G(alpha)12-mediated pathway promotes invasiveness of nasopharyngeal carcinoma by modulating actin cytoskeleton reorganization

New insights into RAS in head and neck cancer

RAS genes are known to be dysregulated in cancer for several decades, and substantial effort has been dedicated to develop agents that reduce RAS expression or block RAS activation. The recent introduction of RAS inhibitors for cancer patients highlights the importance of comprehending RAS alterations in head and neck cancer (HNC). In this regard, we examine the published findings on RAS alterations and pathway activations in HNC, and summarize their role in HNC initiation, progression, and metastasis. Specifically, we focus on the intrinsic role of mutated-RAS on tumor cell signaling and its extrinsic role in determining tumor-microenvironment (TME) heterogeneity, including promoting angiogenesis and enhancing immune escape. Lastly, we summarize the intrinsic and extrinsic role of RAS alterations on therapy resistance to outline the potential of targeting RAS using a single agent or in combination with other therapeutic agents for HNC patients with RAS-activated tumors.

A 3-gene signature comprising CDH4, STAT4 and EBV-encoded LMP1 for early diagnosis and predicting disease progression of nasopharyngeal carcinoma

PURPOSE

Nasopharyngeal carcinoma is highly metastatic but difficult to detect in its early stages. It is critical to develop a simple and highly efficient molecular diagnostic method for early detection of NPC in clinical biopsies.

METHODS

The transcriptomic data of primary NPC cell strains were used as a discovery tool. Linear regression approach was used to define signatures distinctive between early and late stage of NPC. Expressions of candidates were validated with an independent set of biopsies (n = 39). Leave-one-out cross-validation technique was employed to estimate the prediction accuracy on stage classification. The clinical relevance of marker genes was verified using NPC bulk RNA sequencing data and IHC analysis.

RESULTS

Three genes comprising CDH4, STAT4, and CYLD were found to have a significant differentiating power to separate NPC from normal nasopharyngeal samples and predicting disease malignancy. IHC analyses showed stronger CDH4, STAT4, and CYLD immunoreactivity in adjacent basal epithelium compared with that in tumor cells (p < 0.001). EBV-encoded LMP1 was exclusively expressed in NPC tumors. Using an independent set of biopsies, we showed that a model combining CDH4, STAT4, and LMP1 had a 92.86% of diagnostic accuracy, whereas a combination of STAT4 and LMP1 had a 70.59% accuracy for predicting advanced disease. Mechanistic studies suggested that promoter methylation, loss of DNA allele, and LMP1 contributed to the suppressive expression of CDH4, CYLD, and STAT4, respectively.

CONCLUSION

A model combining CDH4 and STAT4 and LMP1 was proposed to be a feasible model for diagnosing NPC and predicting late stage of NPC.

An Update of G-Protein-Coupled Receptor Signaling and Its Deregulation in Gastric Carcinogenesis

G-protein-coupled receptors (GPCRs) belong to a cell surface receptor superfamily responding to a wide range of external signals. The binding of extracellular ligands to GPCRs activates a heterotrimeric G protein and triggers the production of numerous secondary messengers, which transduce the extracellular signals into cellular responses. GPCR signaling is crucial and imperative for maintaining normal tissue homeostasis. High-throughput sequencing analyses revealed the occurrence of the genetic aberrations of GPCRs and G proteins in multiple malignancies. The altered GPCRs/G proteins serve as valuable biomarkers for early diagnosis, prognostic prediction, and pharmacological targets. Furthermore, the dysregulation of GPCR signaling contributes to tumor initiation and development. In this review, we have summarized the research progress of GPCRs and highlighted their mechanisms in gastric cancer (GC). The aberrant activation of GPCRs promotes GC cell proliferation and metastasis, remodels the tumor microenvironment, and boosts immune escape. Through deep investigation, novel therapeutic strategies for targeting GPCR activation have been developed, and the final aim is to eliminate GPCR-driven gastric carcinogenesis.

Gα12 and Gα13: Versatility in Physiology and Pathology

G protein-coupled receptors (GPCRs), as the largest family of receptors in the human body, are involved in the pathological mechanisms of many diseases. Heterotrimeric G proteins represent the main molecular switch and receive cell surface signals from activated GPCRs. Growing evidence suggests that Gα₁₂ subfamily (Gα_12/13)-mediated signaling plays a crucial role in cellular function and various pathological processes. The current research on the physiological and pathological function of Gα_12/13 is constantly expanding, Changes in the expression levels of Gα_12/13 have been found in a wide range of human diseases. However, the mechanistic research on Gα_12/13 is scattered. This review briefly describes the structural sequences of the Gα_12/13 isoforms and introduces the coupling of GPCRs and non-GPCRs to Gα_12/13. The effects of Gα_12/13 on RhoA and other signaling pathways and their roles in cell proliferation, migration, and immune cell function, are discussed. Finally, we focus on the pathological impacts of Gα_12/13 in cancer, inflammation, metabolic diseases, fibrotic diseases, and circulatory disorders are brought to focus.

