prostate tumors become androgen-independent.

Oral caffeine during voluntary exercise markedly inhibits skin carcinogenesis and decreases inflammatory cytokines in UVB-treated mice.

Ultraviolet B (UVB)-pretreated SKH-1 mice were treated with water, caffeine (0.1 mg/ml), voluntary running wheel exercise (RW) or caffeine together with RW for 14 wk. Treatment of the mice with caffeine, RW, or caffeine plus RW decreased skin tumors per mouse by 27%, 35%, and 62%, respectively, and the tumor volume per mouse was decreased by 61%, 70%, and 85%, respectively. In mechanistic studies, mice were treated with water, caffeine, RW, or caffeine plus RW for 2 wk prior to a single irradiation with UVB. Caffeine plus RW increased RW activity by 22% when compared with RW alone. Caffeine ingestion was not significantly different between groups. Treatment of mice with caffeine plus RW for 2 wk decreased the weight of the parametrial fat pads and stimulated the formation of UVB-induced apoptosis to a greater extent than treatment with caffeine or RW alone. An antibody array revealed that caffeine plus RW administered to mice fed a high-fat diet and irradiated with UVB decreased the epidermal levels of lipopolysaccharide-induced CXC chemokine, soluble TNF alpha receptor-1, and macrophage inflammatory protein-1γ. Overall, caffeine during RW exerts a stronger effect than either treatment alone for decreasing tissue fat, increasing UVB-induced apoptosis, lowering the levels of cytokines associated with inflammation and for inhibiting UVB-induced carcinogenesis.

Synthesis and evaluation of curcumin-related compounds containing benzyl piperidone for their effects on human cancer cells.

Eleven curcumin-related compounds containing a benzyl piperidone moiety were synthesized and evaluated for their effects on cultured prostate cancer PC-3 cells, pancreas cancer BxPC-3 cells, colon cancer HT-29 cells and lung cancer H1299 cells. Inhibitory effects of these compounds on the growth of PC-3, BxPC-3, HT-29 and H1299 cells were determined by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and trypan blue exclusion assay. Compounds benzyl piperidone 2 (P2), P4, P7, 4-bromo-2-fluoro-benzyl piperidone 2 (PFBr2), PFBr3 and PFBr4 (see syntheses and structures in Figs. 1, 2) exhibited potent inhibitory effects on the growth of cultured PC-3, BxPC-3, HT-29 and H1299 cells. The IC50 for these compounds was lower than 2 µM in all four cell lines. PFBr4 was 41-, 36-, 40- and 46-fold more active than curcumin for inhibiting the growth of PC-3, BxPC-3, HT-29 and H1299 cells, respectively. The benzyl piperidone-containing compounds studied also stimulated apoptosis in PC-3 cells. Mechanistic studies indicate that the effects of both curcumin and PFBr4 on PC-3 cells were associated with a decrease in phospho-Akt and phospho-extracellular signal-regulated kinase (Erk)1/2. The present study indicates that P2, P4, P7, PFBr2, PFBr3 and PFBr4 may have useful effects on human cancer cells.

Anti-proliferative, anti-inflammatory and antioxidant effects of curcumin analogue A2.

In the present study, we determined the anti-proliferative, anti-inflammatory and antioxidant effects of a curcumin analogue, 2,6-bis(3,4-dihydroxybenzylidene) cyclohexanone (designated as A2). In vitro studies showed that A2 had a stronger inhibitory effect on the growth of mouse macrophage RAW 264.7 cells than curcumin. A2 also showed a stronger inhibitory effect than curcumin on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced increases in NF-κB activation and IL-1ß expression as well as in aldose reductase activity. A2 was a stronger antioxidant than curcumin as determined by inhibition of lipid peroxidation, inhibition of 1,1-diphenyl-2-picryl-hydrazyl free radical formation, and inhibition of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) radical formation. In vivo studies indicated that A2 was more potent than curcumin for inhibiting TPA-induced ear edema and TPA-induced increases in IL-1ß. In addition, oral administration of A2 at a dose of 2,000 mg/kg body weight did not cause acute toxicity in mice. Taken together, the results of our study indicate that the curcumin analogue A2 has stronger anti-proliferative, anti-inflammatory and antioxidant activities than curcumin.

