Cross-talk between G Protein–Coupled Receptor and Epidermal Growth Factor Receptor Signaling Pathways Contributes to Growth and Invasion of Head and Neck Squamous Cell Carcinoma

CX3CL1 (Fractalkine)-CX3CR1 Axis in Inflammation-Induced Angiogenesis and Tumorigenesis

The chemotactic cytokine fractalkine (FKN, chemokine CX3CL1) has unique properties resulting from the combination of chemoattractants and adhesion molecules. The soluble form (sFKN) has chemotactic properties and strongly attracts T cells and monocytes. The membrane-bound form (mFKN) facilitates diapedesis and is responsible for cell-to-cell adhesion, especially by promoting the strong adhesion of leukocytes (monocytes) to activated endothelial cells with the subsequent formation of an extracellular matrix and angiogenesis. FKN signaling occurs via CX3CR1, which is the only known member of the CX3C chemokine receptor subfamily. Signaling within the FKN-CX3CR1 axis plays an important role in many processes related to inflammation and the immune response, which often occur simultaneously and overlap. FKN is strongly upregulated by hypoxia and/or inflammation-induced inflammatory cytokine release, and it may act locally as a key angiogenic factor in the highly hypoxic tumor microenvironment. The importance of the FKN/CX3CR1 signaling pathway in tumorigenesis and cancer metastasis results from its influence on cell adhesion, apoptosis, and cell migration. This review presents the role of the FKN signaling pathway in the context of angiogenesis in inflammation and cancer. The mechanisms determining the pro- or anti-tumor effects are presented, which are the cause of the seemingly contradictory results that create confusion regarding the therapeutic goals.

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.

Cancer-associated fibroblasts: Mediators of head and neck tumor microenvironment remodeling

Cancer-associated fibroblasts (CAFs) are involved in critical aspects of head and neck squamous cell carcinoma (HNSCC) pathogenesis, such as the formation of a tumor-permissive extracellular matrix structure, angiogenesis, or immune and metabolic reprogramming of the tumor microenvironment (TME), with implications for metastasis and resistance to radiotherapy and chemotherapy. The pleiotropic effect of CAFs in TME is likely to reflect the heterogeneity and plasticity of their population, with context-dependent effects on carcinogenesis. The specific properties of CAFs provide many targetable molecules that could play an important role in the future therapy of HNSCC. In this review article, we will focus on the role of CAFs in the TME of HNSCC tumors. We will also discuss clinically relevant agents targeting CAFs, their signals, and signaling pathways, which are activated by CAFs in cancer cells, with the potential for repurposing for HNSCC therapy.

Lipid Raft Facilitated Receptor Organization and Signaling: A Functional Rheostat in Embryonic Development, Stem Cell Biology and Cancer

Molecular views of plasma membrane organization and dynamics are gradually changing over the past fifty years. Dynamics of plasma membrane instigate several signaling nexuses in eukaryotic cells. The striking feature of plasma membrane dynamics is that, it is internally transfigured into various subdomains of clustered macromolecules. Lipid rafts are nanoscale subdomains, enriched with cholesterol and sphingolipids, reside as floating entity mostly on the exoplasmic leaflet of the lipid bilayer. In terms of functionality, lipid rafts are unique among other membrane subdomains. Herein, advances on the roles of lipid rafts in cellular physiology and homeostasis are discussed, precisely, on how rafts dynamically harbor signaling proteins, including GPCRs, catalytic receptors, and ionotropic receptors within it and orchestrate multiple signaling pathways. In the developmental proceedings signaling are designed for patterning of overall organism and they differ from the somatic cell physiology and signaling of fully developed organisms. Some of the developmental signals are characteristic in maintenance of stemness and activated during several types of tumor development and cancer progression. The harmony between extracellular signaling and lineage specific transcriptional programs are extremely important for embryonic development. The roles of plasma membrane lipid rafts mediated signaling in lineage specificity, early embryonic development, stem cell maintenance are emerging. In view of this, we have highlighted and analyzed the roles of lipid rafts in receptor organization, cell signaling, and gene expression during embryonic development; from pre-implantation through the post-implantation phase, in stem cell and cancer biology.

An overview of kinin mediated events in cancer progression and therapeutic applications

Kinins are bioactive peptides generated in the inflammatory milieu of the tissue microenvironment, which is involved in cancer progression and inflammatory response. Kinins signals through activation of two G-protein coupled receptors; inducible Bradykinin Receptor B1 (B1R) and constitutive receptor B2 (B2R). Activation of kinin receptors and its cross-talk with receptor tyrosine kinases activates multiple signaling pathways, including ERK/MAPK, PI3K, PKC, and p38 pathways regulating cancer hallmarks. Perturbations of the kinin-mediated events are implicated in various aspects of cancer invasion, matrix remodeling, and metastasis. In the tumor microenvironment, kinins initiate fibroblast activation, mesenchymal stem cell interactions, and recruitment of immune cells. Albeit the precise nature of kinin function in the metastasis and tumor microenvironment are not completely clear yet, several kinin receptor antagonists show anti-metastatic potential. Here, we showcase an overview of the complex biology of kinins and their role in cancer pathogenesis and therapeutic aspects.

NSAIDs Overcome PIK3CA Mutation-Mediated Resistance to EGFR Inhibition in Head and Neck Cancer Preclinical Models

Epidermal growth factor receptor (EGFR) inhibitors are approved by the Food and Drug Administration (FDA) but remain under active clinical investigation for the treatment of both newly diagnosed and recurrent/metastatic head and neck squamous cell carcinoma (HNSCC). Despite EGFR expression in the majority of HNSCC tumors, the levels of total or phosphorylated EGFR have not consistently been correlated with a response to EGFR targeting agents. The lack of predictive biomarkers represents a major obstacle to successful use of these drugs. Activation of phosphatidylinositol 3-kinase (PI3K) signaling by mutation of the PIK3CA oncogene represents a plausible mechanism for EGFR inhibitor drug resistance. We compared the impact of EGFR inhibitors, alone or in combination with non-steroidal anti-inflammatory drugs (NSAIDs), in preclinical HNSCC models harboring mutant versus wild-type PIK3CA. Our results demonstrate additive or synergistic effects of NSAIDs and EGFR inhibitors in vitro and in vivo in PIK3CA-mutated HNSCC models. These findings suggest that the addition of NSAIDs to EGFR inhibitors for the treatment of HNSCC may represent a promising therapeutic strategy in PIK3CA-mutated cancers.

