Curcumin Suppresses MAPK Pathways to Reverse Tobacco Smoke-induced Gastric Epithelial-Mesenchymal Transition in Mice

The protective effects of curcumin against cigarette smoke-induced toxicity: A comprehensive review

Cigarette smoking (CS) is a crucial modifiable risk of developing several human diseases and cancers. It causes lung, bladder, breast, and esophageal cancers, respiratory disorders, as well as cardiovascular and metabolic diseases. Because of these adverse health effects, continual efforts to decrease the prevalence and toxicity of CS are imperative. Until the past decades, the impacts of natural compounds have been under investigation on the harmful effects of CS. Turmeric (Curcuma longa), a rhizomatous herbaceous perennial plant that belongs to the Zingiberaceae family, is the main source of curcumin. This review is an attempt to find out the current knowledge on CS's harmful effects and protective potential of curcumin in the pulmonary, liver, brain, gastrointestinal, and testis organs. According to the present review, simultaneous consumption of curcumin and CS can attenuate CS toxicities including chronic obstructive pulmonary disease, gastrointestinal toxicity, metabolic diseases, testis injury, and neurotoxicity. Moreover, curcumin suppresses carcinogenesis in the skin, liver, lungs, breast, colon, and stomach. Curcumin mediates these protective effects through antioxidant, anti-inflammatory, anti-apoptotic, and anti-carcinogenicity properties.

Cigarette Smoke-Induced Gastric Cancer Cell Exosomes Affected the Fate of Surrounding Normal Cells via the Circ0000670/Wnt/β-Catenin Axis

Cigarette smoke is a major risk factor for gastric cancer. Exosomes are an important part of intercellular and intra-organ communication systems and can carry circRNA and other components to play a regulatory role in the occurrence and development of gastric cancer. However, it is unclear whether cigarette smoke can affect exosomes and exosomal circRNA to promote the development of gastric cancer. Exosomes secreted by cancer cells promote cancer development by affecting surrounding normal cells. Herein, we aimed to clarify whether the exosomes secreted by cigarette smoke-induced gastric cancer cells can promote the development of gastric cancer by affecting the surrounding gastric mucosal epithelial cells (GES-1). In the present study, we treated gastric cancer cells with cigarette smoke extract for 4 days and demonstrated that cigarette smoke promotes the stemness and EMT of gastric cancer cells and cigarette smoke-induced exosomes promote stemness gene expression, EMT processes and the proliferation of GES-1 cells. We further found that circ0000670 was up-regulated in tissues of gastric cancer patients with smoking history, cigarette smoke-induced gastric cancer cells and their exosomes. Functional assays showed that circ0000670 knockdown inhibited the promoting effects of cigarette smoke-induced exosomes on the stemness and EMT characteristic of GES-1 cells, whereas its overexpression had the opposite effect. In addition, exosomal circ0000670 was found to promote the development of gastric cancer by regulating the Wnt/β-catenin pathway. Our findings indicated that exosomal circ0000670 promotes cigarette smoke-induced gastric cancer development, which might provide a new basis for the treatment of cigarette smoke-related gastric cancer.

Anticancer applications of phytochemicals in gastric cancer: Effects and molecular mechanism

Gastric cancer (GC) is the fourth most common malignant cancer and is a life-threatening disease worldwide. Phytochemicals have been shown to be a rational, safe, non-toxic, and very promising approach to the prevention and treatment of cancer. It has been found that phytochemicals have protective effects against GC through inhibiting cell proliferation, inducing apoptosis and autophagy, suppressing cell invasion and migration, anti-angiogenesis, inhibit Helicobacter pylori infection, regulating the microenvironment. In recent years, the role of phytochemicals in the occurrence, development, drug resistance and prognosis of GC has attracted more and more attention. In order to better understand the relationship between phytochemicals and gastric cancer, we briefly summarize the roles and functions of phytochemicals in GC tumorigenesis, development and prognosis. This review will probably help guide the public to prevent the occurrence and development of GC through phytochemicals, and develop functional foods or drugs for the prevention and treatment of gastric cancer.

