Activator Protein-1 Mediates Induced but not Basal Epidermal Growth Factor Receptor Gene Expression

ER chaperone GRP78/BiP translocates to the nucleus under stress and acts as a transcriptional regulator

Cancer cells are commonly subjected to endoplasmic reticulum (ER) stress. To gain survival advantage, cancer cells exploit the adaptive aspects of the unfolded protein response such as upregulation of the ER luminal chaperone GRP78. The finding that when overexpressed, GRP78 can escape to other cellular compartments to gain new functions regulating homeostasis and tumorigenesis represents a paradigm shift. Here, toward deciphering the mechanisms whereby GRP78 knockdown suppresses EGFR transcription, we find that nuclear GRP78 is prominent in cancer and stressed cells and uncover a nuclear localization signal critical for its translocation and nuclear activity. Furthermore, nuclear GRP78 can regulate expression of genes and pathways, notably those important for cell migration and invasion, by interacting with and inhibiting the activity of the transcriptional repressor ID2. Our study reveals a mechanism for cancer cells to respond to ER stress via transcriptional regulation mediated by nuclear GRP78 to adopt an invasive phenotype.

Upregulated Expression of ErbB1 in Diffuse Large B-Cell Lymphoma as a Predictor of Poor Overall Survival Outcome

We examined the transcript-level expression of ErbB family protein tyrosine kinases, including ERBB1, in primary malignant lymphoma cells from 498 adult patients with diffuse large B-cell lymphoma (DLBCL). ERBB1 expression in DLBCL cells was significantly higher than in normal B-lineage lymphoid cells. An upregulated expression of ERBB1 mRNA in DLBCL cells was correlated with an amplified expression of mRNAs for transcription factors that recognized ERBB1 gene promoter sites. Notably, amplified ERBB1 expression in DLBCL and its subtypes were associated with significantly worse overall survival (OS). Our results encourage the further evaluation of the prognostic significance of high-level ERBB1 mRNA expression and the clinical potential of ERBB1-targeting therapeutics as personalized medicines in high-risk DLBCL.

ERBB1/EGFR and JAK3 Tyrosine Kinases as Potential Therapeutic Targets in High-Risk Multiple Myeloma

Our main objective was to identify abundantly expressed tyrosine kinases in multiple myeloma (MM) as potential therapeutic targets. We first compared the transcriptomes of malignant plasma cells from newly diagnosed MM patients who were risk-categorized based on the patient-specific EMC-92/SKY-92 gene expression signature values vs. normal plasma cells from healthy volunteers using archived datasets from the HOVON65/GMMG-HD4 randomized Phase 3 study evaluating the clinical efficacy of bortezomib induction/maintenance versus classic cytotoxic drugs and thalidomide maintenance. In particular, ERBB1/EGFR was significantly overexpressed in MM cells in comparison to normal control plasma cells, and it was differentially overexpressed in MM cells from high-risk patients. Amplified expression of EGFR/ERBB1 mRNA in MM cells was positively correlated with increased expression levels of mRNAs for several DNA binding proteins and transcription factors with known upregulating activity on EGFR/ERBB1 gene expression. MM patients with the highest ERBB1/EGFR expression level had significantly shorter PFS and OS times than patients with the lowest ERBB1/EGFR expression level. High expression levels of EGFR/ERBB1 were associated with significantly increased hazard ratios for unfavorable PFS and OS outcomes in both univariate and multivariate Cox proportional hazards models. The impact of high EGFR/ERBB1 expression on the PFS and OS outcomes remained significant even after accounting for the prognostic effects of other covariates. These results regarding the prognostic effect of EGFR/ERBB1 expression were validated using the MMRF-CoMMpass RNAseq dataset generated in patients treated with more recently applied drug combinations included in contemporary induction regimens. Our findings provide new insights regarding the molecular mechanism and potential clinical significance of upregulated EGFR/ERBB1 expression in MM.

TGFα-EGFR pathway in breast carcinogenesis, association with WWOX expression and estrogen activation

WWOX is a tumor-suppressive steroid dehydrogenase, which relationship with hormone receptors was shown both in animal models and breast cancer patients. Herein, through nAnT-iCAGE high-throughput gene expression profiling, we studied the interplay of estrogen receptors and the WWOX in breast cancer cell lines (MCF7, T47D, MDA-MB-231, BT20) under estrogen stimulation and either introduction of the WWOX gene by retroviral transfection (MDA-MB-231, T47D) or silenced with shRNA (MCF7, BT20). Additionally, we evaluated the consequent biological characteristics by proliferation, apoptosis, invasion, and adhesion assays. TGFα-EGFR signaling was found to be significantly affected in all examined breast cancer cell lines in response to estrogen and strongly associated with the level of WWOX expression, especially in ER-positive MCF7 cells. Under the influence of 17β-estradiol presence, biological characteristics of the cell lines were also delineated. The study revealed modulation of adhesion, invasion, and apoptosis. The obtained results point at a complex role of the WWOX gene in the carcinogenesis of the breast tissue, which seems to be closely related to the presence of estrogen α and/or β receptors.

The Clinical Significance and Mechanisms of REG4 in Human Cancers

Regenerating islet-derived type 4 (REG4), a member of the calcium-dependent lectin gene superfamily, is abnormally expressed in various cancers, such as colorectal, gastric, gallbladder, pancreatic, ovarian, prostate, and lung cancer. REG4 is associated with a relatively unfavorable prognosis and clinicopathologic features in cancers, including advanced tumor and nodal stage, histological differentiation, and liver and peritoneal metastasis. Moreover, REG4-positive cancer cells show more frequent resistance to chemoradiotherapy, especially 5-FU-based chemotherapy. REG4 participates in many aspects of carcinogenesis, including cell proliferation, apoptosis, cell cycle, invasion, metastasis, and drug resistance. The underlying mechanisms are complex and involve a series of signaling mediators and multiple pathways. Thus, REG4 may be a potential diagnostic and prognostic biomarker as well as a candidate therapeutic target in cancer patients. In this review, we systematically summarize the advances about the clinical significance, biological functions, and mechanisms underlying REG4 in cancer to provide new directions for future cancer research.

FCHSD2 controls oncogenic ERK1/2 signaling outcome by regulating endocytic trafficking

The evolution of transformed cancer cells into metastatic tumors is, in part, driven by altered intracellular signaling downstream of receptor tyrosine kinases (RTKs). The surface levels and activity of RTKs are governed mainly through clathrin-mediated endocytosis (CME), endosomal recycling, or degradation. In turn, oncogenic signaling downstream of RTKs can reciprocally regulate endocytic trafficking by creating feedback loops in cells to enhance tumor progression. We previously showed that FCH/F-BAR and Double SH3 Domain-Containing Protein (FCHSD2) has a cancer-cell specific function in regulating CME in non-small-cell lung cancer (NSCLC) cells. Here, we report that FCHSD2 loss impacts recycling of the RTKs, epidermal growth factor receptor (EGFR) and proto-oncogene c-Met (MET), and shunts their trafficking into late endosomes and lysosomal degradation. Notably, FCHSD2 depletion results in the nuclear translocation of active extracellular signal-regulated kinase 1 and 2 (ERK1/2), leading to enhanced transcription and up-regulation of EGFR and MET. The small GTPase, Ras-related protein Rab-7A (Rab7), is essential for the FCHSD2 depletion-induced effects. Correspondingly, FCHSD2 loss correlates to higher tumor grades of NSCLC. Clinically, NSCLC patients expressing high FCHSD2 exhibit elevated survival, whereas patients with high Rab7 expression display decreased survival rates. Our study provides new insight into the molecular nexus for crosstalk between oncogenic signaling and RTK trafficking that controls cancer progression.

Sofosbuvir Activates EGFR-Dependent Pathways in Hepatoma Cells with Implications for Liver-Related Pathological Processes

Direct acting antivirals (DAAs) revolutionized the therapy of chronic hepatitis C infection. However, unexpected high recurrence rates of hepatocellular carcinoma (HCC) after DAA treatment became an issue in patients with advanced cirrhosis and fibrosis. In this study, we aimed to investigate an impact of DAA treatment on the molecular changes related to HCC development and progression in hepatoma cell lines and primary human hepatocytes. We found that treatment with sofosbuvir (SOF), a backbone of DAA therapy, caused an increase in EGFR expression and phosphorylation. As a result, enhanced translocation of EGFR into the nucleus and transactivation of factors associated with cell cycle progression, B-MYB and Cyclin D1, was detected. Serine/threonine kinase profiling identified additional pathways, especially the MAPK pathway, also activated during SOF treatment. Importantly, the blocking of EGFR kinase activity by erlotinib during SOF treatment prevented all downstream events. Altogether, our findings suggest that SOF may have an impact on pathological processes in the liver via the induction of EGFR signaling. Notably, zidovudine, another nucleoside analogue, exerted a similar cell phenotype, suggesting that the observed effects may be induced by additional members of this drug class.

