Rong Jane Chen

Rapid Activation of Stat3 and ERK1/2 by Nicotine Modulates Cell Proliferation in Human Bladder Cancer Cells

Cigarette smoke is a major risk factor for bladder cancer. The main component in cigarette smoke, nicotine, can be detected in the urine of smokers. Nicotine has been implicated as a cocarcinogen that promotes lung cancer development through prosurvival pathways. Although the mechanisms of nicotine-induced cell proliferation have been well studied in lung epithelial cells, the molecular mechanism of its action in bladder epithelial cells is still unclear. The aims of this study were to investigate whether there is nicotine-induced bladder epithelial cell proliferation and to identify the signaling transduction pathway regulated by nicotine. We found that nicotine simultaneously activates Stat3 and extracellular signal regulated kinase 1/2 (ERK1/2) in T24 cells. Stat3 activation via nicotinic acetylcholine receptor (nAChR)/protein kinase C signaling pathway was closely linked to Stat3 induction and nuclear factor-kappaB DNA binding activity, which is associated with Cyclin D1 expression and cell proliferation. ERK1/2 activation through nAChR and beta-adrenoceptors plays a dual role in cell proliferation; it phosphorylates Stat3 at Ser727 and regulates cell proliferation. We conclude that through nAChR and beta-adrenoceptors, nicotine activates ERK1/2 and Stat3 signaling pathways, leading to Cyclin D1 expression and cell proliferation. This is the first study to investigate signaling effects of nicotine in bladder cells. The current findings suggest that people exposed to nicotine could be at risk for potential deleterious effects, including bladder cancer development.

Long-term Nicotine Exposure–Induced Chemoresistance Is Mediated by Activation of Stat3 and Downregulation of ERK1/2 via nAChR and Beta-Adrenoceptors in Human Bladder Cancer Cells

Previous reports suggested that bladder cancer patients who continue to smoke while receiving chemotherapy have poorer outcomes than their nonsmoking counterparts. Nicotine, the major addictive compound in cigarette smoke, is known to induce chemoresistance in some cancer cells. Chemoresistance has been linked to the activation of Stat3 (signal transducer and activator of transcription). The objective of this study was to identify the role of Stat3 in chemoresistance induced by nicotine in human bladder cancer cell line, T24 cells. Chemoresistant T24 cells were established by persistent nicotine treatment. Apoptosis and cell cycle parameters were analyzed by Annexin V staining, poly(ADP-ribose) polymerase degradation, caspase activity, and propidium iodide staining. Signal transduction mediating the chemoresistance was detected by Western blotting and small interfering RNA (siRNA) transfection. We provide evidence for the first time that nicotine strongly activated Stat3, leading to Cyclin D1 overexpression, cell cycle perturbations, and chemoresistance. Furthermore, nicotine mobilized Stat3 signaling, resulting in the loss of extracellular signal-regulated protein kinase 1/2 (ERK 1/2) activation and reduced chemosensitivity via nicotinic acetylcholine receptors and beta-adrenoceptors. Inhibition of Stat3 by siRNA or a specific inhibitor restored chemosensitivity in T24 cells. Stat3 could be the major target for increasing chemosensitivity in patients who develop chemoresistance during chemotherapy, and avoidance of cigarette smoking or nicotine-based treatments may increase the efficacy of chemotherapy.

In vitro and in vivo studies of the anticancer action of terbinafine in human cancer cell lines: G0/G1 p53‐associated cell cycle arrest

Terbinafine (TB) (Lamisil®), a promising oral antifungal agent used worldwide, has been used in the treatment of superficial mycosis. In our study, we demonstrated that TB dose‐dependently decreased cell number in various cultured human malignant cells. Flow cytometry analysis revealed that TB interrupts the cell cycle at the G0/G1 transition. The TB‐induced cell cycle arrest in colon cancer cell line (COLO 205) occurred when the cyclin‐dependent kinase (cdk) system was inhibited just as the levels of p53, p21/Cip1 and p27/Kip1 proteins were augmented. In the TB‐treated COLO 205, the binding between p53 protein and p53 consensus binding site in p21/Cip1 promoter DNA probe was increased. Pretreatment of COLO 205 with p53‐specific antisense oligodeoxynucleotide decreased the TB‐induced elevations of p53 and p21/Cip1 proteins, which in turn led to arrest in the cell cycle at the G0/G1 phase. Moreover, in the p53 null cells, HL60, TB treatment did not induce cell cycle arrest. Taken together, these results suggest an involvement of the p53‐associated signaling pathway in the TB‐induced antiproliferation in COLO 205. We further examined whether administration of TB could affect the growth of tumors derived from human colon cancer cells in an in vivo setting. COLO 205 cells implanted subcutaneously in nude mice formed solid tumor; subsequent intraperitoneal injections of TB (50 mg/kg) led to obvious decline in tumor size, up to 50–60%. In these tumors, increases in the p21/Cip1, p27/Kip1 and p53 proteins and the occurrence of apoptosis were observed. Combined treatment with TB and nocodazole (ND), a clinically used anticancer agent, potentiated the apoptotic effect in COLO 205. These findings demonstrate for the first time that TB can inhibit the proliferation of tumor cells in vitro and in vivo.