Gastric cancer stem cell-derived exosomes promoted tobacco smoke-triggered development of gastric cancer by inducing the expression of circ670

As one of the most common malignant cancers in the world, gastric cancer is caused by mang factors among which tobacco smoke is an important risk factor. Gastric cancer stem cells (GCSCs) and the derived exosomes play a key role in the occurrence and development of gastric cancer, and exosomal circRNA is considered as a new regulatory factor in the development of gastric cancer. However, it is unclear whether tobacco smoke can affect exosomes and their transport circRNAs to promote the development of gastric cancer. Herein, we provided a new insight into tobacco smoke promoting the progression of gastric cancer. In the present study, we demonstrated that tobacco smoke-induced exosomes promoted the spheroidizing ability, stemness genes expression, and epithelial-mesenchymal transition (EMT) process of GCSCs. We further found that hsa-circRNA-000670 (circ670) was up-regulated in tissues of gastric cancer patients with smoking history, tobacco smoke-induced GCSCs, and their exosomes. Functional assays have shown that circ670 knockdown inhibited the stemness and EMT process of GCSCs, whereas circ670 overexpression appeared to have an opposite effect. Our findings indicated that exosomal circ670 promotes the development of tobacco smoke-induced gastric cancer, which may provide insight into the mechanism of tobacco smoke promoting the progression of gastric cancer.

Regulatory Mechanism and Experimental Verification of Patchouli Alcohol on Gastric Cancer Cell Based on Network Pharmacology

Background

Pogostemon cablin is a traditional Chinese medicine (TCM) that is frequently used to treat various gastrointestinal diseases. Patchouli alcohol (PA), a compound extracted from the Pogostemon cablin, has been shown to have anti-tumor efficacy in human colorectal cancer. However, the mechanism of PA’s anticancer effect on gastric cancer (GC) remains unknown.

Methods

We used the public database to obtain the potential targets of PA and genes related to GC. Bioinformatic analyses, such as the Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and protein-protein interactions (PPI), were used for analyzing the potential signal pathways and targets. Cell experiments were also conducted to further explain the impact and molecular mechanism of PA on GC, as well as to confirm the findings of network pharmacology.

Results

Using network pharmacological analysis, 161 possible targets were identified for the treatment of GC. Network analysis and functional enrichment analysis show that PA produced a marked effect in the treatment of GC through multi-targets and multi-pathways, especially the MAPK and PI3K/AKT signal pathways. In addition, PA showed the inhibition of GC cell proliferation, migration and invasion in cell experiments. According to our findings, PA could also cause G0/G1 phase arrest and apoptosis in GC cells.

Conclusion

Using network pharmacology, we aim to uncover the possible molecular mechanism of PA on GC treatment in this research. Cell experiments were also conducted to confirm the therapeutic effect of PA on GC.

Curcumin inhibits adverse psychological stress-induced proliferation and invasion of glioma cells via down-regulating the ERK/MAPK pathway

Curcumin is a natural polyphenol extracted from the rhizome of Curcuma that has an important antitumour effect, but its effect on adverse psychological stress‐induced tumour proliferation and invasion has not been reported to date. Here, we found that curcumin not only inhibited the growth of xenografts in chronically stressed nude mice, but also decreased the expression of matrix metalloproteinase (MMP)‐2/9 and CD147 in tumour tissues. Exogenous norepinephrine (NE) was used to stimulate glioma cells to simulate the stress environment in vitro, and it was found that curcumin inhibited the NE‐induced proliferation and invasion of glioma cells in a dose‐dependent manner. Further research found that the effects of NE on glioma cells could lead to the activation of the mitogen‐activated protein kinase (MAPK) signalling pathway through β‐adrenergic receptor, while curcumin suppressed the level of extracellular signal–regulated kinase (ERK)1/2 phosphorylation. In addition, blocking ERK1/2 expression with U0126 resulted in the down‐regulated expression of CD147, which further led to the decreased expression of MMP‐2 and MMP‐9. Curcumin could also inhibit the expression of cyclin D1/CDK4/6 and anti‐apoptotic protein Bcl‐2/Bcl‐XL induced by NE, and induced cell cycle changes and increased apoptosis. Therefore, curcumin may be a potential candidate drug for preventing and treating the progression of glioma induced by adverse psychological stress.

