Depletion of beta-arrestin-2 promotes tumor growth and angiogenesis in a murine model of lung cancer

CXCR1 Expression in MDA-PCa-2b Cell Upregulates ITM2A to Inhibit Tumor Growth

BACKGROUND

Chemokines, along with their receptors, exert critical roles in tumor development and progression. In prostate cancer (PCa), interleukin-8 (IL-8/CXCL8) was shown to enhance angiogenesis, proliferation, and metastasis. CXCL8 activates two receptors, CXCR1 and CXCR2. While CXCR2 expression was shown to promote PCa growth and metastasis, the role of CXCR1 remains unclear.

METHODS

In this study, we stably expressed CXCR1 and, as control, CXCR2 in the androgen-dependent PCa cell line MDA-PCa-2b to evaluate the effect of CXCR1 in tumor development.

RESULTS

MDA-PCa-2b-CXCR1 cells showed decreased cell migration, protein kinase-B (AKT) activation, prostate-specific antigen (PSA) expression, cell proliferation, and tumor development in nude mice, relative to MDA-PCa-2b-Vec and MDA-PCa-2b-CXCR2 cells. MDA-PCa-2b-CXCR1 cells also displayed a significant transition to mesenchymal phenotypes as characterized by decreased E-cadherin expression and a corresponding increased level of N-cadherin and vimentin expression. RNA-seq and Western blot analysis revealed a significant increase in the tumor suppressor integral membrane protein 2A (ITM2A) expression in MDA-PCa-2b-CXCR1 compared to control cells. In prostate adenocarcinoma tissue, ITM2A expression was also shown to be downregulated relative to a normal prostate. Interestingly, the overexpression of ITM2A in MDA-PCa-2b cells (MDA-PCa-2b-ITM2A-GFP) inhibited tumor growth similar to that of MDA-PCa-2b-CXCR1.

CONCLUSIONS

Taken together, the data suggest that CXCR1 expression in MDA-PCa-2b cells may upregulate ITM2A to abrogate tumor development.

Comprehensive analyses for the coagulation and macrophage-related genes to reveal their joint roles in the prognosis and immunotherapy of lung adenocarcinoma patients

Purpose

This study aims to explore novel biomarkers related to the coagulation process and tumor-associated macrophage (TAM) infiltration in lung adenocarcinoma (LUAD).

Methods

The macrophage M2-related genes were obtained by Weighted Gene Co-expression Network Analysis (WGCNA) in bulk RNA-seq data, while the TAM marker genes were identified by analyzing the scRNA-seq data, and the coagulation-associated genes were obtained from MSigDB and KEGG databases. Survival analysis was performed for the intersectional genes. A risk score model was subsequently constructed based on the survival-related genes for prognosis prediction and validated in external datasets.

Results

In total, 33 coagulation and macrophage-related (COMAR) genes were obtained, 19 of which were selected for the risk score model construction. Finally, 10 survival-associated genes (APOE, ARRB2, C1QB, F13A1, FCGR2A, FYN, ITGB2, MMP9, OLR1, and VSIG4) were involved in the COMAR risk score model. According to the risk score, patients were equally divided into low- and high-risk groups, and the prognosis of patients in the high-risk group was significantly worse than that in the low-risk group. The ROC curve indicated that the risk score model had high sensitivity and specificity, which was validated in multiple external datasets. Moreover, the model also had high efficacy in predicting the clinical outcomes of LUAD patients who received anti-PD-1/PD-L1 immunotherapy.

Conclusion

The COMAR risk score model constructed in this study has excellent predictive value for the prognosis and immunotherapeutic clinical outcomes of patients with LUAD, which provides potential biomarkers for the treatment and prognostic prediction.

WDR4 promotes the progression and lymphatic metastasis of bladder cancer via transcriptional down-regulation of ARRB2

Lymph node (LN) metastasis is one of the key prognostic factors in bladder cancer, but its underlying mechanisms remain unclear. Here, we found that elevated expression of WD repeat domain 4 (WDR4) in bladder cancer correlated with worse prognosis. WDR4 can promote the LN metastasis and proliferation of bladder cancer cells. Mechanistic studies showed that WDR4 can promote the nuclear localization of DEAD-box helicase 20 (DDX20) and act as an adaptor to bind DDX20 and Early growth response 1 (Egr1), thereby inhibiting Egr1-promoted transcriptional expression of arrestin beta 2 (ARRB2) and ultimately contributing to the progression of bladder cancer. Immunohistochemical analysis confirmed that WDR4 expression is also an independent predictor of LN metastasis in bladder cancer. Our results reveal a novel mechanism of LN metastasis and progression in bladder cancer and identify WDR4 as a potential therapeutic target for metastatic bladder cancer.

Non-small Cell Lung Cancer Epigenomes Exhibit Altered DNA Methylation in Smokers and Never-smokers

Epigenetic alterations are widespread in cancer and can complement genetic alterations to influence cancer progression and treatment outcome. To determine the potential contribution of DNAmethylation alterations to tumor phenotype in non-small cell lung cancer (NSCLC) in both smoker and never-smoker patients, we performed genome-wide profiling of DNA methylation in 17 primary NSCLC tumors and 10 matched normal lung samples using the complementary assays, methylated DNA immunoprecipitation sequencing (MeDIP-seq) and methylation sensitive restriction enzyme sequencing (MRE-seq). We reported recurrent methylation changes in the promoters of several genes, many previously implicated in cancer, including FAM83A and SEPT9 (hypomethylation), as well as PCDH7, NKX2-1, and SOX17 (hypermethylation). Although many methylation changes between tumors and their paired normal samples were shared across patients, several were specific to a particular smoking status. For example, never-smokers displayed a greater proportion of hypomethylated differentially methylated regions (hypoDMRs) and a greater number of recurrently hypomethylated promoters, including those of ASPSCR1, TOP2A, DPP9, and USP39, all previously linked to cancer. Changes outside of promoters were also widespread and often recurrent, particularly methylation loss over repetitive elements, highly enriched for ERV1 subfamilies. Recurrent hypoDMRs were enriched for several transcription factor binding motifs, often for genes involved in signaling and cell proliferation. For example, 71% of recurrent promoter hypoDMRs contained a motif for NKX2-1. Finally, the majority of DMRs were located within an active chromatin state in tissues profiled using the Roadmap Epigenomics data, suggesting that methylation changes may contribute to altered regulatory programs through the adaptation of cell type-specific expression programs.

β-arrestin 2 negatively regulates lung cancer progression by inhibiting the TRAF6 signaling axis for NF-κB activation and autophagy induced by TLR3 and TLR4

β-arrestin 2 (ARRB2) is functionally implicated in cancer progression via various signaling pathways. However, its role in lung cancer remains unclear. To obtain clinical insight on its function in lung cancer, microarray data from lung tumor tissues (LTTs) and matched lung normal tissues (mLNTs) of primary non-small cell lung cancer (NSCLC) patients (n = 37) were utilized. ARRB2 expression levels were markedly decreased in all 37 LTTs compared to those in matched LNTs of NSCLC patients. They were significantly co-related to enrichment gene sets associated with oncogenic and cancer genes. Importantly, Gene Set Enrichment Analysis (GSEA) between three LTTs with highly down-regulated ARRB2 and three LTTs with lowly down-regulated ARRB2 revealed significant enrichments related to toll-like receptor (TLR) signaling and autophagy genes in three LTTs with highly down-regulated ARRB2, suggesting that ARRB2 was negatively involved in TLR-mediated signals for autophagy induction in lung cancer. Biochemical studies for elucidating the molecular mechanism revealed that ARRB2 interacted with TNF receptor-associated factor 6 (TRAF6) and Beclin 1 (BECN1), thereby inhibiting the ubiquitination of TRAF6-TAB2 to activate NF-κB and TRAF6-BECN1 for autophagy stimulated by TLR3 and TLR4, suggesting that ARRB2 could inhibit the TRAF6-TAB2 signaling axis for NF-κB activation and TRAF6-BECN1 signaling axis for autophagy in response to TLR3 and TLR4. Notably, ARRB2-knockout (ARRB2KO) lung cancer cells exhibited marked enhancements of cancer migration, invasion, colony formation, and proliferation in response to TLR3 and TLR4 stimulation. Altogether, our current data suggest that ARRB2 can negatively regulate lung cancer progression by inhibiting TLR3- and TLR4-induced autophagy.

A Novel Splice Variant of BCAS1 Inhibits β-Arrestin 2 to Promote the Proliferation and Migration of Glioblastoma Cells, and This Effect Was Blocked by Maackiain

Brain-enriched myelin-associated protein 1 (BCAS1) is frequently highly expressed in human cancer, but its detailed function is unclear. Here, we identified a novel splice variant of the BCAS1 gene in glioblastoma multiforme (GBM) named BCAS1-SV1. The expression of BCAS1-SV1 was weak in heathy brain cells but high in GBM cell lines. The overexpression of BCAS1-SV1 significantly increased the proliferation and migration of GBM cells, whereas the RNA-interference-mediated knockdown of BCAS1-SV1 reduced proliferation and migration. Moreover, using a yeast-two hybrid assay, immunoprecipitation, and immunofluorescence staining, we confirmed that β-arrestin 2 is an interaction partner of BCAS1-SV1 but not BCAS1. The downregulation of β-arrestin 2 directly enhanced the malignancy of GBM and abrogated the effects of BCAS1-SV1 on GBM cells. Finally, we used a yeast two-hybrid-based growth assay to identify that maackiain (MK) is a potential inhibitor of the interaction between BCAS1-SV1 and β-arrestin 2. MK treatment lessened the proliferation and migration of GBM cells and prolonged the lifespan of tumor-bearing mice in subcutaneous xenograft and intracranial U87-luc xenograft models. This study provides the first evidence that the gain-of-function BCAS1-SV1 splice variant promotes the development of GBM by suppressing the β-arrestin 2 pathway and opens up a new therapeutic perspective in GBM.