Eicosanoids and HB-EGF/EGFR in cancer

Eicosanoids are bioactive lipids that play crucial roles in various pathophysiological conditions, including inflammation and cancer. They include both the COX-derived prostaglandins and the LOX-derived leukotrienes. Furthermore, the epidermal growth factor receptor (EGFR) pathways family of receptor tyrosine kinases also are known to play a central role in the tumorigenesis. Various antitumor modalities have been approved cancer treatments that target therapeutically the COX-2 and EGFR pathways; these include selective COX-2 inhibitors and EGFR monoclonal antibodies. Research has shown that the COX-2 and epidermal growth factor receptor pathways actively interact with each other in order to orchestrate carcinogenesis. This has been used to justify a targeted combinatorial approach aimed at these two pathways. Although combined therapies have been found to have a greater antitumor effect than the administration of single agent, this does not exempt them from the possible fatal cardiac effects that are associated with COX-2 inhibition. In this review, we delineate the contribution of HB-EGF, an important EGFR ligand, to the cardiac dysfunction related to decreased shedding of HB-EGF after COX-2/PGE2 inhibition. A better understanding of the molecular mechanisms underlying these cardiac side effects will make possible more effective regimens that use the dual-targeting approach.

Activin A regulates the epidermal growth factor receptor promoter by activating the PI3K/SP1 pathway in oral squamous cell carcinoma cells

Epidermal growth factor receptor (EGFR) and activin A are both overexpressed in oral cavity squamous cell carcinoma (OSCC). We evaluated their clinical correlation and activin A-mediated EGFR regulation in this study. Overexpression of both transcripts/proteins indicated a poorer prognosis in OSCC patients. Knockdown of endogenous INHBA repressed the expression of EGFR and inhibited activin A-mediated canonical Smads, noncanonical phosphorylation of AKT (ser473) (p-AKT ser473) and SP1. Inhibition of PI3K signaling via its inhibitor attenuated p-AKT ser473 and in turn reduced SP1 and EGFR expression in the presence of recombinant activin A (rActivin A) in OSCC cells, as revealed via a luciferase assay and western blotting. However, canonical Smad signaling repressed the EGFR promoter, as revealed by a luciferase assay. The transcription factor SP1, its coactivator CBP/p300, and Smad proteins were recruited to the EGFR proximal promoter following rActivin A treatment, as revealed by chromatin immunoprecipitation (ChIP). Smad2/3/4 dramatically outcompeted SP1 binding to the EGFR proximal promoter following mithramycin A treatment. Activin A activates the PI3K and Smad pathways to compete for binding to overlapping SP1 consensus sequences on the EGFR proximal promoter. Nevertheless, canonical p-Smad2 was largely repressed in OSCC tumor tissues, suggesting that the activin A-mediated noncanonical pathway is essential for the carcinogenesis of OSCC.

Cigarette smoke upregulates SPRR3 by favoring c-Jun/Fra1 heterodimerization in human bronchial epithelial cells

AIM

The airway epithelium of smokers exhibits upregulated SPRR3, an indicator of pathogenic keratinization. The mechanisms underlying this phenomenon require investigation.

PATIENTS & METHODS

Human bronchial epithelial (HBE) SPRR3 expression was analyzed by smoking status. Primary HBE cells were exposed to cigarette smoke (CS). SPRR3 expression, SPRR3 promoter activity, AP-1 factor binding and AP-1 factors' effects were analyzed.

RESULTS

Current smokers display SPRR3 upregulation relative to never smokers. CS upregulates SPRR3 transcription in an exposure-dependent manner. CS promotes c-Jun and Fra1 binding to the SPRR3-AP-1/TRE site. Wild-type c-Jun and Fra1 upregulate, whereas c-Jun and Fra1, dominant-negative mutants, suppress SPRR3 promoter activity.

CONCLUSION

CS induces SPRR3 upregulation in HBE cells by promoting aberrant c-Jun/Fra1 dimerization.

MAP3K1 and MAP2K4 mutations are associated with sensitivity to MEK inhibitors in multiple cancer models

Activation of the mitogen-activated protein kinase (MAPK) pathway is frequent in cancer. Drug development efforts have been focused on kinases in this pathway, most notably on RAF and MEK. We show here that MEK inhibition activates JNK-JUN signaling through suppression of DUSP4, leading to activation of HER Receptor Tyrosine Kinases. This stimulates the MAPK pathway in the presence of drug, thereby blunting the effect of MEK inhibition. Cancers that have lost MAP3K1 or MAP2K4 fail to activate JNK-JUN. Consequently, loss-of-function mutations in either MAP3K1 or MAP2K4 confer sensitivity to MEK inhibition by disabling JNK-JUN-mediated feedback loop upon MEK inhibition. In a panel of 168 Patient Derived Xenograft (PDX) tumors, MAP3K1 and MAP2K4 mutation status is a strong predictor of response to MEK inhibition. Our findings suggest that cancers having mutations in MAP3K1 or MAP2K4, which are frequent in tumors of breast, prostate and colon, may respond to MEK inhibitors. Our findings also suggest that MAP3K1 and MAP2K4 are potential drug targets in combination with MEK inhibitors, in spite of the fact that they are encoded by tumor suppressor genes.

Monoglyceride lipase gene knockout in mice leads to increased incidence of lung adenocarcinoma

Monoglyceride lipase (MGL) is a recently discovered cancer-related protein. The role of MGL in tumorigenesis remains to be fully elucidated. We have previously shown that MGL expression was reduced or absent in multiple human malignancies, and overexpression of MGL inhibited cancer cell growth. Here, we have generated the MGL knockout mice to further investigate the role of MGL in tumorigenesis in vivo. Our results indicate that MGL-deficient (MGL^+/−, MGL^−/−) mice exhibited a higher incidence of neoplasia in multiple organs, including the lung, spleen, liver and lymphoid tissues. Interestingly, lung neoplasms were the most common neoplastic changes in the MGL-deficient mice. Importantly, MGL-deficient animals developed premalignant high-grade dysplasia and adenocarcinomas in their lungs. Investigation of the MGL expression status in lung cancer specimens from patients also revealed that MGL expression was significantly reduced in the majority of primary human lung cancers when compared to corresponding matched normal tissues. Furthermore, mouse embryonic fibroblasts (MEFs) from MGL-deficient animals showed characteristics of cellular transformation including increased cell proliferation, foci formation and anchorage-independent growth. Our results also indicate that MGL deficiency was associated with activation of EGFR and ERK. In addition, pro-inflammatory molecules COX-2 and TNF-α were also activated in the MGL-deficient lung tissues. Thus, our results provide new insights into the novel role of MGL as an important negative regulator of EGFR, COX-2 and TNF-α. Accordingly, EGFR and COX-2/TNF-α activation/induction is expected to play important roles in MGL deficiency-driven lung tumors. Collectively, our results implicate the tumor suppressive role of MGL in preventing tumor development in vivo, particularly in context to the lung cancer, and highlight its role as a potential tumor suppressor.

RHBDD1 upregulates EGFR via the AP-1 pathway in colorectal cancer

Our previous study showed that RHBDD1 can activate the EGFR signaling pathway to promote colorectal cancer growth. In the present study, EGFR was decreased when RHBDD1 was knocked down or inactivated. Further analysis found that c-Jun and EGFR protein expression was decreased in RHBDD1 knockdown and inactivated cells. c-Jun overexpression in RHBDD1-inactivated cells rescued EGFR expression in a dose-dependent manner. RHBDD1 overexpression in RHBDD1-inactivated cells restored EGFR expression, but this effect was counteracted by c-Jun knockdown. Furthermore, EGFR and c-Jun were attenuated in the RHBDD1 knockdown and inactivated groups in animal tumor models. Tissue microarray assays demonstrated a correlation between RHBDD1 and EGFR in colorectal cancer patients. Therefore, our findings indicate that RHBDD1 stimulates EGFR expression by promoting the AP-1 pathway.

Differential Expression Patterns of EGF, EGFR, and ERBB4 in Nasal Polyp Epithelium

Epidermal growth factor receptors play an important role in airway epithelial cell growth and differentiation. The current study investigates the expression profiles of EGF, EGFR and ERBB4 in patients with nasal polyps (NP), and their response to glucocorticosteroid (GC) treatment. Fifty patients with NP (40 without GC treatment and 10 with oral GC) and 20 control subjects with septal deviation were recruited into the study. Protein levels of EGF, EGFR, and ERBB4 were evaluated by immune-staining. In healthy nasal epithelium, EGF and EGFR localized within p63⁺ basal cells, while ERBB4 localized within ciliated cells. GC-naïve NP epithelium showed weak expression of EGF in 90% of samples versus 5% of controls. EGFR was significantly increased in the epithelium with basal cell hyperplasia from GC-naïve NPs (78%, 31/40) compared to controls (23%, 4/17). EGFR was also found in some degranulating goblet cells. ERBB4 expression was significantly higher in hyperplastic epithelium from GC-naïve NPs (65%, 26/40) than in controls (6%, 1/17). GC treatment restored the EGF expression and normalized the EGFR and ERBB4 expression in NPs. Differential expression patterns of EGF, EGFR, and ERBB4 are essential in epithelial restitution and remodeling in nasal epithelium.