Epigenetic effects and molecular mechanisms of tumorigenesis induced by cigarette smoke: an overview.

Cigarette smoking is one of the major causes of carcinogenesis. Direct genotoxicity induced by cigarette smoke leads to initiation of carcinogenesis. Nongenotoxic (epigenetic) effects of cigarette smoke also act as modulators altering cellular functions. These two effects underlie the mechanisms of tumor promotion and progression. While there is no lack of general reviews on the genotoxic and carcinogenic potentials of cigarette smoke in lung carcinogenesis, updated review on the epigenetic effects and molecular mechanisms of cigarette smoke and carcinogenesis, not limited to lung, is lacking. We are presenting a comprehensive review of recent investigations on cigarette smoke, with special attentions to nicotine, NNK, and PAHs. The current understanding on their molecular mechanisms include (1) receptors, (2) cell cycle regulators, (3) signaling pathways, (4) apoptosis mediators, (5) angiogenic factors, and (6) invasive and metastasis mediators. This review highlighted the complexity biological responses to cigarette smoke components and their involvements in tumorigenesis.

Chemopreventive Effects of Pterostilbene on Urethane-Induced Lung Carcinogenesis in Mice via the Inhibition of EGFR-Mediated Pathways and the Induction of Apoptosis and Autophagy

Lung cancer is the most commonly diagnosed cancer and the leading cause of cancer deaths globally. Due to the lack of successful chemopreventive agents for lung cancer, there is an emerging need to evaluate new and effective agents for lung cancer prevention. Pterostilbene, a naturally occurring analogue of resveratrol, has been reported to be an effective chemopreventive agent against many cancers. The aim of this study is to investigate the chemopreventive effects of pterostilbene in urethane-induced murine lung tumors. Pretreatment with pterostilbene at 50 or 250 mg/kg significantly reduced tumor multiplicity by 26 and 49%, respectively. Pterostilbene also significantly inhibited tumor volume by 25 and 34% and decreased the tumor burden per mouse by 45 and 63%, respectively. The mechanisms by which pterostilbene suppresses lung tumorigenesis have been investigated in lung tissues and homogenates. The results indicate that the pterostilbene-mediated chemopreventive effects in vivo were a result of the inhibition of epidermal growth factor receptor (EGFR) and its downstream pathways, leading to retarded cell cycle progression, and of the induction of apoptosis and autophagy during urethane-induced lung tumorigenesis.

NF-κB-activated tissue transglutaminase is involved in ethanol-induced hepatic injury and the possible role of propolis in preventing fibrogenesis

The increased expression and cross-linking activity of tissue transglutaminase (tTG) have been demonstrated in acute liver injury and fibrosis. We focused on the molecular mechanisms that contribute to ethanol-induced tTG expression and investigated the efficacy of propolis components in preventing both the tTG expression in vitro and fibrogenesis in vivo. We demonstrate herein that both ERK1/2 and PI3K/Akt pathways can regulate the effects of ethanol on NF-kappaB-dependent transcription and these signaling pathways may be involved in activation of ethanol-mediated tTG expression. We also found that administration of pinocembrin (PIN), one of the major components of propolis, inhibited tTG activation and significantly prevented the development of thioacetamide (TAA)-induced liver cirrhosis. The present study suggests that tTG may be an important member of the cascade of factors necessary for ethanol-induced liver fibrogenesis and PIN could serve as an anti-fibrogenic agent.

Induction of apoptosis by S-nitrosoglutathione and Cu2+ or Ni2+ ion through modulation of bax, bad, and bcl-2 proteins in human colon adenocarcinoma cells.

In this study, the amount of S‐nitrosoglutathione (GSNO) was measured spectrophotometrically at 334 nm. A spontaneous decrease in absorbency at 334 nm was detected when GSNO was exposed to 37°C and a high pH (pH 8.0). We investigated the catalytic roles of various metal ions on the decomposition of GSNO. The degradation of GSNO (0.5 mM) was enhanced by the presence of Cu2+ and Ni2+ ions. The amount of nitric oxide (NO) released from GSNO degradation was estimated by the Griess reaction based on nitrite accumulation. The results indicated that nitrite production was elevated at least twofold in the presence of Cu2+. Our study further indicated that Cu2+ enhanced GSNO‐induced apoptosis in human colon adenocarcinoma HT 29 cells. We also found that copper ions modulated the expression of bad, bax, and bcl‐2 in GSNO‐treated HT 29 cells. The levels of bax and bad proteins in treated cells were significantly elevated about fourfold to sixfold when compared with mock‐treated cells 24 h after combined treatment with GSNO plus Cu2+ or Ni2+. On the other hand, significant inhibition of bcl‐2 occurred in HT 29 cells with simultaneous treatment of GSNO with Cu2+ (or Ni2+). It seemed that Cu2+ and Ni2+ can enhance the decomposition of GSNO, which liberates NO to activate the pathways. Our results demonstrated that the apoptotic effects induced by GSNO were promoted by Ni2+ and Cu2+ through two different mechanisms: depletion of intracellular glutathione and triggering of NO release from GSNO, which then promotes NO‐induced apoptosis in human cells. Mol. Carcinog. 26:201–211, 1999.

