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

Molecular phenotype predicts sensitivity of squamous cell carcinoma of the head and neck to epidermal growth factor receptor inhibition

Despite nearly universal expression of the wild-type epidermal growth factor receptor (EGFR) and reproducible activity of EGFR inhibitors in patients with squamous cell carcinoma of the head and neck (SCCHN), the majority of patients will not have objective responses. The mechanisms of this intrinsic resistance are not well established. We hypothesized that sensitivity to EGFR inhibitors can be predicted based on the inhibitors' effects on downstream signaling. Cell viability assays were used to assess sensitivity to the EGFR inhibitor gefitinib (ZD1839) in 8 SCCHN cell lines. Fluorescence in-situ hybridization showed the two most sensitive lines to be highly gene-amplified for EGFR. Western blotting confirmed that phosphoEGFR was inhibited at low concentrations of gefitinib in all lines tested. Phosphorylation of downstream signaling protein AKT was inhibited in sensitive lines while inhibition of phosphoERK displayed no relationship to gefitinib efficacy. Phosphatase and tensin homolog (PTEN) expression was evident in all cell lines. Activating PIK3CA mutations were found in two resistant cell lines where pAKT was not inhibited by gefitinib. In resistant cell lines harboring PIK3CA mutations, a PI3K inhibitor, LY294002, or AKT siRNA reduced cell viability with an additive effect demonstrated in combination with gefitinib. Additionally, LY294002 alone and in combination with gefitinib, was effective at treating PIK3CA mutated tumors xenografted into nude mice. Taken together this suggests that constitutively active AKT is a mechanism of intrinsic gefitinib resistance in SCCHN. This resistance can be overcome through targeting of the PI3K/AKT pathway in combination with EGFR inhibition.

The bradykinin B(2) receptor induces multiple cellular responses leading to the proliferation of human renal carcinoma cell lines

Background

The vasoactive peptide bradykinin (BK) acts as a potent growth factor for normal kidney cells, but there have been few studies on the role of BK in renal cell carcinomas.

Purpose

In this study, we tested the hypothesis that BK also acts as a mitogen in kidney carcinomas, and explored the effects of BK in human renal carcinoma A498 cells.

Methods

The presence of mRNAs for BK B₁ and BK B₂ receptors in A498 cells was demonstrated by reverse transcription–polymerase chain reaction. To study BK signaling pathways, we employed fluorescent measurements of intracellular Ca²⁺, measured changes in extracellular pH as a reflection of Na⁺/H⁺ exchange (NHE) with a Cytosensor microphysiometer, and assessed extracellular signal-regulated kinase (ERK) activation by Western blotting.

Results

Exposure to 100 nM of BK resulted in the rapid elevation of intracellular Ca²⁺, caused a ≥30% increase in NHE activity, and a ≥300% increase in ERK phosphorylation. All BK signals were blocked by HOE140, a BK B₂ receptor antagonist, but not by a B₁ receptor antagonist. Inhibitor studies suggest that BK-induced ERK activation requires phospholipase C and protein kinase C activities, and is Ca²⁺/calmodulin-dependent. The amiloride analog 5-(N-methyl-N-isobutyl)-amiloride (MIA) blocked short-term NHE activation and inhibited ERK phosphorylation, suggesting that NHE is critical for ERK activation by BK. BK induced an approximately 40% increase in the proliferation of A498 cells as assessed by bromodeoxyuridine uptake. This effect was blocked by the ERK inhibitor PD98059, and was dependent on NHE activity.

Conclusion

We conclude that BK exerts mitogenic effects in A498 cells via the BK B₂ receptor activation of growth-associated NHE and ERK.

Serum biomarker modulation following molecular targeting of epidermal growth factor and cyclooxygenase pathways: a pilot randomized trial in head and neck cancer

OBJECTIVE

Targeting the epidermal growth factor receptor (EGFR) using the tyrosine kinase inhibitor (TKI) erlotinib has demonstrated activity in aerodigestive tract malignancies. Co-targeting of the G-protein-coupled receptor cyclooxygenase (COX) with EGFR inhibitors has shown promise in preclinical models and early phase clinical studies.

MATERIALS AND METHODS

We studied the modulation of serum proteins after neoadjuvant treatment with erlotinib with or without sulindac in head and neck cancer patients. In a prospective, randomized, double-blind clinical trial, paired serum samples were obtained before and after neoadjuvant treatment in three groups of patients (n = 23 total), who were randomized to receive 7-14 consecutive days of erlotinib alone, erlotinib plus sulindac, or placebo. Two separate multiplexed ELISA systems (SearchLight™ or Luminex™) were used to measure serum biomarkers. HGF and IL-6 levels were tested on both systems, and validated using single analyte ELISAs.

RESULTS

Several analytes were significantly altered (generally decreased) post-treatment, in patients who received erlotinib (with or without sulindac) as well as in the placebo groups. No single analyte was differentially altered across the three treatment groups using either multiplex platform. Single HGF ELISA suggested a nonspecific decrease in all patients.

CONCLUSION

These results demonstrate the importance of a placebo group when assessing changes in expression of serum biomarkers. While multiplex platforms can provide quantitative information on a large number of serum analytes, results should be cautiously compared across platforms due to their intrinsic features. Furthermore, the dynamic range of expression of a single analyte is constrained in multiplex versus standard ELISA.

Antitumor mechanisms of targeting the PDK1 pathway in head and neck cancer

G-protein-coupled receptors (GPCR) activate the epidermal growth factor receptor (EGFR) and mediate EGFR-independent signaling pathways to promote the growth of a variety of cancers, including head and neck squamous cell carcinoma (HNSCC). Identification of the common signaling mechanisms involved in GPCR-induced EGFR-dependent and EGFR-independent processes will facilitate the development of more therapeutic strategies. In this study, we hypothesized that phosphoinositide-dependent kinase 1 (PDK1) contributes to GPCR-EGFR cross-talk and signaling in the absence of EGFR and suggests that inhibition of the PDK1 pathway may be effective in the treatment of HNSCC. The contribution of PDK1 to the EGFR-dependent and EGFR-independent signaling in HNSCC was determined using RNA interference, a kinase-dead mutant, and pharmacologic inhibition. In vivo xenografts studies were also carried out to determine the efficacy of targeting PDK1 alone or in combination with the U.S. Food and Drug Administration-approved EGFR inhibitor cetuximab. PDK1 contributed to both GPCR-induced EGFR activation and cell growth. PDK1 also mediated activation of p70S6K in the absence of EGFR. Blockade of PDK1 with a small molecule inhibitor (AR-12) abrogated HNSCC growth, induced apoptosis, and enhanced the antiproliferative effects of EGFR tyrosine kinase inhibitors in vitro. HNSCC xenografts expressing kinase-dead PDK1 showed increased sensitivity to cetuximab compared with vector-transfected controls. Administration of AR-12 substantially decreased HNSCC tumor growth in vivo. These cumulative results show that PDK1 is a common signaling intermediate in GPCR-EGFR cross-talk and EGFR-independent signaling, and in which targeting the PDK1 pathway may represent a rational therapeutic strategy to enhance clinical responses to EGFR inhibitors in HNSCC.

The cytoplasmic rhodopsin-protein interface: potential for drug discovery

The mammalian dim-light photoreceptor rhodopsin is a prototypic G protein coupled receptor (GPCR), interacting with the G protein, transducin, rhodopsin kinase, and arrestin. All of these proteins interact with rhodopsin at its cytoplasmic surface. Structural and modeling studies have provided in-depth descriptions of the respective interfaces. Overlap and thus competition for binding surfaces is a major regulatory mechanism for signal processing. Recently, it was found that the same surface is also targeted by small molecules. These ligands can directly interfere with the binding and activation of the proteins of the signal transduction cascade, but they can also allosterically modulate the retinal ligand binding pocket. Because the pocket that is targeted contains residues that are highly conserved across Class A GPCRs, these findings imply that it may be possible to target multiple GPCRs with the same ligand(s). This is desirable for example in complex diseases such as cancer where multiple GPCRs participate in the disease networks.