The emerging roles of Gα12/13 proteins on the hallmarks of cancer in solid tumors

G12 proteins comprise a subfamily of G-alpha subunits of heterotrimeric GTP-binding proteins (G proteins) that link specific cell surface G protein-coupled receptors (GPCRs) to downstream signaling molecules and play important roles in human physiology. The G12 subfamily contains two family members: Gα12 and Gα13 (encoded by the GNA12 and GNA13 genes, respectively) and, as with all G proteins, their activity is regulated by their ability to bind to guanine nucleotides. Increased expression of both Gα12 and Gα13, and their enhanced signaling, has been associated with tumorigenesis and tumor progression of multiple cancer types over the past decade. Despite these strong associations, Gα12/13 proteins are underappreciated in the field of cancer. As our understanding of G protein involvement in oncogenic signaling has evolved, it has become clear that Gα12/13 signaling is pleotropic and activates specific downstream effectors in different tumor types. Further, the expression of Gα12/13 proteins is regulated through a series of transcriptional and post-transcriptional mechanisms, several of which are frequently deregulated in cancer. With the ever-increasing understanding of tumorigenic processes driven by Gα12/13 proteins, it is becoming clear that targeting Gα12/13 signaling in a context-specific manner could provide a new strategy to improve therapeutic outcomes in a number of solid tumors. In this review, we detail how Gα12/13 proteins, which were first discovered as proto-oncogenes, are now known to drive several "classical" hallmarks, and also play important roles in the "emerging" hallmarks, of cancer.

An Insight into GPCR and G-Proteins as Cancer Drivers

G-protein-coupled receptors (GPCRs) are the largest family of cell surface signaling receptors known to play a crucial role in various physiological functions, including tumor growth and metastasis. Various molecules such as hormones, lipids, peptides, and neurotransmitters activate GPCRs that enable the coupling of these receptors to highly specialized transducer proteins, called G-proteins, and initiate multiple signaling pathways. Integration of these intricate networks of signaling cascades leads to numerous biochemical responses involved in diverse pathophysiological activities, including cancer development. While several studies indicate the role of GPCRs in controlling various aspects of cancer progression such as tumor growth, invasion, migration, survival, and metastasis through its aberrant overexpression, mutations, or increased release of agonists, the explicit mechanisms of the involvement of GPCRs in cancer progression is still puzzling. This review provides an insight into the various responses mediated by GPCRs in the development of cancers, the molecular mechanisms involved and the novel pharmacological approaches currently preferred for the treatment of cancer. Thus, these findings extend the knowledge of GPCRs in cancer cells and help in the identification of therapeutics for cancer patients.

Identification of GNA12-driven gene signatures and key signaling networks in ovarian cancer

With the focus on defining the oncogenic network stimulated by lysophosphatidic acid (LPA) in ovarian cancer, the present study sought to interrogate the oncotranscriptome regulated by the LPA-mediated signaling pathway. LPA, LPA-receptor (LPAR) and LPAR-activated G protein 12 α-subunit, encoded by G protein subunit α 12 (GNA12), all serve an important role in ovarian cancer progression. While the general signaling mechanism regulated by LPA/LPAR/GNA12 has previously been characterized, the global transcriptomic network regulated by GNA12 in ovarian cancer pathophysiology remains largely unknown. To define the LPA/LPAR/GNA12-orchestrated oncogenic networks in ovarian cancer, transcriptomic and bioinformatical analyses were conducted using SKOV3 cells, in which the expression of GNA12 was silenced. Array analysis was performed in Agilent SurePrint G3 Human Comparative Genomic Hybridization 8×60 microarray platform. The array results were validated using Kuramochi cells. Gene and functional enrichment analyses were performed using Database for Annotation, Visualization and Integrated Discovery, Search Tool for Retrieval of Interacting Genes and Cytoscape algorithms. The results indicated a paradigm in which GNA12 drove ovarian cancer progression by upregulating a pro-tumorigenic network with AKT1, VEGFA, TGFB1, BCL2L1, STAT3, insulin-like growth factor 1 and growth hormone releasing hormone as critical hub and/or bottleneck nodes. Moreover, GNA12 downregulated a growth-suppressive network involving proteasome 20S subunit (PSM) β6, PSM α6, PSM ATPase 5, ubiquitin conjugating enzyme E2 E1, PSM non-ATPase 10, NDUFA4 mitochondrial complex-associated, NADH:ubiquinone oxidoreductase subunit B8 and anaphase promoting complex subunit 1 as hub or bottleneck nodes. In addition to providing novel insights into the LPA/LPAR/GNA12-regulated oncogenic networks in ovarian cancer, the present study identified several potential nodes in this network that could be assessed for targeted therapy.

G Protein-Coupled receptors and heterotrimeric G proteins as cancer drivers

G protein-coupled receptors (GPCRs) and heterotrimeric G proteins play central roles in a diverse array of cellular processes. As such, dysregulation of GPCRs and their coupled heterotrimeric G proteins can dramatically alter the signalling landscape and functional state of a cell. Consistent with their fundamental physiological functions, GPCRs and their effector heterotrimeric G proteins are implicated in some of the most prevalent human diseases, including a complex disease such as cancer that causes significant morbidity and mortality worldwide. GPCR/G protein-mediated signalling impacts oncogenesis at multiple levels by regulating tumour angiogenesis, immune evasion, metastasis, and drug resistance. Here, we summarize the growing body of research on GPCRs and their effector heterotrimeric G proteins as drivers of cancer initiation and progression, and as emerging antitumoural therapeutic targets.