Deciphering the signaling mechanisms of β-arrestin1 and β-arrestin2 in regulation of cancer cell cycle and metastasis

β-Arrestins are ubiquitously expressed intracellular proteins with many functions which interact directly and indirectly with a wide number of cellular partners and mediate downstream signaling. Originally, β-arrestins were identified for their contribution to GPCR desensitization to agonist-mediated activation, followed by receptor endocytosis and ubiquitylation. However, current investigations have now recognized that in addition to GPCR arresting (hence the name arrestin). β-Arrestins are adaptor proteins that control the recruitment, activation, and scaffolding of numerous cytoplasmic signaling complexes and assist in G-protein receptor signaling, thus bringing them into close proximity. They have participated in various cellular processes such as cell proliferation, migration, apoptosis, and transcription via canonical and noncanonical pathways. Despite their significant recognition in several physiological processes, these activities are also involved in the onset and progression of various cancers. This review delivers a concise overview of the role of β-arrestins with a primary emphasis on the signaling processes which underlie the mechanism of β-arrestins in the onset of cancer. Understanding these processes has important implications for understanding the therapeutic intervention and treatment of cancer in the future.

β-arrestin-2 alleviates rheumatoid arthritis injury by suppressing NLRP3 inflammasome activation and NF- κB pathway in macrophages

Rheumatoid arthritis (RA) is a chronic inflammatory joint disorder that inflicts damage to the joints of the hands and wrist. The aim of this study was to investigate the protective effect of β-Arrestin-2 (βArr2) on RA in vivo and in vitro. The βArr2 adenovirus (βArr2-Ad) or the control (Con-Ad) was injected into the ankle joint cavity of collagen-induced arthritis (CIA) mice. According to the results, an improvement was shown in the symptoms and pathological injury of RA after an upregulation of βArr2. Correspondingly, the inflammatory response was attenuated, as evidenced by the decreased serum pro-inflammatory cytokines levels and NF-κB pathway-related proteins. Nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor 3 (NLRP3) inflammasome activation was inhibited in CIA mice treated with βArr2-Ad injection, as reflected by the diminished IL-18 level and declined protein levels of inflammasome components in the ankle joint. Likewise, the anti-inflammatory effect of macrophages was also validated by in vitro experiments. In summary, βArr2 effectively ameliorates ankle inflammation in CIA mice via NF-κB/NLRP3 inflammasome, providing theoretical and clinical basis for RA therapy.

β-Arrestin2 Inhibits the Apoptosis and Facilitates the Proliferation of Fibroblast-like Synoviocytes in Diffuse-type Tenosynovial Giant Cell Tumor

BACKGROUND/AIM

Diffuse-type tenosynovial giant cell tumor (TGCT) is a rare benign proliferative synovial neoplasm of uncertain etiology, and the efficacy of surgical resection is not satisfactory. Therefore, there is an urgent need to explore the pathogenesis and identify novel therapeutic targets for TGCT.

MATERIALS AND METHODS

Synovial tissues were collected from patients with TGCT and osteoarthritis (OA). Differences of mRNA expression between TGCT and OA were explored using mRNA-seq. In addition, fibroblast-like synoviocytes (FLS) were treated with small interfering RNA (siRNA) or adenovirus in order to knockdown or overexpress β-arrestin2 (Arrb2), respectively. FLS proliferation and apoptosis were evaluated using the MTT assay and the caspase 3 activity assay, respectively.

RESULTS

The expression of Arrb2 in TGCT was significantly higher than that in OA. The overexpression of Arrb2 promoted the proliferation of FLS and inhibited its apoptosis, while knocking down Arrb2 had the opposite effect. Further studies showed that Arrb2 can activate the PI3K-Akt signaling pathway, leading to increased proliferation of TGCT.

CONCLUSION

Arrb2 facilitates the proliferation and inhibits the apoptosis of TGCT FLS through activating the PI3K-Akt cell survival pathway, providing new insight into the molecular mechanism of TGCT.

Host versus cell-dependent effects of β-arrestin 1 expression in prostate tumorigenesis

Prostate cancer (PCa) constitutes a serious health challenge and remains one of the main causes of cancer-related death among men. The more aggressive form of the disease has been attributed to androgen independence, resulting in a lack of response to androgen deprivation therapy and sustained activation of other growth pathways. The scaffold proteins β-arrestin 1 and 2 (βarr1 and βarr2), which are known to mediate G protein-coupled receptor desensitization and internalization, were also shown to modulate prostate tumorigenesis. βarr1 is significantly overexpressed (>4-fold) in PCa cells relative to βarr2. In this study, we investigated the effect of βarr1 overexpression in PCa development and progression using the mouse and human PCa cell xenografts, and autochthonous transgenic adenocarcinoma of the mouse prostate (TRAMP) models deficient in β-arrestin depletion of βarr1 in TRAMP mice (TRAMP/βarr1-/-) increased PCa growth and decreased overall survival relative to control TRAMP or TRAMP/βarr2-/- animals. Prostate tissues from TRAMP/βarr1-/- tumors displayed an increase in androgen receptor (AR) expression, whereas overexpression of βarr1 in TRAMP-C1 (TRAMP-C1-βarr1-GFP) which derived from TRAMP decreased AR expression, cell proliferation and tumor growth in nude mice xenografts, relative to control TRAMP-C1-GFP. Knockdown of βarr1 expression in human MDA PCa 2b cells (MDA PCa 2b-βarr1-/-) also decreased AR expression cell proliferation and tumor growth relative to control (MDA PCa 2b-Sham) cells. Interestingly, both TRAMP-C1-βarr1-GFP and MDA PCa 2b-βarr1-/- xenografts showed a decrease in AKT phosphorylation but an increase in MAPK activation. Altogether, the data indicate that the effect of βarr1 in modulating AR signaling to regulate PCa aggressiveness is cell and host autonomous.

Overexpression of β-Arrestins inhibits proliferation and motility in triple negative breast cancer cells

β-Arrestins (βArrs) are intracellular signal regulating proteins. Their expression level varies in some cancers and they have a significant impact on cancer cell function. In general, the significance of βArrs in cancer research comes from studies examining GPCR signalling. Given the diversity of different GPCR signals in cancer cell regulation, contradictory results are inevitable regarding the role of βArrs. Our approach examines the direct influence of βArrs on cellular function and gene expression profiles by changing their expression levels in breast cancer cells, MDA-MB-231 and MDA-MB-468. Reducing expression of βArr1 or βArr2 tended to increase cell proliferation and invasion whereas increasing their expression levels inhibited them. The overexpression of βArrs caused cell cycle S-phase arrest and differential expression of cell cycle genes, CDC45, BUB1, CCNB1, CCNB2, CDKN2C and reduced HER3, IGF-1R, and Snail. Regarding to the clinical relevance of our results, low expression levels of βArr1 were inversely correlated with CDC45, BUB1, CCNB1, and CCNB2 genes compared to normal tissue samples while positively correlated with poorer prognosis in breast tumours. These results indicate that βArr1 and βArr2 are significantly involved in cell cycle and anticancer signalling pathways through their influence on cell cycle genes and HER3, IGF-1R, and Snail in TNBC cells.

Upregulated β-arrestin1 predicts poor prognosis and promotes metastasis via AKT/ERK signaling pathway in gastric cancer

BACKGROUND

β-Arrestins have been found to regulate cell proliferation, invasion and migration; transmit anti-apoptotic survival signals; and affect other characteristics of tumours. However, their role in gastric cancer (GC) is not clear. We investigated the role and mechanism of β-arrestins in the regulation of GC.

METHODS

We first examined β-arrestins mRNA levels in 17 pairs of GC tissues by qRT-PCR. We also used immunohistochemistry to further examine the expression of β-arrestins in 60 paraffin-embedded primary GC tissues and 20 normal gastric tissues. Then, the function of β-arrestin1 was investigated in vitro and in vivo.

RESULTS

β-Arrestin1 was upregulated in GC tissue and was associated with tumour stage, lymph node metastasis, invasion depth and patient sex. High expression of β-arrestin1 expression predicted poor prognosis in GC. β-Arrestin1 promoted GC cell proliferation, migration and invasion, and it suppressed E-cadherin expression and upregulated Vimentin expression via AKT/ERK signalling pathway. The in vivo metastasis assays showed that knockdown of β-arrestin1 reduced lung metastasis and inhibited EMT.

CONCLUSION

The upregulation of β-arrestin1 predicts poor prognosis and promotes metastasis and epithelial-mesenchymal transition in GC through AKT/ERK signalling pathway. This study may provide therapeutic advances for the treatment and early diagnosis of patients with metastatic GC.