In vivo invasion of head and neck squamous cell carcinoma cells does not require macrophages

Invasion of tumor cells into the local stroma is an important component in cancer progression. Here we report studies of the in vivo invasion of head and neck squamous cell carcinoma (HNSCC) cells in response to applied gradients of a growth factor [epidermal growth factor (EGF)] and a chemokine (CXCL12), using orthotopic floor-of-mouth models. Analysis of the invading cells indicated that >75% of them were tumor cells, about 15% macrophages, and <10% were unidentified. Surprisingly, although macrophages invaded together with tumor cells, macrophage contributions were not required for HNSCC invasion. CXCL12-induced in vivo invasion of HNSCC cells was also observed and found to occur via a unidirectional transactivation of epidermal growth factor receptor (EGFR) through CXCR4. Inhibition of tumor necrosis factor-α-converting enzyme using TNF-α protease inhibitor-2 selectively inhibited CXCL12-induced invasion but not EGF-induced invasion, consistent with CXCL12 activation of EGFR via release of EGFR ligands.

Lipid rafts: signaling and sorting platforms of cells and their roles in cancer

Lipid rafts are defined as microdomains within the lipid bilayer of cellular membranes that assemble subsets of transmembrane or glycosylphosphatidylinisotol-anchored proteins and lipids (cholesterol and sphingolipids) and experimentally resist extraction in cold detergent (detergent-resistant membrane). These highly dynamic raft domains are essential in signaling processes and also form sorting platforms for targeted protein traffic. Lipid rafts are involved in protein endocytosis that occurs via caveolae or flotillin-dependent pathways. Non-constitutive protein components of rafts fluctuate dramatically in cancer with impacts on cell proliferation, signaling, protein trafficking, adhesion and apoptosis. This article focuses on the identification of candidate cancer-associated biomarkers in carcinoma cells using state-of-the-art proteomics.

Targeting GPCR-mediated p70S6K activity may improve head and neck cancer response to cetuximab

PURPOSE

Epidermal growth factor receptor (EGFR) overexpression is correlated with decreased survival in head and neck cancer (HNC) where the addition of EGFR inhibition to standard chemoradiation approaches has improved treatment responses. However, the basis for the limited efficacy of EGFR inhibitors in HNC is incompletely understood. G-protein-coupled receptors (GPCR) have been shown to be overexpressed in HNC where GPCR activation induces HNC growth via both EGFR-dependent and -independent pathways. We hypothesized that targeting GPCR-induced EGFR-independent signaling would improve the efficacy of EGFR inhibition.

EXPERIMENTAL DESIGN

Using a high-throughput phosphoproteome array, we identified proteins that were phosphorylated in HNC cells where EGFR expression was downmodulated by RNA interference (RNAi) in the presence or absence of a GPCR ligand. We confirmed the findings from the array by Western blotting followed by in vitro and in vivo phenotypic assays.

RESULTS

p70S6K phosphorylation was elevated approximately sixfold in EGFR siRNA-transfected cells treated with a GPCR ligand. In addition to RNAi-mediated EGFR downmodulation, GPCR-mediated phosphorylation of p70S6K was modestly increased by EGFR inhibitor cetuximab approved by the Food and Drug Administration. Biopsies from cetuximab-treated patients also displayed increased phospho-p70S6K staining compared with pretreatment biopsies. HNC cells were growth inhibited by both genetic and pharmacologic p70S6K targeting strategies. Furthermore, p70S6K targeting in combination with cetuximab resulted in enhanced antitumor effects in both in vitro and in vivo HNC models.

CONCLUSIONS

These results indicate that increased phosphorylation of p70S6K in cetuximab-treated patients may be due to increased GPCR signaling. Therefore, the addition of p70S6K targeting strategies may improve treatment responses to EGFR inhibition.

The multiple roles of amphiregulin in human cancer

Amphiregulin (AREG) is one of the ligands of the epidermal growth factor receptor (EGFR). AREG plays a central role in mammary gland development and branching morphogenesis in organs and is expressed both in physiological and in cancerous tissues. Various studies have highlighted the functional role of AREG in several aspects of tumorigenesis, including self-sufficiency in generating growth signals, limitless replicative potential, tissue invasion and metastasis, angiogenesis, and resistance to apoptosis. The oncogenic activity of AREG has already been described in the most common human epithelial malignancies, such as lung, breast, colorectal, ovary and prostate carcinomas, as well as in some hematological and mesenchymal cancers. Furthermore, AREG is also involved in resistance to several cancer treatments. In this review, we describe the various roles of AREG in oncogenesis and discuss its translational potential, such as the development of anti-AREG treatments, based on AREG activity. In the last decade, independent groups have reported successful but sometimes contradictory results in relation to the potential of AREG to serve as a prognostic and/or predictive marker for oncology, especially with regard to anti-EGFR therapies. Thus, we also discuss the potential usefulness of using AREG as a therapeutic target and validated biomarker for predicting cancer outcomes or treatment efficacy.

Dual blockade of EGFR and c-Met abrogates redundant signaling and proliferation in head and neck carcinoma cells

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) is usually fatal, and innovative approaches targeting growth pathways are necessary to effectively treat this disease. Both the epidermal growth factor receptor (EGFR) and the hepatocyte growth factor (HGF)/c-Met pathways are overexpressed in HNSCC and initiate similar downstream signaling pathways. c-Met may act in consort with EGFR and/or be activated as a compensatory pathway in the presence of EGFR blockade.

EXPERIMENTAL DESIGN

Expression levels of EGFR and c-Met were determined by Western analysis in HNSCC cell lines and correlated with antitumor responses to inhibitors of these pathways.

RESULTS

Combining the c-Met inhibitor PF2341066 with the EGFR inhibitor gefitinib abrogated HNSCC cell proliferation, invasion, and wound healing significantly more than inhibition of each pathway alone in HNSCC cell lines. When both HGF and the EGFR ligand, TGF-α, were present in vitro, P-AKT and P-MAPK expression were maximally inhibited by targeting both EGFR and c-Met pathways, suggesting that c-Met or EGFR can compensate when phosphorylation of the other receptor is inhibited. We also showed that TGF-α can induce phosphorylation of c-Met over sixfold by 8 hours in the absence of HGF, supporting a ligand-independent mechanism. Combined targeting of c-Met and EGFR resulted in an enhanced inhibition of tumor volumes accompanied by a decreased number of proliferating cells and increased apoptosis compared with single agent treatment in vivo.

CONCLUSIONS

Together, these results suggest that dual blockade of c-Met and EGFR may be a promising clinical therapeutic strategy for treating HNSCC.

GIV/Girdin is a rheostat that fine-tunes growth factor signals during tumor progression

GIV/Girdin is a multidomain signaling molecule that enhances PI3K-Akt signals downstream of both G protein-coupled and growth factor receptors. We previously reported that GIV triggers cell migration via its C-terminal guanine-nucleotide exchange factor (GEF) motif that activates Gαi. Recently we discovered that GIV's C-terminus directly interacts with the epidermal growth factor receptor (EGFR), and when its GEF function is intact, a Gαi-GIV-EGFR signaling complex assembles. By coupling G proteins to growth factor receptors, GIV is uniquely poised to intercept the incoming receptor-initiated signals and modulate them via G protein intermediates. Subsequent work has revealed that expression of the highly specialized C-terminus of GIV undergoes a bipartite dysregulation during oncogenesis-full length GIV with an intact C-terminus is expressed at levels ~20-50-fold above normal in highly invasive cancer cells and metastatic tumors, but its C-terminus is truncated by alternative splicing in poorly invasive cancer cells and non-invasive tumors. The consequences of such dysregulation on graded signal transduction and cellular phenotypes in the normal epithelium and its implication during tumor progression are discussed herein. Based on the fact that GIV grades incoming signals initiated by ligand-activated receptors by linking them to cyclical activation of G proteins, we propose that GIV is a molecular rheostat for signal transduction.