Modulatory function of calmodulin on phagocytosis and potential regulation mechanisms in the blood clam Tegillarca granosa

Unlike vertebrate species, invertebrates lack antigen-antibody mediated immune response and mainly rely on haemocyte phagocytosis to fight against pathogen infection. Recently, studies conducted in model vertebrates demonstrated that the multifunctional protein calmodulin (CaM) plays an important role in regulating immune responses. However, the intrinsic relation between CaM and phagocytosis process remains poorly understood in invertebrate species such as bivalve mollusks. Therefore, in the present study, the immunomodulatory function of CaM on haemocyte phagocytosis was verified in the blood clam, Tegillarca granosa, using the CaM-specific inhibitor N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide hydrochloride (W-7). Results obtained show that CaM inhibition significantly suppressed the phagocytic activity of haemocytes. In addition, CaM inhibition constrained intracellular Ca²⁺ elevation, hampered actin cytoskeleton assembly, suppressed calcineurin (CaN) activity, and disrupted NF-κB activation in haemocytes upon LPS induction. Furthermore, expression of seven selected genes from the actin cytoskeleton regulation- and immune-related pathways were significantly downregulated whereas those of CaM and CaN from the Ca²⁺-signaling pathway were significantly upregulated by in vitro incubation of haemocytes with W-7. For the first time, the present study demonstrated that CaM play an important role in phagocytosis modulation in bivalve species. In addition, the intracellular Ca²⁺ and downstream Ca²⁺-signaling-, actin cytoskeleton regulation-, and immune-related pathways offer candidate routes through which CaM modulates phagocytosis.

Gα12/13 signaling in metabolic diseases

As the key governors of diverse physiological processes, G protein-coupled receptors (GPCRs) have drawn attention as primary targets for several diseases, including diabetes and cardiovascular disease. Heterotrimeric G proteins converge signals from ~800 members of the GPCR family. Among the members of the G protein α family, the Gα₁₂ family members comprising Gα₁₂ and Gα₁₃ have been referred to as gep oncogenes. Gα_12/13 levels are altered in metabolic organs, including the liver and muscles, in metabolic diseases. The roles of Gα_12/13 in metabolic diseases have been investigated. In this review, we highlight findings demonstrating Gα_12/13 amplifying or dampening regulators of phenotype changes. We discuss the molecular basis of G protein biology in the context of posttranslational modifications to heterotrimeric G proteins and the cell signaling axis. We also highlight findings providing insights into the organ-specific, metabolic and pathological roles of G proteins in changes associated with specific cells, energy homeostasis, glucose metabolism, liver fibrosis and the immune and cardiovascular systems. This review summarizes the currently available knowledge on the importance of Gα_12/13 in the physiology and pathogenesis of metabolic diseases, which is presented according to the basic understanding of their metabolic actions and underlying cellular and molecular bases.

Understanding the activities of two members of a vital category of proteins called G proteins, which initiate metabolic changes when signaling molecules bind to cells, could lead to new therapies for many diseases. Researchers in South Korea and Japan, led by Sang Geon Kim at Seoul National University, review the significance of the Gα12 and Gα13 proteins in diseases characterised by significant changes in metabolism, including liver conditions and disorders of the cardiovascular and immune systems. Specific roles for the proteins have been identified by a variety of methods, including studying the effect of disabling the genes that code for them in mice. Recent insights suggest that drugs interfering with the activity of these Gα proteins might help treat many conditions in which the molecular signalling networks involving the proteins are disrupted.

Upregulation of fascin-1 is involved in HIF-1α-dependent invasion and migration of hypopharyngeal squamous cell carcinoma

Fascin‑1 is an actin‑bundling protein, which specifically interacts with F‑actin to form parallel actin bundles, and participates in the regulation of cell adhesion, interactions and migration. However, the expression and regulatory mechanisms of fascin‑1 in hypopharyngeal squamous cell carcinoma (HSCC) remain poorly understood. The present study investigated the effects and underlying molecular mechanism of fascin‑1 on the invasion and metastasis of HSCC. The results demonstrated that fascin‑1 was overexpressed and correlated with lymph node metastasis and tumor‑node‑metastasis stage in HSCC tissues. Further in vitro study revealed that fascin‑1 promoted cell morphology polarization to increase the motility of FaDu cells. In addition, fascin‑1 significantly promoted the migration and invasion of FaDu cells. At the molecular level, fascin‑1 promoted cell invasion and migration by upregulating matrix metalloproteinase‑2 (MMP‑2) expression in FaDu cells. Immunohistochemical analysis revealed that a correlation existed between hypoxia inducible factor (HIF)‑1α and fascin‑1 expression in the HSCC tissues. Furthermore, the results from a cobalt chloride‑induced hypoxia model demonstrated that fascin‑1 may be upregulated by HIF‑1α in FaDu cells. Further analysis revealed that fascin‑1 knockdown significantly decreased the invasion of cells under hypoxia and partially reversed hypoxia‑induced MMP‑2 expression under hypoxia in FaDu cells. In conclusion, fascin‑1 was upregulated by HIF‑1α, and promoted the invasion and migration of HSCC cells; therefore, fascin‑1 may provide a potential target for the treatment of invasion and metastasis in HSCC.