Effect of Curcumin on Severity of Functional Dyspepsia: a Triple Blinded Clinical Trial

BackgroundFunctional dyspepsia is the main cause of upper abdominal discomfort affecting 5-10% of the world population. Despite various therapeutic approaches, up to 50% of patients with functional dyspepsia seek alternative treatments. In the present study we evaluated the effect of curcumin supplementation along with famotidine therapy on severity of functional dyspepsia. A total of 75 patients with functional dyspepsia according to Rome III criteria were allocated into intervention (N = 39) or control (N = 36) groups. The intervention group was treated with a combination of 500 mg curcumin and 40 mg famotidine daily for 1 month. The control group received placebo and 40 mg famotidine. Severity of dyspepsia symptoms was determined using the Hong Kong questionnaire at baseline, after the 1 month treatment and after a 1 month follow-up. The presence of H. pylori antigens in the stool samples was also investigated in all subjects. No significant difference was observed between intervention and control groups in biochemical indices, severity of dyspepsia and rate of H. pylori infection. A significant decrease was observed in severity of dyspepsia (p < 0.001) and rate of H. pylori infection (p = 0.004) immediately after the treatment and follow-up in the curcumin intervention group. This study indicated that curcumin therapy could be a favorable supplementation in the symptom management of functional dyspepsia. Moreover, curcumin could help efficient eradication of H. pylori in these patients.

Curcumin Negatively Regulates Cigarette Smoke-Induced Renal Cell Carcinoma Epithelial-Mesenchymal Transition Through the ERK5/AP-1 Pathway

Background

So far, little research has been conducted regarding the underlying mechanism of renal carcinogenesis at molecular level. Epithelial–mesenchymal transition (EMT) exerts an important part during tumor genesis as well as the development through mitogen-activated protein kinase (MAPK) pathways. Therefore, we hypothesized that EMT could promote renal cell carcinoma (RCC) progression via the ERK5/AP-1pathway.

Materials and Methods

The RCC cell lines were utilized to be the models with in vitro exposure to cigarette smoke extract (CSE). We used the curcumin for the EMT intervention study. In the present study, immunohistochemistry (IHC), Western blotting, and real-time quantitative reverse transcription PCR had been used to determine the experimental results. EMT phenotypic alterations were assessed by changes in cell morphology, invasion and transfer ability, as well as expression of epithelial and mesenchymal markers.

Results

In human renal cell carcinoma tissue, E-cadherin expression within the smoking renal cancer patients was down-regulated compared with that among the non-smokers. However, Vimentin, N-cadherin, and TWIST levels increased (P<0.05). Significantly, we clarified that ERK5/AP-1 exerted positive regulation on the renal cell carcinoma EMT mediated by CS, which was suggested based on the results of CS activating the ERK5/AP-1 pathway, as well as ERK5 inhibition via XMD8-92 reversed AP-1 protein levels and the EMT process. Furthermore, curcumin showed the same inhibitory effect as XMD8-92 and significantly reversed CS-induced EMT through inhibiting the ERK5/AP-1 signaling pathway.

Conclusion

The above results indicated that ERK5/AP-1 signaling pathway exerts a vital part for CS-associated RCC development and cancer intervention.

Effect of Curcumin and Its Derivates on Gastric Cancer: Molecular Mechanisms

Gastric carcinoma is one of the most prevalent malignancies and is associated with a high mortality. Chemotherapy is the principal therapeutic option in the treatment of gastric cancer, but its success rate is restricted by severe side effects and the prevalence of chemo-resistance. Curcumin is a polyphenolic compound derived from turmeric that has potent antioxidant, anti-inflammatory and anti-tumor effects. There is accumulating evidence that curcumin may prevent gastric cancer through regulation of oncogenic pathways. Furthermore some curcumin analogues and novel formulation of curcumin appear to have anti-tumor activity. The aim of this review was to give an overview of the therapeutic potential of curcumin and its derivatives against gastric cancer in preclinical and clinical studies.