Enforced expression of miR-101 inhibits prostate cancer cell growth by modulating the COX-2 pathway in vivo

It is commonly agreed that there is an association of chronic inflammation with tumorigenesis. COX-2, a key regulator of inflammation-producing prostaglandins, promotes cell proliferation and growth; thus, overexpression of COX-2 is often found in tumor tissues. Therefore, a better understanding of the regulatory mechanism(s) of COX-2 could lead to novel targeted cancer therapies. In this study, we investigated the mechanism of microRNA-101 (miR-101)-regulated COX-2 expression and the therapeutic potential of exogenous miR-101 for COX-2-associated cancer. A stably expressing exogenous miR-101 prostate cancer cell line (BPH1(CmiR101)) was generated by using lentiviral transduction as a tool for in vitro and in vivo studies. We found that miR-101 inhibited COX-2 posttranscriptional expression by directly binding to the 3'-untranslated region (3'-UTR) of COX-2 mRNA. The regulatory function of miR-101 was also confirmed by using antisense DNA. As a result, exogenous miR-101 is able to effectively suppress the growth of cultured prostate cancer cells and prostate tumor xenografts. The average tumor weight was significantly lower in the BPH1(CmiR101) group (0.22 g) than the BPH1(Cvec) group (0.46 g). Expression levels of the cell growth regulators, such as cyclin proteins, PCNA (proliferating cell nuclear antigen), EGFR (epidermal growth factor receptor), were also studied. In conclusion, COX-2 is a direct target in miR-101 regulation of posttranscription. Exogenous miR-101 suppresses the proliferation and growth of prostate cancer cells in vitro and in vivo. These data suggest that exogenous miR-101 may provide a new cancer therapy by directly inhibiting COX-2 expression.

HGF-independent potentiation of EGFR action by c-Met

The c-Met receptor is a potential therapeutic target for non-small cell lung cancer (NSCLC). Signaling interactions between c-Met and the mutant Epidermal Growth Factor Receptor (EGFR) have been studied extensively, but signaling intermediates and biological consequences of lateral signaling to c-Met in EGFR wild-type tumors is minimally understood. Our observations indicate that delayed c-Met activation in NSCLC cell lines is initiated by wild-type EGFR, the receptor most often found in NSCLC tumors. EGFR ligands induce accumulation of activated c-Met which begins at 8 h continues for 48 h. This effect is accompanied by an increase in c-Met expression and phosphorylation of critical c-Met tyrosine residues without activation of MAPK or Akt. Gene transcription is required for delayed c-Met activation; however, phosphorylation of c-Met by EGFR occurs without production of HGF or another secreted factor, supporting a ligand-independent mechanism. Lateral signaling is blocked by two selective c-Met tyrosine kinase inhibitors (TKIs), PF2341066 and SU11274, or with gefitinib, an EGFR TKI, suggesting kinase activity of both receptors is required for this effect. Prolonged c-Src phosphorylation is observed, and c-Src pathway is essential for EGFR to c-Met communication. Pre-treatment with pan-SFK inhibitors, PP2 and dasatinib, abolishes delayed c-Met phosphorylation. A c-Src dominant-negative construct reduces EGF-induced c-Met phosphorylation compared to control, further, confirming a c-Src requirement. Inhibition of c-Met with PF2341066 and siRNA decreases EGF-induced phenotypes of invasion by ~86% and motility by ~81%, suggesting that a novel form of c-Met activation is utilized by EGFR to maximize these biological effects. Combined targeting of c-Met and EGFR leads to increased xenograft anti-tumor activity, demonstrating that inhibition of downstream and lateral signaling from the EGFR-c-Src-c-Met axis might be effective in treatment of NSCLC.

Overexpression of GPR39 contributes to malignant development of human esophageal squamous cell carcinoma

Background

By using cDNA microarray analysis, we identified a G protein-coupled receptor, GPR39, that is significantly up-regulated in ESCC. The aim of this study is to investigate the role of GPR39 in human esophageal cancer development, and to examine the prevalence and clinical significance of GPR39 overexpression in ESCC.

Methods

The mRNA expression level of GPR39 was analyzed in 9 ESCC cell lines and 50 primary ESCC tumors using semi-quantitative RT-PCR. Immunohistochemistry was used to assess GPR39 protein expression in tissue arrays containing 300 primary ESCC cases. In vitro and in vivo studies were done to elucidate the tumorigenic role of GPR39 in ESCC cells.

Results

We found that GPR39 was frequently overexpressed in primary ESCCs in both mRNA level (27/50, 54%) and protein level (121/207, 58.5%), which was significantly associated with the lymph node metastasis and advanced TNM stage (P < 0.01). Functional studies showed that GPR39 has a strong tumorigenic ability. Introduction of GPR39 gene into ESCC cell line KYSE30 could promote cell proliferation, increase foci formation, colony formation in soft agar, and tumor formation in nude mice. The mechanism by which amplified GPR39 induces tumorigenesis was associated with its role in promoting G1/S transition via up-regulation of cyclin D1 and CDK6. Further study found GPR39 could enhance cell motility and invasiveness by inducing EMT and remodeling cytoskeleton. Moreover, depletion of endogenous GPR39 by siRNA could effectively decrease the oncogenicity of ESCC cells.

Conclusions

The present study suggests that GPR39 plays an important tumorigenic role in the development and progression of ESCC.

Signaling pathways of ATP-induced PGE2 release in spinal cord astrocytes are EGFR transactivation-dependent

Traumatic spinal cord injury is characterized by an immediate, irreversible loss of tissue at the lesion site, as well as a secondary expansion of tissue damage over time. Although secondary injury should, in principle, be preventable, no effective treatment options currently exist for patients with acute spinal cord injury (SCI). Excessive release of ATP by the traumatized tissue, triggers the rapid release of arachidonic acid (AA) and prostaglandin E2 (PGE2), and has beenimplicated in acute and chronic neuropathic pain and inflammation. But the intracellular pathways between ATP and PGE2 remain largely unknown. We have explored the signaling events involved in this synthesis by primarily culturing spinal cord astrocytes: (1) we determined significant PGE2 production increased by ATP is mainly via Subtype 1 of P2 purinoceptors (P2Y1) but not P2Y2; (2) we found that ATP strongly increased the level of intracellular Ca(2+) via P2Y1 receptor; (3) we indicated that ATP stimulates the definitely release of AA and PGE2 which involved the transactivation of epidermal growth factor (EGF) receptor, the phosphorylation of extracellular-regulated protein kinases 1 and 2 (ERK(1/2) ) and the activation of cytosolic phospholipase A(2) (cPLA(2) ); (4) we examined ATP could increase the phosphorylation of Akt via P2Y1 receptor which also depend on the transactivation of EGFR, but the activation of Akt has no effect on the downstream of cPLA(2) phosphorylation. ATP induced by SCI could mobilize the release of AA and PGE2. And inhibition of PGE2 release reduces behavioral signs of pain after SCI and peripheral nerve injury.

G protein-coupled receptors: novel targets for drug discovery in cancer

G protein-coupled receptors (GPCRs) belong to a superfamily of cell surface signalling proteins that have a pivotal role in many physiological functions and in multiple diseases, including the development of cancer and cancer metastasis. Current drugs that target GPCRs - many of which have excellent therapeutic benefits - are directed towards only a few GPCR members. Therefore, huge efforts are currently underway to develop new GPCR-based drugs, particularly for cancer. We review recent findings that present unexpected opportunities to interfere with major tumorigenic signals by manipulating GPCR-mediated pathways. We also discuss current data regarding novel GPCR targets that may provide promising opportunities for drug discovery in cancer prevention and treatment.

