[Corrigendum] Role of cysteine­rich angiogenic inducer 61 in fibroblast­like synovial cell proliferation and invasion in rheumatoid arthritis.

Following the publication of the above article, an interested reader drew to the authors' attention that Fig. 4A on p. 921, showing the results from cell migration assay experiments, featured a pair of duplicated data panels. After having consulted their original data, the authors have realized that Fig. 3A on the same page, showing the fluorometric images of apoptotic cells, also contained a pair of duplicated data panels. These errors in the presentation of these figures arose inadvertently as a consequence of selecting the wrong images for the 'RA NC' data panel in Fig. 3A and the NOR-FLS data panel in Fig. 5E. The revised versions of Figs. 3 and 4 are shown on the next two pages. All the authors approve of the publication of this corrigendum, and the authors are grateful to the Editor of Molecular Medicine Reports for granting them the opportunity to publish this. The authors regret their oversight in allowing these errors to be included in the paper, and also apologize to the readership for any inconvenience caused. [Molecular Medicine Reports 11: 917­923, 2015; DOI: 10.3892/mmr.2014.2770].

Chinese Herbal Formula Huayu-Qiangshen-Tongbi Decoction Attenuates Rheumatoid Arthritis through Upregulating miR-125b to Suppress NF-κB-Induced Inflammation by Targeting CK2.

The Huayu-Qiangshen-Tongbi (HQT) decoction, a Chinese medical formula, has been identified to show a potent therapeutic effect on rheumatoid arthritis (RA). However, the specific molecular mechanism of HQT in RA has not been well studied. In the present study, LPS-treated human rheumatoid fibroblast-like synoviocyte (FLS) MH7A cells and collagen-induced arthritis (CIA) mice were utilized as in vitro and in vivo models. Our results demonstrated that HQT could efficiently inhibit RA-induced inflammation by reducing the production of cytokines including tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1ß), and interleukin-6 (IL-6). Moreover, HQT significantly upregulated the expression of miR-125b. Besides, analysis of bioinformatics suggested casein kinase 2 (CK2) was a potential target of miR-125b. Luciferase reporter assay was performed and revealed that miR-125b suppressed CK2 expression in MH7A cells. Furthermore, miR-125b inhibited LPS-induced NF-kappa-B (NF-κB) activation, which is a downstream target of CK2. In addition, the NF-κB inhibitor ammonium pyrrolidinedithiocarbamate (PDTC) and NF-kappa-B inhibitor alpha (IkB-α) enhanced the inhibitory effect of miR-125b on the expression of TNF-α, IL-1ß, and IL-6. Taken together, our study revealed that HQT could attenuate RA through upregulating miR-125b to suppress NF-κB-induced inflammation by targeting CK2. The findings of this study should facilitate investigating the mechanism of HQT on RA and discovering novel therapeutic targets for RA.

Nagilactone E increases PD-L1 expression through activation of c-Jun in lung cancer cells.

Nagilactone E (NLE), a natural product with anticancer activities, is isolated from Podocarpus nagi. In this study, we reported that NLE increased programmed death ligand 1 (PD-L1) expressions at both protein and mRNA levels in human lung cancer cells, and enhanced its localization on the cell membrane. Mechanistically, NLE increased the phosphorylation and expression of c-Jun, and promoted the localization of c-Jun in the nucleus, while silencing of c-Jun by small interfering RNA (siRNA) reduced NLE-induced PD-L1. Further study showed that NLE activated the c-Jun N-terminal kinases (JNK), the upstream of c-Jun, and its inhibitor SP600125 reversed the NLE-increased PD-L1. Moreover, NLE-induced PD-L1 increased the binding intensity of PD-1 on the cell surface. In summary, NLE upregulates the expression of PD-L1 in lung cancer cells through the activation of JNK-c-Jun axis, which has the potential to combine with the PD-1/PD-L1 antibody therapies in lung cancer.