Illuminating the Onco-GPCRome: Novel G protein-coupled receptor-driven oncocrine networks and targets for cancer immunotherapy

G protein-coupled receptors (GPCRs) are the largest gene family of cell membrane-associated molecules mediating signal transmission, and their involvement in key physiological functions is well-established. The ability of GPCRs to regulate a vast array of fundamental biological processes, such as cardiovascular functions, immune responses, hormone and enzyme release from endocrine and exocrine glands, neurotransmission, and sensory perception (e.g. vision, odor, and taste), is largely due to the diversity of these receptors and the layers of their downstream signaling circuits. Dysregulated expression and aberrant functions of GPCRs have been linked to some of the most prevalent human diseases, which renders GPCRs one of the top targets for pharmaceutical drug development. However, the study of the role of GPCRs in tumor biology has only just begun to make headway. Recent studies have shown that GPCRs can contribute to the many facets of tumorigenesis, including proliferation, survival, angiogenesis, invasion, metastasis, therapy resistance, and immune evasion. Indeed, GPCRs are widely dysregulated in cancer and yet are underexploited in oncology. We present here a comprehensive analysis of GPCR gene expression, copy number variation, and mutational signatures in 33 cancer types. We also highlight the emerging role of GPCRs as part of oncocrine networks promoting tumor growth, dissemination, and immune evasion, and we stress the potential benefits of targeting GPCRs and their signaling circuits in the new era of precision medicine and cancer immunotherapies.

GNA13 expression promotes drug resistance and tumor-initiating phenotypes in squamous cell cancers

Treatment failure in solid tumors occurs due to the survival of specific subpopulations of cells that possess tumor-initiating (TIC) phenotypes. Studies have implicated G protein-coupled-receptors (GPCRs) in cancer progression and the acquisition of TIC phenotypes. Many of the implicated GPCRs signal through the G protein GNA13. In this study, we demonstrate that GNA13 is upregulated in many solid tumors and impacts survival and metastases in patients. GNA13 levels modulate drug resistance and TIC-like phenotypes in patient-derived head and neck squamous cell carcinoma (HNSCC) cells in vitro and in vivo. Blockade of GNA13 expression, or of select downstream pathways, using small-molecule inhibitors abrogates GNA13-induced TIC phenotypes, rendering cells vulnerable to standard-of-care cytotoxic therapies. Taken together, these data indicate that GNA13 expression is a potential prognostic biomarker for tumor progression, and that interfering with GNA13-induced signaling provides a novel strategy to block TICs and drug resistance in HNSCCs.

Upregulation of CISD2 augments ROS homeostasis and contributes to tumorigenesis and poor prognosis of lung adenocarcinoma

CISD2 is a redox-sensitive gene critical for normal development and mitochondrial integrity. CISD2 was known to have aberrant expression in several types of human cancers. However, its relation with lung cancer is still not clear. In this study we found CISD2 mRNA was significantly upregulated in lung adenocarcinoma (ADC) samples, compared with their adjacent normal counterparts, and was correlated with tumor stage, grade, and prognosis based on analysis of clinical specimens-derived expression data in public domain and our validation assay. Cell based assay indicated that CISD2 expression regulated accumulation of reactive oxygen species (ROS), polarization of mitochondrial membrane potential, as well as cell viability, apoptosis, invasiveness, and tumorigenicity. In addition, CISD2 expression was found significantly correlated with stress response/redox signaling genes such as EGR1 and GPX3, while such correlations were also found valid in many public domain data. Taken together, upregulation of CISD2 is involved in an increased antioxidant capacity in response to elevated ROS levels during the formation and progression of lung ADC. The molecular mechanism underlying how CISD2 regulates ROS homeostasis and augments malignancy of lung cancer warrants further investigations.

Gα12/13 signaling promotes cervical cancer invasion through the RhoA/ROCK-JNK signaling axis

Several reports have indicated a role for the members of the G12 family of heterotrimeric G proteins (Gα12 and Gα13) in oncogenesis and tumor cell growth. The aims of the present study were to evaluate the role of G12 signaling in cervical cancer. We demonstrated that expression of the G12 proteins was highly upregulated in cervical cancer cells. Additionally, expression of the activated forms of Gα12/Gα13 but not expression of activated Gαq induced cell invasion through the activation of the RhoA family of G proteins, but had no effect on cell proliferation in the cervical cancer cells. Inhibition of G12 signaling by expression of the RGS domain of the p115-Rho-specific guanine nucleotide exchange factor (p115-RGS) blocked thrombin-stimulated cell invasion, but did not inhibit cell proliferation in cervical cells, whereas the inhibition of Gαq (RGS2) had no effect. Furthermore, G12 signaling was able to activate Rho proteins, and this stimulation was inhibited by p115-RGS, and Gα12-induced invasion was blocked by an inhibitor of RhoA/B/C (C3 toxin). Pharmacological inhibition of JNK remarkably decreased G12-induced JNK activation. Both a JNK inhibitor (SP600125) and a ROCK inhibitor (Y27632) reduced G12-induced JNK and c-Jun activation, and markedly inhibited G12-induced cellular invasion. Collectively, these findings demonstrate that stimulation of G12 proteins is capable of promoting invasion through RhoA/ROCK-JNK activation.