Elevated Coexpression of KITENIN and the ErbB4 CYT-2 Isoform Promotes the Transition from Colon Adenoma to Carcinoma Following APC loss

PURPOSE AND EXPERIMENTAL DESIGN

The molecular events in the malignant progression of colon adenoma after loss of adenomatous polyposis coli (APC) are not fully understood. KITENIN (KAI1 C-terminal interacting tetraspanin) increases the invasiveness of colorectal cancer cells, and we identified a novel EGFR-independent oncogenic signal of EGF that works under coexpressed KITENIN and ErbB4. Here we tested whether elevated KITENIN and ErbB4 contribute to further progression of intestinal adenoma following APC loss.

RESULTS

The intestinal tissues of villin-KITENIN transgenic mice in which villin-driven KITENIN expression induces increased c-Jun expression exhibit mild epithelial cell proliferation but no epithelial lineage changes compared with those of nontransgenic mice. Among the four ErbB4 isoforms, JM-a/CYT-2 and JM-b/CYT-2 exhibited the highest AP-1 activity when cells coexpressing KITENIN and each isoform were stimulated by EGF. Interestingly, predominant overexpression of the ErB4-CYT-2 mRNA as well as increased EGFR expression were observed in intestinal adenoma of APC(min/+) mice, which makes the microenvironment of activated EGF signaling. When we crossed villin-KITENIN mice with APC(min/+) mice, intestinal tumor tissues in the crossed mice showed the characteristics of early-stage invading adenocarcinoma. In patients with colorectal cancer, ErbB4-CYT-2 mRNA expression was significantly greater in tumor tissues than in normal adjacent tissues, but no significant differences in tumor tissue expression were found between different colorectal cancer stages. Furthermore, the mRNA expression of KITENIN and that of ErbB4-CYT-2 were positively correlated in human colorectal cancer tissue.

CONCLUSIONS

Elevated coexpression of KITENIN and ErbB4-CYT-2 promotes the transition of colon adenoma to adenocarcinoma within an APC loss-associated tumor microenvironment.

EGFR promoter exhibits dynamic histone modifications and binding of ASH2L and P300 in human germinal matrix and gliomas

Several signaling pathways important for the proliferation and growth of brain cells are pathologically dysregulated in gliomas, including the epidermal growth factor receptor (EGFR). Expression of EGFR is high in neural progenitors during development and in gliomas but decreases significantly in most adult brain regions. Here we show that EGFR expression is maintained in the astrocyte ribbon of the adult human subventricular zone. The transcriptional regulation of EGFR expression is poorly understood. To investigate the role of epigenetics on EGFR regulation in the contexts of neural development and gliomagenesis, we measured levels of DNA methylation and histone H3 modifications at the EGFR promoter in human brain tissues, glioma specimens, and EGFR-expressing neural cells, acutely isolated from their native niche. While DNA was constitutively hypomethylated in non-neoplastic and glioma samples, regardless of their EGFR-expression status, the activating histone modifications H3K27ac and H3K4me3 were enriched only when EGFR is highly expressed (developing germinal matrix and gliomas). Conversely, repressive H3K27me3 marks predominated in adult white matter where EGFR is repressed. Furthermore, the histone methyltransferase core enzyme ASH2L was bound at EGFR in the germinal matrix and in gliomas where levels of H3K4me3 are high, and the histone acetyltransferase P300 was bound in samples with H3K27ac enrichment. Our studies use human cells and tissues undisturbed by cell-culture artifact, and point to an important, locus-specific role for chromatin remodeling in EGFR expression in human neural development that may be dysregulated during gliomagenesis, unraveling potential novel targets for future drug therapy.

Aspirin Prevents Colorectal Cancer by Normalizing EGFR Expression

BACKGROUND

Aspirin intake reduces the risk of colorectal cancer (CRC), but the molecular underpinnings remain elusive. Epidermal growth factor receptor (EGFR), which is overexpressed in about 80% of CRC cases, is implicated in the etiology of CRC. Here, we investigated whether aspirin can prevent CRC by normalizing EGFR expression.

METHODS

Immunohistochemistry staining was performed on paraffin-embedded tissue sections from normal colon mucosa, adenomatous polyps from FAP patients who were classified as regular aspirin users or nonusers. The interplay between cyclooxygenase-2 (COX-2) and EGFR was studied in primary intestinal epithelial cells isolated from Apc^Min mice, immortalized normal human colon epithelial cells (HCEC) as well as murine embryonic fibroblasts (MEFs).

RESULTS

Immunohistochemistry staining results established that EGFR overexpression is an early event in colorectal tumorigenesis, which can be greatly attenuated by regular use of aspirin. Importantly, EGFR and COX-2 were co-overexpressed and co-localized with each other in FAP patients. Further mechanistic studies revealed that COX-2 overexpression triggers the activation of the c-Jun-dependent transcription factor, activator protein-1 (AP-1), which binds to the Egfr promoter. Binding facilitates the cellular accumulation of EGFR and lowers the threshold required for pre-neoplastic cells to undergo transformation.

CONCLUSION

Aspirin might exert its chemopreventive activity against CRC, at least partially, by normalizing EGFR expression in gastrointestinal precancerous lesions.

Systematic analysis of BRAF(V600E) melanomas reveals a role for JNK/c-Jun pathway in adaptive resistance to drug-induced apoptosis

Drugs that inhibit RAF/MEK signaling, such as vemurafenib, elicit profound but often temporary anti-tumor responses in patients with BRAF^V600E melanoma. Adaptive responses to RAF/MEK inhibition occur on a timescale of hours to days, involve homeostatic responses that reactivate MAP kinase signaling and compensatory mitogenic pathways, and attenuate the anti-tumor effects of RAF/MEK inhibitors. We profile adaptive responses across a panel of melanoma cell lines using multiplex biochemical measurement, single-cell assays, and statistical modeling and show that adaptation involves at least six signaling cascades that act to reduce drug potency (IC₅₀) and maximal effect (i.e., E_max ≪ 1). Among these cascades, we identify a role for JNK/c-Jun signaling in vemurafenib adaptation and show that RAF and JNK inhibitors synergize in cell killing. This arises because JNK inhibition prevents a subset of cells in a cycling population from becoming quiescent upon vemurafenib treatment, thereby reducing drug E_max. Our findings demonstrate the breadth and diversity of adaptive responses to RAF/MEK inhibition and a means to identify which steps in a signaling cascade are most predictive of phenotypic response.

Epithelial sheet movement requires the cooperation of c-Jun and MAP3K1

Epithelial sheet movement is an essential morphogenetic process during mouse embryonic eyelid closure in which Mitogen-Activated Protein 3 Kinase 1 (MAP3K1) and c-Jun play a critical role. Here we show that MAP3K1 associates with the cytoskeleton, activates Jun N-terminal kinase (JNK) and actin polymerization, and promotes the eyelid inferior epithelial cell elongation and epithelium protrusion. Following epithelium protrusion, c-Jun begins to express and acts to promote ERK phosphorylation and migration of the protruding epithelial cells. Homozygous deletion of either gene causes defective eyelid closure, but non-allelic non-complementation does not occur between Map3k1 and c-Jun and the double heterozygotes have normal eyelid closure. Results from this study suggest that MAP3K1 and c-Jun signal through distinct temporal-spatial pathways and that productive epithelium movement for eyelid closure requires the consecutive action of MAP3K1-dependent cytoskeleton reorganization followed by c-Jun-mediated migration.

Reversible and adaptive resistance to BRAF(V600E) inhibition in melanoma

Treatment of BRAF(V600E) mutant melanoma by small molecule drugs that target the BRAF or MEK kinases can be effective, but resistance develops invariably. In contrast, colon cancers that harbour the same BRAF(V600E) mutation are intrinsically resistant to BRAF inhibitors, due to feedback activation of the epidermal growth factor receptor (EGFR). Here we show that 6 out of 16 melanoma tumours analysed acquired EGFR expression after the development of resistance to BRAF or MEK inhibitors. Using a chromatin-regulator-focused short hairpin RNA (shRNA) library, we find that suppression of sex determining region Y-box 10 (SOX10) in melanoma causes activation of TGF-β signalling, thus leading to upregulation of EGFR and platelet-derived growth factor receptor-β (PDGFRB), which confer resistance to BRAF and MEK inhibitors. Expression of EGFR in melanoma or treatment with TGF-β results in a slow-growth phenotype with cells displaying hallmarks of oncogene-induced senescence. However, EGFR expression or exposure to TGF-β becomes beneficial for proliferation in the presence of BRAF or MEK inhibitors. In a heterogeneous population of melanoma cells having varying levels of SOX10 suppression, cells with low SOX10 and consequently high EGFR expression are rapidly enriched in the presence of drug, but this is reversed when the drug treatment is discontinued. We find evidence for SOX10 loss and/or activation of TGF-β signalling in 4 of the 6 EGFR-positive drug-resistant melanoma patient samples. Our findings provide a rationale for why some BRAF or MEK inhibitor-resistant melanoma patients may regain sensitivity to these drugs after a 'drug holiday' and identify patients with EGFR-positive melanoma as a group that may benefit from re-treatment after a drug holiday.

