Kwang Kyun Park

Molecular mechanisms underlying chemopreventive activities of anti-inflammatory phytochemicals: down-regulation of COX-2 and iNOS through suppression of NF-kappa B activation.

A wide array of phenolic substances, particularly those present in edible and medicinal plants, have been reported to possess substantial anticarcinogenic and antimutagenic activities. The majority of naturally occurring phenolics retain antioxidative and anti-inflammatory properties which appear to contribute to their chemopreventive or chemoprotective activity. Cyclooxygenase-2 (COX-2) inducible and nitric oxide synthase (iNOS) are important enzymes that mediate inflammatory processes. Improper up-regulation of COX-2 and/or iNOS has been associated with pathophysiology of certain types of human cancers as well as inflammatory disorders. Since inflammation is closely linked to tumor promotion, substances with potent anti-inflammatory activities are anticipated to exert chemopreventive effects on carcinogenesis, particularly in the promotion stage. Examples are curcumin, a yellow pigment of turmeric (Curcuma longa L., Zingiberaceae), the green tea polyphenol epigallocatechin gallate (EGCG), and resveratrol from grapes (Vitis vinifera, Vitaceae) that strongly suppress tumor promotion. Recent studies have demonstrated that eukaryotic transcription factor nuclear factor-kappa B (NF-kappa B) is involved in regulation of COX-2 and iNOS expression. Several chemopreventive phytochemicals have been shown to inhibit COX-2 and iNOS expression by blocking improper NF-kappa B activation. Multiple lines of compelling evidence indicate that extracellular-regulated protein kinase and p38 mitogen-activated protein kinase are key elements of the intracellular signaling cascades responsible for NF-kappa B activation in response to a wide array of external stimuli. Curcumin, EGCG and resveratrol have been shown to suppress activation of NF-kappa B. One of the plausible mechanisms underlying inhibition of NF-kappa B activation by aforementioned phytochemicals involves repression of degradation of the inhibitory unit I kappa B alpha, which hampers subsequent nuclear translocation of the functionally active subunit of NF-kappa B.

Inhibitory effects of [6]-gingerol, a major pungent principle of ginger, on phorbol ester-induced inflammation, epidermal ornithine decarboxylase activity and skin tumor promotion in ICR mice

A wide array of phytochemicals have been shown to possess potential cancer chemopreventive properties. Ginger contains pungent phenolic substances with pronounced antioxidative and antiinflammatory activities. In the present study, we have determined the antitumor promotional activity of [6]-gingerol, a major pungent principle of ginger, using a two-stage mouse skin carcinogenesis model. Topical application of [6]-gingerol onto shaven backs of female ICR mice prior to each topical dose of 12-O-tetradecanoylphorbol-13-acetate (TPA) significantly inhibited 7,12-dimethylbenz[a]anthracene-induced skin papillomagenesis. The compound also suppressed TPA-induced epidermal ornithine decarboxylase activity and inflammation.

Inhibitory effects of the ginsenoside Rg3 on phorbol ester-induced cyclooxygenase-2 expression, NF-κB activation and tumor promotion☆

Our previous studies demonstrated the anti-oxidant and anti-tumor promotional properties of the methanol extract of heat-processed Panax ginseng C.A. Meyer [Cancer Lett. 150 (2000) 41]. In the present work, we have evaluated anti-inflammatory as well as anti-tumor promoting effects of Rg(3), a major ginsenoside derived from heat-processed ginseng. Pretreatment of dorsal skins of female ICR mice with Rg(3) significantly inhibited 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase activity and 7,12-dimethylbenz[a]anthracene-initiated papilloma formation. In another experiment, Rg(3) pretreatment abrogated the expression of cyclooxygenase-2 in TPA-stimulated mouse skin. Rg(3) also inhibited the TPA-induced activation of the eukaryotic transcription factor, NF-kappaB in both mouse skin and cultured human pro-myelocytic leukemia (HL-60) cells. Moreover, Rg(3) exerted potent inhibitory effects on the activation of another transcription factor, activator protein-1 (AP-1) that is responsible for c-jun and c-fos oncogenic transactivation. Based on these findings, it is likely that the anti-tumor promoting activity of Rg(3) is mediated possibly through down-regulation of NF-kappaB and AP-1 transcription factors.