Epithelial-mesenchymal transition as a target for botanicals in cancer metastasis

BACKGROUND

The plant kingdom represents an unlimited source of phytotherapeutics with promising perspectives in the field of anticancer drug discovery.

PURPOSE

In this view, epithelial-mesenchymal transition (EMT) represents a novel and major target in anticancer therapy. Therefore, this narrative review aims to provide an updated overview on the bioactive phytochemicals with anti-EMT activity.

CONCLUSION

Among the plant products reviewed, phenylpropanoids were the most investigated at preclinical phase, thus exhibiting a promising potential as anticancer drugs, though an evidence-based clinical efficacy is still lacking.

Tobacco smoke induced hepatic cancer stem cell-like properties through IL-33/p38 pathway

BACKGROUND

Tobacco smoke (TS) critically contributes to the development of hepatocellular carcinoma. Cancer stem cells (CSCs) induced by TS is an early event in the initiation of carcinogenesis. Tumor specific microenvironment including inflammatory factors is key mediator for maintaining the stemness of CSCs through various pathways such as p38 MAPK. However, the mechanisms of inflammatory factors in TS-induced acquisition of liver CSCs properties remain undefined. The aim of this study was to investigate the role of IL-33/p38 axis in long term TS-induced acquisition of hepatic CSCs properties in mouse liver tissues and human liver cells.

METHODS

BALB/c mice were exposed to TS for 12 weeks, along with or without 1 mg/kg SB203580 (p38 inhibitors) treatment. Histopathological analysis, alterations in the levels of IL-33, liver CSCs markers, EMT-like changes and p38 MAPK activation in liver tissues of mice were analyzed by immunohistochemical staining, immunofluorescence assay and Western blot analysis. Moreover, LO2 immortalized human liver cells were exposed to cigarette smoke extract (CSE) and the tumorsphere formation ability was determined. LO2 cells were further treated with IL-33 or CSE and the expression of phosphorylated p38, liver CSCs markers and EMT-related proteins was examined.

RESULTS

Long term TS exposure increased the levels of CSCs markers, induced epithelial-to mesenchymal transition (EMT) and inflammatory factor IL-33 expression. Moreover, we showed that p38 MAPK modulated TS-stimulated hepatic CSC-like properties, as evidenced by the findings that long term TS exposure activated p38, and that TS-induced stemness was abolished by p38 inhibition. In addition, data from in vitro model showed that similar to cigarette smoke extract (CSE), IL-33 treatment promoted the activation of p38, increased the levels of liver CSCs markers expression and EMT-like changes.

CONCLUSIONS

Collectively, these data suggested that IL-33/p38 axis plays an important role in long term TS exposure-induced acquisition of hepatic CSC-like properties.

Potential therapeutic effects of curcumin in gastric cancer

Despite recent advancements in understanding of the biology of gastric cancer, treatment of patients with advanced gastric cancer remains a major problem. Among different type of phytochemicals, curcumin, a welltable -known phytochemical, has been shown to be a promising cancer chemopreventive agent. Pharmacokinetics, safety, and efficacy of curcumin have been evaluated in several clinical trials against numerous diseases, and for the treatment of human cancer. In the present review, we have collected in vitro and in vivo investigations and studied the chemosensitizing and anticancer effects of curcumin against the gastric cancer cells. In summary, curcumin has been found to have efficient chemosensitizing effect and also inhibits viability, proliferation, and migration of gastric cancer cells mainly via cell cycle arrest and induction of apoptosis by both mitochondrial-dependent and -independent pathways.

Cigarette smoke induced urocystic epithelial mesenchymal transition via MAPK pathways

Cigarette smoke has been shown to be a major risk factor for bladder cancer. Epithelial-mesenchymal transition (EMT) is a crucial process in cancer development. The role of MAPK pathways in regulating cigarette smoke-triggered urocystic EMT remains to be elucidated. Human normal urothelial cells and BALB/c mice were used as in vitro and in vivo cigarette smoke exposure models. Exposure of human normal urothelial cells to cigarette smoke induced morphological change, enhanced migratory and invasive capacities, reduced epithelial marker expression and increased mesenchymal marker expression, along with the activation of MAPK pathways. Moreover, we revealed that ERK1/2 and p38 inhibitors, but rather JNK inhibitor, effectively attenuated cigarette smoke-induced urocystic EMT. Importantly, the regulatory function of ERK1/2 and p38 pathways in cigarette smoke-triggered urocystic EMT was further confirmed in mice exposed to CS for 12 weeks. These findings could provide new insight into the molecular mechanisms of cigarette smoke-associated bladder cancer development as well as its potential intervention.