Senescence sensitivity of breast cancer cells is defined by positive feedback loop between CIP2A and E2F1

Senescence induction contributes to cancer therapy responses and is crucial for p53-mediated tumor suppression. However, whether p53 inactivation actively suppresses senescence induction has been unclear. Here, we show that E2F1 overexpression, due to p53 or p21 inactivation, promotes expression of human oncoprotein CIP2A, which in turn, by inhibiting PP2A activity, increases stabilizing serine 364 phosphorylation of E2F1. Several lines of evidence show that increased activity of E2F1-CIP2A feedback renders breast cancer cells resistant to senescence induction. Importantly, mammary tumorigenesis is impaired in a CIP2A-deficient mouse model, and CIP2A-deficient tumors display markers of senescence induction. Moreover, high CIP2A expression predicts for poor prognosis in a subgroup of patients with breast cancer treated with senescence-inducing chemotherapy. Together, these results implicate the E2F1-CIP2A feedback loop as a key determinant of breast cancer cell sensitivity to senescence induction. This feedback loop also constitutes a promising prosenescence target for therapy of cancers with an inactivated p53-p21 pathway.

SIGNIFICANCE

It has been recently realized that most currently used chemotherapies exert their therapeutic effect at least partly by induction of terminal cell arrest, senescence. However, the mechanisms by which cell-intrinsic senescence sensitivity is determined are poorly understood. Results of this study identify the E2F1-CIP2A positive feedback loop as a key determinant of breast cancer cell sensitivity to senescence and growth arrest induction. Our data also indicate that this newly characterized interplay between 2 frequently overexpressed oncoproteins constitutes a promising prosenescence target for therapy of cancers with inactivated p53 and p21. Finally, these results may also facilitate novel stratification strategies for selection of patients to receive senescence-inducing cancer therapies.

EGFR/HER-targeted therapeutics in ovarian cancer

Despite decades of research and evolving treatment modalities, survival among patients with epithelial ovarian cancer has improved only incrementally. During this same period, the development of biologically targeted therapeutics has improved survival for patients with diverse malignancies. Many of these new drugs target the human epidermal growth factor receptor (EGFR/HER/ErbB) family of tyrosine kinases, which play a major role in the etiology and progression of many carcinomas, including epithelial ovarian cancer. While several HER-targeted therapeutics are US FDA approved for the treatment of various malignancies, none have gained approval for the treatment of ovarian cancer. Here, we review the published literature on HER-targeted therapeutics for the treatment of ovarian cancer, including novel HER-targeted therapeutics in various stages of clinical development, as well as the challenges that have limited the use of these inhibitors in clinical settings.

HDAC inhibition decreases the expression of EGFR in colorectal cancer cells

Epidermal growth factor receptor (EGFR), a receptor tyrosine kinase which promotes cell proliferation and survival, is abnormally overexpressed in numerous tumors of epithelial origin, including colorectal cancer (CRC). EGFR monoclonal antibodies have been shown to increase the median survival and are approved for the treatment of colorectal cancer. Histone deacetylases (HDACs), frequently overexpressed in colorectal cancer and several malignancies, are another attractive targets for cancer therapy. Several inhibitors of HDACs (HDACi) are developed and exhibit powerful antitumor abilities. In this study, human colorectal cancer cells treated with HDACi exhibited reduced EGFR expression, thereby disturbed EGF-induced ERK and Akt phosphorylation. HDACi also decreased the expression of SGLT1, an active glucose transporter found to be stabilized by EGFR, and suppressed the glucose uptake of cancer cells. HDACi suppressed the transcription of EGFR and class I HDACs were proved to be involved in this event. Chromatin immunoprecipitation analysis showed that HDACi caused the dissociation of SP1, HDAC3 and CBP from EGFR promoter. Our data suggested that HDACi could serve as a single agent to block both EGFR and HDAC, and may bring more benefits to the development of CRC therapy.

ETS1 mediates MEK1/2-dependent overexpression of cancerous inhibitor of protein phosphatase 2A (CIP2A) in human cancer cells

EGFR-MEK-ERK signaling pathway has an established role in promoting malignant growth and disease progression in human cancers. Therefore identification of transcriptional targets mediating the oncogenic effects of the EGFR-MEK-ERK pathway would be highly relevant. Cancerous inhibitor of protein phosphatase 2A (CIP2A) is a recently characterized human oncoprotein. CIP2A promotes malignant cell growth and is over expressed at high frequency (40–80%) in most of the human cancer types. However, the mechanisms inducing its expression in cancer still remain largely unexplored. Here we present systematic analysis of contribution of potential gene regulatory mechanisms for high CIP2A expression in cancer. Our data shows that evolutionary conserved CpG islands at the proximal CIP2A promoter are not methylated both in normal and cancer cells. Furthermore, sequencing of the active CIP2A promoter region from altogether seven normal and malignant cell types did not reveal any sequence alterations that would increase CIP2A expression specifically in cancer cells. However, treatment of cancer cells with various signaling pathway inhibitors revealed that CIP2A mRNA expression was sensitive to inhibition of EGFR activity as well as inhibition or activation of MEK-ERK pathway. Moreover, MEK1/2-specific siRNAs decreased CIP2A protein expression. Series of CIP2A promoter-luciferase constructs were created to identify proximal −27 to −107 promoter region responsible for MEK-dependent stimulation of CIP2A expression. Additional mutagenesis and chromatin immunoprecipitation experiments revealed ETS1 as the transcription factor mediating stimulation of CIP2A expression through EGFR-MEK pathway. Thus, ETS1 is probably mediating high CIP2A expression in human cancers with increased EGFR-MEK1/2-ERK pathway activity. These results also suggest that in addition to its established role in invasion and angiogenesis, ETS1 may support malignant cellular growth via regulation of CIP2A expression and protein phosphatase 2A inhibition.

Steroid receptor coactivator 1 deficiency increases MMTV-neu mediated tumor latency and differentiation specific gene expression, decreases metastasis, and inhibits response to PPAR ligands

Background

The peroxisome proliferator activated receptor (PPAR) subgroup of the nuclear hormone receptor superfamily is activated by a variety of natural and synthetic ligands. PPARs can heterodimerize with retinoid X receptors, which have homology to other members of the nuclear receptor superfamily. Ligand binding to PPAR/RXRs results in recruitment of transcriptional coactivator proteins such as steroid receptor coactivator 1 (SRC-1) and CREB binding protein (CBP). Both SRC-1 and CBP are histone acetyltransferases, which by modifying nucleosomal histones, produce more open chromatin structure and increase transcriptional activity. Nuclear hormone receptors can recruit limiting amounts of coactivators from other transcription factor binding sites such as AP-1, thereby inhibiting the activity of AP-1 target genes. PPAR and RXR ligands have been used in experimental breast cancer therapy. The role of coactivator expression in mammary tumorigenesis and response to drug therapy has been the subject of recent studies.

Methods

We examined the effects of loss of SRC-1 on MMTV-neu mediated mammary tumorigenesis.

Results

SRC-1 null mutation in mammary tumor prone mice increased the tumor latency period, reduced tumor proliferation index and metastasis, inhibited response to PPAR and RXR ligands, and induced genes involved in mammary gland differentiation. We also examined human breast cancer cell lines overexpressing SRC-1 or CBP. Coactivator overexpression increased cellular proliferation with resistance to PPAR and RXR ligands and remodeled chromatin of the proximal epidermal growth factor receptor promoter.

Conclusions

These results indicate that histone acetyltransferases play key roles in mammary tumorigenesis and response to anti-proliferative therapies.