Novel findings from determination of common expressed plasma exosomal microRNAs in patients with psoriatic arthritis, psoriasis vulgaris, rheumatoid arthritis, and gouty arthritis.

BACKGROUND: Circulating exosomal microRNAs modulate not only cancer cell metabolism but also the immune response, and therefore plasma exosomal microRNAs might have the potential to be the biomarkers for a number of immune disorders. OBJECTIVE: This study was conducted to identify the common mechanisms among psoriatic arthritis (PsA), psoriasis vulgaris (PV), rheumatoid arthritis (RA), and gouty arthritis (GA). The common expressed plasma exosomal microRNAs in these diseases were determined. METHODS: The expression of microRNAs derived from plasma exosome of patients with PsA (n=30), PV (n=15), RA (n=15), GA (n=15), and healthy controls (n=15) was evaluated via sequencing. Function analysis of common expressed microRNAs was conducted by the Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analyses. Coexpression analysis was conducted to identify novel and significant genes and proteins by using the Search Tool for the Retrieval of Interacting Genes (STRING). A systematic literature review was conducted to uncover the role of the common microRNAs in the pathogenesis of PsA, PV, RA, and GA. RESULTS: A total of 36 common expressed microRNAs were detected in patients with PsA, PV, RA, and GA. The most significantly enriched biological processes, cellular components, and molecular functions were "homophilic cell adhesion via plasma membrane adhesion molecules," "CCR4-NOT complex," and "calcium ion binding," respectively. "Antigen processing and presentation" was the most significantly enriched pathway. A total of 91 validated coexpressed gene pairs were identified and 16 common expressed microRNAs and 85 potential target genes were screened based on Cytoscape. Of 36 common expressed microRNAs, 5 microRNAs, including hsa-miR-151a-3p, hsa-miR-199a-5p, hsa-miR-370-3p, hsa-miR-589-5p, and hsa-miR-769-5p, were considered to be connected with the common pathogenesis of PsA, PV, RA, and GA. Systemic review revealed that the roles of these 5 microRNAs are related to immune disorder and bone injury, which matches the conclusion from GO and KEGG analyses. CONCLUSION: (1) Both immune disorder and bone metabolic dysregulation could be the shared mechanism in the development of PsA, PV, RA, and GA. (2) Immune dysfunction is involved in GA. Our study may shed new light on the diagnosis and treatment strategy of these autoimmune diseases and GA, which warrants further studies.

Platycodin D triggers the extracellular release of programed death Ligand-1 in lung cancer cells.

Programmed death ligand-1 (PD-L1) is an important immune checkpoint for cancer immunotherapy in clinic. In this study, we reported that platycodin D, a natural product isolated from an edible and medicinal plant Platycodon grandiflorus (Jacq.) A. DC., down-regulated the protein level of PD-L1 in lung cancer cells. Flow cytometry and immunofluorescence assay showed a weaker surface PD-L1 signal in NCI-H1975 cells after the incubation with platycodin D (10 µM) for 15 min compared to the control group. Jurkat T cells showed enhancive interleukin-2 secretion when co-cultured with platycodin D-treated NCI-H1975 cells, suggesting that platycodin D-induced PD-L1 reduction increases the activation of Jurkat T cells. An augmentation of PD-L1 protein was detected in the cell culture medium from platycodin D treatment group. Chlorpromazine (60 µM) almost abolished the platycodin D-mediated PD-L1 extracellular release and restored the membrane PD-L1. Finally, hemolysis assay exhibited that platycodin D-triggered PD-L1 extracellular release was independent of the hemolytic mechanism. Taken together, our study demonstrates that platycodin D reduces the protein level of PD-L1 in lung cancer cells via triggering its release into the cell culture medium, which sheds new light for the application of natural products in cancer immunotherapy.

The differential profiles of long non-coding RNAs between rheumatoid arthritis and gouty arthritis.