β-Arrestin1 and β-Arrestin2 Are Required to Support the Activity of the CXCL12/HMGB1 Heterocomplex on CXCR4

The chemokine receptor CXCR4 plays a fundamental role in homeostasis and pathology by orchestrating recruitment and positioning of immune cells, under the guidance of a CXCL12 gradient. The ability of chemokines to form heterocomplexes, enhancing their function, represents an additional level of regulation on their cognate receptors. In particular, the multi-faceted activity of the heterocomplex formed between CXCL12 and the alarmin HMGB1 is emerging as an unexpected player able to modulate a variety of cell responses, spanning from tissue regeneration to chronic inflammation. Nowadays, little is known on the selective signaling pathways activated when CXCR4 is triggered by the CXCL12/HMGB1 heterocomplex. In the present work, we demonstrate that this heterocomplex acts as a CXCR4 balanced agonist, activating both G protein and β-arrestins-mediated signaling pathways to sustain chemotaxis. We generated β-arrestins knock out HeLa cells by CRISPR/Cas9 technology and show that the CXCL12/HMGB1 heterocomplex-mediated actin polymerization is primarily β-arrestin1 dependent, while chemotaxis requires both β-arrestin1 and β-arrestin2. Triggering of CXCR4 with the CXCL12/HMGB1 heterocomplex leads to an unexpected receptor retention on the cell surface, which depends on β-arrestin2. In conclusion, the CXCL12/HMGB1 heterocomplex engages the β-arrestin proteins differently from CXCL12, promoting a prompt availability of CXCR4 on the cell surface, and enhancing directional cell migration. These data unveil the signaling induced by the CXCL12/HMGB1 heterocomplex in view of identifying biased CXCR4 antagonists or agonists targeting the variety of functions it exerts.

β-arrestin 2 Is a Prognostic Factor for Survival of Ovarian Cancer Patients Upregulating Cell Proliferation

Establishing reliable prognostic factors as well as specific targets for new therapeutic approaches is an urgent requirement in advanced ovarian cancer. For several tumor entities, the ubiquitously spread scaffold protein β-arrestin 2, a multifunctional scaffold protein regulating signal transduction and internalization of activated G protein-coupled receptors (GPCRs), has been considered with rising interest for carcinogenesis. Therefore, we aimed to elucidate the prognostic impact of β-arrestin 2 and its functional role in ovarian cancer. β-arrestin 2 expression was analyzed in a subset of 156 samples of ovarian cancer patients by immunohistochemistry. Cytoplasmic expression levels were correlated with clinical as well as pathological characteristics and with prognosis. The biologic impact of β-arrestin 2 on cell proliferation and survival was evaluated, in vitro. Following transient transfection by increasing concentrations of plasmid encoding β-arrestin 2, different cell lines were evaluated in cell viability and death. β-arrestin 2 was detected in all histological ovarian cancer subtypes with highest intensity in clear cell histology. High β-arrestin 2 expression levels correlated with high-grade serous histology and the expression of the gonadotropin receptors FSHR and LHCGR, as well as the membrane estrogen receptor GPER and hCGβ. Higher cytoplasmic β-arrestin 2 expression was associated with a significantly impaired prognosis (median 29.88 vs. 50.64 months; P = 0.025). Clinical data were confirmed in transfected HEK293 cells, human immortalized granulosa cell line (hGL5) and the ovarian cancer cell line A2780 in vitro, where the induction of β-arrestin 2 cDNA expression enhanced cell viability, while the depletion of the molecule by siRNA resulted in cell death. Reflecting the role of β-arrestin 2 in modulating GPCR-induced proliferative and anti-apoptotic signals, we propose β-arrestin 2 as an important prognostic factor and also as a promising target for new therapeutic approaches in advanced ovarian cancer.

C-X-C chemokine receptor 2 correlates with unfavorable prognosis and facilitates malignant cell activities via activating JAK2/STAT3 pathway in non-small cell lung cancer

This study aimed to investigate the correlation of C-X-C chemokine receptor 2 (CXCR2) with clinicopathological characteristics and survival in non-small cell lung cancer (NSCLC) patients and further explore its effect on proliferation, apoptosis, invasion, stemness, chemosensitivity as well as JAK2/STAT3 pathway in NSCLC cells. The expression of CXCR2 in tumor tissues and adjacent tissues from 340 NSCLC patients received surgery was detected by immunohistochemistry. CXCR2 overexpression and knockdown were constructed through plasmid transfection and the effect of CXCR2 dysregulation on cell proliferation, apoptosis, invasion, stemness, chemosensitivity as well as its regulatory effect on JAK2/STAT signaling pathway was assessed in NCI-H1437 cells and NCI-H1299 cells. CXCR2 expression was higher in tumor tissues than that in paired adjacent tissues, and it was correlated with poor pathological differentiation, greater tumor size, lymph node metastasis, higher TNM stage and poor survival in NSCLC patients. In vitro, CXCR2 expression was increased in human NSCLC cell lines compared with human normal lung bronchus epithelial cells. CXCR2 promoted cell proliferation and invasion, while suppressed cell apoptosis in NCI-H1437/NCI-H1299 cells. Additionally, CXCR2 increased CD133⁺ cell rate and cell sphere-forming ability, while reduced chemosensitivity to cisplatin and gemcitabine in NCI-H1437/NCI-H1299 cells. Besides, CXCR2 activated the JAK2/STAT3 signaling pathway in NCI-H1437/NCI-H1299 cells. In conclusion, the clinical implication and the molecular function of CXCR2 discovered in our study reveal the potential of CXCR2 as a future target for disease monitoring and treatment of NSCLC.

Chemerin and Cancer

Chemerin is a multifunctional adipokine with established roles in inflammation, adipogenesis and glucose homeostasis. Increasing evidence suggest an important function of chemerin in cancer. Chemerin's main cellular receptors, chemokine-like receptor 1 (CMKLR1), G-protein coupled receptor 1 (GPR1) and C-C chemokine receptor-like 2 (CCRL2) are expressed in most normal and tumor tissues. Chemerin's role in cancer is considered controversial, since it is able to exert both anti-tumoral and tumor-promoting effects, which are mediated by different mechanisms like recruiting innate immune defenses or activation of endothelial angiogenesis. For this review article, original research articles on the role of chemerin and its receptors in cancer were considered, which are listed in the PubMed database. Additionally, we included meta-analyses of publicly accessible DNA microarray data to elucidate the association of expression of chemerin and its receptors in tumor tissues with patients' survival.

Regulators of the RAS-ERK pathway as therapeutic targets in thyroid cancer

Thyroid cancer is mostly an ERK-driven carcinoma, as up to 70% of thyroid carcinomas are caused by mutations that activate the RAS/ERK mitogenic signaling pathway. The incidence of thyroid cancer has been steadily increasing for the last four decades; yet, there is still no effective treatment for advanced thyroid carcinomas. Current research efforts are focused on impairing ERK signaling with small-molecule inhibitors, mainly at the level of BRAF and MEK. However, despite initial promising results in animal models, the clinical success of these inhibitors has been limited by the emergence of tumor resistance and relapse. The RAS/ERK pathway is an extremely complex signaling cascade with multiple points of control, offering many potential therapeutic targets: from the modulatory proteins regulating the activation state of RAS proteins to the scaffolding proteins of the pathway that provide spatial specificity to the signals, and finally, the negative feedbacks and phosphatases responsible for inactivating the pathway. The aim of this review is to give an overview of the biology of RAS/ERK regulators in human cancer highlighting relevant information on thyroid cancer and future areas of research.

β-Arrestins Regulate Stem Cell-Like Phenotype and Response to Chemotherapy in Bladder Cancer

β-Arrestins are classic attenuators of G-protein-coupled receptor signaling. However, they have multiple roles in cellular physiology, including carcinogenesis. This work shows for the first time that β-arrestins have prognostic significance for predicting metastasis and response to chemotherapy in bladder cancer. β-Arrestin-1 (ARRB1) and β-arrestin-2 (ARRB2) mRNA levels were measured by quantitative RT-PCR in two clinical specimen cohorts (n = 63 and 43). The role of ARRBs in regulating a stem cell-like phenotype and response to chemotherapy treatments was investigated. The consequence of forced expression of ARRBs on tumor growth and response to Gemcitabine in vivo were investigated using bladder tumor xenografts in nude mice. ARRB1 levels were significantly elevated and ARRB2 levels downregulated in cancer tissues compared with normal tissues. In multivariate analysis only ARRB2 was an independent predictor of metastasis, disease-specific-mortality, and failure to Gemcitabine + Cisplatin (G+C) chemotherapy; ∼80% sensitivity and specificity to predict clinical outcome. ARRBs were found to regulate stem cell characteristics in bladder cancer cells. Depletion of ARRB2 resulted in increased cancer stem cell markers but ARRB2 overexpression reduced expression of stem cell markers (CD44, ALDH2, and BMI-1), and increased sensitivity toward Gemcitabine. Overexpression of ARRB2 resulted in reduced tumor growth and increased response to Gemcitabine in tumor xenografts. CRISPR-Cas9-mediated gene-knockout of ARRB1 resulted in the reversal of this aggressive phenotype. ARRBs regulate cancer stem cell-like properties in bladder cancer and are potential prognostic indicators for tumor progression and chemotherapy response.