Curcumin reverses tobacco smoke‑induced epithelial‑mesenchymal transition by suppressing the MAPK pathway in the lungs of mice

Tobacco smoke is a major risk factor for lung cancer. Epithelial‑mesenchymal transition (EMT) is decisive in cancer invasion and metastasis, and therefore promotes cancer progression. Mitogen‑activated protein kinase (MAPK) pathways are implicated in various aspects of cancer development and progression, including the EMT process. The chemopreventive effect of curcumin on carcinogenesis has been reported in vivo and in vitro. The present study investigated tobacco smoke‑induced alterations in the MAPK/activator protein‑1 (AP‑1) pathways, and pulmonary EMT changes in the lungs of mice, and further observed the chemopreventive effect of curcumin. The protein expression levels analyzed by western blot analysis demonstrated that 12 weeks of tobacco smoke exposure activated extracellular‑signal‑regulated kinase (ERK) 1/2, c‑Jun N‑terminal kinase (JNK) and p38 MAPK pathways, in addition to AP‑1, in the lungs of mice, while reducing the activation of ERK5/MAPK pathways. The results also indicated that the mRNA and protein levels of the epithelial markers E‑cadherin and zona occludens‑1 were reduced following tobacco smoke exposure. Conversely, the expression levels of mRNA and protein for the mesenchymal markers vimentin and N‑cadherin were increased. Curcumin treatment inhibited tobacco smoke‑induced MAPK/AP‑1 activation, including ERK1/2, JNK and p38 MAPK pathways, and AP‑1 proteins, and reversed EMT alterations in lung tissue. The results of the present study provide new insights into the molecular mechanisms of tobacco smoke‑associated lung cancer and may open up new avenues in the search for potential therapeutic targets in lung tumorigenesis.

ITGBL1 Predicts a Poor Prognosis and Correlates EMT Phenotype in Gastric Cancer

Integrin, beta-like 1 (ITGBL1), a β-integrin-related extracellular matrix protein, was found more commonly up-regulated in gastric cancer (GC) by screening and analyzing Gene Expression Omnibus (GEO) and Oncomine databases, reminding us to explore its prognostic significance in GC. In our current study, we observed that ITGBL1 expression was significantly up-regulated in GC compared with normal controls in clinical specimens. In addition, elevated ITGBL1 expression was positively correlated with patients' tumor-node-metastasis (TNM) stage and distant metastasis. Kaplan-Meier analysis indicated that high ITGBL1 expression was significantly associated with shorter survival times in GC patients. Multivariate Cox regression analysis confirmed ITGBL1 expression as an independent prognostic factor in GC. Gene set enrichment analysis (GSEA) of multiple GEO datasets revealed a close relationship between ITGBL1 expression and the KRAS/epithelial-mesenchymal transition (EMT) signaling pathway. In conclusion, these data provide evidences that ITGBL1 is a potential predictor and may be involved in cancer cell invasion and metastasis via inducing EMT, and the ITGBL1-related pathways may represent a novel therapeutic strategy for treatment of GC.