Alcohol and Head and Neck Cancer: Updates on the Role of Oxidative Stress, Genetic, Epigenetics, Oral Microbiota, Antioxidants, and Alkylating Agents

Head and neck cancer (HNC) concerns more than 890,000 patients worldwide annually and is associated with the advanced stage at presentation and heavy outcomes. Alcohol drinking, together with tobacco smoking, and human papillomavirus infection are the main recognized risk factors. The tumorigenesis of HNC represents an intricate sequential process that implicates a gradual acquisition of genetic and epigenetics alterations targeting crucial pathways regulating cell growth, motility, and stromal interactions. Tumor microenvironment and growth factors also play a major role in HNC. Alcohol toxicity is caused both directly by ethanol and indirectly by its metabolic products, with the involvement of the oral microbiota and oxidative stress; alcohol might enhance the exposure of epithelial cells to carcinogens, causing epigenetic modifications, DNA damage, and inaccurate DNA repair with the formation of DNA adducts. Long-term markers of alcohol consumption, especially those detected in the hair, may provide crucial information on the real alcohol drinking of HNC patients. Strategies for prevention could include food supplements as polyphenols, and alkylating drugs as therapy that play a key role in HNC management. Indeed, polyphenols throughout their antioxidant and anti-inflammatory actions may counteract or limit the toxic effect of alcohol whereas alkylating agents inhibiting cancer cells' growth could reduce the carcinogenic damage induced by alcohol. Despite the established association between alcohol and HNC, a concerning pattern of alcohol consumption in survivors of HNC has been shown. It is of primary importance to increase the awareness of cancer risks associated with alcohol consumption, both in oncologic patients and the general population, to provide advice for reducing HNC prevalence and complications.

Neuregulins: protective and reparative growth factors in multiple forms of cardiovascular disease

Neuregulins (NRGs) are protein ligands that act through ErbB receptor tyrosine kinases to regulate tissue morphogenesis, plasticity, and adaptive responses to physiologic needs in multiple tissues, including the heart and circulatory system. The role of NRG/ErbB signaling in cardiovascular biology, and how it responds to physiologic and pathologic stresses is a rapidly evolving field. While initial concepts focused on the role that NRG may play in regulating cardiac myocyte responses, including cell survival, growth, adaptation to stress, and proliferation, emerging data support a broader role for NRGs in the regulation of metabolism, inflammation, and fibrosis in response to injury. The constellation of effects modulated by NRGs may account for the findings that two distinct forms of recombinant NRG-1 have beneficial effects on cardiac function in humans with systolic heart failure. NRG-4 has recently emerged as an adipokine with similar potential to regulate cardiovascular responses to inflammation and injury. Beyond systolic heart failure, NRGs appear to have beneficial effects in diastolic heart failure, prevention of atherosclerosis, preventing adverse effects on diabetes on the heart and vasculature, including atherosclerosis, as well as the cardiac dysfunction associated with sepsis. Collectively, this literature supports the further examination of how this developmentally critical signaling system functions and how it might be leveraged to treat cardiovascular disease.

The landscape of GPCR signaling in the regulation of epidermal stem cell fate and skin homeostasis

Continuous integration of signals from the micro and macro-environment is necessary for somatic stem cells to adapt to changing conditions, maintain tissue homeostasis and activate repair mechanisms. G-protein coupled receptors (GPCRs) facilitate this integration by binding to numerous hormones, metabolites and inflammatory mediators, influencing a diverse network of pathways that regulate stem cell fate. This adaptive mechanism is particularly relevant for tissues that are exposed to environmental assault, like skin. The skin is maintained by a set of basal keratinocyte stem and progenitor cells located in the hair follicle and interfollicular epidermis, and several GPCRs and their signaling partners serve as makers and regulators of epidermal stem cell activity. GPCRs utilize heterotrimeric G protein dependent and independent pathways to translate extracellular signals into intracellular molecular cascades that dictate the activation of keratinocyte proliferative and differentiation networks, including Hedgehog GLI, Hippo YAP1 and WNT/β-catenin, ultimately regulating stem cell identity. Dysregulation of GPCR signaling underlines numerous skin inflammatory diseases and cancer, with smoothened-driven basal cell carcinoma being a main example of a GPCR associated cancer. In this review, we discuss the impact of GPCRs and their signaling partners in skin keratinocyte biology, particularly in the regulation of the epidermal stem cell compartment.

GPR50 Promotes Hepatocellular Carcinoma Progression via the Notch Signaling Pathway through Direct Interaction with ADAM17

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide, and it is thus critical to identify novel molecular biomarkers of HCC prognosis and elucidate the molecular mechanisms underlying HCC progression. Here, we show that G-protein-coupled receptor 50 (GPR50) in HCC is overexpressed and that GPR50 knockdown may downregulate cancer cell progression through attenuation of the Notch signaling pathway. GPR50 knockdown was found to reduce HCC progression by inactivating Notch signaling in a ligand-independent manner through a disintegrin and metalloproteinase metallopeptidase domain 17 (ADAM17), a proteolytic enzyme that cleaves the Notch receptor, which was corroborated by GPR50 overexpression in hepatocytes. GPR50 silencing also downregulated transcription and translation of ADAM17 through the AKT/specificity protein-1 (SP1) signaling axis. Notably, GPR50 was found to directly interact with ADAM17. Overall, we demonstrate a novel GPR50-mediated regulation of the ADAM17-Notch signaling pathway, which can provide insights into HCC progression and prognosis and development of Notch-based HCC treatment strategies.

P2Y2 receptors mediate nucleotide-induced EGFR phosphorylation and stimulate proliferation and tumorigenesis of head and neck squamous cell carcinoma cell lines

OBJECTIVES

To assess functional expression of the P2Y2 nucleotide receptor (P2Y2R) in head and neck squamous cell carcinoma (HNSCC) cell lines and define its role in nucleotide-induced epidermal growth factor receptor (EGFR) transactivation. The use of anti-EGFR therapeutics to treat HNSCC is hindered by intrinsic and acquired drug resistance. Defining novel pathways that modulate EGFR signaling could identify additional targets to treat HNSCC.

MATERIALS AND METHODS

In human HNSCC cell lines CAL27 and FaDu and the mouse oral cancer cell line MOC2, P2Y2R contributions to extracellular nucleotide-induced changes in intracellular free Ca2+ concentration and EGFR and extracellular signal-regulated kinase (ERK1/2) phosphorylation were determined using the ratiometric Ca2+ indicator fura-2 and immunoblot analysis, respectively. Genetic knockout of P2Y2Rs using CRISPR technology or pharmacological inhibition with P2Y2R-selective antagonist AR-C118925 defined P2Y2R contributions to in vivo tumor growth.

RESULTS

P2Y2R agonists UTP and ATP increased intracellular Ca2+ levels and ERK1/2 and EGFR phosphorylation in CAL27 and FaDu cells, responses that were inhibited by AR-C118925 or P2Y2R knockout. P2Y2R-mediated EGFR phosphorylation was also attenuated by inhibition of the adamalysin family of metalloproteases or Src family kinases. P2Y2R knockout reduced UTP-induced CAL27 cell proliferation in vitro and significantly reduced CAL27 and FaDu tumor xenograft volume in vivo. In a syngeneic mouse model of oral cancer, AR-C118925 administration reduced MOC2 tumor volume.

CONCLUSION

P2Y2Rs mediate HNSCC cell responses to extracellular nucleotides and genetic or pharmacological blockade of P2Y2R signaling attenuates tumor cell proliferation and tumorigenesis, suggesting that the P2Y2R represents a novel therapeutic target in HNSCC.