New Routes in GPCR/β-Arrestin-Driven Signaling in Cancer Progression and Metastasis

Tumor cells acquire invasive and metastatic behavior by sensing changes in the localization and activation of signaling pathways, which in turn determine changes in actin cytoskeleton. The core-scaffold machinery associated to β-arrestin (β-arr) is a key mechanism of G-protein coupled receptors (GPCR) to achieve spatiotemporal specificity of different signaling complexes driving cancer progression. Within different cellular contexts, the scaffold proteins β-arr1 or β-arr2 may now be considered organizers of protein interaction networks involved in tumor development and metastatic dissemination. Studies have uncovered the importance of the β-arr engagement with a growing number of receptors, signaling molecules, cytoskeleton regulators, epigenetic modifiers, and transcription factors in GPCR-driven tumor promoting pathways. In many of these molecular complexes, β-arrs might provide a physical link to active dynamic cytoskeleton, permitting cancer cells to adapt and modify the tumor microenvironment to promote the metastatic spread. Given the complexity and the multidirectional β-arr-driven signaling in cancer cells, therapeutic targeting of specific GPCR/β-arr molecular mechanisms is an important avenue to explore when considering future new therapeutic options. The focus of this review is to integrate the most recent developments and exciting findings of how highly connected components of β-arr-guided molecular connections to other pathways allow precise control over multiple signaling pathways in tumor progression, revealing ways of therapeutically targeting the convergent signals in patients.

β-Arrestins: Multitask Scaffolds Orchestrating the Where and When in Cell Signalling

The β-arrestins (β-arrs) were initially appreciated for the roles they play in the desensitization and endocytosis of G protein-coupled receptors (GPCRs). They are now also known to act as multifunctional adaptor proteins binding many non-receptor protein partners to control multiple signalling pathways. β-arrs therefore act as key regulatory hubs at the crossroads of external cell inputs and functional outputs in cellular processes ranging from gene transcription to cell growth, survival, cytoskeletal regulation, polarity, and migration. An increasing number of studies have also highlighted the scaffolding roles β-arrs play in vivo in both physiological and pathological conditions, which opens up therapeutic avenues to explore. In this introductory review chapter, we discuss the functional roles that β-arrs exert to control GPCR function, their dynamic scaffolding roles and how this impacts signal transduction events, compartmentalization of β-arrs, how β-arrs are regulated themselves, and how the combination of these events culminates in cellular regulation.

Sub-chronic inhalation of reclaimed water-induced fibrotic lesion in a mouse model

When reclaimed water is used as municipal miscellaneous water, acute exposure of the generated aerosol with high levels of endotoxins can cause severe inflammation in the lungs. However, the potential risks of long-term inhalation of reclaimed water remains unclear. To identify the adverse effects of sub-chronic reclaimed water inhalation and explain the underlying mechanisms, a mouse model of 12-week sub-chronic exposure was established, and wastewater before a membrane bioreactor (MBR, positive control) and the MBR effluent (reclaimed water, which met the quality standard of urban use and was currently used for landscape irrigation) were tested in this study. The exposure dose was set to approach the real working scenarios. Lung lavage and histology were analyzed. Obvious epithelial cell apoptosis in the bronchi was observed, along with the accumulation of myofibroblasts and the collagen deposition both in main bronchi and terminal bronchioles. All these symptoms were persistent after 4 weeks of recovery. Inflammation and induced bronchus-associated lymphoid tissues (iBALT) were also observed but diminished after recovery indicating inflammation may not be the direct cause of the symptom. Furthermore, two fibrogenic cytokines (TNF-α and TGF-β) were constantly high in the lung during the study. They might be the biomarkers of lung damage after the inhalation of reclaimed water. Adaptive immune responses were also detected as elevated levels of IgG and IgA, but not for IgE. Inhalation of reclaimed water causes sustained fibrotic lesions in the lungs, which suggests potential health risks during urban application where aerosols generated.

Identification of mRNA of the Inflammation-associated Proteins CXCL8, CXCR2, CXCL10, CXCR3, and β-Arrestin-2 in Equine Wounded Cutaneous Tissue: a Preliminary Study

Horses often sustain cutaneous wounds and healing can be prolonged and difficult to treat. Compared to body wounds, limb wounds heal slower and are more likely to develop exuberant granulation tissue. Differences in healing rates and exuberant granulation tissue formation is attributed to abnormal cytokine profiles. CXCL8 and its receptor CXCR2 are involved in acute inflammation whereas CXCL10 and its receptor CXCR3 are involved in inflammation resolution. β- arrestin-2 regulates inflammation through internalization of G-protein coupled receptors (GPCRs) including CXCR2 and CXCR3. Gene expression of these five inflammation associated proteins have not been previously identified in equine cutaneous tissue and may play a role in dysregulation of inflammation in equine limb wounds. The mRNA expression levels were measured using QuantiGene Plex Assay from cutaneous biopsies collected from surgically created wounds on the limb and thorax on days 0, 1, 2, 7, 14, and 33 from two horses. The mRNA expression levels were measured in mean fluorescent intensity and graphed. We were successful in identifying all five proteins for the first time in equine cutaneous tissue. Preliminary results suggest that there are different expression patterns for CXCL8, CXCR2 and β-arrestin-2 between the limb and thorax but not for CXCL10 and CXCR3. Differential regulation of CXCL8, CXCR2 and β-arrestin-2 may further explain why limb wounds heal differently than body wounds and warrants further investigation.

β-Arrestin2 mediates progression of murine primary myelofibrosis

Primary myelofibrosis is a myeloproliferative neoplasm associated with significant morbidity and mortality, for which effective therapies are lacking. β-Arrestins are multifunctional adaptor proteins involved in developmental signaling pathways. One isoform, β-arrestin2 (βarr2), has been implicated in initiation and progression of chronic myeloid leukemia, another myeloproliferative neoplasm closely related to primary myelofibrosis. Accordingly, we investigated the relationship between βarr2 and primary myelofibrosis. In a murine model of MPLW515L-mutant primary myelofibrosis, mice transplanted with donor βarr2-knockout (βarr2-/-) hematopoietic stem cells infected with MPL-mutant retrovirus did not develop myelofibrosis, whereas controls uniformly succumbed to disease. Although transplanted βarr2-/- cells homed properly to marrow, they did not repopulate long-term due to increased apoptosis and decreased self-renewal of βarr2-/- cells. In order to assess the effect of acute loss of βarr2 in established primary myelofibrosis in vivo, we utilized a tamoxifen-induced Cre-conditional βarr2-knockout mouse. Mice that received Cre (+) donor cells and developed myelofibrosis had significantly improved survival compared with controls. These data indicate that lack of antiapoptotic βarr2 mediates marrow failure of murine hematopoietic stem cells overexpressing MPLW515L. They also indicate that βarr2 is necessary for progression of primary myelofibrosis, suggesting that it may serve as a novel therapeutic target in this disease.

The Diverse Roles of Arrestin Scaffolds in G Protein-Coupled Receptor Signaling

The visual/β-arrestins, a small family of proteins originally described for their role in the desensitization and intracellular trafficking of G protein-coupled receptors (GPCRs), have emerged as key regulators of multiple signaling pathways. Evolutionarily related to a larger group of regulatory scaffolds that share a common arrestin fold, the visual/β-arrestins acquired the capacity to detect and bind activated GPCRs on the plasma membrane, which enables them to control GPCR desensitization, internalization, and intracellular trafficking. By acting as scaffolds that bind key pathway intermediates, visual/β-arrestins both influence the tonic level of pathway activity in cells and, in some cases, serve as ligand-regulated scaffolds for GPCR-mediated signaling. Growing evidence supports the physiologic and pathophysiologic roles of arrestins and underscores their potential as therapeutic targets. Circumventing arrestin-dependent GPCR desensitization may alleviate the problem of tachyphylaxis to drugs that target GPCRs, and find application in the management of chronic pain, asthma, and psychiatric illness. As signaling scaffolds, arrestins are also central regulators of pathways controlling cell growth, migration, and survival, suggesting that manipulating their scaffolding functions may be beneficial in inflammatory diseases, fibrosis, and cancer. In this review we examine the structure-function relationships that enable arrestins to perform their diverse roles, addressing arrestin structure at the molecular level, the relationship between arrestin conformation and function, and sites of interaction between arrestins, GPCRs, and nonreceptor-binding partners. We conclude with a discussion of arrestins as therapeutic targets and the settings in which manipulating arrestin function might be of clinical benefit.

The role and mechanism of β‑arrestins in cancer invasion and metastasis (Review)

β-arrestins are a family of adaptor proteins that regulate the signaling and trafficking of various G protein-coupled receptors (GPCRs). They consist of β-arrestin1 and β-arrestin2 and are considered to be scaffolding proteins. β-arrestins regulate cell proliferation, promote cell invasion and migration, transmit anti-apoptotic survival signals and affect other characteristics of tumors, including tumor growth rate, angiogenesis, drug resistance, invasion and metastatic potential. It has been demonstrated that β-arrestins serve roles in various physiological and pathological processes and exhibit a similar function to GPCRs. β-arrestins serve primary roles in cancer invasion and metastasis via various signaling pathways. The present review assessed the function and mechanism of β-arrestins in cancer invasion and metastasis via multiple signaling pathways, including mitogen-activated protein kinase/extracellular signal regulated kinase, Wnt/β-catenin, nuclear factor-κB and phosphoinositide-3 kinase/Akt.

Loss of β-arrestin-2 and Activation of CXCR2 Correlate with Lymph Node Metastasis in Non-small Cell Lung Cancer

Background: Although β-arrestin-2 (β-arr2) and CXCR2 have been shown to affect various malignant tumors, their exact roles in lung cancer remain unclear. We investigated expression of β-arr2 and CXCR2 in patients with non-small cell lung cancer (NSCLC) and their correlation with lymph node metastasis and prognosis.

Methods: We reviewed medical records of 136 patients with NSCLC who underwent surgical resection, and assessed their specimens immunohistochemically for expression of β-arr2 and CXCR2 in primary tumors and metastatic lymph nodes (MLNs), respectively.