Mechanisms of Caffeine-Induced Inhibition of UVB Carcinogenesis.

Sunlight-induced non-melanoma skin cancer is the most prevalent cancer in the United States with more than two million cases per year. Several studies have shown an inhibitory effect of caffeine administration on UVB-induced skin cancer in mice, and these studies are paralleled by epidemiology studies that indicate an inhibitory effect of coffee drinking on non-melanoma skin cancer in humans. Strikingly, decaffeinated coffee consumption had no such inhibitory effect. Mechanism studies indicate that caffeine has a sunscreen effect that inhibits UVB-induced formation of thymine dimers and sunburn lesions in the epidermis of mice. In addition, caffeine administration has a biological effect that enhances UVB-induced apoptosis thereby enhancing the elimination of damaged precancerous cells, and caffeine administration also enhances apoptosis in tumors. Caffeine administration enhances UVB-induced apoptosis by p53-dependent and p53-independent mechanisms. Exploration of the p53-independent effect indicated that caffeine administration enhanced UVB-induced apoptosis by inhibiting the UVB-induced increase in ATR-mediated formation of phospho-Chk1 (Ser345) and abolishing the UVB-induced decrease in cyclin B1 which resulted in caffeine-induced premature and lethal mitosis in mouse skin. In studies with cultured primary human keratinocytes, inhibition of ATR with siRNA against ATR inhibited Chk1 phosphorylation and enhanced UVB-induced apoptosis. Transgenic mice with decreased epidermal ATR function that were irradiated chronically with UVB had 69% fewer tumors at the end of the study compared with irradiated littermate controls with normal ATR function. These results, which indicate that genetic inhibition of ATR (like pharmacologic inhibition of ATR via caffeine) inhibits UVB-induced carcinogenesis support the concept that ATR-mediated phosphorylation of Chk1 is an important target for caffeine's inhibitory effect on UVB-induced carcinogenesis.

Mutagenicity and tumorigenicity of the four enantiopure bay-region 3,4-diol-1,2-epoxide isomers of dibenz[a,h]anthracene.

Each enantiomer of the diastereomeric pair of bay-region dibenz[a,h]anthracene 3,4-diol-1,2-epoxides in which the benzylic 4-hydroxyl group and epoxide oxygen are either cis (isomer 1) or trans (isomer 2) were evaluated for mutagenic activity. In strains TA 98 and TA 100 of Salmonella typhimurium, the diol epoxide with (1S,2R,3S,4R) absolute configuration [(-)-diol epoxide-1] had the highest mutagenic activity. In Chinese hamster V-79 cells, the diol epoxide with (1R,2S,3S,4R) absolute configuration [(+)-diol epoxide-2] had the highest mutagenic activity. The (1R,2S,3R,4S) diol epoxide [(+)-diol epoxide-1] also had appreciable activity, whereas the other two bay-region diol epoxide enantiomers had very low activity. In tumor studies, the (1R,2S,3S,4R) enantiomer was the only diol epoxide isomer tested that had strong activity as a tumor initiator on mouse skin and in causing lung and liver tumors when injected into newborn mice. This stereoisomer was about one-third as active as the parent hydrocarbon, dibenz[a,h]anthracene as a tumor initiator on mouse skin; it was several-fold more active than dibenz[a,h]anthracene as a lung and liver carcinogen when injected into newborn mice. (-)-(3R,4R)-3ß,4α-dihydroxy-3,4-dihydro-dibenz[a,h]anthracene [(-)-3,4-dihydrodiol] was slightly more active than dibenz[a,h]anthracene as a tumor initiator on mouse skin, whereas (+)-(3S,4S)-3α,4ß-dihydroxy-3,4-dihydro-dibenz[a,h]anthracene [(+)-3,4-dihydrodiol] had only very weak activity. The present investigation and previous studies with the corresponding four possible enantiopure bay-region diol epoxide enantiomers/diastereomers of benzo[a]pyrene, benz[a]anthracene, chrysene, benzo[c]phenanthrene, dibenz[c,h]acridine, dibenz[a,h]acridine and dibenz[a,h]anthracene indicate that the bay-region diol epoxide enantiomer with [R,S,S,R] absolute stereochemistry has high tumorigenic activity on mouse skin and in newborn mice.