OBJECTIVE: This study was designed to determine the differential profiles of long non-coding RNAs (lncRNAs) between rheumatoid arthritis (RA) and gouty arthritis (GA), which may lead to the discovery of specific biomarkers for RA diagnosis and treatment in the future. METHODS: The profiles of lncRNAs were determined by Agilent microarray. Bioinformatics analyses, including Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses, of the large dataset obtained from microarray experiments were performed. RESULTS: A total of 765 lncRNAs and 2,808 mRNAs were significantly and differentially expressed in RA samples as compared to GA samples. Moreover, of 2,808 differentially expressed mRNAs, 178 upregulated mRNAs and 21 downregulated mRNAs were identified to be strongly correlated with lncRNAs examined in this study. Bioinformatics analyses revealed the tumor-like phenotype of synovial cells in RA and the involvement of immune system process in GA. In addition, this study demonstrated the significantly different molecular origins of two Chinese Medicine syndrome patterns of RA patients -- blood stasis and non-blood stasis. CONCLUSIONS: Our study showed for the first time the differentially expressed lncRNA profiles in synovial tissues between RA and GA and between two clinical phenotypes of RA patients differentiated by Chinese Medicine. This study helps achieving personalized medicine in RA. Larger-scale studies are required to validate the data presented.

NF-κB pathways are involved in M1 polarization of RAW 264.7 macrophage by polyporus polysaccharide in the tumor microenvironment.

Bladder cancer is one of the most malignant tumors closely associated with macrophages. Polyporus polysaccharide (PPS) has shown excellent efficacy in treating bladder cancer with minimal side effects. However, the molecular mechanisms underlying the effects of PPS in inhibiting bladder cancer remain unclear. In this study, we used macrophages cultured alone or with T24 human bladder cancer cell culture supernatant as study models. We found that PPS enhanced the activities of IFN-γ-stimulated RAW 264.7 macrophages, as shown by the release of inducible nitric oxide synthase (INOS), secretion of tumor necrosis factor (TNF)-α and interleukin (IL)-6, phagocytosis activity, as well as expression of M1 phenotype indicators, such as CD40, CD284 and CD86. PPS acted upstream in activation cascade of nuclear factor (NF)-κB signaling pathways by interfering with IκB phosphorylation. In addition, PPS regulated NF-κB (P65) signaling by interfering with Toll-like receptor (TLR)-4, INOS and cyclooxygenase (COX)-2. Our results indicate that PPS activates macrophages through TLR4/NF-κB signaling pathways.

Effects of Glycyrrhizin in a Mouse Model of Lung Adenocarcinoma.

BACKGROUND: Currently, there is a global attempt to identify potential anti-cancer agents with low toxicity. Previous studies have found that glycyrrhizin exerts anti-cancer action with low toxicity through suppressing thromboxane A2 (TxA2) in lung cancer cell lines. However, these effects have not yet been determined in animal models of lung cancer. METHODS: Human lung adenocarcinoma xenografts were established in nude mice by the introduction of A549 cells with stable transfection of the TxA2 receptor (TPα). The animal model was confirmed by the hematoxylin and eosin (H&E) method. Tumor-bearing mice were then administered graded concentrations of glycyrrhizin, cisplatin or both. After the treatments, body weights of all animals were recorded, and immunohistochemistry staining of lung tissues and serum biochemistry detection of aspartate amino transferase (AST), alanine amino transferase (ALT), urea and creatinine were carried out. RESULTS: Treatment with glycyrrhizin alone or the combination of cisplatin and glycyrrhizin profoundly reduced expression of thromboxane synthase (TxAS) as well as proliferating cell nuclear antigen (PCNA), recovered the body weight, and rescued damage of liver and kidney in tumor-bearing mice. Although it inhibited PCNA expression, cisplatin could not significantly suppress TxAS expression. Because of a positive feedback loop between TPα and TxAS, the effects of glycyrrhizin are possibly attributable to the suppression of the TxA2 pathway. CONCLUSIONS: This study provides in vivo evidence to support glycyrrhizin as a potential candidate for developing new regimens to overcome tumor progression and the resistance and toxicity of cisplatin.