Results: High β-arr2 expression was seen in 63 specimens (46.3%), and was significantly associated with male patients (P=0.011), squamous cell carcinoma (P=0.003), and lymph node metastasis (P<0.001). High CXCR2 expression was seen in 62 specimens (45.6%), and was significantly correlated only with lymph node metastasis (P<0.001). Expression of β-arr2 was significantly lower at MLNs than at primary lesions (Z=-2.315; P=0.021; Wilcoxon signed-rank), whereas CXCR2 expression was significantly higher in MLNs than in primary lesions (Z=-3.712; P<0.001; Wilcoxon signed-rank). No relationship was seen between β-arr2 and CXCR2 expression in primary lesions (r=-0.065, P=0.548; Spearman rank coefficient), but they were inversely related in MLNs (r=-0.263, P=0.012). Kaplan-Meier survival curve was shown that low β-arr2 and high CXCR2 expressions was associated with poor survival (log-rank: χ²=5.926, P=0.015).

Conclusions: β-arr2 may promote lymph node metastasis in NSCLC by modulating CXCR2 activation.

β-arrestin 1 Overexpression Increases Temozolomide Resistance in Human Malignant Glioma Cells

Many studies highlighted β-arrestins (β-arr) as essential proteins behind the regulation of major cell signaling pathways in different types of cancer. An impaired β-arrestin 1 (β-arr 1) activation/phosphorylation was suggested to be associated with a high malignant phenotype of glioma. Elevated levels of β-arrestin 2 (β-arr 2) mRNA were also found in advanced stages of breast cancer compared to early stages. In addition, β2-arrestin was also linked to a suppressive effect on tumor growth in other types of cancers such as prostate or non-small cell lung cancer. In this study, we analyzed the effect of β-arr 1 overexpression on the cytotoxic effect of Temozolomide (TMZ) in two malignant glioma (MG) cell lines: U-343MGa and Cl2:6. For this purpose, the cells were transected with β-arr 1 and then treated with different concentrations of TMZ for 24, 48 and 72 hours. At the end of the treatment, the cell viability was analyzed by Prestoblue viability assay. Our results showed that TMZ treatment induced cytotoxicity in MG cells while β-arr 1 transfection significantly reduced the TMZ cytotoxic effect in both U-343MGa and Cl2:6 MG cell lines. These results suggest that β-arr 1 overexpression may be a cause of TMZ resistance in MG.

Down-regulation of β-arrestin2 promotes tumour invasion and indicates poor prognosis of hepatocellular carcinoma

β-arrestins, including β-arrestin1 and β-arrestin2, are multifunctional adaptor proteins. β-arrestins have recently been found to play new roles in regulating intracellular signalling networks associated with malignant cell functions. Altered β-arrestin expression has been reported in many cancers, but its role in hepatocellular carcinoma (HCC) is not clear. We therefore examined the roles of β-arrestins in HCC using an animal model of progressive HCC, HCC patient samples and HCC cell lines with stepwise metastatic potential. We demonstrated that β-arrestin2 level, but not β-arrestin1 level, decreased in conjunction with liver tumourigenesis in a mouse diethylnitrosamine-induced liver tumour model. Furthermore, β-arrestin2 expression was reduced in HCC tissues compared with noncancerous tissues in HCC patients. β-arrestin2 down-regulation in HCC was significantly associated with poor patient prognoses and aggressive pathologic features. In addition, our in vitro study showed that β-arrestin2 overexpression significantly reduced cell migration and invasion in cultured HCC cells. Furthermore, β-arrestin2 overexpression up-regulated E-cadherin expression and inhibited vimentin expression and Akt activation. These results suggest that β-arrestin2 down-regulation increases HCC cell migration and invasion ability. Low β-arrestin2 expression may be indicative of a poor prognosis or early cancer recurrence in patients who have undergone surgery for HCC.

On Predicting lung cancer subtypes using 'omic' data from tumor and tumor-adjacent histologically-normal tissue

BACKGROUND

Adenocarcinoma (ADC) and squamous cell carcinoma (SCC) are the most prevalent histological types among lung cancers. Distinguishing between these subtypes is critically important because they have different implications for prognosis and treatment. Normally, histopathological analyses are used to distinguish between the two, where the tissue samples are collected based on small endoscopic samples or needle aspirations. However, the lack of cell architecture in these small tissue samples hampers the process of distinguishing between the two subtypes. Molecular profiling can also be used to discriminate between the two lung cancer subtypes, on condition that the biopsy is composed of at least 50 % of tumor cells. However, for some cases, the tissue composition of a biopsy might be a mix of tumor and tumor-adjacent histologically normal tissue (TAHN). When this happens, a new biopsy is required, with associated cost, risks and discomfort to the patient. To avoid this problem, we hypothesize that a computational method can distinguish between lung cancer subtypes given tumor and TAHN tissue.

METHODS

Using publicly available datasets for gene expression and DNA methylation, we applied four classification tasks, depending on the possible combinations of tumor and TAHN tissue. First, we used a feature selector (ReliefF/Limma) to select relevant variables, which were then used to build a simple naïve Bayes classification model. Then, we evaluated the classification performance of our models by measuring the area under the receiver operating characteristic curve (AUC). Finally, we analyzed the relevance of the selected genes using hierarchical clustering and IPA® software for gene functional analysis.

RESULTS

All Bayesian models achieved high classification performance (AUC > 0.94), which were confirmed by hierarchical cluster analysis. From the genes selected, 25 (93 %) were found to be related to cancer (19 were associated with ADC or SCC), confirming the biological relevance of our method.

CONCLUSIONS

The results from this study confirm that computational methods using tumor and TAHN tissue can serve as a prognostic tool for lung cancer subtype classification. Our study complements results from other studies where TAHN tissue has been used as prognostic tool for prostate cancer. The clinical implications of this finding could greatly benefit lung cancer patients.

β-Arrestin-2 Counters CXCR7-Mediated EGFR Transactivation and Proliferation

The atypical 7-transmembrane chemokine receptor, CXCR7, transactivates the EGFR leading to increased tumor growth in several tumor types. However, the molecular mechanism of CXCR7 ligand-independent EGFR transactivation is unknown. We used cDNA knock-in, RNAi and analysis of mitogenic signaling components in both normal prostate epithelial cells and prostate cancer cells to decipher the proliferation-inducing mechanism of the CXCR7-EGFR interaction. The data demonstrate that CXCR7-induced EGFR transactivation is independent of both the release of cryptic EGFR ligands (e.g., AREG/amphiregulin) and G-protein-coupled receptor signaling. An alternate signaling mechanism involving β-arrestin-2 (ARRB2/β-AR2) was examined by manipulating the levels of β-AR2 and analyzing changes in LNCaP cell growth and phosphorylation of EGFR, ERK1/2, Src, and Akt. Depletion of β-AR2 in LNCaP cells increased proliferation/colony formation and significantly increased activation of Src, phosphorylation of EGFR at Tyr-1110, and phosphorylation/activation of ERK1/2 compared with that with control shRNA. Moreover, β-AR2 depletion downregulated the proliferation suppressor p21. Stimulation of β-AR2-expressing cells with EGF resulted in rapid nuclear translocation of phosphorylated/activated EGFR. Downregulation of β-AR2 enhanced this nuclear translocation. These results demonstrate that β-AR2 is a negative regulator of CXCR7/Src/EGFR-mediated mitogenic signaling.

IMPLICATIONS

This study reveals that β-AR2 functions as a tumor suppressor, underscoring its clinical importance in regulating CXCR7/EGFR-mediated tumor cell proliferation. Mol Cancer Res; 14(5); 493-503. ©2016 AACR.

β-Arrestin2 Contributes to Cell Viability and Proliferation via the Down-Regulation of FOXO1 in Castration-Resistant Prostate Cancer

β-Arrestin2 has been identified to act as a corepressor of androgen receptor (AR) signaling by binding to AR and serving as a scaffold to affect the activity and expression of AR in androgen-dependent prostate cancer cells; however, little is known regarding its role in castration-resistant prostate cancer (CRPC) progression. Here, our data demonstrated that β-arrestin2 contributes to the cell viability and proliferation of CRPC via the downregulation of FOXO1 activity and expression. Mechanistically, in addition to its requirement for FOXO1 phosphorylation induced by IGF-1, β-arrestin2 could inhibit FOXO1 activity in an Akt-independent manner and delay FOXO1 dephosphorylation through the inhibition of PP2A phosphatase activity and the attenuation of the interaction between FOXO1 and PP2A. Furthermore, β-arrestin2 could downregulate FOXO1 expression via ubiquitylation and proteasomal degradation. Together, our results identified a novel role for β-arrestin2 in the modulation of the CRPC progress through FOXO1. Thus, the characterization of β-arrestin2 may represent an alternative therapeutic target for CRPC treatment.

Conditioning solid tumor microenvironment through inflammatory chemokines and S100 family proteins

Recently, there has been growing attention to the role of the tumor microenvironment (TME) in cancer growth, metastasis and emergence of chemotherapy resistance. Stromal and tumor cells make up the TME and interact with each other through a complex cross-talk manner. This interaction is facilitated by a variety of growth factors, cytokines, chemokines and S100 proteins. In this review, we focus on chemokines and their cognate receptors in regulating the tumorigenic process. Chemokines are cytokines that have chemotactic potential. Chemokine receptors are expressed on tumor cells and stromal cells. Chemokines and their cognate receptors modulate tumor growth and metastasis in a paracrine and autocrine manner. They play a major role in the modulation of stromal cell recruitment, angiogenic potential, cancer cell proliferation, survival, adhesion, invasion and metastasis to distant sites. In addition, a new class of calcium binding family S100 proteins has been getting attention as they play significant roles in tumor progression and metastasis by modulating TME. Here, we highlight recent developments regarding the inflammatory chemokine/S100 protein systems in the TME. We also focus on how chemokines/S100 proteins, through their role in the TME, modulate cancer cell ability to grow, proliferate, invade and metastasize to different organs. This review highlights the possibility of using the chemokine/chemokine receptor axis as a promising strategy in cancer therapy, the current difficulties in achieving this goal, and how it could be overcome for successful future therapeutic intervention.