Increased EFG- and PDGFalpha-receptor signaling by mutant FGF-receptor 2 contributes to osteoblast dysfunction in Apert craniosynostosis

Dysregulations of osteoblast function induced by gain-of-function genetic mutations in fibroblast growth factor receptors (FGFRs) cause premature fusion of cranial sutures in syndromic craniosynostosis. The pathogenic signaling mechanisms induced by FGFR genetic mutations in human craniosynostosis remain largely unknown. In this study, we have used microarray analysis to investigate the signaling pathways that are activated by FGFR2 mutations in Apert craniosynostosis. Transcriptomic analysis revealed that EGFR and PDGFRalpha expression is abnormally increased in human Apert calvaria osteoblasts compared with wild-type cells. Quantitative RT-PCR and western blot analyses in Apert osteoblasts and immunohistochemical analysis of Apert sutures confirmed the increased EGFR and PDGFRalpha expression in vitro and in vivo. We demonstrate that pharmacological inhibition of EGFR and PDGFR reduces the pathological upregulation of phenotypic osteoblast genes and in vitro matrix mineralization in Apert osteoblasts. Investigation of the underlying molecular mechanisms revealed that activated FGFR2 enhances EGFR and PDGFRalpha mRNA expression via activation of PKCalpha-dependent AP-1 transcriptional activity. We also show that the increased EGFR protein expression in Apert osteoblasts results in part from a post-transcriptional mechanism involving increased Sprouty2-Cbl interaction, leading to Cbl sequestration and reduced EGFR ubiquitination. These data reveal novel molecular crosstalks between activated FGFR2, EGFR and PDGFRalpha that functionally contribute to the osteoblastic dysfunction in Apert craniosynostosis, which may provide a molecular basis for novel therapeutic approaches in this severe skeletal disorder.

Thrombin induces EGF receptor expression and cell proliferation via a PKC(delta)/c-Src-dependent pathway in vascular smooth muscle cells

OBJECTIVE

Thrombin upregulates expression of several proteins in vascular smooth muscle cells (VSMCs) which may contribute to atherosclerosis. Here, we investigated the mechanisms underlying thrombin-induced EGF receptor (EGFR) expression and its effect on VSMCs.

METHODS AND RESULTS

Normal rat VSMCs were used. First, Western blotting and RT-PCR analyses showed that thrombin induces the expression of EGFR at transcription and translation levels in VSMCs. Second, pharmacological inhibitors, dominant negative mutants, and short hairpin RNA interference (shRNA) technology enabled us to demonstrate that thrombin-induced EGFR expression is mediated through PKC(delta)/c-Src-dependent transactivation of EGFR linking to PI3K/Akt and ERK1/2. We further investigated whether the transcription factors AP-1 and NF-kappaB are involved in this response by a promoter assay. Finally, data obtained by using EGFR shRNA technology and XTT assay demonstrated that thrombin-enhanced VSMC proliferation was mediated through upregulation of EGFR.

CONCLUSIONS

Our results demonstrate that thrombin-enhanced VSMC proliferation was mediated through upregulation of EGFR via a PKC(delta)/c-Src-dependent transactivation of EGFR, PI3K-Akt, and ERK, and AP-1/NF-kappaB pathway.

Epigenetic reprogramming during wound healing: loss of polycomb-mediated silencing may enable upregulation of repair genes

Tissue repair is a complex process that requires wound-edge cells to proliferate and migrate, which in turn necessitates induction of a large repair transcriptome. Epigenetic modifications have emerged as crucial regulators of gene expression. Here, we ask whether epigenetic reprogramming might contribute to the concerted induction of repair genes by wound-edge cells. Polycomb group proteins (PcGs) co-operatively silence genes by laying down repressive marks such as histone H3 lysine 27 trimethylation (H3K27me3), which can be removed by specific demethylases. We show that PcGs Eed, Ezh2 and Suz12 are significantly downregulated during murine skin repair, whereas the newly described demethylases Jmjd3 and Utx are markedly upregulated. Correspondingly, we find a striking reduction of repressive H3K27me3 in the wound epidermis. Quantitative chromatin immunoprecipitation studies have revealed that there is less Eed bound to the regulatory regions of two paradigm wound-induced genes, Myc and Egfr, suggesting that loss of polycomb-mediated silencing might contribute to the induction of repair genes.

Enhancive effect of N,N'-dinitrosopiperazine on inducing precancerous lesion on nasal and/or nasopharyngeal epithelia of TgN(p53mt-LMP1)/HT mice

OBJECTIVE

To investigate the enhancive effect of N,N'-dinitrosopiperazine (DNP) on induced carcinogenesis in nasal and/or nasopharyngeal epithelia among TgN(p53mt-LMP1)/HT transgenic mice to examine the underlying mechanism for the development of nasopharyngeal carcinoma (NPC).

METHODS

TgN(p53mt-LMP1)/HT transgenic mice and the same strain of C(57)BL/6J wild-type mice both at the age of 5 months were randomly divided into 2 groups in parallel, respectively, i.e., TgN(p53mt-LMP1)/HT cancerous lesion-inducing group (TI), TgN(p53mt-LMP1)/HT control group (TC), C57BL/6J cancerous lesion-inducing group (CI), and C57BL/6J control group (CC). TI and CI mice were treated only with DNP for 16 weeks, twice each week, while TC and CC mice were given the same volume of saline as controls. At the end of treatment, animals were sacrificed to collect epithelial tissue samples from nasal cavity and nasopharynx for pathohistological evaluation by haematoxylin and eosin (HE) staining and for determination on the expression of TRAF2, c-Jun, and p16 by immunohistochemistry.

RESULTS

Atypical hyperplasia was more significant in the samples of TI than in those of TC, CI, and CC, with the rates of lesions being 90%, 10%, 0, and 0 (P<0.01) respectively, though DNP was used alone in a much shortened inducing period at less dosage and without the use of carcinogenic promoter 12-O-tetradecanoylphorbol-13-acetate as usual. The expressions of tumor necrosis factor (TNF) receptor-associated factor 2 (TRAF2) and c-Jun in these samples were significantly up-regulated in TI (P<0.01), while the expression of p16 was significantly lower in TI than in the other groups (P<0.01).

CONCLUSION

TgN(p53mt-LMP1)/HT mice hold inherited constitutional defect in immune surveillance function, which can be aggravated by environmental carcinogens, such as DNP used even though in a much less strength. The enhanced carcinogenesis-inducing effect of DNP on TgN(p53mt-LMP1)/HT mice should be closely associated with abnormal signaling of activator protein-1 (AP-1) pathway, especially up-regulated expressions of TRAF2 and c-Jun, and down-regulated expression of p16.

Angiotensin II enhances EGF receptor expression levels via ROS formation in HaCaT cells

BACKGROUND

Recent work has shown a novel function of angiotensin II (Ang II) in skin wound healing in which reactive oxygen species might be involved. As Ang II is known to increase superoxide production by activating NADPH oxidase in some non-phagocytic cells, we hypothesized that the produced superoxide by NADPH activation could contribute to the regulation of epidermal growth factor receptor (EGFR) in keratinocytes.

OBJECTIVE

We examined whether Ang II could generate superoxide and enhance EGFR expression levels in HaCaT cells.

METHODS

Superoxide formation was assessed by using hydroethidine. EGFR expression levels were examined by Western blotting.

RESULTS

Ang II (1-100 microM) increased the superoxide formation. Ang II (1-100 microM) resulted in a dose-dependent increase in cell proliferation in HaCaT cells. Heparin-binding epidermal growth factor activated the EGFR at 5-10 min. Although Ang II did not activate the EGFR, the expression levels of EGFR protein were increased in HaCaT cells treated with Ang II (1 microM) at 6h. Apocynin, a NADPH oxidase inhibitor, decreased the expression levels of EGFR. Xanthine/xanthine oxidase system, an exogenous superoxide generating system, enhanced the EGFR protein expression. Although Ang II did not affect the nitric oxide (NO) production, a NO synthase inhibitor N(omega)-nitro-l-arginine methyl ester suppressed the Ang II-induced EGFR expression levels in HaCaT cells. Thus, constitutive NO is required for the Ang II-induced EGFR expression in HaCaT cells.

CONCLUSION

These results suggest that Ang II enhances the cell proliferation and EGFR expression via superoxide production under the regulation of NO in HaCaT cells, implying that Ang II may regulate the proliferation, differentiation and tumorigenesis of the epidermis by harmonizing the superoxide and NO production.

NEAP causes down-regulation of EGFR, subsequently induces the suppression of NGF-induced differentiation in PC12 cells

Neuroendocrine-associated phosphatase (NEAP), an atypical dual specificity phosphatase is preferentially expressed in neuroendocrine cells. In this study we found that NEAP, but not NEAP-(C152S) mutant, evidently reduced epidermal growth factor (EGF) receptor (EGFR) downstream signaling, and impaired cell growth in response to EGF stimulation in PC12 cells. These phenomena were associated with NEAP-mediated down-regulation of EGFR mRNA and protein. NEAP had no significant effect on ErbB2/3 expression and phosphorylation levels in response to heregulin, indicating that the negative effect of NEAP on EGFR was selective. We showed that NEAP suppressed EGFR expression via decreasing the EGFR promoter activity and this was mediated through down-regulations of the Akt pathway and Wilms' tumor gene product (WT1). Consistent with these results, expression of WT1 reversed the suppressive effect of NEAP on EGFR promoter activity. Additionally, NEAP knockdown by RNA interference enhanced EGFR protein expression and nerve growth factor-induced differentiation, and an EGFR-specific inhibitor could reverse the later event. Taken together, our study indicated that NEAP modulates PC12 differentiation via suppression of EGFR expression and signaling.

c-Fos overexpression increases the proliferation of human hepatocytes by stabilizing nuclear Cyclin D1

AIM: To investigate the effect of stable c-Fos overexpression on immortalized human hepatocyte (IHH) proliferation.