Epithelial mesenchymal transition related molecular markers and invasion and metastasis of cholangiocarcinoma

Tumor metastasis is a major cause of death in patients with solid tumors. Epithelial mesenchymal transition (EMT) is a process in which the epithelial cells are transformed into the stroma cells. This process is accompanied by changes in gene expression and cell phenotype, which are often activated during tumor invasion and metastasis. Cholangiocarcinoma is a kind of malignancy originating from the bile duct epithelium, and its main biological characteristics are early invasion, metastasis and recurrence. The research of cholangiocarcinoma metastasis could provide a theoretical basis for the development of new treatment strategies to manage this malignancy. This paper reviews the roles of EMT related molecular markers metastasis in the invasion and metastasis of cholangiocarcinoma.

Heterotrimeric G-protein alpha-12 (Gα12) subunit promotes oral cancer metastasis

Oral squamous cell carcinoma (OSCC) has a propensity to spread to the cervical lymph nodes (LN). The presence of cervical LN metastases severely impacts patient survival, whereby the two-year survival for oral cancer patients with involved LN is ~30% compared to over 80% in patients with non-involved LN. Elucidation of key molecular mechanisms underlying OSCC metastasis may afford an opportunity to target specific genes, to prevent the spread of OSCC and to improve patient survival. In this study, we demonstrated that expression of the heterotrimeric G-protein alpha-12 (Gα12) is highly up-regulated in primary tumors and LN of OSCC patients, as assessed by quantitative polymerase chain reaction (qPCR) and immunohistochemistry (IHC). We also found that exogenous expression of the constitutively activated-form of Gα12 promoted cell migration and invasion in OSCC cell lines. Correspondingly, inhibition of Gα12 expression by shRNA consistently inhibited OSCC cell migration and invasion in vitro. Further, the inhibition of G12 signaling by regulator of G-protein signaling (RGS) inhibited Gα12-mediated RhoA activation, which in turn resulted in reduced LN metastases in a tongue-orthotopic xenograft mouse model of oral cancer. This study provides a rationale for future development and evaluation of drug candidates targeting Gα12-related pathways for metastasis prevention.

Transcriptome meta-analysis reveals dysregulated pathways in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is a malignant cancer arising from the epithelial surface of the nasopharynx that mostly appears in advanced stages of the disease, leading to a poor prognosis. To date, a number of mRNA profiling investigations on NPC have been reported in order to identify suitable biomarkers for early detection. However, the results may be specific to each study with distinct sample types. In this study, an integrative meta-analysis of NPC transcriptome data was performed to determine dysregulated pathways, potentially leading to identification of molecular markers. Ten independent NPC gene expression profiling microarray datasets, including 135 samples from NPC cell lines, primary cell lines, and tissues were assimilated into a meta-analysis and cross-validation to identify a cohort of genes that were significantly dysregulated in NPC. Bioinformatics analyses of these genes revealed the significant pathways and individual players involving in cellular metabolism, cell cycle regulation, DNA repair, as well as ErbB pathway. Altogether, we propose that dysregulation of these molecular pathways in NPC might play a role in the NPC pathogenesis, providing clues, which could eventually translate into diagnostic and therapeutic approaches.

Gα12 gep oncogene deregulation of p53-responsive microRNAs promotes epithelial-mesenchymal transition of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a poor prognosis owing to aggressive phenotype. Gα12 gep oncogene product couples to G-protein-coupled receptors, whose ligand levels are frequently increased in tumor microenvironments. Here, we report Gα12 overexpression in human HCC and the resultant induction of zinc-finger E-box-binding homeobox 1 (ZEB1) as mediated by microRNA deregulation. Gα12 expression was higher in HCC than surrounding non-tumorous tissue. Transfection of Huh7 cell with an activated mutant of Gα12 (Gα12QL) deregulated microRNA (miRNA or miR)-200b/a/429, -194-2/192 and -194-1/215 clusters in the miRNome. cDNA microarray analyses disclosed the targets affected by Gα12 gene knockout. An integrative network of miRNAs and mRNA changes enabled us to predict ZEB1 as a key molecule governed by Gα12. Decreases of miR-200a/b, -192 and -215 by Gα12 caused ZEB1 induction. The ability of Gα12 to decrease p53 levels, as a result of activating protein-1 (AP-1)/c-Jun-mediated mouse double minute 2 homolog induction, contributed to transcriptional deregulation of the miRNAs. Gα12QL induced ZEB1 and other epithelial-mesenchymal transition markers with fibroblastoid phenotype change. Consistently, transfection with miR-200b, -192 or -215 mimic prevented the ability of Gα12QL to increase tumor cell migration/invasion. In xenograft studies, sustained knockdown of Gα12 decreased the overall growth rate and average volume of tumors derived from SK-Hep1 cell (mesenchymal-typed). In HCC patients, miR-192, -215 and/or -200a were deregulated with microvascular invasion or growth advantage. In the HCC samples with higher Gα12 level, a correlation existed in the comparison of relative changes of Gα12 and ZEB1. In conclusion, Gα12 overexpressed in HCC causes ZEB1 induction by deregulating p53-responsive miRNAs, which may facilitate epithelial-mesenchymal transition and growth of liver tumor. These findings highlight the significance of Gα12 upregulation in liver tumor progression, implicating Gα12 as an attractive therapeutic target.