Beneficial and adverse effects of chemopreventive agents

The beneficial and adverse effects of some chemopreventive agents, such as Vitamins A, C, E, beta-carotene, indole-3-carbinol, capsaicin, garlic, and aloe are reviewed. Two large randomized trials with a lung cancer endpoint, the Alpha-Tocopherol, Beta-Carotene (ATBC) Prevention Study and the Beta-Carotene and Retinol Efficacy Trial (CARET), suggested that antioxidants might be harmful in smokers. However, the results of the Linxian study and of the ATBC or the CARET studies were significantly different in this respect, and therefore, the relationship between antioxidant and carcinogenesis remains open to debate. Indole-3-carbinol has cancer promoting activities in the colon, thyroid, pancreas, and liver, whereas capsaicin alters the metabolism of chemical carcinogens and may promote carcinogenesis at high doses. Organosulfur compounds and selenium from garlic have no or a little enhancing effect on cancer promotion stage. Information upon chemopreventive mechanisms that inhibit carcinogenesis is imperfect, although the causes and natures of certain human cancers are known. Therefore, definitive preventive guidelines should be carefully offered for various types of tumors, which properly consider ethnic variations, and the efficacies and the safety of chemopreventive agents.

Antioxidative and antitumor promoting effects of [6]-paradol and its homologs

Recently, considerable attention is focused on anti-carcinogenic phytochemicals, particularly those derived from medicinal or edible plants. [6]-Paradol, a pungent phenolic compound present in certain Zingiberaceae plants, is known to have antimicrobial and analgesic activities. The compound has been reported to attenuate promotion of skin carcinogenesis and TPA-induced ear edema in female ICR mice, and to induce apoptosis in cultured human promyelocytic leukemia (HL-60) cells. In this study, we performed several biochemical studies to evaluate and compare the cancer chemopreventive potential of [6]-paradol and its synthetic derivatives. [6]-Paradol and its synthetic nonpungent analog, [6]-dehydroparadol significantly decreased the incidence and the multiplicity of skin tumors initiated by 7,12-dimethylbenz[a]anthracene (DMBA) and promoted by 12-O-tetradecanoylphorbol-13-acetate (TPA). Topical application of [6]-paradol and its derivatives inhibited TPA-induced ear edema and H(2)O(2) production and myeloperoxidase activity in the dorsal skin of mice. Induction of TPA-induced mouse epidermal ornithine decarboxylase (ODC) activity and H(2)O(2)- and UV-induced formation of oxidized DNA bases in vitro were also attenuated by the above compounds. These results indicate that [6]-paradol and its derivatives possess the cancer chemopreventive potential.

Induction of apoptosis and caspase-3 activation by chemopreventive [6]-paradol and structurally related compounds in KB cells

[6]-paradol, a pungent phenolic substance found in ginger and other Zingiberaceae plants, has been demonstrated to be an effective inhibitor of tumor promotion in mouse skin carcinogenesis. In the present study, we found that [6]-paradol and other structurally related derivatives, [10]-paradol, [3]-dehydroparadol, [6]-dehydroparadol, and [10]-dehydroparadol, with the exception of [3]-paradol induce apoptosis in an oral squamous carcinoma cell line, KB, in a dose-dependent manner. [10]-paradol and [10]-dehydroparadol exhibited a similar extent of cytotoxicity to that of [6]-paradol. [6]-Dehydroparadol and [3]-dehydroparadol appeared to be more potent, with an IC50 less than 40 microM. Treatment of KB cells with an apoptosis-inducing concentration of [6]-dehydroparadol caused induction of proteolytic cleavage of pro-caspase-3. These results suggest that [6]-paradol and structurally related derivatives induce apoptosis through a caspase-3-dependent mechanism.

Inhibitory effects of the standardized extract (DA-9601) of Artemisia asiatica Nakai on phorbol ester–induced ornithine decarboxylase activity, papilloma formation, cyclooxygenase-2 expression, inducible nitric oxide synthase expression and nuclear transcription factor κB activation in mouse skin

Artemisia asiatica Nakai has been used in traditional Asian medicine for the treatment of inflammatory and other disorders. Previous studies have revealed that the formulated ethanol extract (DA‐9601) of A. asiatica has pronounced antioxidative and antiinflammatory activities and exhibits cytoprotective effects against experimentally induced gastrointestinal, hepatic and pancreatic damage. In the present study, we assessed the inhibitory effect of DA‐9601 on tumor promotion, which is closely linked to inflammatory tissue damage. As an initial approach to evaluating the possible antitumor‐promoting potential of DA‐9601, its effects on TPA‐induced ear edema were examined in female ICR mice. Pretreatment of the inner surface of the mouse ear with DA‐9601 30 min prior to topical application of TPA inhibited ear edema at 5 hr. TPA‐stimulated expression of epidermal COX‐2 and iNOS was also mitigated by topical application of the same extract. Moreover, DA‐9601 abrogated the TPA‐mediated activation of NF‐κB/Rel and AP‐1 in mouse epidermis. Suppression of epidermal NF‐κB by DA‐9601 appeared to be mediated in part through inhibition of IκBα degradation, thereby blocking the nuclear translocation of p65, the functional subunit of NF‐κB. DA‐9601 also significantly suppressed TPA‐induced ODC activity and papilloma formation in mouse skin. Taken together, these findings suggest that DA‐9601 derived from A. asiatica possesses potential chemopreventive activities.