METHODS: IHHs stably transfected with c-Fos (IHH-Fos) or an empty vector (IHH-C) were grown in medium supplemented with 1% serum or stimulated with 10% serum. Cell proliferation was assessed by cell counts, 3H-thymidine uptake and flow cytometry analyses. The levels of cell cycle regulatory proteins (Cyclin D1, E, A) cyclin dependent kinases (cdk) cdk2, cdk4, cdk6, and their inhibitors p15, p16, p21, p27, total and phosphorylated GSK-3β and epidermal growth factor receptor (EGF-R) were assayed by Western blotting. Analysis of Cyclin D1 mRNA levels was performed by reverse transcription-polymerase chain reaction and real-time polymerase chain reaction (PCR) analysis. Stability of Cyclin D1 was studied by cycloheximide blockade experiments.

RESULTS: Stable c-Fos overexpression increased cell proliferation under low serum conditions and resulted in a two-fold increase in [³H]-thymidine incorporation following serum addition. Cell cycle analysis by flow cytometry showed that c-Fos accelerated the cell cycle kinetics. Following serum stimulation, Cyclin D1 was more abundantly expressed in c-Fos overexpressing cells. Cyclin D1 accumulation did not result from increased transcriptional activation, but from nuclear stabilization. Overexpression of c-Fos correlated with higher nuclear levels of inactive phosphorylated GSK-3β, a kinase involved in Cyclin D1 degradation and higher levels of EGF-R mRNA, and EGF-R protein compared to IHH-C both in serum starved, and in serum stimulated cells. Abrogation of EGF-R signalling in IHH-Fos by treatment with AG1478, a specific EGF-R tyrosine kinase inhibitor, prevented the phosphorylation of GSK-3β induced by serum stimulation and decreased Cyclin D1 stability in the nucleus.

CONCLUSION: Our results clearly indicate a positive role for c-Fos in cell cycle regulation in hepatocytes. Importantly, we delineate a new mechanism by which c-Fos could contribute to hepatocarcinogenesis through stabilization of Cyclin D1 within the nucleus, evoking a new feature to c-Fos implication in hepatocellular carcinoma.

Sphingosine 1-phosphate induces EGFR expression via Akt/NF-kappaB and ERK/AP-1 pathways in rat vascular smooth muscle cells

Sphingosine 1-phosphate (S1P) has been shown to regulate expression of several genes in vascular smooth muscle cells (VSMCs) and contributes to arteriosclerosis. However, the mechanisms regulating epidermal growth factor receptor (EGFR) expression by S1P in aortic VSMCs remain unclear. Western blotting and RT-PCR analyses showed that S1P induced EGFR mRNA and protein expression in a time- and concentration-dependent manner, which was attenuated by inhibitors of MEK1/2 (U0126) and phosphatidylinositide 3-kinase (PI3K; wortmannin), and transfection with dominant negative mutants of ERK and Akt, respectively. These results suggested that S1P-induced EGFR expression was mediated through p42/p44 MAPK and PI3K/Akt pathways in VSMCs. In accordance with these findings, S1P stimulated phosphorylation of p42/p44 MAPK and Akt which was attenuated by U0126 and wortmannin, respectively. Furthermore, S1P-induced EGFR upregulation was blocked by a selective NF-kappaB inhibitor helenalin. Immunofluorescent staining and reporter gene assay revealed that S1P-induced activation of NF-kappaB was blocked by wortmannin, but not by U0126, suggesting that activation of NF-kappaB was mediated through PI3K/Akt. Moreover, S1P-induced EGFR expression was inhibited by an AP-1 inhibitor curcumin and tanshinone IIA. S1P-stimulated AP-1 subunits (c-Jun and c-Fos mRNA) expression was attenuated by U0126 and wortmannin, suggesting that MEK and PI3K/ERK cascade linking to AP-1 was involved in EGFR expression. Upregulation of EGFR by S1P may exert a phenotype modulation of VSMCs. This hypothesis was supported by pretreatment with AG1478 or transfection with shRNA of EGFR that attenuated EGF-stimulated proliferation of VSMCs pretreated with S1P, determined by XTT assay. These results demonstrated that in VSMCs, activation of Akt/NF-kappaB and ERK/AP-1 pathways independently regulated S1P-induced EGFR expression in VSMCs. Understanding the mechanisms involved in S1P-induced EGFR expression on VSMCs may provide potential therapeutic targets in the treatment of arteriosclerosis.

Loss of p53 induces epidermal growth factor receptor promoter activity in normal human keratinocytes

Overexpression of the epidermal growth factor receptor (EGFR) in human papillomavirus type 16-immortalized human keratinocytes (HKc) is caused by the viral oncoprotein E6, which targets p53 for degradation. We have previously observed that expression of p53 RNAi in normal HKc is associated with an increase in EGFR mRNA and protein. We now report that p53 RNAi induces EGFR promoter activity up to approximately 10-fold in normal HKc, and this effect does not require intact p53 binding sites on the EGFR promoter. Exogenous wild-type p53 inhibits the EGFR promoter at low levels, and activates it at higher concentrations. Yin Yang 1 (YY1), which negatively regulates p53, induces EGFR promoter activity, and this effect is augmented by p53 RNAi. Intact p53 binding sites on the EGFR promoter are not required for activation by YY1. In addition, Sp1 and YY1 synergistically induce the EGFR promoter in normal HKc, indicating that Sp1 may recruit YY1 as a co-activator. Wild-type p53 suppressed Sp1- and YY1-mediated induction of the EGFR promoter. We conclude that acute loss of p53 in normal HKc induces EGFR expression by a mechanism that involves YY1 and Sp1 and does not require p53 binding to the EGFR promoter.

Clinical implications of the ErbB/epidermal growth factor (EGF) receptor family and its ligands in ovarian cancer

The ERBB or EGF receptor (EGFR) proto-oncogene family, which consists of four structurally-related transmembrane receptors (i.e., EGFR, ErbB2, ErbB3, and ErbB4), plays an etiological role in the molecular pathogenesis of cancer and is a key therapeutic target in many types of cancer, including ovarian cancer. These ErbB/EGF receptor tyrosine kinases play important physiologic roles in cell proliferation, survival, adhesion, motility, invasion, and angiogenesis. It is, therefore, not surprising that gene amplification, genetic mutation, and altered transcription/translation result in aberrant ErbB/EGF receptor expression and/or signal transduction, contributing to the development of malignant transformation. Clinically, the diagnostic, prognostic, and theragnostic significance of any single ErbB receptor and/or ErbB ligand is controversial, but generally, ErbB receptor overexpression has been correlated with poor prognosis and decreased therapeutic responsiveness in ovarian cancer patients. Thus, anticancer agents targeting ErbB/EGF receptors hold great promise for personalized cancer treatment. Yet, challenges remain in designing prospective clinical trials to assess the clinical utility of ErbB receptors and their ligands to diagnose cancer; to predict progression-free and overall survival, therapeutic responsiveness, and disease recurrence; and to monitor treatment responsiveness. Here, we review the tissue expression and serum biomarker studies that have evaluated the diagnostic, prognostic, and theragnostic utility of ErbB/EGF receptors, their circulating soluble isoforms (sEGFR/sErbBs), and their cognate ligands in ovarian cancer patients.

Loss of p53 expression correlates with metastatic phenotype and transcriptional profile in a new mouse model of head and neck cancer

Squamous cell carcinoma of the head and neck (HNSCC) is the sixth most frequent cancer worldwide. Because HNSCC is largely acquired by environmental carcinogen exposure rather than through germ line mutations, there are no known familial forms of the disease in humans nor are there inbred rodent strains prone to spontaneous head and neck tumors. Transgenic animals with inactivation of tumor suppressor genes commonly mutated in human cases of HNSCC provide attractive models for studying the pathogenesis of head and neck cancer. p53 is the most frequently inactivated tumor suppressor gene in HNSCC. We used a chemical induction protocol in mice heterozygous for the p53 gene to evaluate how p53 inactivation contributed to head and neck carcinogenesis the mouse model. Metastatic squamous cell carcinomas developed in 100% of animals. Histopathologically, the tumors ranged from well to poorly differentiated and showed many molecular features of human HNSCC. Mice carrying only one p53 allele developed tumors with significantly reduced latency compared with wild-type controls (average, 18 versus 22 weeks). Metastatic cancer cells showed complete loss of p53 expression when compared with primary tumors. Transcriptional profiling showed not only distinct genetic differences between primary and metastatic tumors, but also when cancers from heterozygous null and wild-type animals were compared. Our results provide novel insights into the molecular genetics of tumor progression in head and neck cancer.