EGF receptor activation by GPCRs: an universal pathway reveals different versions

About one decade ago has been demonstrated that G protein-coupled receptors (GPCRs) are able to utilize the epidermal growth factor (EGF) receptor (EGFR) as signalling intermediate. Thereby GPCRs are enabled to regulate cell growth, differentiation, and migration. A molecular mechanism for this process has been proposed that involves the activation of a distinct set of metalloproteases and the subsequent generation and release of particular members of the EGF peptide family which in turn activate the EGFR in an autocrine/paracrine manner. This model that allows GPCRs direct access to the signalling network of the EGFR family has emerged as a valid concept in a variety of cell types including cancer cells. The present review briefly summarizes the current knowledge but will be focussed on the ligand-dependency of EGFR transactivation. Several alternative mechanisms and novel aspects will be introduced. Using the example of head and neck squamous carcinoma, the potency of EGFR transactivation as a therapeutical target will be discussed.

Tissue kallikrein promotes prostate cancer cell migration and invasion via a protease-activated receptor-1-dependent signaling pathway

We recently demonstrated that tissue kallikrein (TK) promotes keratinocyte migration through activation of protease-activated receptor-1 (PAR(1)) and transactivation of the epi-dermal growth factor receptor (EGFR). In this study, we investigated the potential role of PAR(1) in mediating the effect of TK on cancer cell migration, invasion and proliferation. Our results show that TK promotes DU145 prostate cancer cell migration in a concentration-dependent manner, but has no effect on A549 lung cancer cells. Active TK markedly increases DU145 cell migration and invasion, which are blocked by aprotinin but minimally affected by icatibant; kinin treatment has little effect. TK-induced cell migration and invasion are abolished by inhibition of PAR(1) using a pharmacological inhibitor or RNA interference. The effect of TK on cell migration and invasion are also blocked by inhibitors of protein kinase C, c-Src, matrix metalloproteinase, EGFR and extracellular signal-regulated kinase (ERK). Moreover, TK stimulates ERK phosphorylation, which is inhibited by an EGFR antagonist. Additionally, TK but not kinin stimulates DU145 cell proliferation through activation of the kinin B2 receptor, but not PAR(1) and EGFR. These results indicate differential signaling pathways mediated by TK in promoting prostate cancer cell migration and invasion via PAR(1) activation, and proliferation via kinin B2 receptor stimulation.

NF-κB addiction and its role in cancer: 'one size does not fit all'

Activation of nuclear factor (NF)-κB, one of the most investigated transcription factors, has been found to control multiple cellular processes in cancer including inflammation, transformation, proliferation, angiogenesis, invasion, metastasis, chemoresistance and radioresistance. NF-κB is constitutively active in most tumor cells, and its suppression inhibits the growth of tumor cells, leading to the concept of 'NF-κB addiction' in cancer cells. Why NF-κB is constitutively and persistently active in cancer cells is not fully understood, but multiple mechanisms have been delineated including agents that activate NF-κB (such as viruses, viral proteins, bacteria and cytokines), signaling intermediates (such as mutant receptors, overexpression of kinases, mutant oncoproteins, degradation of IκBα, histone deacetylase, overexpression of transglutaminase and iNOS) and cross talk between NF-κB and other transcription factors (such as STAT3, HIF-1α, AP1, SP, p53, PPARγ, β-catenin, AR, GR and ER). As NF-κB is 'pre-active' in cancer cells through unrelated mechanisms, classic inhibitors of NF-κB (for example, bortezomib) are unlikely to mediate their anticancer effects through suppression of NF-κB. This review discusses multiple mechanisms of NF-κB activation and their regulation by multitargeted agents in contrast to monotargeted agents, thus 'one size does not fit all' cancers.

Quantitative proteomics analysis reveals molecular networks regulated by epidermal growth factor receptor level in head and neck cancer

Epidermal growth factor receptor (EGFR) is overexpressed in up to 90% of head and neck cancer (HNC), where increased expression levels of EGFR correlate with poor prognosis. To date, EGFR expression levels have not predicted the clinical response to the EGFR-targeting therapies. Elucidation of the molecular mechanisms underlying anti-EGFR-induced antitumor effects may shed some light on the mechanisms of HNC resistance to EGFR-targeting therapeutics and provide novel targets for improving the treatment of HNC. Here, we conducted a quantitative proteomics analysis to determine the molecular networks regulated by EGFR levels in HNC by specifically knocking-down EGFR and employing stable isotope labeling with amino acids in cell culture (SILAC). Following data normalization to minimize systematic errors and Western blotting validation, 12 proteins (e.g., p21, stratifin, and maspin) and 24 proteins (e.g., cdc2 and MTA2) were found to be significantly upregulated or downregulated by EGFR knockdown, respectively. Bioinformatic analysis revealed that these proteins were mainly involved in long-chain fatty acid biosynthesis and beta-oxidation, cholesterol biosynthesis, cell proliferation, DNA replication, and apoptosis. Cell cycle analysis confirmed that G(2)/M phase progression was significantly inhibited by EGFR knockdown, a hypothesis generated from network modeling. Further investigation of these molecular networks may not only enhance our understanding of the antitumor mechanisms of EGFR targeting but also improve patient selection and provide novel targets for better therapeutics.

Human β-defensin 3 promotes NF-κB-mediated CCR7 expression and anti-apoptotic signals in squamous cell carcinoma of the head and neck

The microenvironment of aerodigestive cancers contains tumor-promoting inflammatory signals often involved in innate immunity. The epithelial malignancy, squamous cell carcinoma of the head and neck (SCCHN), is characterized by secretion of inflammatory mediators that can promote tumorigenesis and lymph node metastasis. Human β-defensin (hBD) 3 is one such antimicrobial mediator of innate immunity produced by squamous epithelial cells in response to tissue damage and inflammation. Here, we hypothesized that the observed overexpression of hBD3 in SCCHN may have a tumor-promoting effect or contribute to nodal metastasis, which has previously been linked to chemokine receptor (CCR) 7 overexpression. Indeed, treatment of non-metastatic SCCHN cells with hBD3 induced surface CCR7 expression and migration toward its ligand, CCL19. The hBD3-induced CCR7 upregulation in SCCHN cells was significantly reduced by inhibition of nuclear factor (NF)-κB, an inflammatory transcription factor known to influence CCR7 expression. Moreover, hBD3 stimulation provided anti-apoptotic signals to SCCHN cells, as evidenced by tumor resistance to cisplatin-induced cell death, which was regulated by phosphoinositide-3-kinase/Akt activation. Interestingly, the observed hBD3-mediated effects were not dependent on G-protein coupled receptors or toll-like receptors, as has been previously published, but hBD3 was internalized through endocytosis, allowing intracellular signal transduction. Our findings suggest that hBD3 represents a novel NF-κB-regulated mediator of CCR7 expression and anti-apoptotic pathways, which may be exploited by developing SCCHN tumors to enhance their survival and metastasis.

Allosteric Modulation of G Protein Coupled Receptors by Cytoplasmic, Transmembrane and Extracellular Ligands

G protein coupled receptors (GPCRs) bind diverse classes of ligands, and depending on the receptor, these may bind in their transmembrane or the extracellular domains, demonstrating the principal ability of GPCRs to bind ligand in either domains. Most recently, it was also observed that small molecule ligands can bind in the cytoplasmic domain, and modulate binding and response to extracellular or transmembrane ligands. Thus, all three domains in GPCRs are potential sites for allosteric ligands, and whether a ligand is allosteric or orthosteric depends on the receptor. Here, we will review the evidence supporting the presence of putative binding pockets in all three domains of GPCRs and discuss possible pathways of communication between these pockets.

Tumor antigen-targeted, monoclonal antibody-based immunotherapy: clinical response, cellular immunity, and immunoescape

PURPOSE

Tumor antigen (TA) -targeted monoclonal antibodies (mAb), rituximab, trastuzumab, and cetuximab, are clinically effective for some advanced malignancies, especially in conjunction with chemotherapy and/or radiotherapy. However, these results are only seen in a subset (20% to 30%) of patients. We discuss the immunologic mechanism(s) underlying these clinical findings and their potential role in the variability in patients' clinical response.