β-Arrestin1 promotes the progression of chronic myeloid leukaemia by regulating BCR/ABL H4 acetylation

BACKGROUND

β-Arrestins are scaffold proteins that interact with various cellular signals. Although β-arrestin2 mediates the initiation and progression of myeloid leukaemia, the critical role of β-arrestin1 in the chronic myeloid leukaemia (CML) is still unknown. The aim of this study is to investigate the essential function of β-arrestin1 in CML.

METHODS

The expressions of β-arrestin1 and BCR/ABL in CML patients, animal models and K562 cells were measured by RT-PCR, immunofluorescence and western blotting. The effect of β-arrestin1 on CML animal models and K562 cells by colony formation, MTT and survival analysis were assessed. BCR/ABL H4 acetylation was analysed through the use of Chromatin-immunoprecipitation (ChIP) -on-chip and confirmed by ChIP respectively. Co-immunoprecipitation and confocal were examined for the binding of β-arrestin1 with enhancer of zeste homologue 2 (EZH2).

RESULTS

The higher expression of β-arrestin1 is positively correlated with clinical phases of CML patients. Depletion of β-arrestin1 decelerates progression of K562 and primary cells, and increases survival of CML mice. Importantly, silenced β-arrestin1 results in the decrease of BCR/ABL H4 acetylation level in K562 cells. Further data illustrate that nuclear β-arrestin1 binds to EZH2 to mediate BCR/ABL acetylation and thus regulates cell progression in K562 cells and the survival of CML mice.

CONCLUSIONS

Our findings reveal a novel function of β-arrestin1 binding to EZH2 to promote CML progression by regulating BCR/ABL H4 acetylation.

G Protein-coupled receptor kinase-6 interacts with activator of G protein signaling-3 to regulate CXCR2-mediated cellular functions

The IL-8 (CXCL8) receptors CXCR1 and CXCR2 couple to Gαi to induce leukocyte recruitment and activation at sites of inflammation. We recently showed that CXCR1 couples predominantly to the G protein-coupled receptor kinase (GRK)2, whereas CXCR2 interacts with GRK6 to regulate cellular responses. In addition to G protein-coupled receptors, GRKs displayed a more diverse protein/protein interaction in cells. In this study, we sought to identify GRK6 binding partner(s) that may influence CXCL8 activities, using RBL-2H3 cells stably expressing CXCR1 (RBL-CXCR1) or CXCR2 (RBL-CXCR2), as well as human and murine neutrophils. Our data demonstrated that, upon CXCR2 activation, GRK6 interacts with activator of G protein signaling (AGS)3 and Gαi2 to form a GRK6/AGS3/Gαi2 complex. This complex is time dependent and peaked at 2-3 min postactivation. GTPγS pretreatment blocked GRK6/AGS3/Gαi2 formation, suggesting that this assembly depends on G protein activation. Surprisingly, CXCR2 activation induced AGS3 phosphorylation in a PKC-dependent, but GRK6-independent, fashion. Overexpression of AGS3 in RBL-CXCR2 significantly inhibited CXCL8-induced Ca(2+) mobilization, phosphoinositide hydrolysis, and chemotaxis. In contrast, short hairpin RNA inhibition of AGS3 enhanced CXCL8-induced Ca(2+) mobilization, receptor resistance to desensitization, and recycling to the cell surface, with no effect on receptor internalization. Interestingly, RBL-CXCR2-AGS3(-/-) cells displayed a significant increase in CXCR2 expression on the cell surface but decreased ERK1/2 and P38 MAPK activation. Taken together, these results indicate that GRK6 complexes with AGS3-Gαi2 to regulate CXCR2-mediated leukocyte functions at different levels, including downstream effector activation, receptor trafficking, and expression at the cell membrane.

Arrestins as regulatory hubs in cancer signalling pathways

Non-visual arrestins were initially appreciated for the roles they play in the negative regulation of G protein-coupled receptors through the processes of desensitisation and endocytosis. The arrestins are also now known as protein scaffolding platforms that act downstream of multiple types of receptors, ensuring relevant transmission of information for an appropriate cellular response. They function as regulatory hubs in several important signalling pathways that are often dysregulated in human cancers. Interestingly, several recent studies have documented changes in expression and localisation of arrestins that occur during cancer progression and that correlate with clinical outcome. Here, we discuss these advances and how changes in expression/localisation may affect functional outputs of arrestins in cancer biology.

Arresting inflammation: contributions of plasma membrane and endosomal signalling to neuropeptide-driven inflammatory disease

GPCR (G-protein-coupled receptor) signalling at the plasma membrane is under tight control. In the case of neuropeptides such as SP (substance P), plasma membrane signalling is regulated by cell-surface endopeptidases (e.g. neprilysin) that degrade extracellular neuropeptides, and receptor interaction with β-arrestins, which uncouple receptors from heterotrimeric G-proteins and mediate receptor endocytosis. By recruiting GPCRs, kinases and phosphatases to endocytosed GPCRs, β-arrestins assemble signalosomes that can mediate a second wave of signalling by internalized receptors. Endosomal peptidases, such as ECE-1 (endothelin-converting enzyme-1), can degrade SP in acidified endosomes, which destabilizes signalosomes and allows receptors, freed from β-arrestins, to recycle and resensitize. By disassembling signalosomes, ECE-1 terminates β-arrestin-mediated endosomal signalling. These mechanisms have been studied in model cell systems, and the relative importance of plasma membrane and endosomal signalling to complex pathophysiological processes, such as inflammation, pain and proliferation, is unclear. However, deletion or inhibition of metalloendopeptidases that control neuropeptide signalling at the plasma membrane and in endosomes has marked effects on inflammation. Neprilysin deletion exacerbates inflammation because of diminished degradation of pro-inflammatory SP. Conversely, inhibition of ECE-1 attenuates inflammation by preventing receptor recycling/resensitization, which is required for sustained pro-inflammatory signals from the plasma membrane. β-Arrestin deletion also affects inflammation because of the involvement of β-arrestins in pro-inflammatory signalling and migration of inflammatory cells. Knowledge of GPCR signalling in specific subcellular locations provides insights into pathophysiological processes, and can provide new opportunities for therapy. Selective targeting of β-arrestin-mediated endosomal signalling or of mechanisms of receptor recycling/resensitization may offer more effective and selective treatments than global targeting of cell-surface signalling.

G protein-coupled receptor kinase 6 deficiency promotes angiogenesis, tumor progression, and metastasis

G protein-coupled receptor kinases (GRKs) phosphorylate the activated form of G protein-coupled receptors leading to receptor desensitization and downregulation. We have recently shown that the chemokine receptor, CXCR2, couples to GRK6 to regulate cellular responses including chemotaxis, angiogenesis, and wound healing. In this study, we investigate the role of GRK6 in tumorigenesis using murine models of human lung cancer. Mice deficient in GRK6 (GRK6(-/-)) exhibited a significant increase in Lewis lung cancer growth and metastasis relative to control littermates (GRK6(+/+)). GRK6 deletion had no effect on the expression of proangiogenic chemokine or vascular endothelial growth factor, but upregulated matrix metalloproteinase (MMP)-2 and MMP-9 release, tumor-infiltrating PMNs, and microvessel density. Because β-arrestin-2-deficient (βarr2(-/-)) mice exhibited increased Lewis lung cancer growth and metastasis similar to that of GRK6(-/-), we developed a double GRK6(-/-)/βarr2(-/-) mouse model. Surprisingly, GRK6(-/-)/βarr2(-/-) mice exhibited faster tumor growth relative to GRK6(-/-) or βarr2(-/-) mice. Treatment of the mice with anti-CXCR2 Ab inhibited tumor growth in both GRK6(-/-) and GRK6(-/-)/βarr2(-/-) animals. Altogether, the results indicate that CXCR2 couples to GRK6 to regulate angiogenesis, tumor progression, and metastasis. Deletion of GRK6 increases the activity of the host CXCR2, resulting in greater PMN infiltration and MMP release in the tumor microenvironment, thereby promoting angiogenesis and metastasis. Because GRK6(-/-)/βarr2(-/-) showed greater tumor growth relative to GRK6(-/-) or βarr2(-/-) mice, the data further suggest that CXCR2 couples to different mechanisms to mediate tumor progression and metastasis.