Melittin suppresses PMA-induced tumor cell invasion by inhibiting NF-κB and AP-1-dependent MMP-9 expression

Matrix metalloproteinase-9 (MMP-9) plays an important role in the invasion and metastasis of cancer cells. In this study, we examined the inhibitory effect of bee venom (BV) and its major peptides, melittin and apamin, on PMA-induced invasion induced by MMP-9 expression in Caki-1 renal cancer cells. BV and melittin, but not apamin, significantly suppressed PMA-induced invasion by inhibiting MMP-9 expression in Caki-1 cells. Furthermore, as evidenced by MMP-9 promoter assays, melittin inhibited MMP-9 gene expression by blocking the PMA-stimulated activations of activator protein-1 (AP-1) and nuclear factor-kappa B (NF-κB). In addition, melittin suppressed the PMA-induced phosphorylations of ERK and JNK mitogenactivated protein kinases, upstream factors involved in Ap-1 and NF-κB. These results suggest that the suppression of MMP-9 expression contributes to the anti-tumor properties of melittin.

Kalopanaxsaponin A inhibits PMA-induced invasion by reducing matrix metalloproteinase-9 via PI3K/Akt- and PKCδ-mediated signaling in MCF-7 human breast cancer cells

Induction of matrix metalloproteinase (MMP)-9 is particularly important for the invasiveness of breast cancers. We investigated the inhibitory effect of kalopanaxsaponin A (KPS-A) on cell invasion and MMP-9 activation in phorbol 12-myristate 13-acetate (PMA)-treated MCF-7 human breast cancer cells. KPS-A inhibited PMA-induced cell proliferation and invasion. PMA-induced cell invasion was blocked in the presence of a primary antibody of MMP-9, and KPS-A suppressed the increased expression and/or secretion of MMP-9 and tissue inhibitor of metalloproteinase (TIMP)-1. Using specific inhibitors, we confirmed that PMA-induced cell invasion and MMP-9 expression is primarily regulated by nuclear factor-kappa B (NF-kappaB) activation via phosphatidylinositol 3-kinase (PI3K)/Akt and activator protein-1 (AP-1) activation via extracellular signal-regulated kinase (ERK)1/2. KPS-A decreased PMA-induced transcriptional activation of NF-kappaB and AP-1 and inhibited PMA-induced phosphorylation of ERK1/2 and Akt. Treatment with the protein kinase C (PKC)delta inhibitor rottlerin caused a marked decrease in PMA-induced MMP-9 secretion and cell invasion, as well as ERK/AP-1 activation, and KPS-A reduced PMA-induced membrane localization of PKCdelta. Furthermore, oral administration of KPS-A led to a substantial decrease in tumor volume and expression of proliferating cell nuclear antigen, MMP-9, TIMP-1 and PKCdelta in mice with MCF-7 breast cancer xenografts in the presence of 17beta-estradiol. These results suggest that KPS-A inhibits PMA-induced invasion by reducing MMP-9 activation, mainly via the PI3K/Akt/NF-kappaB and PKCdelta/ERK/AP-1 pathways in MCF-7 cells and blocks tumor growth and MMP-9-mediated invasiveness in mice with breast carcinoma. Therefore, KPS-A may be a promising anti-invasive agent with the advantage of oral dosing.

Inhibition of mouse skin tumor promotion by anti-inflammatory diarylheptanoids derived from Alpinia oxyphylla Miquel (Zingiberaceae)

Alpinia oxphylla Miquel, which belongs to the ginger family (Zingiberaceae), has been used in Oriental herbal medicine. Our recent studies have revealed that the methanolic extract of A. oxyphylla suppresses mouse skin tumor promotion and induces apoptosis in cultured human promyelocytic leukemia cells. In the present work, we have assessed effects of yakuchinone A and yakuchinone B, phenolic diarylheptanoids derived from A. oxyphylla, on 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced inflammation and epidermal ornithine decarboxylase (ODC) activity as well as on skin tumor promotion in female ICR mice. Thus, topical application of 2 or 6 micromol of the diarylheptanoids prior to each topical dose of TPA significantly ameliorated 7,12-dimethylbenz[a]anthracene-initiated mouse skin tumor formation. In parallel with suppression of tumor promotion, topically applied yakuchinone A and B markedly inhibited TPA-induced epidermal ODC activity and ODC mRNA expression. In another experiment, yakuchinone A and B reduced production of tumor necrosis factor-alpha in TPA-stimulated mouse skin. Furthermore, both compounds inhibited the TPA-induced expression of cyclooxygenase-2 at both transcriptional and translational levels. These findings indicate that pungent diarylheptanoids from A. oxyphylla Miquel have an antitumor promotional activity that might be related to their anti-inflammatory properties.