Synthesis and biological evaluation of unsymmetrical curcumin analogues as tyrosinase inhibitors.

Synthesis and biological evaluation of unsymmetrical curcumin analogues (UCAs) have been achieved. Tyrosinase inhibitory activities were found for most of the prepared synthetic UCAs. Among them, compounds containing 4-hydroxyl-substituted phenolic rings with C-2/C-4- or C-3/C-4-dihydroxyl-substituted diphenolic rings were more active (IC(50) = 1.74~16.74 µM) than 4-butylresorcinol and kojic acid, which suggested that the 4-hydroxyl groups in UCAs play a crucial role in tyrosinase inhibitory activities. The inhibition kinetics analyzed by Lineweaver-Burk plots revealed compounds 3c and 3i containing catecholic rings were mixed-competitive inhibitors, whereas compounds 3d and 3j containing resorcinolic rings were competitive inhibitors. The preliminary evaluation results of acute toxicity showed the representative 3d and 3j were non-toxic in mice dosed at 1,200 mg/kg. This research suggests that, with the advantage of being readily prepared small molecules, polyphenolic UCAs have the potential to develop into pharmacological inhibitors of tyrosinase.

Effects of pyridine analogs of curcumin on growth, apoptosis and NF-κB activity in prostate cancer PC-3 cells.

Twelve pyridine analogs of curcumin were studied for their effects on growth and apoptosis in human prostate cancer PC-3 cells. The ability of these compounds to inhibit the transcriptional activity of nuclear factor-kappa B (NF-κB) and the level of phosphorylated extracellular signal-regulated kinases (phospho-ERK1/2) in PC-3 cells was also determined. Treatment of PC-3 cells with the pyridine analogs of curcumin resulted in concentration-dependent growth inhibition and apoptosis stimulation. Only pyridine analogs of curcumin with a tetrahydrothiopyrane-4-one linker (FN compounds) exhibited a strong inhibitory effect on growth and a strong stimulatory effect on apoptosis at low concentrations (≤ 1 µM). Mechanistic studies showed that NF-κB transcriptional activity in PC-3 cells was strongly inhibited by treatment with group FN compounds. Treatment of PC-3 cells with 1 µM FN1 resulted in a decrease of activated ERK1/2. Results from the present study indicate that FN compounds warrant further in vivo studies using suitable animal models of prostate cancer.

Epigenetic reactivation of Nrf2 in murine prostate cancer TRAMP C1 cells by natural phytochemicals Z-ligustilide and Radix angelica sinensis via promoter CpG demethylation.

Cancer development has been linked to epigenetic modifications of cancer oncogenes and tumor suppressor genes; in advanced metastatic cancers, severe epigenetic modifications are present. We previously demonstrated that the progression of prostate tumors in TRAMP mice is associated with methylation silencing of the Nrf2 promoter and a reduced level of transcription of Nrf2 and Nrf2 target genes. Radix Angelicae Sinensis (RAS; Danggui) is a medicinal herb and health food supplement that has been widely used in Asia for centuries. Z-Ligustilide (Lig) is one of the bioactive components of RAS. We investigated the potential of Lig and RAS to restore Nrf2 gene expression through epigenetic modification in TRAMP C1 cells. Lig and RAS induced the mRNA and protein expression of endogenous Nrf2 and Nrf2 downstream target genes, such as HO-1, NQO1, and UGT1A1. Bisulfite genomic sequencing revealed that Lig and RAS treatment decreased the level of methylation of the first five CpGs of the Nrf2 promoter. A methylation DNA immunoprecipitation assay demonstrated that Lig and RAS significantly decreased the relative amount of methylated DNA in the Nrf2 gene promoter region. Lig and RAS also inhibited DNA methyltransferase activity in vitro. Collectively, these results suggest that Lig and RAS are able to demethylate the Nrf2 promoter CpGs, resulting in the re-expression of Nrf2 and Nrf2 target genes. Epigenetic modifications of genes, including Nrf2, may therefore contribute to the overall health benefits of RAS, including the anticancer effect of RAS and its bioactive component, Lig.