A new coumarin isolated from Sarcandra glabra as potential anti-inflammatory agent.

One new coumarin, 3,5-dihydroxy-7-O-α-L-rhamno pyranosyl-2H-chromen-2-one (1), was isolated from the whole plant of Sarcandra glabra. The structure was elucidated by spectroscopic methods. Our results indicated that 1 significantly inhibit nitric oxide (NO) production in LPS-induced RAW264.7 macrophages. RT-PCR analysis indicated it inhibited iNOS mRNA expression. In addition, Western blot analysis showed that 1 attenuated LPS-induced synthesis of iNOS protein in the macrophages. These results suggest that 1 could be potential anti-inflammatory agent by down-regulating iNOS expression.

BLZF1 expression is of prognostic significance in hepatocellular carcinoma.

BLZF1, a member of b-ZIP family, has been implicated in epigenetic regulation and Wnt/ß-catenin signaling. Its expression and clinical significance in human cancers remain largely unknown. In this study, we showed that BLZF1 expression was reduced in hepatocellular carcinoma (HCC) tissues, compared to the paracarcinoma tissues, at both mRNA and protein levels. Results of immunohistochemistry revealed that BLZF1 was presented in both nuclear and cytoplasm. Decreased expression of nuclear and cytosolic BLZF1 in HCC was depicted in 68.2% and 79.2% of the 634 cases. Nuclear BLZF1 expression was significantly associated with tumor multiplicity (P = 0.048) and tumor capsule (P = 0.028), while cytosolic BLZF1 expression was correlated with serum AFP level (P = 0.017), tumor differentiation (P = 0.001) and tumor capsule (P = 0.003). Kaplan-Meier analysis indicated both nuclear and cytosolic BLZF1 expression was associated with poor overall survival. Low nuclear BLZF1 also indicated unfavorable disease-free survival and high tendency of tumor recurrence. Furthermore, multiple Cox regression analysis revealed nuclear BLZF1 as an independent factor for overall survival (Hazard Ratio (HR) = 0.827, 95% confident interval (95%CI): 0.697-0.980, P = 0.029). The prognostic value of BLZF1 was further confirmed by stratified analyses. Collectively, our data suggest BLZF1 is a novel unfavorable biomarker for prognosis of patients with HCC.

Role of cysteine­rich angiogenic inducer 61 in fibroblast­like synovial cell proliferation and invasion in rheumatoid arthritis.

Cysteine­rich angiogenic inducer 61 (Cyr61) is a novel molecule that has been shown to be increased in the synovial tissues of patients with rheumatoid arthritis (RA). The present study was conducted in order to investigate the role of Cyr61 in the pathogenesis of RA. A human genome­wide gene assay was used to screen gene expression in synovial tissues obtained from four patients with RA and three patients with osteoarthritis (OA). To examine the role of Cyr61 in the phenotype of RA­fibroblast­like synovial (FLS) cells, Cyr61 expression in RA­FLS cells was knocked down using small interfering RNA (siRNA). Normal FLS cells transduced with lentiviral vectors encoding Cyr61 cDNA were used to further explore the effects of this molecule on FLS cell apoptosis, proliferation and invasion. The study found that the Cyr61 gene was highly expressed in the synovial cells from patients with RA compared with those from patients with OA. Downregulation of Cyr61 by siRNA led to impaired cell proliferation and invasion. Furthermore, it decreased the levels of matrix metalloproteinase (MMP)­3 and MMP­13, and induced apoptosis in RA­FLS cells. Conversely, overexpression of Cyr61 in normal FLS cells led to opposite effects. In conclusion, these results indicate that Cyr61 is capable of promoting RA­FLS cell proliferation and invasion via the suppression of apoptosis and the regulation of MMP expression. Therefore, Cyr61 may be a good target molecule for the treatment and prevention of RA.