Breast cancer cell invasion mediated by Gα12 signaling involves expression of interleukins-6 and -8, and matrix metalloproteinase-2

Background

Recent studies on the involvement of the G12 family of heterotrimeric G proteins (Gα12 and Gα13, the products of the GNA12 and GNA13 genes, respectively) in oncogenic pathways have uncovered a link between G12 signaling and cancer progression. However, despite a well characterized role of Rho GTPases, the potential role of secreted factors in the capacity of G12 signaling to promote invasion of cancer cells is just beginning to be addressed.

Methods

MDA-MB-231 and MCF10A breast cancer cell lines were employed as a model system to explore the involvement of secreted factors in G12-stimulated cell invasion. Factors secreted by cells expressing dominant-active Gα12 were identified by protein array, and their involvement in breast cancer cell invasion was assessed through both RNAi-mediated knockdown and antibody neutralization approaches. Bioinformatics analysis of the promoter elements of the identified factors suggested NF-κB elements played a role in their enhanced expression, which was tested by chromatin immunoprecipitation.

Results

We found that signaling through the Gα12 in MDA-MB-231 and MCF10A breast cancer cell lines enhances expression of interleukins (IL)-6 and −8, and matrix metalloproteinase (MMP)-2, and that these secreted factors play a role in G12-stimulated cell invasion. Furthermore, the enhanced expression of these secreted factors was found to be facilitated by the activation of their corresponding promoters, where NF-κB seems to be one of the major regulators. Inhibition of IL-6 and IL-8, or MMP-2 activity significantly decreased Gα12-mediated cell invasion.

Conclusions

These studies confirm and extend findings that secreted factors contribute to the oncogenic potential of G12 signaling, and suggest potential therapeutic targets to control this process.

Gα₁₂ drives invasion of oral squamous cell carcinoma through up-regulation of proinflammatory cytokines

Oral squamous cell carcinoma (OSCC) ranks among the top ten most prevalent cancers worldwide. Like most head and neck squamous cell carcinomas (HNSCCs), OSCC is highly inflammatory and aggressive. However, the signaling pathways triggering the activation of its inflammatory processes remain elusive. G protein-coupled receptor signaling regulates the inflammatory response and invasiveness of cancers, but it remains unclear whether Gα₁₂ is a critical player in the inflammatory cytokine pathway during the tumorigenesis of OSCC. This study was undertaken to determine the role of Gα₁₂ signaling in the regulation of proinflammatory cytokines in their mediation of OSCC invasion. We found that both the transcription and protein levels of Gα₁₂ are up-regulated in OSCC tumors. The elevated Gα₁₂ expressions in OSCC patients also correlated with extra-capsular spread, an indicator of tumor invasiveness in HNSCCs. This clinical finding was supported by the studies of overexpression and RNAi knockdown of Gα₁₂ in OSCC cells, which demonstrated that Gα₁₂ promoted tumor cell migration and invasion. To understand how Gα₁₂ modulates OSCC invasiveness, we analyzed key biological processes in microarray data upon depletion of Gα₁₂ and found that cytokine- and other immune-related pathways were severely impaired. Importantly, the mRNA levels of IL-6 and IL-8 proinflammatory cytokines in clinical samples were found to be significantly correlated with the increased Gα₁₂ levels, suggesting a potential role of Gα₁₂ in modulating the IL-6 and IL-8 expressions. Supporting this hypothesis, overexpression or RNAi knockdown of Gα₁₂ in OSCC cell lines both showed that Gα₁₂ positively regulated the mRNA and protein levels of IL-6 and IL-8. Finally, we demonstrated that the Gα₁₂ promotion of tumor cell invasiveness was suppressed by the neutralization of IL-6 and IL-8 in OSCC cells. Together, these findings suggest that Gα₁₂ drives OSCC invasion through the up-regulation of IL-6 and IL-8 cytokines.

Expression of Gα12 predicts progression and prognosis of oral squamous cell carcinomas in Taiwan

BACKGROUND

Expression of Gα12 is found to be associated with cancer cell proliferation, migration, invasion, and metastasis.

METHODS

This study used immunohistochemistry to examine the expression of Gα12 protein in 100 specimens of oral squamous cell carcinoma (OSCC), 45 specimens of oral epithelial dysplasia (OED), and 36 specimens of normal oral mucosa (NOM).

RESULTS

The mean Gα12 labeling indices (LIs, defined as the percentage of positive cells in total cells) increased significantly from NOM (7 ± 11%) through OED (21 ± 20%) to OSCC samples (53 ± 33%, P < 0.001). The higher mean Gα12 LI was significantly associated with OSCCs with larger tumor size (P = 0.003), positive lymph node metastasis (P = 0.002), or more advanced clinical stages (P = 0.003). Positive lymph node metastasis (P = 0.039) and Gα12 LI > 50% (P = 0.009) were identified as independent unfavorable prognosis factors by multivariate analyses with Cox regression model. Moreover, Kaplan-Meier curve showed that OSCC patients with a Gα12 LI > 50% had a significantly poorer cumulative survival than those with a Gα12 LI ≤ 50% (log-rank test, P = 0.009).