FADS1 promotes the progression of laryngeal squamous cell carcinoma through activating AKT/mTOR signaling

Metabolic abnormality is the major feature of laryngeal squamous cell carcinoma (LSCC), however, the underlying mechanism remain largely elusive. Fatty acid desaturase 1 (FADS1), as the key rate-limiting enzyme of polyunsaturated fatty acids (PUFAs), catalyzes dihomo-gamma-linolenic acid (DGLA) to arachidonic acid (AA). In this study, we reported that the expression of FADS1 was upregulated in LSCC, high FADS1 expression was closely associated with the advanced clinical features and poor prognosis of the recurrent LSCC patients after chemotherapy. Liquid chromatograph-mass spectrometry (LC-MS) analysis revealed that FADS1 overexpression induced greater conversion of DGLA to AA, suggesting an increased activity of FADS1. Similarly, the level of prostaglandin E2 (PGE₂), a downstream metabolite of AA, was also elevated in cancerous laryngeal tissues. Functional assays showed that FADS1 knockdown suppressed the proliferation, migration and invasion of LSCC cells, while FADS1 overexpression had the opposite effects. Bioinformatic analysis based on microarray data found that FADS1 could activate AKT/mTOR signaling. This hypothesis was further validated by both in vivo and in vitro assays. Hence, our data has supported the viewpoint that FADS1 is a potential promoter in LSCC progression, and has laid the foundation for further functional research on the PUFA dietary supplementation interventions targeting FADS1/AKT/mTOR pathway for LSCC prevention and treatment.

Neuropeptide bombesin receptor activation stimulates growth of lung cancer cells through HER3 with a MAPK-dependent mechanism

Despite recent advances in treatment of non-small cell lung cancer (NSCLC), prognosis still remains poor and new therapeutic approaches are needed. Studies demonstrate the importance of the EGFR/HER-receptor family in NSCLC growth, as well as that of other tumors. Recently, HER3 is receiving increased attention because of its role in drug resistance and aggressive growth. Activation of overexpressed G-protein-coupled receptors (GPCR) can also initiate growth by transactivating EGFR/HER-family members. GPCR transactivation of EGFR has been extensively studied, but little is known of its ability to transactivate other EGFR/HER-members, especially HER3. To address this, we studied the ability of bombesin receptor (BnR) activation to transactivate all EGFR/HER-family members and their principal downstream signaling cascades, the PI3K/Akt- and MAPK/ERK-pathways, in human NSCLC cell-lines. In all three cell-lines studied, which possessed EGFR, HER2 and HER3, Bn rapidly transactivated EGFR, HER2 and HER3, as well as Akt and ERK. Immunoprecipitation studies revealed Bn-induced formation of both HER3/EGFR- and HER3/HER2-heterodimers. Specific EGFR/HER3 antibodies or siRNA-knockdown of EGFR and HER3, demonstrated Bn-stimulated activation of EGFR/HER members is initially through HER3, not EGFR. In addition, specific inhibition of HER3, HER2 or MAPK, abolished Bn-stimulated cell-growth, while neither EGFR nor Akt inhibition had an effect. These results show HER3 transactivation mediates all growth effects of BnR activation through MAPK. These results raise the possibility that targeting HER3 alone or with GPCR activation and its signal cascades, may be a novel therapeutic approach in NSCLC. This is especially relevant with the recent development of HER3-blocking antibodies.

Predicting the Lung Squamous Cell Carcinoma Diagnosis and Prognosis Markers by Unique DNA Methylation and Gene Expression Profiles

The early diagnosis of lung squamous cell carcinoma (LUSC) is difficult, causing an unsatisfactory prognosis. Therefore, the 5-year survival rate of LUSC is poor. This study aimed at screening the potential diagnostic and prognostic markers for LUSC. The data of LUSC gene expression profiles and DNA methylation were obtained from The Cancer Genome Atlas (TCGA) database; the differentially expressed genes (DEGs) and the differentially methylated genes (DMGs) were screened out by an independent t-test and Benjamini/Hochberg methods. Further, the classifiers of the gene expression and DNA methylation markers in LUSC were constructed. After that, diagnostic and prognostic markers in LUSC were analyzed by the protein-protein interaction (PPI) network. The DEGs and the DMGs from TCGA database of LUSC were screened out. After strict filtration, we identified three potential DMGs (POU domain, class 4, transcription factor 2 [POU4F2], EN1, single-minded homolog 1 [SIM1]) for early diagnosis and seven potential DEGs (G-protein coupled receptor 78 [GPR78], PCDHA5, myosin binding protein H [MYBPH], RTL3, KIAA0408, HSD3B2, PCDHA12) for prognosis of LUSC. The tumor-normal tissue classification model and prognosis model were validated in two independent datasets. In addition, the PPI network was constructed, including three DMGs and the five DEGs (GPR78, MYBPH, KIAA0408, HSD3B2, PCDHA12) of the seven DEGs. The potential DMGs (POU4F2, EN1, SIM1) and DEGs (GPR78, MYBPH, KIAA0408, HSD3B2, PCDHA12) for the diagnosis and prognosis of LUSC identified in this article are expected to be further applied in clinical practice of the treatment of LUSC.

A Brief History of Single-Particle Tracking of the Epidermal Growth Factor Receptor

Single-particle tracking (SPT) has been used and developed over the last 25 years as a method to investigate molecular dynamics, structure, interactions, and function in the cellular context. SPT is able to show how fast and how far individual molecules move, identify different dynamic populations, measure the duration and strength of intermolecular interactions, and map out structures on the nanoscale in cells. In combination with other techniques such as macromolecular crystallography and molecular dynamics simulation, it allows us to build models of complex structures, and develop and test hypotheses of how these complexes perform their biological roles in health as well as in disease states. Here, we use the example of the epidermal growth factor receptor (EGFR), which has been studied extensively by SPT, demonstrating how the method has been used to increase our understanding of the receptor’s organization and function, including its interaction with the plasma membrane, its activation, clustering, and oligomerization, and the role of other receptors and endocytosis. The examples shown demonstrate how SPT might be employed in the investigation of other biomolecules and systems.

ALDH1 as a prognostic marker for lymph node metastasis in OSCC

Long-term survival in cases of head and neck squamous cell carcinoma, particularly oral squamous cell carcinoma (OSCC), remains a rare achievement in the field of clinical oncology. In recent years, the theory of cancer stem cells (CSCs) has emerged and been used to offer explanations for tumour recurrence and metastasis. The present aim was to investigate the role of aldehyde dehydrogenase 1 (ALDH1) as a CSC-marker for OSCC and to determine the role of p16^ink4a, which is also a surrogate marker of human papilloma virus (HPV), in the expression of ALDH1. The study cohort comprised of 186 surgically-treated cases of OSCC. The primaries were located in the oral cavity. The expression of the CSC marker (CSCM) ALDH1 was evaluated via immunohistochemistry (IHC) of a tissue microarray. HPV detection was performed by polymerase chain reaction and an HPV Array kit. Furthermore, the IHC expression of p16^ink4a was also analysed. Risk regression models as the Kruskal Wallis test was used to assess the association of CSCM and p16^ink4a expression with tumour size and lymph node metastasis, and cox proportional hazards were analysed. Additionally, coexpression of the markers ALDH1 and p16^ink4a was analysed with regard to associations with tumour classification. Overall, high expression of ALDH1 in lymph nodes was significantly associated with Union for International Cancer Control (UICC) stage IV (P=0.044) and T4 stage cancer (P=0.03). p16^ink4a positivity, in cases of HPV negativity, was associated with worse survival rate compared with that of the total cohort (P=0.048). Collectively the data indicate that ALDH1 expression may be suitable for detection of unfavourable prognosis in OSCC patients, based in part on its apparent role as a marker of metastasis. HPV status was not statistically predictive of patient outcome or CSCM expression; however, p16^ink4a remains a potential marker in HNSCC Further in vitro studies with ALDH1 and p16^ink4a should be performed to evaluate the expression of ALDH1 and HPV in cell culture and to clarify the role of ALDH1 as a marker for increased invasiveness of OSCC cells.