The cyclooxygenase-2/thromboxane A2 pathway: a bridge from rheumatoid arthritis to lung cancer?

Patients with rheumatoid arthritis (RA) appear to be at a higher risk of lung cancer (LC). Although the connection between RA and LC has been an active area of research for many years, the molecular pathogenesis of the disease process remains unclear. The cyclooxygenase (COX)-2/thromboxane A2 (TxA2) pathway has been shown to play a potential role in LC development through an auto-regulatory feedback loop. An increased level of TxA2 has been found in RA patients, and intriguingly, the positive feedback loop for the COX-2/TxA2 pathway was shown to have a potential function in RA fibroblast-like synoviocytes (RA-FLS). Thus, the molecular basis of LC development in patients with RA has been at least in partly described. It is possible that COX-2-derived TxA2 could be monitored for the early detection of LC in RA patients, and targeting this molecular pathway may decrease the risk of LC in patients with RA.

Anti-inflammatory activity of extracts of Bushen-Qiangdu-Zhilv decoction, a Chinese medicinal formula, in M1-polarized RAW264.7.

BACKGROUND: Bushen-Qiangdu-Zhilv Decoction (BQZ) is one of famous traditional Chinese medical formula for treating ankylosing spondylitis (AS). However, the mechanisms underlying effects of BQZ remains unknown. Pro-inflammatory cytokines, tumor necrosis factor (TNF)-α and interleukin (IL)-1, play an important role in AS. We therefore evaluated if BQZ could affect the expression of these cytokines. METHODS: Crude extracts were prepared and fractioned with petroleum ether (PE), ethyl acetate (EA), n-butanol (BU) and finally water (ACE). The stability of the extracts was confirmed by high-pressure liquid chromatography (HPLC) analysis. M1-polarized RAW264.7 was induced and subsequently treated with BQZ extracts. Quantitative real-time PCR experiments were performed to measure mRNA expression of TNF-α and IL-1. RESULTS: It was found that TNF-α could be significantly suppressed by ACE extracts, whereas IL-1 was dramatically inhibited by BU extracts, which was further confirmed by dose-dependent experiments. Importantly, MTS assays showed that both ACE and BU extracts had a low cytotoxicity. CONCLUSION: Altogether, our study indicates that BQZ decoction exerts anti-AS effects via its anti-inflammatory activity and may have a low side-effect. Further analysis of the extracts of BQZ decoction could lead to a discovery of some novel drugs adding to therapeutic strategy for AS patients.

18ß-Glycyrrhetinic acid suppresses cell proliferation through inhibiting thromboxane synthase in non-small cell lung cancer.

18ß-Glycyrrhetinic acid (18ß-GA) is a bioactive component of licorice. The anti-cancer activity of 18ß-GA has been studied in many cancer types, whereas its effects in lung cancer remain largely unknown. We first showed that 18ß-GA effectively suppressed cell proliferation and inhibited expression as well as activity of thromboxane synthase (TxAS) in non-small cell lung cancer (NSCLC) cells A549 and NCI-H460. In addition, the administration of 18ß-GA did not have any additional inhibitory effect on the decrease of cell proliferation induced by transfection with TxAS small interference RNA (siRNA). Moreover, 18ß-GA failed to inhibit cell proliferation in the immortalized human bronchial epithelial cells 16HBE-T and another NSCLC cell line NCI-H23, both of which expressed minimal level of TxAS as compared to A549 and NCI-H460. However, 18ß-GA abolished the enhancement of cell proliferation induced by transfection of NCI-H23 with pCMV6-TxAS plasmid. Further study found that the activation of both extracellular signal-regulated kinase (ERK)1/2 and cyclic adenosine monophosphate response element binding protein (CREB) induced by TxAS cDNA transfection could be totally blocked by 18ß-GA. Altogether, we have delineated that, through inhibiting TxAS and its initiated ERK/CREB signaling, 18ß-GA suppresses NSCLC cell proliferation. Our study has highlighted the significance of 18ß-GA with respect to prevention and treatment of NSCLC.