METHODS

We reviewed the evidence indicating that the effects of TA-targeted mAb-based immunotherapy are mediated not only by inhibition of signaling pathways, but also by cell-mediated cytotoxicity triggered by the infused TA-targeted mAb. We analyzed the immunologic variables that can influence the outcome of antibody-dependent cell-mediated cytotoxicity (ADCC) in vitro and in animal model systems. We also analyzed the correlation reported between these variables and the clinical response to mAb-based immunotherapy.

RESULTS

Of the variables that influence ADCC mediated by TA-targeted mAb, only polymorphisms of Fcγ receptors (FcγR) expressed by patients' lymphocytes were correlated with clinical efficacy. However, this correlation is not absolute and is not observed in all malignancies. Thus other variables may be responsible for the antitumor effects seen in mAb-treated patients. We discuss the evidence that triggering of TA-specific cellular immunity by TA-targeted mAb, in conjunction with immune escape mechanisms used by tumor cells, may contribute to the differential clinical responses to mAb-based immunotherapy.

CONCLUSION

Identification of the mechanism(s) underlying the clinical response of patients with cancer treated with TA-targeted mAb is crucial to optimizing their application in the clinic and to selecting the patients most likely to benefit from their use.

Investigational EGFR-targeted therapy in head and neck squamous cell carcinoma

IMPORTANCE OF THE FIELD

EGFR is an established therapeutic target in head and neck squamous cell carcinoma (HNSCC). The EGFR-targeting monoclonal antibody cetuximab (Erbitux, Imclone Systems, Inc., Branchburg, USA) was FDA-approved for use in HNSCC in 2006. The molecular basis for the efficacy of an antibody approach compared with inhibition of EGFR tyrosine kinase function using small-molecule inhibitors, or downregulation of protein expression via antisense strategies, remains incompletely understood.

AREAS COVERED IN THIS REVIEW

A literature search was performed to identify studies elucidating mechanisms of action of several approaches to targeting EGFR in HNSCC (monoclonal antibodies, tyrosine kinase inhibitors, antisense approaches, and ligand-toxin conjugates).

WHAT THE READER WILL GAIN

Monoclonal antibodies decrease tumor growth via receptor endocytosis and recruitment of host immune defenses. Tyrosine kinase inhibitors bind to the ATP binding pocket of the tyrosine kinase domain, inhibiting signaling. Antisense approaches decrease EGFR expression with high specificity, though drug delivery remains problematic. Ligand-toxin conjugates facilitate the entry of toxin and the ADP-ribosylation of the ribosome, thereby inhibiting translation.

TAKE HOME MESSAGE

Elucidation mechanisms by which these different strategies inhibit EGFR function may enhance the development of more effective treatments for HNSCC and enable prospective identification of individuals who will benefit from EGFR inhibition.

Bradykinin-induced cell migration and COX-2 production mediated by the bradykinin B1 receptor in glioma cells

Bradykinin is produced and acts at the site of injury and inflammation. Recent reports have also shown that bradykinin selectively modulates blood-tumor barrier permeability. However, the molecular mechanisms and pathologic roles underlying bradykinin-induced glioma migration remain unclear. Glioma is the most common primary adult brain tumor, with a poor prognosis because of the ease with which tumor cells spread to other regions of the brain. In this study, we found that bradykinin increases the cell migration and expression of cyclo-oxygenase-2 (COX-2) in glioma cells. Bradykinin-mediated migration was attenuated by the selective COX-2 inhibitor NS-398. Moreover, increased motility of glioma cells and expression of COX-2 were mimicked by a bradykinin B1 receptor (B1R) agonist and markedly inhibited by a B1R antagonist. Bradykinin-mediated migration was attenuated by phosphoinositide 3-kinase (PI-3 kinase)/AKT inhibitors LY 294002 and wortmannin. Bradykinin stimulation also increased the phosphorylation of the p85 subunit of PI-3 kinase and serine 473 of AKT. Treatment of bradykinin with AP-1 inhibitors Tanshinone IIA and curcumin also reduced COX-2 expression and glioma cell migration. Moreover, treatment of bradykinin also induced phosphorylation of c-Jun in glioma cells. AP-1 promoter analysis in the luciferase reporter construct showed that bradykinin increased AP-1 transcription activity and was inhibited by LY 294002 and wortmannin. One mechanism underlying bradykinin-directed migration is transcriptional up-regulation of COX-2 and activation of the B1R receptor, PI-3 kinase, AKT, c-Jun, and AP-1 pathways.

Systematic prediction of human membrane receptor interactions

Membrane receptor-activated signal transduction pathways are integral to cellular functions and disease mechanisms in humans. Identification of the full set of proteins interacting with membrane receptors by high-throughput experimental means is difficult because methods to directly identify protein interactions are largely not applicable to membrane proteins. Unlike prior approaches that attempted to predict the global human interactome, we used a computational strategy that only focused on discovering the interacting partners of human membrane receptors leading to improved results for these proteins. We predict specific interactions based on statistical integration of biological data containing highly informative direct and indirect evidences together with feedback from experts. The predicted membrane receptor interactome provides a system-wide view, and generates new biological hypotheses regarding interactions between membrane receptors and other proteins. We have experimentally validated a number of these interactions. The results suggest that a framework of systematically integrating computational predictions, global analyses, biological experimentation and expert feedback is a feasible strategy to study the human membrane receptor interactome.

Progesterone is essential for maintenance of Tace/Adam17 mRNA expression, but not EGF-like factor, in cumulus cells, which enhances the EGF receptor signaling pathway during in vitro maturation of porcine COCs

During in vitro maturation of porcine cumulus-oocyte complexes (COCs), progesterone was secreted from cumulus cells and acted on the cumulus cells themselves, which required for cumulus expansion and oocyte maturation. EGF-like factor (amphiregulin, AREG; epiregulin, EREG) and its protease, TACE/ADAM17, are also expressed in cumulus cells, and thereby, soluble EGF domain was acted on the EGF receptor expressed on cumulus cells. In this study, we examined the relationship between progesterone function and EGF-like factor stimuli in cumulus cells of porcine COCs. When COCs were cultured with FSH and LH, Areg, Ereg and Tace/Adam17 were expressed in cumulus cells. Treatment with a progesterone receptor (PGR) antagonist, RU486, did not affect the Areg and Ereg mRNA expression levels at any culture time points. However, the Tace/Adam17 mRNA level, protein level and its activity were significantly suppressed by RU486 at the 30 or 40 h time point. At 20 h of culture, phosphorylation of ERK1/2 and the expressions of target genes (Has2, Tnfaip6 and Ptgs2) were not suppressed by RU486; however, at 40 h, ERK1/2 phosphorylation and the target gene expression levels were significantly downregulated by RU486 in cumulus cells. Furthermore, the negative effects of RU486 at 40 h were overcome by the addition of EGF. These results indicated that the level of TACE/ADAM17 in cumulus cells was regulated by the progesterone-PGR pathway during in vitro maturation of porcine COCs. Therefore, we concluded that the progesterone-induced TACE/ADAM17 leads to production of soluble EGF domain from cumulus cells, which enhances functional changes of cumulus cells and progresses meiotic maturation of oocytes during in vitro maturation of porcine COCs.

Targeting the epidermal growth factor receptor in epithelial ovarian cancer: current knowledge and future challenges

The epidermal growth factor receptor is overexpressed in up to 60% of ovarian epithelial malignancies. EGFR regulates complex cellular events due to the large number of ligands, dimerization partners, and diverse signaling pathways engaged. In ovarian cancer, EGFR activation is associated with increased malignant tumor phenotype and poorer patient outcome. However, unlike some other EGFR-positive solid tumors, treatment of ovarian tumors with anti-EGFR agents has induced minimal response. While the amount of information regarding EGFR-mediated signaling is considerable, current data provides little insight for the lack of efficacy of anti-EGFR agents in ovarian cancer. More comprehensive, systematic, and well-defined approaches are needed to dissect the roles that EGFR plays in the complex signaling processes in ovarian cancer as well as to identify biomarkers that can accurately predict sensitivity toward EGFR-targeted therapeutic agents. This new knowledge could facilitate the development of rational combinatorial therapies to sensitize tumor cells toward EGFR-targeted therapies.