EGF-R regulates MMP function in fibroblasts through MAPK and AP-1 pathways

EGF-R regulates cell proliferation, migration, and invasion in fibroblasts. However, the connection of EGF-R with downstream signaling pathways mediating these responses has remained elusive. Here we provide genetic and biochemical evidence that EGF-R- and AP-1-mediated signals are required for MMP expression and collagen contraction in fibroblasts. In EGF-R (-/-) mouse embryonal fibroblasts, basal and inducible expression of several MMPs, including MMP-2, -3, and -14 is impaired in comparison to wild-type counterparts. The loss of MMP expression is associated with a suppression of EGF-induced Erk and Jnk activities, and AP-1 DNA-binding and transactivation capacities. While inhibition of Jnk mainly prevents EGF-induced phosphorylation of c-Jun, inhibition of Erk pathway suppresses both the expression and phosphorylation of c-Jun and c-Fos proteins. Moreover, the expression of MMP-3 and -14, and collagen contraction is partially prevented by Mek/Erk and Jnk inhibitors. However, Jnk inhibitor also suppresses cell growth independently of EGF-R activity. The central role of AP-1 as a mediator of EGF-R signaling in fibroblasts is emphasized by the finding that expression of a dominant negative c-Jun downregulates the expression of MMP-3. Conversely, expression of a constitutively active Mek1 can induce MMP-3 expression independently of upstream signals. The results indicate that ERK pathway and AP-1 are downstream effectors of the EGF-R-mediated MMP-3 expression and collagen contraction in fibroblasts.

Epidermal growth factor receptor signaling is up-regulated in human colonic aberrant crypt foci

Aberrant crypt foci (ACF) are collections of abnormal colonic crypts with heterogeneous molecular and pathologic characteristics. Large and dysplastic ACF are putative precursors of colon cancer with neoplastic risk related to increased proliferation. In this study, we examined the role of epidermal growth factor receptor (EGFR) signaling in regulating ACF proliferation. Using magnification chromoendoscopy, we collected large ACF with endoscopic features of dysplasia and separately biopsied adjacent mucosa. Transcript levels were measured by real-time PCR, proteins were assessed by Western blotting, and levels were expressed as fold changes of adjacent mucosa. K-ras and B-Raf mutations were assessed by PCR and Ras activation by the ratio Ras-GTP / (Ras-GTP + Ras-GDP). At the RNA level, 38% of ACF were hyperproliferative, with proliferating cell nuclear antigen (PCNA) mRNA >/=2-fold of adjacent mucosa. Hyperproliferative ACF had significantly increased mRNA levels of EGFR (6.0 +/- 1.7-fold), transforming growth factor-alpha (14.4 +/- 5.0-fold), heparin-binding EGF-like growth factor (4.5 +/- 1.4-fold), cyclin D1 (4.6 +/- 0.7-fold), and cyclooxygenase-2 (COX-2; 9.3 +/- 4.2-fold; P < 0.05). At the protein level, 46% of ACF were hyperproliferative (PCNA, 3.2 +/- 1.2-fold). In hyperproliferative ACF, 44% possessed significant increases in four EGFR signaling components: EGFR (9.5 +/- 1.3-fold), phosphoactive ErbB2 (2.6 +/- 0.4-fold), phosphoactive extracellular signal-regulated kinase (3.7 +/- 1.1-fold), and cyclin D1 (3.4 +/- 0.8-fold; P < 0.05). Ras was activated in 46% of ACF (3.2 +/- 0.4-fold; P < 0.05), but K-ras mutations were present in only 7% of ACF. In contrast to COX-2 mRNA, the protein was not increased in hyperproliferative ACF. In summary, we have shown that ACF with up-regulated PCNA possess increased EGFR signaling components that likely contribute to the enhanced proliferative state of dysplastic-appearing ACF.

The complexity of targeting EGFR signalling in cancer: from expression to turnover

The epidermal growth factor receptor (ErbB1 or EGFR) has been found to be altered in a variety of human cancers. A number of agents targeting these receptors, including specific antibodies directed against the ligand-binding domain of the receptor and small molecules that inhibit kinase activity are either in clinical trials or are already approved for clinical treatment. However, identifying patients that are likely to respond to such treatments has been challenging. As a consequence, it still remains important to identify additional alterations of the tumor cell that contribute to the response to EGFR-targeted agents. While EGFR-mediated signalling pathways have been well established, there is still a rather limited understanding of how intracellular protein-protein interactions, ubiquitination, endocytosis and subsequent degradation of EGFR contribute to the determination of sensitivity to EGFR targeting agents and are emerging areas of investigation. This review primarily focuses on the basic signal transduction pathways mediated through activated membrane bound and/or endosomal EGFR and emphasizes the need to co-target additional proteins that function either upstream or downstream of EGFR to improve cancer therapy.

p53 apoptotic response to DNA damage dependent on bcl2 but not bax in head and neck squamous cell carcinoma lines

BACKGROUND

In many tumors, the p53 gene has been mutated or deleted. p53 null mutant mice are prone to development of a variety of neoplasms at an early age. In head and neck cancer, p53 mutations are detected in most cases. p53 has been shown to induce growth arrest, differentiation, and death when overexpressed in cancer cell lines. p53 responds to DNA damage by arresting the cell cycle in G1 or G2 phase until repair can be completed. If DNA damage is severe, p53 may trigger programmed cell death by means of proapoptotic genes such as bax. Studies have suggested that p53 target genes must be intact for proper functioning of the tumor suppressor.

METHODS

We stably expressed transcriptionally active p53 in head and neck squamous cell carcinoma (SCC) lines in which the endogenous gene was inactivated by mutation. We performed proliferation, cell death, cell cycle, and gene expression analysis in control clones and those treated with the DNA damaging agent etoposide.

RESULTS

These clones proliferated slowly with accumulation of cells at the G1/S phase boundary but did not undergo growth arrest or apoptosis. Coexpression of the proapoptotic gene bax (a known target of p53) failed to induce apoptosis in these clones. However, p53 expression sensitized these cells to DNA damage-induced apoptosis by means of inhibition of bcl2 protein levels.

CONCLUSION

We concluded that the p53 apoptotic response to DNA damage was dependent on bcl2 but not bax in head and neck SCC lines.

Reg IV activates the epidermal growth factor receptor/Akt/AP-1 signaling pathway in colon adenocarcinomas

BACKGROUND & AIMS

Reg IV, a secreted protein and member of the Reg multigene family, is up-regulated in malignancies of the human gastrointestinal tract, including colorectal carcinoma (CRC). However, in vitro signal transduction pathway(s) utilized by Reg IV are not yet known.

METHODS

To determine the signaling pathway(s) responsive to Reg IV, we examined the effects of purified recombinant human Reg IV (rhR4) on HCT116 and HT29 colon adenocarcinoma cells.

RESULTS

Addition of rhR4 to cultures led to a dose-dependent increase in cell number similar to that observed after treatment with epidermal growth factor (EGF). In addition, rhR4 treatment resulted in rapid phosphorylation of EGF receptor at Tyr992 and Tyr1068 and Akt at Thr308 and Ser473. Using luciferase reporter gene assays, we demonstrated that Reg IV signaling through EGF receptor and Akt results in increased activator protein-1 (AP-1) transcription factor activity. Real-time reverse-transcription polymerase chain reaction and Western blot analyses revealed quantitative increases in c-Jun, JunB, JunD, and FosB expression associated with increased AP-1 activity. Electrophoretic mobility shift assay further revealed significant increases in AP-1 binding activity in rhR4-treated cells, with increased supershift in the presence of antibodies to JunB, JunD, and FosB. Furthermore, rhR4 treatments led to the increased expression of Bcl-2, Bcl-XL, survivin, and matrilysin, genes associated with a poor prognosis in advanced CRC.

CONCLUSIONS

Reg IV is a potent activator of the EGF receptor/Akt/AP-1 signaling pathway in CRC. Disruption of Reg signaling may have utility as a therapeutic intervention for human gastrointestinal adenocarcinomas.