Bifunctional ligands of the bradykinin B2 and B1 receptors: An exercise in peptide hormone plasticity

Kinins are the small and fragile hydrophilic peptides related to bradykinin (BK) and derived from circulating kininogens via the action of kallikreins. Kinins bind to the preformed and widely distributed B₂ receptor (B₂R) and to the inducible B₁ receptor (B₁R). B₂Rs and B₁Rs are related G protein coupled receptors that possess natural agonist ligands of nanomolar affinity (BK and Lys BK for B₂Rs, Lys-des-Arg⁹-BK for B₁R). Decades of structure-activity exploration have resulted in the production of peptide analogs that are antagonists, one of which is clinically used (the B₂R antagonist icatibant), and also non-peptide ligands for both receptor subtypes. The modification of kinin receptor ligands has made them resistant to extracellular or endosomal peptidases and/or produced bifunctional ligands, defined as agonist or antagonist peptide ligands conjugated with a chemical fluorophore (emitting in the whole spectrum, from the infrared to the ultraviolet), a drug-like moiety, an epitope, an isotope chelator/carrier, a cleavable sequence (thus forming a pro-drug) and even a fused protein. Dual molecular targets for specific modified peptides may be a source of side effects or of medically exploitable benefits. Biotechnological protein ligands for either receptor subtype have been produced: they are enhanced green fluorescent protein or the engineered peroxidase APEX2 fused to an agonist kinin sequence at their C-terminal terminus. Antibodies endowed with pharmacological actions (agonist, antagonist) at B₂R have been reported, though not monoclonal antibodies. These findings define classes of alternative ligands of the kinin receptor of potential therapeutic and diagnostic value.

PGE2/EP3/SRC signaling induces EGFR nuclear translocation and growth through EGFR ligands release in lung adenocarcinoma cells

Prostaglandin E₂ (PGE₂) interacts with tyrosine kinases receptor signaling in both tumor and stromal cells supporting tumor progression. Here we demonstrate that in non-small cell lung carcinoma (NSCLC) cells, A549 and GLC82, PGE₂ promotes nuclear translocation of epidermal growth factor receptor (nEGFR), affects gene expression and induces cell growth. Indeed, cyclin D1, COX-2, iNOS and c-Myc mRNA levels are upregulated following PGE₂ treatment. The nuclear localization sequence (NLS) of EGFR as well as its tyrosine kinase activity are required for the effect of PGE₂ on nEGFR and downstream signaling activities. PGE₂ binds its bona fide receptor EP3 which by activating SRC family kinases, induces ADAMs activation which, in turn, releases EGFR-ligands from the cell membrane and promotes nEGFR. Amphiregulin (AREG) and Epiregulin (EREG) appear to be involved in nEGFR promoted by the PGE₂/EP3-SRC axis. Pharmacological inhibition or silencing of the PGE₂/EP3/SRC-ADAMs signaling axis or EGFR ligands i.e. AREG and EREG expression abolishes nEGFR induced by PGE₂. In conclusion, PGE₂ induces NSCLC cell proliferation by EP3 receptor, SRC-ADAMs activation, EGFR ligands shedding and finally, phosphorylation and nEGFR. Since nuclear EGFR is a hallmark of cancer aggressiveness, our findings reveal a novel mechanism for the contribution of PGE₂ to tumor progression.

Bradykinin Promotes Cell Proliferation, Migration, Invasion, and Tumor Growth of Gastric Cancer Through ERK Signaling Pathway

Bradykinin (BK) has been reported to be involved in the progression of diverse types of cancer. In the present study, we investigated the possible role of BK in cell proliferation, migration, invasion, and tumor growth of gastric cancer (GC). Cell proliferation was evaluated by MTT assays. Cell migration and invasion were assessed by Transwell assays. Tumor growth of nude mice was detected by establishing subcutaneous xenograft tumor model. Silencing of bradykinin B1 receptor (B1R) and the bradykinin B2 receptor (B2R) was performed by transfecting cells with si-B1R and si-B2R, respectively. The protein expression levels of phospho-ERK1/2 (p-ERK1/2), matrix metalloproteinase (MMP)-2, MMP-9, and E-Cadherin were examined by Western blot. Data revealed that BK promoted cell proliferation, migration, invasion, and the in vivo tumor growth of GC cells SGC-7901 and HGC-27. Furthermore, BK elevated the protein levels of p-ERK1/2, MMP-2, and MMP-9, but reduced E-Cadherin. In addition, by repressing B2R using si-B2R or inhibiting ERK signaling pathway using PD98059, BK-mediated promotion of cell proliferation, migration, and invasion and upregulation of p-ERK1/2, MMP-2/9, as well as downregulation of E-Cadherin were attenuated. Taken together, the present study demonstrated that BK promoted cell proliferation, migration, invasion, and tumor growth by binding to B2R via ERK signaling pathway. Our findings may provide promising options for the further treatment of GC. J. Cell. Biochem. 118: 4444-4453, 2017. © 2017 Wiley Periodicals, Inc.

Randomized, placebo-controlled window trial of EGFR, Src, or combined blockade in head and neck cancer

BACKGROUND. EGFR and Src family kinases are upregulated in head and neck squamous cell carcinoma (HNSCC). EGFR interacts with Src to activate STAT3 signaling, and dual EGFR-Src targeting is synergistic in HNSCC preclinical models. pSrc overexpression predicted resistance to the EGFR inhibitor, erlotinib, in a prior window trial. We conducted a 4-arm window trial to identify biomarkers associated with response to EGFR and/or Src inhibition. METHODS. Patients with operable stage II-IVa HNSCC were randomized to 7-21 days of neoadjuvant erlotinib, the Src inhibitor dasatinib, the combination of both, or placebo. Paired tumor specimens were collected before and after treatment. Pharmacodynamic expression of EGFR and Src pathway components was evaluated by IHC of tissue microarrays and reverse-phase protein array of tissue lysates. Candidate biomarkers were assessed for correlation with change in tumor size. RESULTS. From April 2009 to December 2012, 58 patients were randomized and 55 were treated. There was a significant decrease in tumor size in both erlotinib arms (P = 0.0014); however, no effect was seen with dasatinib alone (P = 0.24). High baseline pMAPK expression was associated with response to erlotinib (P = 0.03). High baseline pSTAT3 was associated with resistance to dasatinib (P = 0.099). CONCLUSIONS. Brief exposure to erlotinib significantly decreased tumor size in operable HNSCC, with no additive effect from dasatinib. Baseline pMAPK expression warrants further study as a response biomarker for anti-EGFR therapy. Basal expression of pSTAT3 may be independent of Src, explain therapeutic resistance, and preclude development of dasatinib in biomarker-unselected cohorts. TRIAL REGISTRATION. NCT00779389. FUNDING. National Cancer Institute, American Cancer Society, Pennsylvania Department of Health, V Foundation for Cancer Research, Bristol-Myers Squibb, and Astellas Pharma.