Activation of PKA, p38 MAPK and ERK1/2 by gonadotropins in cumulus cells is critical for induction of EGF-like factor and TACE/ADAM17 gene expression during in vitro maturation of porcine COCs

Objectives

During ovulation, it has been shown that LH stimulus induces the expression of numerous genes via PKA, p38 MAPK, PI3K and ERK1/2 in cumulus cells and granulosa cells. Our recent study showed that EGF-like factor and its protease (TACE/ADAM17) are required for the activation of EGF receptor (EGFR), cumulus expansion and oocyte maturation of porcine cumulus-oocyte complexes (COCs). In the present study, we investigated which signaling pathways are involved in the gene expression of EGF-like factor and in Tace/Adam17 expression in cumulus cells of porcine COC during in vitro maturation.

Methods

Areg, Ereg, Tace/Adam17, Has2, Tnfaip6 and Ptgs2 mRNA expressions were detected in cumulus cells of porcine COCs by RT-PCR. Protein level of ERK1/2 phosphorylation in cultured cumulus cells was analyzed by westernblotting. COCs were visualized using a phase-contrast microscope.

Results

When COCs were cultured with FSH and LH up to 2.5 h, Areg, Ereg and Tace/Adam17 mRNA were expressed in cumulus cells of COCs. Areg, Ereg and Tace/Adam17 gene expressions were not suppressed by PI3K inhibitor (LY294002), whereas PKA inhibitor (H89), p38 MAPK inhibitor (SB203580) and MEK inhibitor (U0126) significantly suppressed these gene expressions. Phosphorylation of ERK1/2, and the gene expression of Has2, Tnfaip6 and Ptgs2 were also suppressed by H89, SB203580 and U0126, however, these negative effects were overcome by the addition of EGF to the medium, but not in the U0126 treatment group.

Conclusion

The results showed that PKA, p38 MAPK and ERK1/2 positively controlled the expression of EGF-like factor and TACE/ADMA17, the latter of which impacts the cumulus expansion and oocyte maturation of porcine COCs via the EGFR-ERK1/2 pathway in cumulus cells.

Epidermal growth factor-induced cyclooxygenase-2 expression in oral squamous cell carcinoma cell lines is mediated through extracellular signal-regulated kinase 1/2 and p38 but is Src and nuclear factor-kappa B independent

The intracellular signalling cascade(s) mediating epidermal growth factor (EGF)-induced cyclooxygenase-2 (COX-2) expression is poorly defined in oral carcinomas. Investigation of two different oral squamous cell carcinoma (OSCC) cell lines with high EGF-induced COX-2 expression revealed, however, that this expression was dependent on two mitogen-activated protein kinase (MAPK) pathways [extracellular signal-regulated kinase 1/2 (ERK1/2) and p38] because combined inhibition of these pathways was needed to abolish EGF-induced COX-2 expression. Surprisingly, inhibition of phosphoinositide-3 kinase (PI3K) increased EGF-induced COX-2 expression in the basaloid OSCC cell line (C12), suggesting a PI3K-controlled, inhibitory COX-2-regulating pathway. Neither the transcription factor nuclear factor-kappaB (NF-kappaB), nor Src, was involved in EGF-induced COX-2 expression. The results suggest that EGF-induced COX-2 expression is regulated by several pathways, and emphasizes that individual tumors use different strategies for intracellular signalling.

A novel signaling pathway of tissue kallikrein in promoting keratinocyte migration: activation of proteinase-activated receptor 1 and epidermal growth factor receptor

Biological functions of tissue kallikrein (TK, KLK1) are mainly mediated by kinin generation and subsequent kinin B2 receptor activation. In this study, we investigated the potential role of TK and its signaling pathways in cultured human keratinocyte migration and in a rat skin wound healing model. Herein, we show that TK promoted cell migration and proliferation in a concentration- and time-dependent manner. Inactive TK or kinin had no significant effect on cell migration. Interestingly, cell migration induced by active TK was not blocked by icatibant or L-NAME, indicating an event independent of kinin B2 receptor and nitric oxide formation. TK's stimulatory effect on cell migration was inhibited by small interfering RNA for proteinase-activated receptor 1 (PAR(1)), and by PAR(1) inhibitor. TK-induced migration was associated with increased phosphorylation of epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase (ERK), which was blocked by inhibition of protein kinase C (PKC), Src, EGFR and ERK. TK-induced cell migration and EGFR phosphorylation were blocked by metalloproteinase (MMP) inhibitor, heparin, and antibodies against EGFR external domain, heparin-binding EGF-like growth factor (HB-EGF) and amphiregulin (AR). Local application of TK promoted skin wound healing in rats, whereas icatibant and EGFR inhibitor blocked TK's effect. Skin wound healing was further delayed by aprotinin and neutralizing TK antibody. This study demonstrates a novel role of TK in skin wound healing and uncovers new signaling pathways mediated by TK in promoting keratinocyte migration through activation of the PAR(1)-PKC-Src-MMP pathway and HB-EGF/AR shedding-dependent EGFR transactivation.

Nuclear NF-kappaB p65 phosphorylation at serine 276 by protein kinase A contributes to the malignant phenotype of head and neck cancer

PURPOSE

Aberrant nuclear activation and phosphorylation of the canonical NF-kappaB subunit RELA/p65 at Serine-536 by inhibitor kappaB kinase is prevalent in head and neck squamous cell carcinoma (HNSCC), but the role of other kinases in NF-kappaB activation has not been well defined. Here, we investigated the prevalence and function of p65-Ser276 phosphorylation by protein kinase A (PKA) in the malignant phenotype and gene transactivation, and studied p65-Ser276 as a potential target for therapy.

EXPERIMENTAL DESIGN

Phospho and total p65 protein expression and localization were determined in HNSCC tissue array and in cell lines. The effects of the PKA inhibitor H-89 on NF-kappaB activation, downstream gene expression, cell proliferation and cell cycle were examined. Knockdown of PKA by specific siRNA confirmed the specificity.

RESULTS

NF-kappaB p65 phosphorylated at Ser276 was prevalent in HNSCC and adjacent dysplastic mucosa, but localized to the cytoplasm in normal mucosa. In HNSCC lines, tumor necrosis factor-alpha (TNF-alpha) significantly increased, whereas H-89 inhibited constitutive and TNF-alpha-induced nuclear p65 (Ser276) phosphorylation, and significantly suppressed NF-kappaB and target gene IL-8 reporter activity. Knockdown of PKA by small interfering RNA inhibited NF-kappaB, IL-8, and BCL-XL reporter gene activities. H-89 suppressed cell proliferation, induced cell death, and blocked the cell cycle in G(1)-S phase. Consistent with its biological effects, H-89 down-modulated expression of NF-kappaB-related genes Cyclin D1, BCL2, BCL-XL, COX2, IL-8, and VEGF, as well as induced cell cycle inhibitor p21(CIP1/WAF1), while suppressing proliferative marker Ki67.

CONCLUSIONS

NF-kappaB p65 (Ser276) phosphorylation by PKA promotes the malignant phenotype and holds potential as a therapeutic target in HNSCC.