β-Arrestin2 regulates lysophosphatidic acid-induced human breast tumor cell migration and invasion via Rap1 and IQGAP1

β-Arrestins play critical roles in chemotaxis and cytoskeletal reorganization downstream of several receptor types, including G protein-coupled receptors (GPCRs), which are targets for greater than 50% of all pharmaceuticals. Among them, receptors for lysophosphatidic acid (LPA), namely LPA(1) are overexpressed in breast cancer and promote metastatic spread. We have recently reported that β-arrestin2 regulates LPA(1)-mediated breast cancer cell migration and invasion, although the underlying molecular mechanisms are not clearly understood. We show here that LPA induces activity of the small G protein, Rap1 in breast cancer cells in a β-arrestin2-dependent manner, but fails to activate Rap1 in non-malignant mammary epithelial cells. We found that Rap1A mRNA levels are higher in human breast tumors compared to healthy patient samples and Rap1A is robustly expressed in human ductal carcinoma in situ and invasive tumors, in contrast to the normal mammary ducts. Rap1A protein expression is also higher in aggressive breast cancer cells (MDA-MB-231 and Hs578t) relative to the weakly invasive MCF-7 cells or non-malignant MCF10A mammary cells. Depletion of Rap1A expression significantly impaired LPA-stimulated migration of breast cancer cells and invasiveness in three-dimensional Matrigel cultures. Furthermore, we found that β-arrestin2 associates with the actin binding protein IQGAP1 in breast cancer cells, and is necessary for the recruitment of IQGAP1 to the leading edge of migratory cells. Depletion of IQGAP1 blocked LPA-stimulated breast cancer cell invasion. Finally, we have identified that LPA enhances the binding of endogenous Rap1A to β-arrestin2, and also stimulates Rap1A and IQGAP1 to associate with LPA(1). Thus our data establish novel roles for Rap1A and IQGAP1 as critical regulators of LPA-induced breast cancer cell migration and invasion.

β-Arrestins in the immune system

β-Arrestins regulate G protein-coupled receptors through receptor desensitization while also acting as signaling scaffolds to facilitate numerous effector pathways. Recent studies have provided evidence that β-arrestins play a key role in inflammatory responses. Here, we summarize these advances on the roles of β-arrestins in immune regulation and inflammatory responses under physiological and pathological conditions, with an emphasis on translational implications of β-arrestins on human diseases.

CXCR2 expression in tumor cells is a poor prognostic factor and promotes invasion and metastasis in lung adenocarcinoma

CXCR2 in non-small cell lung cancer (NSCLC) has been studied mainly in stromal cells and is known to increase tumor inflammation and angiogenesis. Here, we examined the prognostic importance of CXCR2 in NSCLC and the role of CXCR2 and its ligands in lung cancer cells. The effect of CXCR2 expression on tumor cells was studied using stable knockdown clones derived from a murine KRAS/p53-mutant lung adenocarcinoma cell line with high metastatic potential and an orthotopic syngeneic mouse model and in vitro using a CXCR2 small-molecule antagonist (SB225002). CXCR2 protein expression was analyzed in tumor cells from 262 NSCLC. Gene expression profiles for CXCR2 and its ligands (CXCR2 axis) were analyzed in 52 human NSCLC cell lines and 442 human lung adenocarcinomas. Methylation of CXCR2 axis promoters was determined in 70 human NSCLC cell lines. Invasion and metastasis were decreased in CXCR2 knockdown clones in vitro and in vivo. SB225002 decreased invasion in vitro. In lung adenocarcinomas, CXCR2 expression in tumor cells was associated with smoking and poor prognosis. CXCR2 axis gene expression profiles in human NSCLC cell lines and lung adenocarcinomas defined a cluster driven by CXCL5 and associated with smoking, poor prognosis, and RAS pathway activation. Expression of CXCL5 was regulated by promoter methylation. The CXCR2 axis may be an important target in smoking-related lung adenocarcinoma.

Involvement of β-arrestins in cancer progression

β-arrestins, including β-arrestin1 and β-arrestin2, are ubiquitous cytosolic proteins which localize in the cytoplasm and plasma membrane, initially be regarded as an potential character in G protein-coupled receptors (GPCR) desensitization, sequestration, and internalization. Besides, recent many studies increasingly revealed that β-arrestins served widely as versatile adapter proteins for scaffolding many intracellular signaling networks to modulate the strength and duration of signaling by diverse types of receptors and downstream kinases. As we known, the biologic and clinical behaviors of many tumors are largely determined by multiple molecular signal pathways. More recently, accumulating evidences established that β-arrestins got widely involved in many cancer developmental signaling events which responsible for tumor viability and metastasis, suggesting an impressive role of β-arrestins in tumor progression. Because of the regulation and biological output of β-arrestins is so complex, the role of β-arrestins in cancer development still remains enigmatic. However, the further understanding with the clinical prognosis and oncogenic potential of β-arrestins might facilitate the identification of diagnosis biomarkers and development of drug targets in cancer. In this article, we reviewed a comprehensive summary of the β-arrestins-mediated functions in human cancers.

The chemokine receptors CXCR1 and CXCR2 couple to distinct G protein-coupled receptor kinases to mediate and regulate leukocyte functions

The chemokine receptors, CXCR1 and CXCR2, couple to Gαi to induce leukocyte recruitment and activation at sites of inflammation. Upon activation by CXCL8, these receptors become phosphorylated, desensitized, and internalized. In this study, we investigated the role of different G protein-coupled receptor kinases (GRKs) in CXCR1- and CXCR2-mediated cellular functions. To that end, short hairpin RNA was used to inhibit GRK2, 3, 5, and 6 in RBL-2H3 cells stably expressing CXCR1 or CXCR2, and CXCL8-mediated receptor activation and regulation were assessed. Inhibition of GRK2 and GRK6 increased CXCR1 and CXCR2 resistance to phosphorylation, desensitization, and internalization, respectively, and enhanced CXCL8-induced phosphoinositide hydrolysis and exocytosis in vitro. GRK2 depletion diminished CXCR1-induced ERK1/2 phosphorylation but had no effect on CXCR2-induced ERK1/2 phosphorylation. GRK6 depletion had no significant effect on CXCR1 function. However, peritoneal neutrophils from mice deficient in GRK6 (GRK6(-/-)) displayed an increase in CXCR2-mediated G protein activation but in vitro exhibited a decrease in chemotaxis, receptor desensitization, and internalization relative to wild-type (GRK6(+/+)) cells. In contrast, neutrophil recruitment in vivo in GRK6(-/-) mice was increased in response to delivery of CXCL1 through the air pouch model. In a wound-closure assay, GRK6(-/-) mice showed enhanced myeloperoxidase activity, suggesting enhanced neutrophil recruitment, and faster wound closure compared with GRK6(+/+) animals. Taken together, the results indicate that CXCR1 and CXCR2 couple to distinct GRK isoforms to mediate and regulate inflammatory responses. CXCR1 predominantly couples to GRK2, whereas CXCR2 interacts with GRK6 to negatively regulate receptor sensitization and trafficking, thus affecting cell signaling and angiogenesis.

Inhibiting NF-κB in the developing lung disrupts angiogenesis and alveolarization

Bronchopulmonary dysplasia (BPD), a chronic lung disease of infancy, is characterized by arrested alveolar development. Pulmonary angiogenesis, mediated by the vascular endothelial growth factor (VEGF) pathway, is essential for alveolarization. However, the transcriptional regulators mediating pulmonary angiogenesis remain unknown. We previously demonstrated that NF-κB, a transcription factor traditionally associated with inflammation, plays a unique protective role in the neonatal lung. Therefore, we hypothesized that constitutive NF-κB activity is essential for postnatal lung development. Blocking NF-κB activity in 6-day-old neonatal mice induced the alveolar simplification similar to that observed in BPD and significantly reduced pulmonary capillary density. Studies to determine the mechanism responsible for this effect identified greater constitutive NF-κB in neonatal lung and in primary pulmonary endothelial cells (PEC) compared with adult. Moreover, inhibiting constitutive NF-κB activity in the neonatal PEC with either pharmacological inhibitors or RNA interference blocked PEC survival, decreased proliferation, and impaired in vitro angiogenesis. Finally, by chromatin immunoprecipitation, NF-κB was found to be a direct regulator of the angiogenic mediator, VEGF-receptor-2, in the neonatal pulmonary vasculature. Taken together, our data identify an entirely novel role for NF-κB in promoting physiological angiogenesis and alveolarization in the developing lung. Our data suggest that disruption of NF-κB signaling may contribute to the pathogenesis of BPD and that enhancement of NF-κB may represent a viable therapeutic strategy to promote lung growth and regeneration in pulmonary diseases marked by impaired angiogenesis.

S100A7 enhances mammary tumorigenesis through upregulation of inflammatory pathways

S100A7/psoriasin, a member of the epidermal differentiation complex, is widely overexpressed in invasive estrogen receptor (ER)α-negative breast cancers. However, it has not been established whether S100A7 contributes to breast cancer growth or metastasis. Here, we report the consequences of its expression on inflammatory pathways that impact breast cancer growth. Overexpression of human S100A7 or its murine homologue mS100a7a15 enhanced cell proliferation and upregulated various proinflammatory molecules in ERα-negative breast cancer cells. To examine in vivo effects, we generated mice with an inducible form of mS100a7a15 (MMTV-mS100a7a15 mice). Orthotopic implantation of MVT-1 breast tumor cells into the mammary glands of these mice enhanced tumor growth and metastasis. Compared with uninduced transgenic control mice, the mammary glands of mice where mS100a7a15 was induced exhibited increased ductal hyperplasia and expression of molecules involved in proliferation, signaling, tissue remodeling, and macrophage recruitment. Furthermore, tumors and lung tissues obtained from these mice showed further increases in prometastatic gene expression and recruitment of tumor-associated macrophages (TAM). Notably, in vivo depletion of TAM inhibited the effects of mS100a7a15 induction on tumor growth and angiogenesis. Furthermore, introduction of soluble hS100A7 or mS100a7a15 enhanced chemotaxis of macrophages via activation of RAGE receptors. In summary, our work used a powerful new model system to show that S100A7 enhances breast tumor growth and metastasis by activating proinflammatory and metastatic pathways.