Therapeutic implication of mTORC2 in oral squamous cell carcinoma

The aim of the present study was to clarify the association of mTORC2 expression with the cancer progression and the anti-tumor effects of Torin-1 alone and combined treatment with Cetuximab in OSCC cells. The expressions of Rictor and SGK1 were immunohistochemically evaluated and the relationships between the expressions of molecular markers and clinicopathological factors were determined. Moreover, OSCC cells were treated with Torin-1, Cetuximab or combined agents, and anti-tumor effects of OSCC cells were examined in vitro and in vivo. Rictor and SGK1 expressions were significantly associated with tumor stage and pattern of invasion in OSCC sections (P<0.05 and P<0.01, respectively). Treatment of OSCC cell lines with Torin-1 resulted in dose and time-dependent inhibition of proliferation with decrease of phosphorylation on downstream molecules. Combined treatment with Torin-1 and Cetuximab resulted in enhanced anti-tumor effects in vitro compared with either agent alone. Furthermore, treatment of mice bearing OSCC xenografts with Torin-1 and Cetuximab also demonstrated a remarked growth inhibition of tumor volumes. The results suggested that new regimens of systemic therapy combined with Cetuximab and Torin-1 may be useful for very advanced OSCC patients.

GPR171 expression enhances proliferation and metastasis of lung cancer cells

G protein-coupled receptors (GPCRs) are among the most significant therapeutic targets and some of them promote the growth and metastasis of cancer. Here, we show that an increase in the levels of GPR171 is crucial for lung cancer tumor progression in vitro and in vivo. Immunostaining of clinical samples indicated that GPR171 was overexpressed in 46.8% of lung carcinoma tissues. Depletion of GPR171 with an anti-GPR171 antibody decreased proliferation of lung carcinoma cells and attenuated tumor progression in a mouse xenograft model. Knockdown of GPR171 also inhibited migration and invasion of the lung cancer cell lines. Notably, inhibition of GPR171 synergistically enhanced the tumoricidal activity of an epidermal growth factor receptor (EGFR) inhibitor in lung cancer cells. These results indicate that GPR171 blockade is a promising antineoplastic strategy and provide a preclinical rationale for combined inhibition of GPR171 and EGFR.

Regulation of cell migration via the EGFR signaling pathway in oral squamous cell carcinoma cells

Cell migration potency is essential in cancer metastasis and is often regulated by extracellular stimuli. Oral squamous cell carcinoma cell lines include those that are sensitive, as well as resistant, to the effects of the epidermal growth factor receptor (EGFR) inhibitor cetuximab on cell migration. In the present study, the molecular differences in the EGFR response to cell migration between the SAS cetuximab-sensitive and HSC4 cetuximab-resistant cell lines was examined. Treatment with the EGFR inhibitors AG1478 and cetuximab reduced the migration potency of SAS cells, but not HSC4 cells. The migration of the two cell lines was inhibited under serum-free culture conditions, and the addition of EGF to the serum-free medium promoted the migration of SAS cells, but not HSC4 cells. In addition, SAS cell migration was reduced by the mitogen-activated protein kinase kinase and protein kinase B (Akt) inhibitors PD98059 and MK2206, whereas HSC4 cell migration was only inhibited by MK2206. EGF induced an increase in extracellular signal-regulated kinase phosphorylation levels in HSC4 cells, and stimulated Akt phosphorylation levels in SAS cells. Furthermore, the staining of actin filaments with phalloidin was significantly increased by the inhibition of EGFR in SAS cells, but was not observed as altered in HSC4 cells. Conversely, the addition of EGF to the culture medium decreased the accumulation of actin filaments in SAS cells. The results suggest that the EGF-EGFR signaling pathway has an important role in SAS cell migration via the modulation of actin dynamics, and that HSC4 cell migration is regulated by a serum component other than EGFR.

Compounds From Celastraceae Targeting Cancer Pathways and Their Potential Application in Head and Neck Squamous Cell Carcinoma: A Review

Squamous cell carcinoma of the head and neck is one of the most common cancer types worldwide. It initiates on the epithelial lining of the upper aerodigestive tract, at most instances as a consequence of tobacco and alcohol consumption. Treatment options based on conventional therapies or targeted therapies under development have limited efficacy due to multiple genetic alterations typically found in this cancer type. Natural products derived from plants often possess biological activities that may be valuable in the development of new therapeutic agents for cancer treatment. Several genera from the family Celastraceae have been studied in this context. This review reports studies on chemical constituents isolated from species from the Celastraceae family targeting cancer mechanisms studied to date. These results are then correlated with molecular characteristics of head and neck squamous cell carcinoma in an attempt to identify constituents with potential application in the treatment of this complex disease at the molecular level.

The double trouble of metabolic diseases: the diabetes-cancer link

The recent recognition of the clinical association between type 2 diabetes (T2D) and several types of human cancer has been further highlighted by reports of antidiabetic drugs treating or promoting cancer. At the cellular level, a plethora of molecules operating within distinct signaling pathways suggests cross-talk between the multiple pathways at the interface of the diabetes–cancer link. Additionally, a growing body of emerging evidence implicates homeostatic pathways that may become imbalanced during the pathogenesis of T2D or cancer or that become chronically deregulated by prolonged drug administration, leading to the development of cancer in diabetes and vice versa. This notion underscores the importance of combining clinical and basic mechanistic studies not only to unravel mechanisms of disease development but also to understand mechanisms of drug action. In turn, this may help the development of personalized strategies in which drug doses and administration durations are tailored to individual cases at different stages of the disease progression to achieve more efficacious treatments that undermine the diabetes–cancer association.

G Protein-Coupled Receptor Signaling in Stem Cells and Cancer

G protein-coupled receptors (GPCRs) are a large superfamily of cell-surface signaling proteins that bind extracellular ligands and transduce signals into cells via heterotrimeric G proteins. GPCRs are highly tractable drug targets. Aberrant expression of GPCRs and G proteins has been observed in various cancers and their importance in cancer stem cells has begun to be appreciated. We have recently reported essential roles for G protein-coupled receptor 84 (GPR84) and G protein subunit Gαq in the maintenance of cancer stem cells in acute myeloid leukemia. This review will discuss how GPCRs and G proteins regulate stem cells with a focus on cancer stem cells, as well as their implications for the development of novel targeted cancer therapies.

