Won Yoon Chung

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.

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.

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.

Isoliquiritigenin induces G2 and M phase arrest by inducing DNA damage and by inhibiting the metaphase/anaphase transition

Isoliquiritigenin, a natural flavonoid found in licorice, shallots, and bean sprouts, has been demonstrated to inhibit proliferation and to induce apoptosis in a variety of human cancer cells. We attempted to ascertain the underlying mechanism by which isoliquiritigenin induced cell cycle arrest and cytotoxicity in HeLa human cervical cancer cells. Isoliquiritigenin treatment arrested cells in both G2 and M phase. The cells arrested in interphase (G2) showed markers for DNA damage including the formation of gamma-H2AX foci and the phosphorylation of ATM and Chk2, whereas the cells arrested in M phase evidenced separate poles and mitotic metaphase-like spindles with partially unaligned chromosomes. The induction of DNA damage and blockade at the metaphase/anaphase transition implied that isoliquiritigenin might function as a topoisomerase II poison, which was further demonstrated via an in vitro topoisomerase II inhibition assay. These results show that isoliquiritigenin inhibits topoiosmerase II activity, and the resultant DNA damage and arrest in mitotic metaphase-like stage contributes to the antiproliferative effects of isoliquiritigenin.

Licochalcone A Inhibits the Growth of Colon Carcinoma and Attenuates Cisplatin‐Induced Toxicity without a Loss of Chemotherapeutic Efficacy in Mice

Although chemotherapy has an important function in the treatment of most solid tumours, its clinical applications are limited by severe side effects such as nephrotoxicity, hepatotoxicity, ototoxicity and neurotoxicity. Recently, a growing amount of attention has been focused on the investigation of the effects of chemopreventive agents on the inhibition of cancer cell growth and toxicity in combination with chemotherapeutics. The aim of this study was to determine whether licochalcone A (LCA) has the potential to serve as a beneficial supplement during cisplatin chemotherapy. We found that the administration of LCA alone significantly inhibited the size of the solid tumours in CT-26 cell-inoculated Balb/c mice, without any detectable induction of nephrotoxicity, hepatotoxicity and oxidative stress. LCA also suppressed cell proliferation by reducing DNA synthesis of CT-26 murine colon cancer cells in a dose-dependent manner. LCA did not affect the therapeutic efficacy of cisplatin. Furthermore, LCA inhibited the cisplatin-induced kidney damage characterized by increases in the serum creatinine and blood urea nitrogen, as well as the cisplatin-induced liver damage characterized by increases in the serum alanine aminotransferase and aspartate aminotransferase. The repeated oral administration of LCA prior to cisplatin treatment exerted a preventive effect on the cisplatin-mediated increases in the serum nitric oxide and the tissue lipid peroxidation levels, and recovered the depleted reduced glutathione levels in the tissues. These results suggest that supplementation with LCA may be beneficial in counteracting the side effects of cisplatin therapy in cancer patients.

Decursin and decursinol inhibit VEGF-induced angiogenesis by blocking the activation of extracellular signal-regulated kinase and c-Jun N-terminal kinase

The root of Angelica gigas Nakai contains two major coumarins, which have been previously identified as decursin and decursinol. Decursin has been demonstrated to exhibit potent anti-cancer activity both in vitro and in vivo. In this study, we found that decursin and decursinol at non-cytotoxic doses inhibited the VEGF-induced proliferation, migration, and capillary-tube formation of HUVECs. Moreover, decursin and decursinol suppressed microvessel formation on chorioallantoic membranes in fertilized eggs and into mouse Matrigel plugs. The oral administration of decursin and decursinol also reduced VEGF-induced angiogenesis in Matrigel. Furthermore, decursin and decursinol reduced the phosphorylation of ERK and JNK, but not p38 MAPK, in VEGF-stimulated HUVECs. Taken together, our results reveal that decursin and decursinol inhibit VEGF-induced angiogenesis by reducing the activation of ERK and JNK in HUVECs, and possess potent in vivo anti-angiogenic activity, coupled with the advantage of oral dosing. Thus, these compounds may have the potential for the treatment of cancers dependent on VEGF-induced vascularization.

Secretion of IL-6 and IL-8 from lysophosphatidic acid-stimulated oral squamous cell carcinoma promotes osteoclastogenesis and bone resorption

Lysophosphatidic acid (LPA) is a bioactive lipid with a growth factor-like activity on a large range of cell types. Several pieces of evidence raise the possibility that LPA may play an important role in bone metastasis. Bone is a frequent metastatic site for oral cancer. However, the role of LPA in the progression of oral cancer metastasis to the bone is poorly understood. Here, we provide evidence for the role of LPA in the progression of oral cancer bone metastases and its regulatory mechanism. LPA induced the secretion of IL-6 and IL-8 in oral squamous cell carcinoma (OSCC). LPA-stimulated secretion of IL-6 and IL-8 is partly dependent on the LPA and EGF receptor (EGFR) pathways. ERK1/2 and Akt-mediated NF-κB and AP-1 were responsible for the LPA-induced IL-6 and IL-8 secretion. Moreover, conditioned medium (CM) derived from the LPA-stimulated OSCC supported osteoclast formation in bone marrow-derived macrophages (BMMs). Neutralization against both human IL-6 and IL-8 suppressed osteoclast formation induced by CM derived from the LPA-stimulated OSCC. Direct treatment with recombinant IL-6 (rIL-6) and/or soluble IL-6 receptor (sIL-6R), or IL-8 (rIL-8) reproduced the effect of the CM derived from the LPA-stimulated OSCC on osteoclast formation. In addition, CM derived from the LPA-stimulated OSCC induced receptor activator of nuclear factor (NF)-κB ligand (RANKL) expression in human osteoblasts and direct treatment with rIL-6 and/or sIL-6R or rIL-8 mimicked the effect of the CM derived from the LPA-stimulated OSCC for RANKL expression. Taken together, LPA may be a potent inducer of osteolytic factor IL-6 and IL-8 in OSCC. LPA-induced IL-6 and IL-8 exerted propound effects on RANKL expression in osteoblast and thereby promoted osteoclast formation from osteoclast precursors.