Novel insight into the role of α-actinin-1 in rheumatoid arthritis.

The knowledge of rheumatoid arthritis (RA) pathology is rapidly advancing and becoming more and more complex, and a simple fact is that the major organ targeted by RA pathogenic factors is the synovium. It is well known that fibroblast-like synovial (FLS) cell is the major cell-type for constructing synovium. Following stimulation by pro-inflammatory cytokines, FLS cells are phenotypically changed to have the capability to proliferate abnormally. Recently we demonstrated that α-actinin-1 (ACTN1) gene is significantly increased in synovial tissues obtained from RA, as compared to osteoarthritis (OA). We therefore reviewed the literature about α-actinins (ACTNs) and we now propose that ACTN1 may function as a "terminal effector" of intracellular signalings initiated by tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1) in RA. Future research on ACTN1 may help to improve the current therapeutic and diagnostic strategies of RA.

Glycyrrhizin suppresses lung adenocarcinoma cell growth through inhibition of thromboxane synthase.

BACKGROUND/AIMS: The effects of glycyrrhizin treatment in lung cancer remain undetermined, despite extensive studies of the anti-tumor activities of glycyrrhizin. METHODS: Lung adenocarcinoma A549 and NCI-H23 cell lines were used in this study. Cell growth was examined by MTS assays, while apoptosis and cell cycle were determined by flow cytometric analysis. Both real-time PCR and western blotting were used to examine the expression levels of thromboxane synthase (TxAS), and TxAS activity was measured using EIA detection of the biosynthesis of TxA2. TxAS was overexpressed in NCI-H23 cells by transfection with TxAS cDNA, while TxAS was inhibited by transfection with TxAS siRNA in A549 cells. For the mouse model of lung adenocarcinoma, the effects of glycyrrhizin on tumor growth were analyzed by western blot evaluation of TxAS, PTEN and survivin. TxAS activity was determined by EIA assay. RESULTS: Glycyrrhizin suppressed cell growth in A549 cells, but not in NCI-H23 cells, by induction of apoptosis. TxAS was overexpressed in A549 cells, but the TxAS levels in NCI-H23 cells were minimal. Moreover, TxAS expression and activity were suppressed by glycyrrhizin. Glycyrrhizin had no additive effects with TxAS siRNA knockdown in suppressing A549 cell growth, whereas it completely suppressed cell growth of NCI-H23 cells transfected with TxAS cDNA. These results were further confirmed by the in vivo study. CONCLUSION: Our study suggests that the anti-tumor effect of glycyrrhizin in lung adenocarcinoma is, at least in part, TxAS-dependent. Therefore, glycyrrhizin is a promising anti-cancer agent for the treatment of lung adenocarcinoma.

Thromboxane A2 exerts promoting effects on cell proliferation through mediating cyclooxygenase-2 signal in lung adenocarcinoma cells.

BACKGROUND: Lung cancer concerns a worldwide health problem and the efficacy of available treatments is unsatisfactory. Recently, thromboxane A2 (TXA2) synthase (TXAS) and receptor (TXA2R) have been documented to play a role in lung cancer development. Therefore, dual TXA2R modulator (i.e., the dual blocker of TXAS and TXA2R) may be more efficacious to kill lung tumor cells than single TXAS inhibitor or TXA2R antagonism. The close relationship between cyclooxygenase (COX)-2 and TXAS also raises whether or how TXA2 contributes to the oncogenic activity of COX-2. This study is therefore conducted to answer these questions. METHODS: Various inhibitors and siRNA were used to evaluate the roles of TXA2 and COX-2 in the proliferation and apoptosis of lung adenocarcinoma cells. Cell proliferation was detected using both MTS ELISA and BrdU labeling ELISA. Cell cycle distribution and apoptosis were examined by flow cytometric analysis. TXB2 level, reflecting the biosynthesis of TXA2, was detected by peroxidase-labeled TXB2 conjugates using an enzyme immunoassay kit. Western blotting was performed to evaluate many biomarkers for cell cycles, apoptosis and proliferation. The levels of COXs were screened by reverse transcriptase and real-time quantitative PCR. RESULTS: We found either single TXAS inhibitor/TXA2R antagonist or the dual TXA2 modulators offered a similar inhibition on cell proliferation. Moreover, inhibition of TXA2 arrested cells at the G2/M phase and induced apoptosis. It is further demonstrated that TXA2 was able to function as a critical mediator for tumor-promoting effects of COX-2 in lung adenocarcinoma cells. CONCLUSION: The present study has for the first shown that dual TXA2 modulators and the single blocker of TXAS or TXA2R offer a similar inhibitory role in lung adenocarcinoma cell proliferation and that the tumor-promoting effects of COX-2 can largely be relayed by TXA2. Thus, TXA2 should be regarded as a critical molecule in COX-2-mediated tumor growth and a valuable target against lung cancer.