DNA topoisomerase I is a cofactor for c-Jun in the regulation of epidermal growth factor receptor expression and cancer cell proliferation

DNA topoisomerase I (Topo I) is a molecular target for the anticancer agent topotecan in the treatment of small cell lung cancer and ovarian carcinomas. However, the molecular mechanisms by which topotecan treatment inhibits cancer cell proliferation are unclear. We describe here the identification of Topo I as a novel endogenous interaction partner for transcription factor c-Jun. Reciprocal coimmunoprecipitation analysis showed that Topo I and c-Jun interact in transformed human cells in a manner that is dependent on JNK activity. c-Jun target gene epidermal growth factor receptor (EGFR) was identified as a novel gene whose expression was specifically inhibited by topotecan. Moreover, Topo I overexpression supported c-Jun-mediated reporter gene activation and both genetic and chemical inhibition of c-Jun converted cells resistant to topotecan-elicited EGFR downregulation. Topotecan-elicited suppression of proliferation was rescued by exogenously expressed EGFR. Furthermore, we demonstrate the cooperation of the JNK-c-Jun pathway, Topo I, and EGFR in the positive regulation of HT-1080 cell proliferation. Together, these results have identified transcriptional coactivator Topo I as a first endogenous cofactor for c-Jun in the regulation of cell proliferation. In addition, the results of the present study strongly suggest that inhibition of EGFR expression is a novel mechanism by which topotecan inhibits cell proliferation in cancer therapy.

Interference effect of epigallocatechin-3-gallate on targets of nuclear factor kappaB signal transduction pathways activated by EB virus encoded latent membrane protein 1

AIM

To elucidate the interference effect of epigallocatechin-3-gallate (EGCG) on targets of nuclear factor kappaB (NF-kappaB) signal transduction pathway activated by EB virus encoded latent membrane protein 1 (LMP1) in nasopharyngeal carcinoma (NPC) cell lines.

METHODS

The survival rates of CNE1 and CNE-LMP1 cell lines after the EGCG treatment were determined by MTT assay. NF-kappaB activation in CNE1 and CNE-LMP1 cells after EGCG treatment was analyzed by promoter luciferase reporter system. And then nuclear translocation of NF-kappaB (p65) after the EGCG treatment was analyzed by immunofluorescence and western blotting. Meanwhile, the changes of IkappaBalpha phosphorylation were observed after the EGCG treatment. EGFR promoter activity was analyzed by promoter luciferase reporter system and EGFR phosphorylation was observed by western blotting after the EGCG treatment.

RESULTS

EGCG inhibited the survival rates of CNE1 and CNE-LMP1 cells and NF-kappaB activation caused by LMP1 in CNE-LMP1 cells. EGCG also suppressed the nuclear translocation of NF-kappaB (p65) and IkappaBalpha phosphorylation. Meanwhile, EGCG inhibited EGFR promoter activity and EGFR phosphorylation.

CONCLUSIONS

EGCG inhibited not only the dose-dependent survival rate of NPC cells, but also the dose-dependent activation of NF-kappaB. This inhibition of LMP1-caused NF-kappaB activation was mediated via the phosphorylative degradation of its inhibitory protein IkappaBalpha, and then EGCG inhibited EGFR activity which was a downstream gene from NF-kappaB. This study suggests that interference effect of EGCG on targets of signal transduction pathway plays an important role in the anticancer function.

Global Gene Expression Analysis of Estrogen Receptor Transcription Factor Cross Talk in Breast Cancer: Identification of Estrogen-Induced/Activator Protein-1-Dependent Genes

There is a growing body of literature supporting estrogen’s ability to affect gene expression through a nonclassical pathway, in which estrogen receptor (ER) modulates the activity of other transcription factors such as activator protein (AP)-1, specificity protein (Sp-1), or nuclear factor-κB (NFκB). We hypothesized that many estrogen-induced genes are dependent on AP-1 for their expression and that these genes can be identified using genomic strategies. Using cells expressing an inducible cJun dominant negative, we studied the estrogen induction of genes under conditions in which AP-1 was normal or blocked. We show that the expression of AP-1-dependent genes was inhibited by the cJun dominant negative and that AP-1 blockade does not affect mRNA ERα expression or estrogen induction of estrogen-responsive element activity. Using a microarray approach, we then identified 20 new estrogen-induced/AP-1-dependent genes. These estrogen-induced/AP-1-dependent genes contain a higher frequency of consensus AP-1 sites in their promoters and have increased sensitivity to the AP-1 stimulant tetradecanoyl phorbol acetate when compared with estrogen-induced genes whose expression was not affected by AP-1 blockade. We also show estrogen and AP-1-dependent recruitment of ER, steroid receptor coactivator-1, and p300 to the promoter of these genes by chromatin immunoprecipitation. These studies demonstrate that microarrays can be used in a reverse genetics approach to predict the functional promoter structure of large numbers of genes that are regulated by multiple transcription factors.

Epstein-Barr virus latent membrane protein 1 modulates epidermal growth factor receptor promoter activity in a nuclear factor kappa B-dependent manner

The Epstein-Barr virus (EBV) latent membrane protein 1 (LMP1) oncoprotein may cause multiple cellular changes including the induction of epidermal growth factor receptor (EGFR) expression and activation of the NFkappaB transcription factor. LMP1 increases the levels of both EGFR protein and mRNA, but does not stabilize EGFR mRNA. Thus, the effects of LMP1 are likely to be mediated by the direct activation of the EGFR promoter. In this study, induction of LMP1 increased the EGFR in both protein and promoter levels in a dose-dependent manner using tetracycline-regulated LMP1 expression in nasopharyngeal carcinoma (NPC) cell line. Mutational analysis of the LMP1 protein indicated that the C-terminal activation region-1 (CTAR1) domain was mainly involved in the EGFR promoter induction, while CTAR2 was necessary but not sufficient to induce EGFR promoter. Inhibition of LMP1-mediated NFkappaB activation by constitutive repressive IkappaBalpha marginally decreased EGFR promoter activity using transiently transfected IkappaBalpha dominant negative mutant. Promoter mutagenesis analysis demonstrated that two putative NFkappaB binding sites of EGFR promoter were very necessary for the transcriptional activity of EGFR induced by LMP1, the proximal NFkappaB binding site was more important than the distal NFkappaB binding site, and both NFkappaB binding sites played a cooperative role. Taken together, Epstein-Barr virus latent membrane protein 1 modulated the EGFR promoter activity in a NFkappaB-dependent manner.

Invasion of normal human fibroblasts induced by v-Fos is independent of proliferation, immortalization, and the tumor suppressors p16INK4a and p53

Invasion is generally perceived to be a late event during the progression of human cancer, but to date there are no consistent reports of alterations specifically associated with malignant conversion. We provide evidence that the v-Fos oncogene induces changes in gene expression that render noninvasive normal human diploid fibroblasts highly invasive, without inducing changes in growth factor requirements or anchorage dependence for proliferation. Furthermore, v-Fos-stimulated invasion is independent of the pRb/p16(INK4a) and p53 tumor suppressor pathways and telomerase. We have performed microarray analysis using Affymetrix GeneChips, and the gene expression profile of v-Fos transformed cells supports its role in the regulation of invasion, independent from proliferation. We also demonstrate that invasion, but not proliferation, is dependent on the activity of the up-regulated epidermal growth factor receptor. Taken together, these results indicate that AP-1-directed invasion could precede deregulated proliferation during tumorigenesis and that sustained activation of AP-1 could be the epigenetic event required for conversion of a benign tumor into a malignant one, thereby explaining why many malignant human tumors present without an obvious premalignant hyperproliferative dysplastic lesion.

Aldosterone stimulates epidermal growth factor receptor expression

The steroid hormone aldosterone plays an important role during pathological tissue modifications, similar to cardiovascular or renal fibrosis. The underlying mechanisms for the pathological actions are not understood. Interaction of aldosterone with the epidermal growth factor (EGF) receptor is an attractive hypothesis to explain pathological tissue remodeling elicited by aldosterone, because (i) mineralocorticoids can sensitize cells for EGF, (ii) mineralocorticoid receptor (MR)-antagonists reduce EGFR-mRNA expression, (iii) EGFR itself supports the development of cardiovascular or renal fibrosis, and (iv) signaling elements involved in the pathological action of aldosterone (similar to ERK1/2 or NFkB) are typical downstream modules during EGF signaling. In addition, an interaction of aldosterone and EGF with respect to ERK1/2 activation has been described. Here we show that aldosterone stimulates EGFR expression in renal tissue of adrenalectomized rats and in human renal primary cell cultures. Furthermore, Chinese hamster ovary (CHO) cells normally devoid of EGFR or MR express EGFR after transfection with human MR (CHO-MR cells) but not after transfection with human glucocorticoid receptor (CHO-GR cells). In CHO-MR cells, EGFR-expression is up-regulated by aldosterone and inhibited by spironolactone. CHO-MR cells but not CHO-GR cells respond with ERK1/2 phosphorylation to EGF exposure. The responsiveness to other peptide hormones was virtually not affected. These data suggest that EGFR is an aldosterone-induced protein and is involved in the manifold (patho)biological actions of aldosterone.