Epidermal Growth Factor Receptor Signaling to the Mitogen Activated Protein Kinase Pathway Bypasses Ras in Pancreatic Cancer Cells

OBJECTIVE

Epidermal growth factor (EGF) receptor (EGFR/HER1) is overexpressed in human pancreatic cancers. However, anti-EGFR therapy does not exhibit significant therapeutic activity with oncogenic K-ras mutation. We sought to assess the signaling relationship between EGFR and mutant K-ras, which is commonly detected in pancreatic cancer.

METHODS

Pancreatic cancer cells harboring mutated K-ras were treated with EGF to assess signaling from EGFR to mitogen-activated protein kinase (MAPK) pathway. The role of Ras family of proteins in transducing EGFR signals was assessed using short interfering RNA. Other components of MAPK and PI3K (phosphoinositide 3-kinase) pathways were examined for their roles in EGFR signaling.

RESULTS

First, EGF signaling in pancreatic cancer cells occurs selectively through HER1. Second, knockdown of all Ras isoforms failed to block EGF-mediated phosphorylation of extracellular signal-regulated kinase (ERK). Inhibition of Raf was observed to partially abrogate ERK phosphorylation, whereas MEK inhibition resulted in complete attenuation of EGF-mediated ERK phosphorylation. Finally, inhibition of phosphoinositide 3-kinase/AKT and CDC42/PAK pathways did not block EGFR signaling.

CONCLUSIONS

Our study results demonstrate that EGFR-mediated signaling in mutant K-ras pancreatic cancer cells does not follow canonical MAPK signaling. Our novel findings suggest the existence of alternate signaling pathways to downstream MAPK in the presence of mutant K-ras.

Transactivation of Epidermal Growth Factor Receptor by G Protein-Coupled Receptors: Recent Progress, Challenges and Future Research

Both G protein-coupled receptors (GPCRs) and receptor-tyrosine kinases (RTKs) regulate large signaling networks, control multiple cell functions and are implicated in many diseases including various cancers. Both of them are also the top therapeutic targets for disease treatment. The discovery of the cross-talk between GPCRs and RTKs connects these two vast signaling networks and complicates the already complicated signaling networks that regulate cell signaling and function. In this review, we focus on the transactivation of epidermal growth factor receptor (EGFR), a subfamily of RTKs, by GPCRs. Since the first report of EGFR transactivation by GPCR, significant progress has been made including the elucidation of the mechanisms underlying the transactivation. Here, we first provide a basic picture for GPCR, EGFR and EGFR transactivation by GPCR. We then discuss the progress made in the last five years and finally provided our view of the future challenge and future researches needed to overcome these challenges.

Insights into bombesin receptors and ligands: Highlighting recent advances

This following article is written for Prof. Abba Kastin's Festschrift, to add to the tribute to his important role in the advancement of the role of peptides in physiological, as well as pathophysiological processes. There have been many advances during the 35 years of his prominent role in the Peptide field, not only as editor of the journal Peptides, but also as a scientific investigator and editor of two volumes of the Handbook of Biological Active Peptides [146,147]. Similar to the advances with many different peptides, during this 35 year period, there have been much progress made in the understanding of the pharmacology, cell biology and the role of (bombesin) Bn receptors and their ligands in various disease states, since the original isolation of bombesin from skin of the European frog Bombina bombina in 1970 [76]. This paper will briefly review some of these advances over the time period of Prof. Kastin 35 years in the peptide field concentrating on the advances since 2007 when many of the results from earlier studies were summarized [128,129]. It is appropriate to do this because there have been 280 articles published in Peptides during this time on bombesin-related peptides and it accounts for almost 5% of all publications. Furthermore, 22 Bn publications we have been involved in have been published in either Peptides [14,39,55,58,81,92,93,119,152,216,225,226,231,280,302,309,355,361,362] or in Prof. Kastin's Handbook of Biological Active Peptides [137,138,331].

Mechanisms of Invasion in Head and Neck Cancer

CONTEXT

The highly invasive properties demonstrated by head and neck squamous cell carcinoma (HNSCC) are often associated with locoregional recurrence and lymph node metastasis in patients and is a key factor leading to an expected 5-year survival rate of approximately 50% for patients with advanced disease. It is important to understand the features and mediators of HNSCC invasion so that new treatment approaches can be developed.

OBJECTIVES

To provide an overview of the characteristics, mediators, and mechanisms of HNSCC invasion.

DATA SOURCES

A literature review of peer-reviewed articles in PubMed on HNSCC invasion.

CONCLUSIONS

Histologic features of HNSCC tumors can help predict prognosis and influence clinical treatment decisions. Cell surface receptors, signaling pathways, proteases, invadopodia function, epithelial-mesenchymal transition, microRNAs, and tumor microenvironment are all involved in the regulation of the invasive behavior of HNSCC cells. Identifying effective HNSCC invasion inhibitors has the potential to improve outcomes for patients by reducing the rate of spread and increasing responsiveness to chemoradiation.

Molecular mechanisms of ethanol-associated oro-esophageal squamous cell carcinoma

Alcohol drinking is a major etiological factor of oro-esophageal squamous cell carcinoma (OESCC). Both local and systemic effects of ethanol may promote carcinogenesis, especially among chronic alcoholics. However, molecular mechanisms of ethanol-associated OESCC are still not well understood. In this review, we summarize current understandings and propose three mechanisms of ethanol-associated OESCC: (1) Disturbance of systemic metabolism of nutrients: during ethanol metabolism in the liver, systemic metabolism of retinoids, zinc, iron and methyl groups is altered. These nutrients are known to be associated with the development of OESCC. (2) Disturbance of redox metabolism in squamous epithelial cells: when ethanol is metabolized in oro-esophageal squamous epithelial cells, reactive oxygen species are generated and produce oxidative damage. Meanwhile, ethanol may also disturb fatty-acid metabolism in these cells. (3) Disturbance of signaling pathways in squamous epithelial cells: due to its physico-chemical properties, ethanol changes cell membrane fluidity and shape, and may thus impact multiple signaling pathways. Advanced molecular techniques in genomics, epigenomics, metabolomics and microbiomics will help us elucidate how ethanol promotes OESCC.

RNA interference-mediated silencing of G protein-coupled receptor 137 inhibits human gastric cancer cell growth

G protein-coupled receptor 137 (GPR137) is an integral membrane protein, which belongs to the GPR137 family of cell surface mediators of signal transduction. GPF137 was recently identified; however, its role in human disease onset has remained to be elucidated. GPR137 is highly expressed in multiple human gastric cancer cell lines. A GPR137 short hairpin RNA (shRNA)-expressing vector was transfected into AGS and MGC80-3 gastric cancer cells, and the subsequent depletion of GPR137 resulted in a significant reduction in cell proliferation and colony formation, as determined by MTT and colony formation assays. In addition, cell cycle analysis indicated that GPR137 knockdown arrested MGC80-3 cells in G₂/M phase. To the best of our knowledge, the present study was the first to investigate the role of GPR137 in gastric tumorigenesis and revealed that knockdown of GPR137 by lentivirus-mediated shRNA transfection inhibited the growth of gastric cancer cells in vitro. These results indicated that GPR137 may present a novel target for the development of pharmacological therapeutics for human gastric cancer.