CONCLUSIONS

Our results showed a stepwise and significant elevation in Gα12 protein expression from NOM through OED to OSCCs, suggesting that overexpression of Gα12 protein may be an early event in oral carcinogenesis and may play a pivotal role in oral cancer development. Moreover, the Gα12 protein can be a biomarker for prediction of the progression of OSCCs and the prognosis of patients with OSCC in Taiwan.

Epithelial to mesenchymal transition in head and neck squamous cell carcinoma

Epithelial to mesenchymal transition (EMT) is a dynamic cellular process that is essential for the development of metastatic disease. During EMT, a tumor cell with epithelial characteristics transitions to a tumor cell with mesenchymal characteristics through modulation of cell polarity and adhesion. Two hallmark EMT proteins, E-Cadherin and Vimentin, are tightly controlled during EMT through multiple signal transduction pathways. Epidermal growth factor (EGF) and transforming growth factorβ (TGFβ) promote EMT by regulating a distinct set of transcription factors, including Snail and Twist. Snail, Twist, and Slug are integral to the induction of EMT through direct regulation of genes involved in cellular adhesion, migration, and invasion. This review highlights the current literature on EMT in HNSCC. Understanding the role of EMT will provide insight to the pathogenesis of disease progression and may lead to the development of novel anti-cancer therapeutics for metastatic HNSCC.

G12 signaling through c-Jun NH2-terminal kinase promotes breast cancer cell invasion

Signaling through the heterotrimeric G protein, G12, via Rho induces a striking increase in breast cancer cell invasion. In this study, evidence is provided that the c-Jun NH₂-terminal kinase (JNK) is a key downstream effector of G12 on this pathway. Expression of constitutively-active Gα12 or activation of G12 signaling by thrombin leads to increased JNK and c-Jun phosphorylation. Pharmacologic inhibition of JNK or knockdown of JNK expression by siRNA significantly decreases G12-induced JNK activation as well as the ability of breast cancer cells to invade a reconstituted basement membrane. Furthermore, expression of dominant-negative Rho or treatment of cells with an inhibitor of the Rho kinase, ROCK, reduces G12-induced JNK and c-Jun activation, and ROCK inhibitor treatment also inhibits G12-induced cellular invasion. JNK knockdown or ROCK inhibitor treatment has no effect on activation of Rho by G12. Taken together, our data indicate that JNK activation is required for G12-induced invasion of breast cancer cells and that JNK is downstream of Rho and ROCK on this pathway. This study implicates a G12-stimulated mitogen-activated protein kinase cascade in cancer cell invasion, and supports a role for JNK in cancer progression.

G(alpha)12/13 induction of CYR61 in association with arteriosclerotic intimal hyperplasia: effect of sphingosine-1-phosphate

OBJECTIVE

Gα(12/13) play a role in oncogenic transformation and tumor growth. Cysteine-rich protein 61 (CYR61) is a growth-factor-inducible angiogenic factor. In view of potential overlapping functions between Gα(12/13) and CYR61, this study investigated the role of these G proteins in CYR61 induction in association with hyperplastic vascular abnormality.

METHODS AND RESULTS

Overexpression of activated Gα(12) or Gα(13) induced CYR61 expression in vascular smooth muscle cells (VSMCs). Gene knockdown and knockout experiments revealed that sphingosine-1-phosphate (S1P) treatment induced CYR61 via Gα(12/13). JunD/activator protein-1 (AP-1) was identified as a transcription factor required for CYR61 transactivation by S1P. Deficiencies in Gα(12/13) abrogated AP-1 activation and AP-1-mediated CYR61 induction. c-Jun N-terminal kinase was responsible for CYR61 induction. Moreover, deficiencies of Gα(12/13) abolished c-Jun N-terminal kinase-dependent CYR61 induction by S1P. N-acetyl-l-cysteine or NADPH oxidase inhibitor treatment reversed CYR61 induction by S1P, indicating that reactive oxygen species are responsible for this process. The levels of Gα(12/13) were increased within thickened intimas and medias in wire-injured mouse femoral arteries, which was accompanied by simultaneous CYR61 induction. Moreover, Gα(12/13) and CYR61 were costained in the arteriosclerotic lesions immediately adjacent to human tumor tissues.

CONCLUSIONS

Gα(12/13) regulate AP-1-dependent CYR61 induction in VSMCs and promote VSMC migration, and they are upregulated with CYR61 in arteriosclerotic lesions.

A role for L-alpha-lysophosphatidylinositol and GPR55 in the modulation of migration, orientation and polarization of human breast cancer cells

BACKGROUND AND PURPOSE

Increased circulating levels of L-alpha-lysophosphatidylinositol (LPI) are associated with cancer and LPI is a potent, ligand for the G-protein-coupled receptor GPR55. Here we have assessed the modulation of breast cancer cell migration, orientation and polarization by LPI and GPR55.