Monascuspiloin Induces Apoptosis and Autophagic Cell Death in Human Prostate Cancer Cells via the Akt and AMPK Signaling Pathways

Monascus pigments have been reported to possess anticancer effects in various cancer cells; however, the molecular mechanisms of their anticancer properties remain largely unknown. Monascuspiloin is an analogue of the Monascus pigment monascin, and its anticancer growth activity against human prostate cancer cells was evaluated using in vitro and in vivo models. Monascuspiloin effectively inhibits the growth of both androgen-dependent LNCaP and androgen-independent PC-3 human prostate cancer cells. Monascuspiloin preferentially induces apoptosis in LNCaP cells by attenuating the PI3K/Akt/mTOR pathway. In androgen-independent PC-3 cells, monascuspiloin induces G2/M arrest and autophagic cell death by an AMPK-dependent pathway. Induction of autophagy in PC-3 cells further sensitizes cells to apoptosis induced by monascuspiloin. Monascuspiloin inhibits tumor growth in nude mice bearing PC-3 xenografts through induction of apoptosis and autophagy. This study is the first to demonstrate that monascuspiloin has therapeutic potential for the treatment of both androgen-dependent and -independent human prostate cancers.

Ketoconazole potentiates the antitumor effects of nocodazole: In vivo therapy for human tumor xenografts in nude mice

Our previous studies demonstrated that the oral antifungal agent ketoconazole (KT) induces apoptosis and G0/G1 phase cell cycle arrest in human cancer cell lines. In this study, we first demonstrated that KT (1 μM) potentiated the apoptotic effects of nocodazole (ND, 1 nM) in COLO 205 cancer cells. We further demonstrated the therapeutic efficacy of a combined treatment of KT (50 mg/kg/three times per week) and ND (5 mg/kg/three times per week) in vivo by treating athymic mice bearing COLO 205 tumor xenografts. The antitumor effects of ND were significantly potentiated by KT in mice after 6 wk of treatment. No gross signs of toxicity were observed in mice receiving these treatment regimens. The apoptotic cells were detected in a microscopic view of the terminal deoxynucleotidyl transferase–mediated dUTP nick‐end labeling staining and by observation of DNA fragmentation in KT + ND–treated tumor tissues. The levels of cell cycle regulatory proteins were determined by Western blot analysis. Treatment with KT inhibits tumor growth through elevation of p53, p21/CIP1, and p27/KIP1 as well as inhibition of cyclin D3 and cyclin‐dependent kinase 4 protein expression. Immunohistochemical staining analysis showed that p53, p21/CIP1, and p27/KIP1 immunoreactivity were induced in the tumor tissues. To clarify the roles of the p21/CIP1 and p27/KIP1 protein expression involved in G0/G1 arrest and/or apoptosis induced by a combined treatment with KT and ND, antisense oligodeoxynucleotides (ODNs) specific to p21/CIP1 and p27/KIP1 were used. Our results demonstrated that apoptotic phenomena, including BAX induction and cytochrome C released from mitochondria induced by KT + ND, were significantly attenuated by pretreatment the cells with the p27/KIP1–specific antisense ODNs. These results indicate that p27/KIP1 protein does indeed play a critical role in the KT + ND–induced apoptosis. Our study revealed the molecular mechanism of KT + ND in regression of the tumor growth. The apoptotic effects of KT in a great variety of cancer cells make it a very attractive agent for cancer chemotherapy.

Strategies to prevent and reverse liver fibrosis in humans and laboratory animals

Liver fibrosis results from chronic damage to the liver in conjunction with various pathways and is mediated by a complex microenvironment. Based on clinical observations, it is now evident that fibrosis is a dynamic, bidirectional process with an inherent capacity for recovery and remodeling. The major mechanisms involved in liver fibrosis include the repetitive injury of hepatocytes, the activation of the inflammatory response after injury stimulation, and the activation and proliferation of hepatic stellate cells (HSCs), which represents the major extracellular matrix (ECM)-producing cells, stimulated by hepatocyte injury and inflammation. The microenvironment in the liver is synergistically regulated abnormal ECM deposition, scar formation, angiogenesis, and fibrogenesis. Moreover, recent studies have clarified novel mechanism in fibrosis such as epigenetic regulation of HSCs, the leptin and PPARγ pathways, the coagulation system, and even autophagy. Uncovering the mechanisms of liver fibrogenesis provides a basis to develop potential therapies to reverse and treat the fibrotic response, thereby improving the outcomes of patients with chronic liver disease. Although both scientific and clinical challenges remain, emerging studies attempt to reveal the ideal anti-fibrotic drug that could be easily delivered to the liver with high specificity and low toxicity. This review highlights the mechanisms, including novel pathways underlying fibrogenesis that may be translated into preventive and treatment strategies, reviews both current and novel agents that target specific pathways or multiple targets, and discusses novel drug delivery systems such as nanotechnology that can be applied in the treatment of liver fibrosis. In addition, we also discuss some current treatment strategies that are being applied in animal models and in clinical trials.