G protein-coupled receptors as oncogenic signals in glioma: emerging therapeutic avenues

Gliomas are the most common malignant intracranial tumors. Newly developed targeted therapies for these cancers aim to inhibit oncogenic signals, many of which emanate from receptor tyrosine kinases, including the epidermal growth factor receptor (EGFR) and the vascular endothelial growth factor receptor (VEGFR). Unfortunately, the first-generation treatments targeting these oncogenic signals provide little survival benefit in both mouse xenograft models and human patients. The search for new treatment options has uncovered several G protein-coupled receptor (GPCR) candidates and generated a growing interest in this class of proteins as alternative therapeutic targets for the treatment of various cancers, including glioblastoma multiforme (GBM). GPCRs constitute a large family of membrane receptors that influence oncogenic pathways through canonical and non-canonical signaling. Accordingly, evidence indicates that GPCRs display a unique ability to crosstalk with receptor tyrosine kinases, making them important molecular components controlling tumorigenesis. This review summarizes the current research on GPCR functionality in gliomas and explores the potential of modulating these receptors to treat this devastating disease.

A low level of GPR37 is associated with human hepatocellular carcinoma progression and poor patient survival

GPR37, also known as parkin-associated endothelin-like receptor (Pael-R), is an orphan G protein-coupled receptor (GPCR). It has been reported that GPCRs play vital roles in the development and progression of cancer. To investigate the potential roles of GPR37 in hepatocellular carcinoma (HCC), expression of GPR37 was examined in human HCC samples. Immunohistochemistry and Western blot analyses were performed for GPR37 in 57 hepatocellular carcinoma samples. GPR37 expression was low in hepatocellular carcinoma as compared with the adjacent non-tumorous tissues. Clinicopathological analysis showed that GPR37 expression was significantly correlated with histological grade and the level of alpha fetal protein (AFP) (P = 0.000 and 0.002, respectively). The Kaplan-Meier survival curves revealed that decreasing GPR37 expression was associated with poor prognosis in HCC patients, while in vitro, following the release from serum starvation of HuH7 HCC cell, the expression of GPR37 was downregulated. In addition, the transient GPR37 knockdown by siRNA in HuH7 cells significantly decreased the apoptosis of hepatoma cells with activation of the phosphatidylinositol 3-kinase-Akt signaling pathway. Our data suggest that GPR37 may play an important role in the pathogenesis of hepatocellular carcinoma by affecting the proliferation of H CC cells, and it could be a novel potential molecular therapy target for HCC.

Targeting the sheddase activity of ADAM17 by an anti-ADAM17 antibody D1(A12) inhibits head and neck squamous cell carcinoma cell proliferation and motility via blockage of bradykinin induced HERs transactivation

A disintegrin and metalloproteinase 17 (ADAM17) regulates key cellular processes including proliferation and migration through the shedding of a diverse array of substrates such as epidermal growth factor receptor (EGFR) ligands. ADAM17 is implicated in the pathogenesis of many diseases including rheumatoid arthritis and cancers such as head and neck squamous cell carcinoma (HNSCC). As a central mediator of cellular events, overexpressed EGFR is a validated molecular target in HNSCC. However, EGFR inhibition constantly leads to tumour resistance. One possible mechanism of resistance is the activation of alternative EGFR family receptors and downstream pathways via the release of their ligands. Here, we report that treating human HNSCC cells in vitro with a human anti-ADAM17 inhibitory antibody, D1(A12), suppresses proliferation and motility in the absence or presence of the EGFR tyrosine kinase inhibitor (TKI) gefitinib. Treatment with D1(A12) decreases both the endogenous and the bradykinin (BK)-stimulated shedding of HER ligands, accompanied by a reduction in the phosphorylation of HER receptors and downstream signalling pathways including STAT3, AKT and ERK. Knockdown of ADAM17, but not ADAM10, also suppresses HNSCC cell proliferation and migration. Furthermore, we show that heregulin (HRG) and heparin-binding epidermal growth factor like growth factor (HB-EGF) predominantly participate in proliferation and migration, respectively. Taken together, these results demonstrate that D1(A12)-mediated inhibition of cell proliferation, motility, phosphorylation of HER receptors and downstream signalling is achieved via reduced shedding of ADAM17 ligands. These findings underscore the importance of ADAM17 and suggest that D1(A12) might be an effective targeted agent for treating EGFR TKI-resistant HNSCC.

Erlotinib, erlotinib-sulindac versus placebo: a randomized, double-blind, placebo-controlled window trial in operable head and neck cancer

PURPOSE

The EGF receptor (EGFR) and COX2 pathways are upregulated in head and neck squamous cell carcinoma (HNSCC). Preclinical models indicate synergistic antitumor activity from dual blockade. We conducted a randomized, double-blind, placebo-controlled window trial of erlotinib, an EGFR inhibitor; erlotinib plus sulindac, a nonselective COX inhibitor; versus placebo.

EXPERIMENTAL DESIGN

Patients with untreated, operable stage II-IVb HNSCC were randomized 5:5:3 to erlotinib, erlotinib-sulindac, or placebo. Tumor specimens were collected before and after seven to 14 days of treatment. The primary endpoint was change in Ki67 proliferation index. We hypothesized an ordering effect in Ki67 reduction: erlotinib-sulindac > erlotinib > placebo. We evaluated tissue microarrays by immunohistochemistry for pharmacodynamic modulation of EGFR and COX2 signaling intermediates.

RESULTS

From 2005-2009, 47 patients were randomized for the target 39 evaluable patients. Thirty-four tumor pairs were of sufficient quality to assess biomarker modulation. Ki67 was significantly decreased by erlotinib or erlotinib-sulindac (omnibus comparison, two-sided Kruskal-Wallis, P = 0.04). Wilcoxon pairwise contrasts confirmed greater Ki67 effect in both erlotinib groups (erlotinib-sulindac vs. placebo, P = 0.043; erlotinib vs. placebo, P = 0.027). There was a significant trend in ordering of Ki67 reduction: erlotinib-sulindac > erlotinib > placebo (two-sided exact Jonckheere-Terpstra, P = 0.0185). Low baseline pSrc correlated with greater Ki67 reduction (R(2) = 0.312, P = 0.024).

CONCLUSIONS

Brief treatment with erlotinib significantly decreased proliferation in HNSCC, with additive effect from sulindac. Efficacy studies of dual EGFR-COX inhibition are justified. pSrc is a potential resistance biomarker for anti-EGFR therapy, and warrants investigation as a molecular target.