GPR54 (KISS1R) transactivates EGFR to promote breast cancer cell invasiveness

Kisspeptins (Kp), peptide products of the Kisspeptin-1 (KISS1) gene are endogenous ligands for a G protein-coupled receptor 54 (GPR54). Previous findings have shown that KISS1 acts as a metastasis suppressor in numerous cancers in humans. However, recent studies have demonstrated that an increase in KISS1 and GPR54 expression in human breast tumors correlates with higher tumor grade and metastatic potential. At present, whether or not Kp signaling promotes breast cancer cell invasiveness, required for metastasis and the underlying mechanisms, is unknown. We have found that kisspeptin-10 (Kp-10), the most potent Kp, stimulates the invasion of human breast cancer MDA-MB-231 and Hs578T cells using Matrigel-coated Transwell chamber assays and induces the formation of invasive stellate structures in three-dimensional invasion assays. Furthermore, Kp-10 stimulated an increase in matrix metalloprotease (MMP)-9 activity. We also found that Kp-10 induced the transactivation of epidermal growth factor receptor (EGFR). Knockdown of the GPCR scaffolding protein, β-arrestin 2, inhibited Kp-10-induced EGFR transactivation as well as Kp-10 induced invasion of breast cancer cells via modulation of MMP-9 secretion and activity. Finally, we found that the two receptors associate with each other under basal conditions, and FRET analysis revealed that GPR54 interacts directly with EGFR. The stability of the receptor complex formation was increased upon treatment of cells by Kp-10. Taken together, our findings suggest a novel mechanism by which Kp signaling via GPR54 stimulates breast cancer cell invasiveness.

β-arrestin1 mediates metastatic growth of breast cancer cells by facilitating HIF-1-dependent VEGF expression

β-Arrestins 1 and 2 are multifunctional adaptor proteins originally discovered for their role in desensitizing seven-transmembrane receptor signaling via the heterotrimeric guanine nucleotide-binding proteins. Recently identified roles of β-arrestins include regulation of cancer cell chemotaxis and proliferation. Herein, we report that β-arrestin1 expression regulates breast tumor colonization in nude mice and cancer cell viability during hypoxia. β-Arrestin1 robustly interacts with nuclear hypoxia-induced factor-1α (HIF-1α) that is stabilized during hypoxia and potentiates HIF-1-dependent transcription of the angiogenic factor vascular endothelial growth factor-A (VEGF-A). Increased expression of β-arrestin1 in human breast cancer (infiltrating ductal carcinoma or IDC and metastatic IDC) correlates with increased levels of VEGF-A. While the anti-angiogenic drug thalidomide inhibits HIF-1-dependent VEGF transcription in breast carcinoma cells, it does not prevent HIF-1α stabilization, but leads to aberrant localization of HIF-1α to the perinuclear compartments and surprisingly stimulates nuclear export of β-arrestin1. Additionally, imatinib mesylate that inhibits release of VEGF induces nuclear export of β-arrestin1-HIF-1α complexes. Our findings suggest that β-arrestin1 regulates nuclear signaling during hypoxia to promote survival of breast cancer cells via VEGF signaling and that drugs that induce its translocation from the nucleus to the cytoplasm could be useful in anti-angiogenic and breast cancer therapies.

[The clinical significance of β-arrestin 2 expression in the serum of non-small cell lung cancer patients]

BACKGROUND AND OBJECTIVE

Non-small cell lung cancer (NSCLC) with high morbidity and mortality is the most common types of lung cancer. beta-arrestin 2 is a kind of soluble protein regulating signal transduction mediated by G protein coupling receptor. The aim of this research is to evaluate the clinical significance of β-arrestin 2 expression in the serum of NSCLC patients.

METHODS

The clinical and follow-up data of 20 healthy candidates and 67 patients diagnosed with NSCLC in Sun Yat-sen University Cancer Center from January 2005 to December 2006 was retrospectively analyzed. ELISA was applied to detect the expression of beta-arrestin 2.

RESULTS

The serum level of β-arrestin 2 in NSCLC patients were all Significantly lower than those in healthy controls (P<0.001, P<0.001, P<0.001). The serum level of β-arrestin 2 in stage I NSCLC patients were higher than those in stage III as well as in stage IV (P<0.001, P<0.001). No statistical difference of β-arrestin 2' serum level was found between with stage III and stage IV patients (P=0.273). Univariate prognostic factor analyzed by Kaplan-Meier method indicated patients' prognosis with high serum level of β-arrestin 2 was better than patients with low and middle (P<0.001, P<0.001). The serum level of β-arrestin 2 and the stage of NSCLC signally affected prognosis in COX regression model (P=0.003, P=0.004).

CONCLUSION

The serum level of β-arrestin 2 had significant difference between NSCLC patients and healthy controls, likewise between the early and advanced NSCLC patients. The serum level of β-arrestin 2 affected NSCLC patients' prognosis.

Distinct and shared roles of β-arrestin-1 and β-arrestin-2 on the regulation of C3a receptor signaling in human mast cells

Background

The complement component C3a induces degranulation in human mast cells via the activation of cell surface G protein coupled receptors (GPCR; C3aR). For most GPCRs, agonist-induced receptor phosphorylation leads to the recruitment of β-arrestin-1/β-arrestin-2; resulting in receptor desensitization and internalization. Activation of GPCRs also leads to ERK1/2 phosphorylation via two temporally distinct pathways; an early response that reflects G protein activation and a delayed response that is G protein independent but requires β-arrestins. The role of β-arrestins on C3aR activation/regulation in human mast cells, however, remains unknown.

Methodology/Principal Findings

We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of β-arrestin-1 and β-arrrestin-2 in human mast cell lines, HMC-1 and LAD2 that endogenously expresses C3aR. Silencing β-arrestin-2 attenuated C3aR desensitization, blocked agonist-induced receptor internalization and rendered the cells responsive to C3a for enhanced NF-κB activity as well as chemokine generation. By contrast, silencing β-arrestin-1 had no effect on these responses but resulted in a significant decrease in C3a-induced mast cell degranulation. In shRNA control cells, C3a caused a transient ERK1/2 phosphorylation, which peaked at 5 min but disappeared by 10 min. Knockdown of β-arrestin-1, β-arrestin-2 or both enhanced the early response to C3a and rendered the cells responsive for ERK1/2 phosphorylation at later time points (10–30 min). Treatment of cells with pertussis toxin almost completely blocked both early and delayed C3a-induced ERK1/2 phosphorylation in β-arrestin1/2 knockdown cells.

Conclusion/Significance

This study demonstrates distinct roles for β-arrestins-1 and β-arrestins-2 on C3aR desensitization, internalization, degranulation, NF-κB activation and chemokine generation in human mast cells. It also shows that both β-arrestin-1 and β-arrestin-2 play a novel and shared role in inhibiting G protein-dependent ERK1/2 phosphorylation. These findings reveal a new level of complexity for C3aR regulation by β-arrestins in human mast cells.

Differential expression of arrestins is a predictor of breast cancer progression and survival

Emerging evidence has implicated G protein-coupled receptors, such as CXCR4 and PAR2, in breast cancer progression and the development of metastatic breast cancer. However, the role of proteins that regulate the function of these receptors, such as arrestins, in breast cancer has yet to be determined. Examination of the expression of the two nonvisual arrestins, arrestin2 and 3, in various breast cancer cell lines revealed comparable expression of arrestin3 in basal and luminal lines while arrestin2 expression was much higher in the luminal lines compared to the more aggressive basal lines. Analysis of normal human breast tissue revealed that arrestin2 and 3 were expressed in both luminal and myoepithelial cells of mammary epithelia with arrestin2 highest in myoepithelial cells and arrestin3 comparable in both cell types. Quantitative immunofluorescence-based examination of primary breast tumors revealed that arrestin2 expression significantly decreased with cancer progression from ductal carcinoma in situ to invasive carcinoma and further to lymph node metastasis (P < 0.001). Moreover, decreased arrestin2 expression was associated with decreased survival (P = 0.0007) as well as positive lymph node status and increased tumor size and nuclear grade. In contrast, arrestin3 expression significantly increased during breast cancer progression (P < 0.001) and increased expression was associated with decreased survival (P = 0.014). Arrestin3 was also an independent prognostic marker of breast cancer with a hazard ratio of 1.65. Overall, these studies demonstrate that arrestin2 levels decrease while arrestin3 levels increase during breast cancer progression and these changes correlate with a poor clinical outcome.

NF-kappaB in lung cancer, a carcinogenesis mediator and a prevention and therapy target

Lung cancer ranks as the first malignant tumor killer worldwide. Despite the knowledge that carcinogens from tobacco smoke and the environment constitute the main causes of lung cancer, the mechanisms for lung carcinogenesis are still elusive. Cancer development and progression depend on the balance between cell survival and death signals. Common cell survival signaling pathways are activated by carcinogens as well as by inflammatory cytokines, which contribute substantially to cancer development. As a major cell survival signal, nuclear factor-kappaB (NF-kappaB) is involved in multiple steps in carcinogenesis and in cancer cell's resistance to chemo- and radio-therapy. Recent studies with animal models and cell culture systems have established the links between NF-kappaB and lung carcinogenesis, highlighting the significance of targeting NF-kappa signaling pathway for lung cancer treatment and chemoprevention. In this review, we summarize progresses in understanding the NF-kappaB pathway in lung cancer development as well as in modulating NF-kappaB for lung cancer prevention and therapy.