Curcumin reversed chronic tobacco smoke exposure induced urocystic EMT and acquisition of cancer stem cells properties via Wnt/β-catenin

Tobacco smoke (TS) is the most important single risk factor for bladder cancer. Epithelial–mesenchymal transition (EMT) is a transdifferentiation process, involved in the initiation of TS-related cancer. Cancer stem cells (CSCs) have an essential role in the progression of many tumors including TS-related cancer. However, the molecular mechanisms of TS exposure induced urocystic EMT and acquisition of CSCs properties remains undefined. Wnt/β-catenin pathway is critical for EMT and the maintenance of CSCs. The aim of our present study was to investigate the role of Wnt/β-catenin pathway in chronic TS exposure induced urocystic EMT, stemness acquisition and the preventive effect of curcumin. Long time TS exposure induced EMT changes and the levels of CSCs’ markers were significant upregulated. Furthermore, we demonstrated that Wnt/β-catenin pathway modulated TS-triggered EMT and stemness, as evidenced by the findings that TS elevated Wnt/β-catenin activation, and that TS-mediated EMT and stemness were attenuated by Wnt/β-catenin inhibition. Treatment of curcumin reversed TS-elicited activation of Wnt/β-catenin, EMT and CSCs properties. Collectively, these data indicated the regulatory role of Wnt/β-catenin in TS-triggered urocystic EMT, acquisition of CSCs properties and the chemopreventive effect of curcumin.

Effects of Curcumin on Tobacco Smoke-induced Hepatic MAPK Pathway Activation and Epithelial-Mesenchymal Transition In Vivo

Tobacco smoke is a major risk factor for hepatic cancer. Epithelial-mesenchymal transition (EMT) induced by tobacco smoke is crucially involved in the initiation and development of cancer. Mitogen-activated protein kinase (MAPK) pathways play important roles in tobacco smoke-associated carcinogenesis including EMT process. The chemopreventive effect of curcumin supplementation against cancers has been reported. In this study, we investigated the effects of tobacco smoke on MAPK pathway activation and EMT alterations, and then the preventive effect of curcumin was examined in the liver of BALB/c mice. Our results indicated that exposure of mice to tobacco smoke for 12 weeks led to activation of ERK1/2, JNK, p38 and ERK5 pathways as well as activator protein-1 (AP-1) proteins in liver tissue. Exposure of mice to tobacco smoke reduced the hepatic mRNA and protein expression of the epithelial markers, while the hepatic mRNA and protein levels of the mesenchymal markers were increased. Treatment of curcumin effectively attenuated tobacco smoke-induced activation of ERK1/2 and JNK MAPK pathways, AP-1 proteins and EMT alterations in the mice liver. Our data suggested the protective effect of curcumin in tobacco smoke-triggered MAPK pathway activation and EMT in the liver of BALB/c mice, thus providing new insights into the chemoprevention of tobacco smoke-associated hepatic cancer. Copyright © 2017 John Wiley & Sons, Ltd.

Gap junction protein connexin43 deregulation contributes to bladder carcinogenesis via targeting MAPK pathway

High expression of connexins was found in a variety of cancers, but their role is still controversial. We investigated whether connexin43 (Cx43) contributed to bladder carcinogenesis through MAPK activation. In this study, we found that Cx43 expression was significantly increased in bladder cancer tissues and cell line. Overexpression of Cx43 in bladder cancer 5637 cells increased cell proliferation, promoted cell cycle progression, and inhibited apoptosis. Western blot showed that JNK and ERK pathways were dramatically activated in Cx43-overexpressed cells. Conversely, knockdown of Cx43 inhibited cell proliferation by increasing apoptosis and causing cell cycle arrest, concomitant with inhibition of JNK and ERK signaling. In addition, JNK and ERK pathways were also activated in bladder cancer tissues. In conclusion, abnormal high expression and cytoplasmic localization of Cx43 contributed to bladder cancer. Inhibition of Cx43 activity could be a potential therapeutic strategy for preventing the progression of bladder cancer.

Recent highlights of Chinese herbs in treatment of allergic disease: Acting via mitogen-activated protein kinase signal pathway

The histamine receptor antagonists in the treatment of allergic disease have limitations. The treatments of Chinese herbs have some curative effects on allergic skin lesions. Present research indicates that the mitogen-activated protein kinase (MAPK) signaling pathway might be equally important in allergic reactions. It was found that the inhibition of MAPK signaling pathways might relieve allergy symptoms, and some herbs can inhibit the MAPK pathway, which yields anti-allergy effects. Chinese medicines (CMs) have immense potential in the development of treatments for allergic disease.