The role of kinin receptors in cancer and therapeutic opportunities

Kinins are generated within inflammatory tissue microenvironments, where they exert diverse functions, including cell proliferation, leukocyte activation, cell migration, endothelial cell activation and nociception. These pleiotropic functions depend on signaling through two cross talking receptors, the constitutively expressed kinin receptor 2 (B2R) and the inducible kinin receptor 1 (B1R). We have reviewed evidence, which supports the concept that kinin receptors, especially kinin receptor 1, are promising targets for cancer therapy, since (1) many tumor cells express aberrantly high levels of these receptors; (2) some cancers produce kinins and use them as autocrine factors to stimulate their growth; (3) activation of kinin receptors leads to activation of macrophages, dendritic cells and other cells from the tumor microenvironment; (4) kinins have pro-angiogenic properties; (5) kinin receptors have been implicated in cancer migration, invasion and metastasis; and (6) selective antagonists for either B1R or B2R have shown anti-proliferative, anti-inflammatory, anti-angiogenic and anti-migratory properties. The multiple cross talks between kinin receptors and renin-angiotensin system (RAS) as well as its implications for targeting KKS or RAS for the treatment of malignancies are also discussed. It is expected that B1R antagonists would interfere less with housekeeping functions and therefore would be attractive compounds to treat selected types of cancer. Reliable clinical studies are needed to establish the translatability of these data to human settings and the usefulness of kinin receptor antagonists.

Epithelial wounds induce differential phosphorylation changes in response to purinergic and EGF receptor activation

Protein phosphorylation is a dynamic post-translational modification. Mass spectrometry-based quantitation was performed to determine the phosphoproteome profile of epithelial cells in response to injury, nucleotide, or epidermal growth factor. Phosphotyrosine enrichment used immunoprecipitation and immobilized metal affinity chromatography. Nucleotides released after scratch wounding activate purinergic receptors, leading to a distinct phosphorylation profile on epidermal growth factor receptor (EGFR) compared with its natural ligand. ATP induced a 2- to 15-fold phosphorylation increase over control on EGFR Y974, Y1086, and Y1148, with minimal phosphorylation intensity on EGFR Y1173 compared with the level measured in response to epidermal growth factor. Differential phosphorylation induced by epidermal growth factor or ATP was site specific on Src, Shc, phospholipase Cγ, protein kinase C, focal adhesion kinase, paxillin, and mitogen-activated protein kinases 1, 12, and 13. After wounding, the P2Y2 receptor mRNA expression increased, and after knockdown, migration and Ca(2+) mobilization were impaired. To examine phosphorylation mediated by P2Y2, cells were cultured in media containing stable isotope-labeled amino acids, the receptor was knocked down, and the cells were stimulated. Mass spectrometry-based comparison of the phosphorylation profiles of control versus transfected cells revealed a 50-fold decrease in phosphorylation of EGFR Y974 and 1086, with no decrease in Y1173 phosphorylation. A similarfold decrease in Src Y421 and Y446 and paxillin Y118 was detected, indicating the far-reaching importance of the P2Y2 receptor in mediating migration.

KISS1R induces invasiveness of estrogen receptor-negative human mammary epithelial and breast cancer cells

Kisspeptins (KPs), peptide products of the KISS1 metastasis-suppressor gene, are endogenous ligands for a G protein-coupled receptor (KISS1R). KISS1 acts as a metastasis suppressor in numerous human cancers. However, recent studies have demonstrated that an increase in KISS1 and KISS1R expression in patient breast tumors correlates with higher tumor grade and metastatic potential. We have shown that KP-10 stimulates invasion of estrogen receptor α (ERα)-negative MDA-MB-231 breast cancer cells via transactivation of the epidermal growth factor receptor (EGFR). Here, we report that either KP-10 treatment of ERα-negative nonmalignant mammary epithelial MCF10A cells or expression of KISS1R in MCF10A cells induced a mesenchymal phenotype and stimulated invasiveness. Similarly, exogenous expression of KISS1R in ERα-negative SKBR3 breast cancer cells was sufficient to trigger invasion and induced extravasation in vivo. In contrast, KP-10 failed to transactivate EGFR or stimulate invasiveness in the ERα-positive MCF7 and T47D breast cancer cells. This suggested that ERα negatively regulates KISS1R-dependent breast cancer cell migration, invasion, and EGFR transactivation. In support of this, we found that these KP-10-induced effects were ablated upon exogenous expression of ERα in the MDA-MB-231 cells, by down-regulating KISS1R expression. Lastly, we have identified IQGAP1, an actin cytoskeletal binding protein as a novel binding partner of KISS1R, and have shown that KISS1R regulates EGFR transactivation in breast cancer cells in an IQGAP1-dependent manner. Overall, our data strongly suggest that the ERα status of mammary cells dictates whether KISS1R may be a novel clinical target for treating breast cancer metastasis.

Targeting TORC1/2 enhances sensitivity to EGFR inhibitors in head and neck cancer preclinical models

Head and neck squamous cell carcinoma (HNSCC) is characterized by overexpression of the epidermal growth factor receptor (EGFR) where treatments targeting EGFR have met with limited clinical success. Elucidation of the key downstream-pathways that remain activated in the setting of EGFR blockade may reveal new therapeutic targets. The present study was undertaken to test the hypothesis that inhibition of the mammalian target of rapamycin (mTOR) complex would enhance the effects of EGFR blockade in HNSCC preclinical models. Treatment of HNSCC cell lines with the newly developed TORC1/TORC2 inhibitor OSI-027/ASP4876 resulted in dose-dependent inhibition of proliferation with abrogation of phosphorylation of known downstream targets including phospho-AKT (Ser473), phospho-4E-BP1, phospho-p70s6K, and phospho-PRAS40. Furthermore, combined treatment with OSI-027 and erlotinib resulted in enhanced biochemical effects and synergistic growth inhibition in vitro. Treatment of mice bearing HNSCC xenografts with a combination of the Food and Drug Administration (FDA)-approved EGFR inhibitor cetuximab and OSI-027 demonstrated a significant reduction of tumor volumes compared with either treatment alone. These findings suggest that TORC1/TORC2 inhibition in conjunction with EGFR blockade represents a plausible therapeutic strategy for HNSCC.

Ripples in the pond--using a systems approach to decipher the cellular functions of membrane microdomains

Membrane microdomains such as lipid rafts and caveolae regulate a myriad of cellular functions including cell signalling, protein trafficking, cell viability, and cell movement. They have been implicated in diseases such as cancer, diabetes and Alzheimer's disease, highlighting the essential role they play in cell processes. Despite much research and debate on the size, composition and dynamics of membrane microdomains, the molecular mechanism(s) of their action remain poorly understood. Most studies have dealt solely with the content and properties of the membrane microdomain as an entity in itself. However, recent work shows that membrane microdomain disruption has wide ranging effects on other subcellular compartments, and the cell as a whole. Hence we propose that a systems approach incorporating many cellular attributes such as subcellular localisation is required in order to understand the global impact of microdomains on cell function. Although analysis of sub-proteome changes already provides additional insight, we further propose biological network analysis of functional proteomics data to capture effects at the systems level. In this review, we highlight the use of protein-protein interactions networks and mixed networks to portray and visualize the relationships between proteins within and between subcellular fractions. Such a systems analysis will be required to improve our understanding of the full cellular function of membrane microdomains.