EXPERIMENTAL APPROACH

Quantitative RT-PCR was used to measure GPR55 expression in breast cancer cell lines. Cell migration and invasion were measured using a Boyden chamber chemotaxis assay and Cultrex invasion assay, respectively. Cell polarization and orientation in response to the microenvironment were measured using slides containing nanometric grooves.

KEY RESULTS

GPR55 expression was detected in the highly metastatic MDA-MB-231 breast cancer cell line. In these cells, LPI stimulated binding of [(35)S]GTPgammaS to cell membranes (pEC(50) 6.47 +/- 0.45) and significantly enhanced cell chemotaxis towards serum. MCF-7 cells expressed low levels of GPR55 and did not migrate or invade towards serum factors. When GPR55 was over-expressed in MCF-7 cells, serum induced a robust migratory and invasive response, which was further enhanced by LPI and prevented by siRNA to GPR55. The physical microenvironment has been identified as a key factor in determining breast tumour cell metastatic fate. LPI endowed MDA-MB-231 cells with the capacity to detect shallow (40 nm deep) grooved slides and induced marked cancer cell polarization on both flat and grooved surfaces.

CONCLUSIONS AND IMPLICATIONS

LPI and GPR55 play a role in the modulation of migration, orientation and polarization of breast cancer cells in response to the tumour microenvironment.

Quantitative proteomics reveals myosin and actin as promising saliva biomarkers for distinguishing pre-malignant and malignant oral lesions

Background

Oral cancer survival rates increase significantly when it is detected and treated early. Unfortunately, clinicians now lack tests which easily and reliably distinguish pre-malignant oral lesions from those already transitioned to malignancy. A test for proteins, ones found in non-invasively-collected whole saliva and whose abundances distinguish these lesion types, would meet this critical need.

Methodology/Principal Findings

To discover such proteins, in a first-of-its-kind study we used advanced mass spectrometry-based quantitative proteomics analysis of the pooled soluble fraction of whole saliva from four subjects with pre-malignant lesions and four with malignant lesions. We prioritized candidate biomarkers via bioinformatics and validated selected proteins by western blotting. Bioinformatic analysis of differentially abundant proteins and initial western blotting revealed increased abundance of myosin and actin in patients with malignant lesions. We validated those results by additional western blotting of individual whole saliva samples from twelve other subjects with pre-malignant oral lesions and twelve with malignant oral lesions. Sensitivity/specificity values for distinguishing between different lesion types were 100%/75% (p = 0.002) for actin, and 67%/83% (p<0.00001) for myosin in soluble saliva. Exfoliated epithelial cells from subjects' saliva also showed increased myosin and actin abundance in those with malignant lesions, linking our observations in soluble saliva to abundance differences between pre-malignant and malignant cells.

Conclusions/Significance

Salivary actin and myosin abundances distinguish oral lesion types with sensitivity and specificity rivaling other non-invasive oral cancer tests. Our findings provide a promising starting point for the development of non-invasive and inexpensive salivary tests to reliably detect oral cancer early.

G(alpha)12/13 inhibition enhances the anticancer effect of bortezomib through PSMB5 downregulation

Bortezomib is a proteasome inhibitor approved for anticancer therapy. However, variable sensitivity of tumor cells exists in this therapy probably due to differences in the expression of proteasome subunits. G(alpha)(12/13) serves modulators or signal transducers in diverse pathways. This study investigated whether cancer cells display differential sensitivity to bortezomib with reference to G(alpha)(12/13) expression, and if so, whether G(alpha)(12/13) affects the expression of proteasome subunits and their activities. Bortezomib treatment exhibited greater sensitivities in Huh7 and SNU886 cells (epithelial type) than SK-Hep1 and SNU449 cells (mesenchymal type) that exhibited higher levels of G(alpha)(12/13). Overexpression of an active mutant of G(alpha)(12) (Galpha(12)QL) or G(alpha)(13) (G(alpha)(13)QL) diminished the ability of bortezomib to induce cytotoxicity in Huh7 cells. Moreover, transfection with the minigene that disturbs G protein-coupled receptor-G protein coupling (CT12 or CT13) increased it in SK-Hep1 cells. Consistently, MiaPaCa2 cells transfected with CT12 or CT13 exhibited a greater sensitivity to bortezomib. Evidence of G(alpha)(12/13)'s antagonism on the anticancer effect of bortezomib was verified in the reversal by G(alpha)(12)QL or G(alpha)(13)QL of the minigenes' enhancement of cytotoxity. Real-time polymerase chain reaction assay enabled us to identify PSMB5, multicatalytic endopeptidase complex-like-1, and proteasome activator subunit-1 repression by CT12 or CT13. Furthermore, G(alpha)(12/13) inhibition enhanced the ability of bortezomib to repress PSMB5, as shown by immunoblotting and proteasome activity assay. Moreover, this inhibitory effect on PSMB5 was attenuated by G(alpha)G(alpha)(12)QL or G(alpha)(13)QL. In conclusion, the inhibition of G(alpha)(12/13) activities may enhance the anticancer effect of bortezomib through PSMB5 repression, providing insight into the G(alpha)(12/13) pathway for the regulation of proteasomal activity.