EGCG Suppresses ERK5 Activation to Reverse Tobacco Smoke-Triggered Gastric Epithelial-Mesenchymal Transition in BALB/c Mice

Tobacco smoke is an important risk factor of gastric cancer. Epithelial-mesenchymal transition is a crucial pathophysiological process in cancer development. ERK5 regulation of epithelial-mesenchymal transition may be sensitive to cell types and/or the cellular microenvironment and its role in the epithelial-mesenchymal transition process remain elusive. Epigallocatechin-3-gallate (EGCG) is a promising chemopreventive agent for several types of cancers. In the present study we investigated the regulatory role of ERK5 in tobacco smoke-induced epithelial-mesenchymal transition in the stomach of mice and the preventive effect of EGCG. Exposure of mice to tobacco smoke for 12 weeks reduced expression of epithelial markers E-cadherin, ZO-1, and CK5, while the expression of mesenchymal markers Snail-1, Vimentin, and N-cadherin were increased. Importantly, we demonstrated that ERK5 modulated tobacco smoke-mediated epithelial-mesenchymal transition in mice stomach, as evidenced by the findings that tobacco smoke elevated ERK5 activation, and that tobacco smoke-triggered epithelial-mesenchymal transition was reversed by ERK5 inhibition. Treatment of EGCG (100 mg/kg BW) effectively attenuated tobacco smoke-triggered activation of ERK5 and epithelial-mesenchymal transition alterations in mice stomach. Collectively, these data suggested that ERK5 was required for tobacco smoke-triggered gastric epithelial-mesenchymal transition and that EGCG suppressed ERK5 activation to reverse tobacco smoke-triggered gastric epithelial-mesenchymal transition in BALB/c mice. These findings provide new insights into the mechanism of tobacco smoke-associated gastric tumorigenesis and the chemoprevention of tobacco smoke-associated gastric cancer.

Curcumin reverses benzidine-induced cell proliferation by suppressing ERK1/2 pathway in human bladder cancer T24 cells

Bladder cancer is one of the leading causes of cancer-related death in the world. Prolonged exposure to benzidine is a known cause of bladder cancer. Curcumin has been clinically used in chemoprevention and treatment of cancer. However, it remains unknown whether mitogen-activated protein kinase (MAPK) pathways are involved in curcumin-mediated protection from benzidine-associated promotive effects on bladder cancer. In our study, we found that benzidine increased the proliferation of human bladder cancer T24 cells, triggered transition of the cells from G1 to S phase, elevated the expression of cyclin D1 and proliferating cell nuclear antigen (PCNA) and decreased p21 expression. Meanwhile, exposure of T24 cells to benzidine resulted in activation of extracellular regulated protein kinases 1 and 2 (ERK1/2) pathway as well as activator protein 1 (AP-1) proteins. Treatment with ERK1/2 inhibitor U0126 or curcumin effectively abrogated benzidine-triggered cell proliferation and ERK1/2/AP-1 activation. These results suggested for the first time that curcumin in low concentrations played a protective role in benzidine-induced ERK1/2/AP-1 activation and proliferation of bladder cancer cells, therefore providing new insights into the pathogenesis and chemoprevention of benzidine-associated bladder cancer.

Curcumin enhances poly(ADP-ribose) polymerase inhibitor sensitivity to chemotherapy in breast cancer cells

Poly(ADP-ribose) polymerase (PARP) inhibitor has shown promising responses in homologous recombination (HR) repair-deficient cancer cells. More specifically, targeting HR pathway in combination with PARP inhibitor has been an effective chemotherapy strategy by so far. Curcumin has been recognized as anticancer agents for several types of cancers. Here, we demonstrate that curcumin inhibits a critical step in HR pathway, Rad51 foci formation, and accumulates γ-H2AX levels in MDA-MB-231 breast cancer cells. Curcumin also directly reduces HR and induces cell death with cotreatment of PARP inhibitor in MDA-MB-231 breast cancer cells. Moreover, curcumin, when combined with ABT-888, could effectively delayed breast tumor formation in vivo. Our study indicates that cotreatment of curcumin and PARP inhibitor might be useful for the combination chemotherapy for aggressive breast cancer treatment as a natural bioactive compound.