Ginsenoside Rg3 enhances the chemosensitivity of tumors to cisplatin by reducing the basal level of nuclear factor erythroid 2-related factor 2-mediated heme oxygenase-1/NAD(P)H quinone oxidoreductase-1 and prevents normal tissue damage by scavenging cisplatin-induced intracellular reactive oxygen species

The clinical use of cisplatin (cis-diamminedichloroplatinum II) has been limited by the frequent emergence of cisplatin-resistant cell populations and numerous other adverse effects. Therefore, new agents are required to improve the therapy and health of cancer patients. Oral administration of ginsenoside Rg3 significantly inhibited tumor growth and promoted the anti-neoplastic efficacy of cisplatin in mice inoculated with CT-26 colon cancer cells. In addition, Rg3 administration remarkably inhibited cisplatin-induced nephrotoxicity, hepatotoxicity and oxidative stress. In cell-based experiments, Rg3 inhibited cisplatin-induced cytotoxicity in LLC-RK1 kidney and NCTC1469 liver cells but not in CT-26 cancer cells and significantly decreased cisplatin-induced intracellular ROS levels in these cells. In normal cells with cytoplasmically localized Nrf2 and negligible levels of HO-1 and NQO-1, Rg3 substantially decreased cisplatin-induced elevation in HO-1/NQO-1 levels and inhibited cisplatin-induced translocation of Nrf2 into the nucleus. In chemoresistant cancer cells with high levels of HO-1/NQO-1 and nuclear Nrf2, both basal and cisplatin-induced levels of HO-1/NQO-1 and nuclear Nrf2 were decreased by Rg3 treatment, thereby enhancing the susceptibility of cancer cells to cisplatin. Collectively, Rg3 promotes the efficacy of cisplatin by inhibiting HO-1 and NQO-1 expression in cancer cells and protects the kidney and liver against tissue damage by preventing cisplatin-induced intracellular ROS generation.

Anti-inflammatory effects of licorice and roasted licorice extracts on TPA-induced acute inflammation and collagen-induced arthritis in mice.

The anti-inflammatory activity of licorice (LE) and roated licorice (rLE) extracts determined in the murine phorbol ester-induced acute inflammation model and collagen-induced arthritis (CIA) model of human rheumatoid arthritis. rLE possessed greater activity than LE in inhibiting phorbol ester-induced ear edema. Oral administration of LE or rLE reduced clinical arthritis score, paw swelling, and histopathological changes in a murine CIA. LE and rLE decreased the levels of proinflammatory cytokines in serum and matrix metalloproteinase-3 expression in the joints. Cell proliferation and cytokine secretion in response to type II collagen or lipopolysaccharide stimulation were suppressed in spleen cells from LE or rLE-treated CIA mice. Furthermore, LE and rLE treatment prevented oxidative damages in liver and kidney tissues of CIA mice. Taken together, LE and rLE have benefits in protecting against both acute inflammation and chronic inflammatory conditions including rheumatoid arthritis. rLE may inhibit the acute inflammation more potently than LE.

Induction of cell cycle arrest in prostate cancer cells by the dietary compound isoliquiritigenin.

Isoliquiritigenin (ISL), a flavonoid chalcone that is present in licorice, shallot, and bean sprouts, is known to have antitumorigenic activities. The present study examined whether ISL alters prostate cancer cell cycle progression. DU145 human and MatLyLu (MLL) rat prostate cancer cells were cultured with various concentrations of ISL. In both DU145 and MLL cells treated with ISL, the percentage of cells in the G1 phase increased, and the incorporation of [(3)H]thymidine decreased. ISL decreased the protein levels of cyclin D1, cyclin E, and cyclin-dependent kinase (CDK) 4, whereas cyclin A and CDK2 expressions were unaltered in cells treated with ISL. The expression of the CDK inhibitor p27(KIP1) was increased in cells treated with 20 micromol/L ISL. In addition, treatment of cells with 20 micromol/L ISL for 24 hours led to G2/M cell cycle arrest. Cell division control (CDC) 2 protein levels remained unchanged. The protein levels of phospho-CDC2 (Tyr15) and cyclin B1 were increased, and the CDC25C level was decreased by ISL dose-dependently. We demonstrate that ISL promotes cell cycle arrest in DU145 and MLL cells, thereby providing insights into the mechanisms underlying its antitumorigenic activities.