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

The molecular mechanisms behind the aggressiveness of nasopharyngeal carcinoma (NPC), a highly invasive and metastatic head and neck malignancy, have not been made clear. In this study investigating these mechanisms, guanine nucleotide-binding protein alpha(12) subunit (G(alpha)(12)) signaling was found by microarray analysis to be increased in primary NPC cells and NPC-derived cell lines. Using small interfering RNA to knock down G(alpha)(12) in NPC cells resulted in a reduction in cell migration and invasion as well as a reversal in fibroblastoid morphology. Using microarray analysis, we also found a reduction in expression of key actin dynamics regulators and several epithelial-to-mesenchymal transition-related genes in G(alpha)(12)-depleted NPC cells. Knocking down one of those genes, IQ motif containing GTPase activating protein 1, reduced the migration and formation of adherens junctions and reversed the fibroblastoid morphology of NPC cells, as knocking down G(alpha)(12) was found to do. Immunohistochemical analysis found NPC tumors to have significantly greater levels of G(alpha)(12) protein than the normal basal epithelial cells. Quantitative real-time PCR analysis revealed a significant correlation between G(alpha)(12) mRNA levels and NPC lymph node metastasis. Together, our findings support a model in which activation of G(alpha)(12) signaling promotes tumorigenesis and progression of NPC by modulating actin cytoskeleton reorganization and expression of epithelial-to-mesenchymal transition-related genes. =

Promotion of human trophoblasts invasion by gonadotropin-releasing hormone (GnRH) I and GnRH II via distinct signaling pathways

The potential roles of GnRH I and GnRH II have been assigned in promoting the invasive capacity of human trophoblasts by regulating matrix metalloproteinases-2 and -9, type I tissue inhibitor of matrix metalloproteinase, and urokinase plasminogen activator/plasminogen activator inhibitor protease systems during human placentation, and GnRH II has been shown to be more potent than GnRH I. However, the mechanisms for the differential effects of these two hormones remain unclear. In this study, we examined the invasion-promoting effects and the signaling pathways of GnRH I and GnRH II in human trophoblasts. The data revealed that both GnRH I and GnRH II were key autocrine and/or paracrine regulators in facilitating trophoblast invasion. The GnRH receptor antagonist (Antide) and specific small interfering RNA for GnRH receptor inhibited the regulatory effects of GnRH I, but not GnRH II, on trophoblast invasion. Both GnRH I and II activated protein kinase C, ERK1/2, and c-Jun N-terminal kinase to mediate their effects on trophoblast invasion, whereas only GnRH II elicited invasion-promoting action through transactivating the tyrosine kinase activity of epidermal growth factor receptor in trophoblasts. Our observations elucidate a ligand-dependent selective cross-communication between GnRH receptor and epidermal growth factor receptor signaling systems in human trophoblastic cell, and this would further our understanding on the differentially biological significance of these two forms of GnRH in extrapituitary tissues.

Association study of the G-protein beta3 subunit C825T polymorphism with disease progression an overall survival in patients with head and neck squamous cell carcinoma

The T-allele of a common C825T single nucleotide polymorphism (SNP) in the gene GNB3, encoding the G3 subunit of heterotrimeric G-proteins, is associated with a truncated form of the G3 protein that imparts a greater signaling capacity than the alternative C-allele encoding a nontruncated protein. We analyzed the C825T-allele status with regard to disease progression in patients with head and neck squamous cell carcinoma (HNSCC). The prognostic value of the SNP was evaluated in an unselected series of 341 patients treated with curative intent for HNSCC including all tumor stages with different therapeutic regimens. Genotype analysis was done by Pyrosequencing using DNA from paraffin-embedded tissue samples. Genotypes were correlated with relapse-free and overall survival. Proportions of 5-year relapse-free intervals were 62% for CC, 60% for TC, and 42% for TT genotypes. Kaplan-Meier curves revealed a significant genotype-dependent relapse-free interval (P = 0.036). In multivariate analysis with stage, localization, grade, gender, and smoking habits as covariates, GNB3 825T homozygous patients displayed a higher risk for relapse than C825 homozygous patients (TT versus CC, hazard ratio; 95% confidence interval, 1.4-4.8; P = 0.002). The same genotype effect was found for overall survival, TT genotypes were at higher risk for death compared with CC genotypes (hazard ratio, 2.6; 95% confidence interval, 1.6-4.3; P < 0.001), and 5-year survival proportions were 60% for CC, 52% for TC, and 33% for TT. The GNB3 C825T SNP thus represents a host derived prognostic marker in HNSCC, which allows identifying high-risk patients, which could benefit from novel and/or more aggressive therapeutic regimes.

Epigenetic inactivation of galanin receptor 1 in head and neck cancer

PURPOSE

One copy of the galanin receptor 1 (GALR1) locus on 18q is often deleted and expression is absent in some head and neck squamous cell carcinoma (HNSCC) cell lines. To determine if loss of heterozygosity and hypermethylation might silence the GALR1 gene, promoter methylation status and gene expression were assessed in a large panel of HNSCC cell lines and tumors.

EXPERIMENTAL DESIGN

Promoter methylation of GALR1 in 72 cell lines and 100 primary tumor samples was analyzed using methylation-specific PCR. GALR1 expression and methylation status were analyzed further by real-time PCR and bisulfite sequencing analysis.

RESULTS

The GALR1 promoter was fully or partially methylated in 38 of 72 (52.7%) HNSCC cell lines but not in the majority 18 of 20 (90.0%) of nonmalignant lines. GALR1 methylation was also found in 38 of 100 (38%) primary tumor specimens. Methylation correlated with decreased GALR1 expression. In tumors, methylation was significantly correlated with increased tumor size (P = 0.0036), lymph node status (P = 0.0414), tumor stage (P = 0.0037), cyclin D1 expression (P = 0.0420), and p16 methylation (P = 0.0494) and survival (P = 0.045). Bisulfite sequencing of 36 CpG sites upstream of the transcription start site revealed that CpG methylation within transcription factor binding sites correlated with complete suppression of GALR1 mRNA. Treatment with trichostatin A and 5-azacytidine restored GALR1 expression. In UM-SCC-23 cells that have total silencing of GALR1, exogenous GALR1 expression and stimulation with galanin suppressed cell proliferation.

CONCLUSIONS

Frequent promoter hypermethylation, gene silencing, association with prognosis, and growth suppression after reexpression support the hypothesis that GALR1 is a tumor suppressor gene in HNSCC.

Kinin b2 receptor mediates induction of cyclooxygenase-2 and is overexpressed in head and neck squamous cell carcinomas

Bradykinin has been shown to promote growth and migration of head and neck squamous cell carcinoma (HNSCC) cells via epidermal growth factor receptor (EGFR) transactivation. It has also been reported that bradykinin can cause the induction of cyclooxygenase-2 (COX-2), a protumorigenic enzyme, via the mitogen-activated protein kinase (MAPK) pathway in human airway cells. To determine whether COX-2 is up-regulated by bradykinin in HNSCC, the current study investigated bradykinin-induced EGFR transactivation, MAPK activation, and COX-2 expression in human HNSCC cells. Bradykinin induced a concentration- and time-dependent induction of COX-2 protein in HNSCC, which was preceded by phosphorylation of EGFR and MAPK. These effects were abolished by the B2 receptor (B2R) antagonist HOE140 but not by the B1 receptor (B1R) antagonist Lys-[Leu(8)]des-Arg(9)-bradykinin. COX-2 induction was accompanied by increased release of prostaglandin E(2). No effect of a B1R agonist (des-Arg(9)-bradykinin) on p-MAPK or COX-2 expression was observed. B2R protein was found to be expressed in all four head and neck cell lines tested. Immunohistochemical analysis and immunoblot analysis revealed that B2R, but not B1R, was significantly overexpressed in HNSCC tumors compared with levels in normal mucosa from the same patient. In HNSCC cells, the bradykinin-induced expression of COX-2 was inhibited by the EGFR kinase inhibitor gefitinib or mitogen-activated protein kinase kinase inhibitors (PD98059 or U0126). These results suggest that EGFR and MAPK are required for COX-2 induction by bradykinin. Up-regulation of the B2R in head and neck cancers suggests that this pathway is involved in HNSCC tumorigenesis.