Thromboxane A2 receptor α promotes tumor growth through an autoregulatory feedback pathway.

Tobacco smoking can cause a number of cancers. The role of thromboxane synthase (TxAS) in smoking-related cancers is largely unknown. In this study, 37 pairs of tumor and non-tumor lung tissues of non-small-cell lung cancer, 5 lung cancer cell lines, and a mouse tumor model were used to study TxAS and its related molecules. A mouse model of smoking carcinogen 4-methylnitrosamino-1-3-pyridyl-1-butanone (NNK)-induced lung tumor showed an increase in TxAS. Thromboxane A2 receptor (TP) was aberrant in lung cancer tissues of smokers. TxAS and TP were increased in lung tissues of NNK-treated mice. The in vitro studies showed that TPα rather than TPß promoted tumor growth, and NNK increased TPα. NNK-induced TxAS, which depended on activation of cyclooxygenase-2 (COX-2), ERK and NF-κB, could be inhibited by miR-34b/c. TPα played a positive role in NNK-induced COX-2/ERK/NF-κB activation, leading to the upregulation of TxAS expression and thromboxane A2 (TxA2) synthesis. The newly synthesized TxA2 could further activate TPα, forming an autoregulatory feedback loop for TPα activation. Collectively, NNK promotes lung tumor growth via inducing TxAS and TPα, which constitutes an auto-positive feedback loop to exaggerate the growth. This study suggests that TPα and TxAS are the ideal targets against smoking-related lung cancer.

Cigarette smoking, cyclooxygenase-2 pathway and cancer.

Cigarette smoking is a major cause of mortality and morbidity worldwide. Cyclooxygenase (COX) and its derived prostanoids, mainly including prostaglandin E2 (PGE2), thromboxane A2 (TxA2) and prostacyclin (PGI2), have well-known roles in cardiovascular disease and cancer, both of which are associated with cigarette smoking. This article is focused on the role of COX-2 pathway in smoke-related pathologies and cancer. Cigarette smoke exposure can induce COX-2 expression and activity, increase PGE2 and TxA2 release, and lead to an imbalance in PGI2 and TxA2 production in favor of the latter. It exerts pro-inflammatory effects in a PGE2-dependent manner, which contributes to carcinogenesis and tumor progression. TxA2 mediates other diverse biologic effects of cigarette smoking, such as platelet activation, cell contraction and angiogenesis, which may facilitate tumor growth and metastasis in smokers. Among cigarette smoke components, nicotine and its derived nitrosamines 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are the most potent carcinogens. COX-2 and PGE2 have been shown to play a pivotal role in many cancers associated with cigarette smoking, including cancers of lung, gastric and bladder, while the information for the role of TxA2 and PGI2 in smoke-associated cancers is limited. Recent findings from our group have revealed how NNK influences the TxA2 to promote the tumor growth. Better understanding in the above areas may help to generate new therapeutic protocols or to optimize the existing treatment strategy.