Integrating biologically targeted therapy in head and neck squamous cell carcinomas

The integration of targeted therapies such as cetuximab to radiation therapy has revolutionized the management of head and neck cancers in the last decade. However, the use of targeted therapies raised several clinically relevant questions that have yet to be answered. These questions include the optimal patient and tumor profile for biologically targeted therapy, the optimal radiation fractionation to use with targeted therapies, how to integrate them into standard or new chemoradiation regimens, their schedule and duration of administration, their toxicity, and which direction to consider for novel targeted treatment. In this review, we highlight several of these important issues, discuss the clinical trials that are designed to address these issues, and introduce some novel targeted therapies that may contribute to the improvement of the therapeutic ratio for head and neck cancer therapy.

Prostaglandin E2 regulates tumor angiogenesis in prostate cancer

In cancer management, the cyclooxygenase (COX)-targeted approach has shown great promise in anticancer therapeutics. However, the use of COX-2 inhibitors has side effects and health hazards; thus, targeting its major metabolite prostaglandin E(2) (PGE(2))-mediated signaling pathway might be a rational approach for the next generation of cancer management. Recent studies on several in vitro and in vivo models have revealed that elevated expression of COX-2 correlates with prostate tumor growth and angiogenesis. In this study, we have shown the in-depth molecular mechanism and the PGE(2) activation of the epidermal growth factor receptor and beta3 integrin through E prostanoid 2 (EP2)-mediated and EP4-mediated pathways, which lead to activator protein-1 (AP-1) activation. Moreover, PGE(2) also induces activating transcription factor-4 (ATF-4) activation and stimulates cross-talk between ATF-4 and AP-1, which is unidirectional toward AP-1, which leads to the increased expressions of urokinase-type plasminogen activator and vascular endothelial growth factor and, eventually, regulates prostate tumor cell motility. In vivo Matrigel angiogenesis assay data revealed that PGE(2) induces angiogenesis through EP2 and EP4. Human prostate cancer specimen analysis also supported our in vitro and in vivo studies. Our data suggest that targeting PGE(2) signaling pathway (i.e., blocking EP2 and EP4 receptors) might be a rational therapeutic approach for overcoming the side effects of COX-2 inhibitors and that this might be a novel strategy for the next generation of prostate cancer management.

Molecular signature and therapeutic perspective of the epithelial-to-mesenchymal transitions in epithelial cancers

The mechanisms involved in the epithelial to mesenchymal transition (EMT) are integrated in concert with master developmental and oncogenic pathways regulating in tumor growth, angiogenesis, metastasis, as well as the reprogrammation of specific gene repertoires ascribed to both epithelial and mesenchymal cells. Consequently, it is not unexpected that EMT has profound impacts on the neoplastic progression, patient survival, as well as the resistance of cancers to therapeutics (taxol, vincristine, oxaliplatin, EGF-R targeted therapy and radiotherapy), independent of the "classical" resistance mechanisms linked to genotoxic drugs. New therapeutic combinations using genotoxic agents and/or EMT signaling inhibitors are therefore expected to circumvent the chemotherapeutic resistance of cancers characterized by transient or sustained EMT signatures. Thus, targeting critical orchestrators at the convergence of several EMT pathways, such as the transcription pathways NF-kappaB, AKT/mTOR axis, MAPK, beta-catenin, PKC and the AP-1/SMAD factors provide a realistic strategy to control EMT and the progression of human epithelial cancers. Several inhibitors targeting these signaling platforms are already tested in preclinical and clinical oncology. In addition, upstream EMT signaling pathways induced by receptor and nonreceptor tyrosine kinases (e.g. EGF-R, IGF-R, VEGF-R, integrins/FAK, Src) and G-protein-coupled receptors (GPCR) constitute practical options under preclinical research, clinical trials or are currently used in the clinic for cancer treatment: e.g. small molecule inhibitors (Iressa: targeting selectively the EGF-R; CP-751,871, AMG479, NVP-AEW541, BMS-536924, PQIP, AG1024: IGF-R; AZD2171, ZD6474: VEGF-R; AZD0530, BMS-354825, SKI606: Src; BIM-46174: GPCR; rapamycin, CCI-779, RAD-001: mTOR) and humanized function blocking antibodies (Herceptin: ErbB2; Avastin: VEGF-A; Erbitux: EGF-R; Abegrin: alphavbeta3 integrins). We can assume that silencing RNA and adenovirus-based gene transfer of therapeutic miR and dominant interferring expression vectors targeting EMT pathways and signaling elements will bring additional ways for the treatment of epithelial cancers. Identification of the factors that initiate, modulate and effectuate EMT signatures and their underlying upstream oncogenic pathways should provide the basis of more efficient strategies to fight cancer progression as well as genetic and epigenetic forms of drug resistance. This goal can be accomplished using global screening of human clinical tumors by EMT-associated cDNA, proteome, miRome, and tissue arrays.

Human rhomboid family-1 gene silencing causes apoptosis or autophagy to epithelial cancer cells and inhibits xenograft tumor growth

The rhomboid family of genes carry out a wide range of important functions in a variety of organisms. Little is known, however, about the function of the human rhomboid family-1 gene (RHBDF1). We show here that RHBDF1 function is essential to epithelial cancer cell growth. RHBDF1 mRNA level is significantly elevated in clinical specimens of invasive ductal carcinoma of the breast, and the protein is readily detectable in human breast cancer or head and neck cancer cell lines. Silencing the RHBDF1 gene with short interfering RNA (siRNA) results in apoptosis in breast cancer MDA-MB-435 cells and autophagy in head and neck squamous cell cancer 1483 cells. The treatment also leads to significant down-modulation of activated AKT and extracellular signal-regulated kinase in the cells, suggesting that critically diminished strength of these growth signals may be the key attributes of the induction of cell death. Furthermore, silencing the RHBDF1 gene in MDA-MB-435 or 1483 xenograft tumors on athymic nude mice by using i.v. administered histidine-lysine polymer nanoparticle-encapsulated siRNA results in marked inhibition of tumor growth. Our findings indicate that RHBDF1 has a pivotal role in sustaining growth signals in epithelial cancer cells and thus may serve as a therapeutic target for treating epithelial cancers.

Immunohistochemical analysis of phosphotyrosine signal transducer and activator of transcription 3 and epidermal growth factor receptor autocrine signaling pathways in head and neck cancers and metastatic lymph nodes

PURPOSE

To determine the effect of tyrosine-phosphorylated signal transducer and activator of transcription 3 (pSTAT3) immunoexpression on survival in two independent cohorts of patients with squamous cell carcinoma of the head and neck (SCCHN) and to evaluate pSTAT3, transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), and gastrin-releasing peptide receptor (GRPR) expression in matched tumor and lymph node metastases in one of these cohorts. EXPERIMENTAL TECHNIQUE: Immunostaining for pSTAT3, TGF-alpha, EGFR, and GRPR was done in two SCCHN cohorts (cohort 1, 61 tumors; cohort 2, 69 paired primary tumors and lymph node metastases). Semiquantitative scores derived from the product of staining intensity (scale 0-3) score and percentage of positive tumor cells were correlated with clinical outcome.

RESULTS

Immunoexpression of pSTAT3 did not correlate with clinical outcome in either cohort (cohort 1, P = 0.914; cohort 2, P = 0.312). In cohort 2, TGF-alpha and EGFR expression in the primary tumors showed some association with decreased disease-free survival (P = 0.0306 and P = 0.0985, respectively). Both pSTAT3 and EGFR showed a correlation of expression between tumor and matched lymph node metastasis (P < 0.0001 and P = 0.0046, respectively). In addition, the expression of EGFR and GRPR in the primary tumors correlated with TGF-alpha expression in paired nodal metastases (P = 0.0043 and P = 0.0268, respectively). In the nodal metastases, TGF-alpha expression correlated with EGFR expression (P = 0.0069). In primary tumors, GRPR expression correlated with TGF-alpha and EGFR expression (P = 0.0378 and P = 0.0026, respectively).

CONCLUSIONS

These findings support an autocrine signaling pathway involving TGF-alpha, EGFR, and pSTAT3 in metastatic SCCHN as well as transactivation of EGFR by GRPR via TGF-alpha, but fails to identify an independent prognostic role for pSTAT3 immunoexpression.