The antagonistic regulation of human MUC4 and ErbB-2 genes by the Ets protein PEA3 in pancreatic cancer cells: implications for the proliferation/differentiation balance in the cells

A Double-Negative Feedback Interaction between miR-21 and PPAR-α in Clear Renal Cell Carcinoma

Clear cell renal cell carcinoma (ccRCC) is the main histotype of kidney cancer, which is typically highly resistant to conventional therapies and known for abnormal lipid accumulation. In this context, we focused our attention on miR-21, an oncogenic miRNA overexpressed in ccRCC, and peroxysome proliferator-activated receptor-α (PPAR- α), one master regulator of lipid metabolism targeted by miR-21. First, in a cohort of 52 primary ccRCC samples, using RT-qPCR and immunohistochemistry, we showed that miR-21 overexpression was correlated with PPAR-α downregulation. Then, in ACHN and 786-O cells, using RT-qPCR, the luciferase reporter gene, chromatin immunoprecipitation, and Western blotting, we showed that PPAR-α overexpression (i) decreased miR-21 expression, AP-1 and NF-κB transcriptional activity, and the binding of AP-1 and NF-κB to the miR-21 promoter and (ii) increased PTEN and PDCD4 expressions. In contrast, using pre-miR-21 transfection, miR-21 overexpression decreased PPAR-α expression and transcriptional activity mediated by PPAR-α, whereas the anti-miR-21 (LNA-21) strategy increased PPAR-α expression, but also the expression of its targets involved in fatty acid oxidation. In this study, we showed a double-negative feedback interaction between miR-21 and PPAR-α. In ccRCC, miR-21 silencing could be therapeutically exploited to restore PPAR-α expression and consequently inhibit the oncogenic events mediated by the aberrant lipid metabolism of ccRCC.

Mucin glycoproteins block apoptosis; promote invasion, proliferation, and migration; and cause chemoresistance through diverse pathways in epithelial cancers

Overexpression of mucin glycoproteins has been demonstrated in many epithelial-derived cancers. The significance of this overexpression remains uncertain. The aim of this paper was to define the association of mucin glycoproteins with apoptosis, cell growth, invasion, migration, adhesion, and clonogenicity in vitro as well as tumor growth, tumorigenicity, and metastasis in vivo in epithelial-derived cancers by performing a systematic review of all published data. A systematic review of PubMed, Embase, and the Cochrane Central Register of Controlled Trials was performed to identify all papers that evaluated the association between mucin glycoproteins with apoptosis, cell growth, invasion, migration, adhesion, and clonogenicity in vitro as well as tumor growth, tumorigenicity, and metastasis in vivo in epithelial-derived cancers. PRISMA guidelines were adhered to. Results of individual studies were extracted and pooled together based on the organ in which the cancer was derived from. The initial search revealed 2031 papers, of which 90 were deemed eligible for inclusion in the study. The studies included details on MUC1, MUC2, MUC4, MUC5AC, MUC5B, MUC13, and MUC16. The majority of studies evaluated MUC1. MUC1 overexpression was consistently associated with resistance to apoptosis and resistance to chemotherapy. There was also evidence that overexpression of MUC2, MUC4, MUC5AC, MUC5B, MUC13, and MUC16 conferred resistance to apoptosis in epithelial-derived cancers. The overexpression of mucin glycoproteins is associated with resistance to apoptosis in numerous epithelial cancers. They cause resistance through diverse signaling pathways. Targeting the expression of mucin glycoproteins represents a potential therapeutic target in the treatment of epithelial-derived cancers.

The mucin MUC4 is a transcriptional and post-transcriptional target of K-ras oncogene in pancreatic cancer. Implication of MAPK/AP-1, NF-κB and RalB signaling pathways

The membrane-bound mucinMUC4 is a high molecularweight glycoprotein frequently deregulated in cancer. In pancreatic cancer, one of the most deadly cancers in occidental countries, MUC4 is neo-expressed in the preneoplastic stages and thereafter is involved in cancer cell properties leading to cancer progression and chemoresistance. K-ras oncogene is a small GTPase of the RAS superfamily, highly implicated in cancer. K-ras mutations are considered as an initiating event of pancreatic carcinogenesis and K-ras oncogenic activities are necessary components of cancer progression. However, K-ras remains clinically undruggable. Targeting early downstream K-ras signaling in cancer may thus appear as an interesting strategy and MUC4 regulation by K-ras in pancreatic carcinogenesis remains unknown. Using the Pdx1-Cre; LStopL-K-rasG12D mouse model of pancreatic carcinogenesis, we show that the in vivo early neo-expression of the mucin Muc4 in pancreatic intraepithelial neoplastic lesions (PanINs) induced by mutated K-ras is correlated with the activation of ERK, JNK and NF-κB signaling pathways. In vitro, transfection of constitutively activated K-rasG12V in pancreatic cancer cells led to the transcriptional upregulation of MUC4. This activation was found to be mediated at the transcriptional level by AP-1 and NF-κB transcription factors via MAPK, JNK and NF-κB pathways and at the posttranscriptional level by a mechanism involving the RalB GTPase. Altogether, these results identify MUC4 as a transcriptional and post-transcriptional target of K-ras in pancreatic cancer. This opens avenues in developing new approaches to target the early steps of this deadly cancer.

Transcriptional regulation of human MUC4 gene: identification of a novel inhibitory element and its nuclear binding protein

The human mucin 4 (MUC4) is aberrantly expressed in pancreatic adenocarcinoma and tumor cell lines, while remaining undetectable in normal pancreas, indicating its important role in pancreatic cancer development. Although its transcriptional regulation has been investigated in considerable detail, some important elements remain unknown. The aim of the present study was to demonstrate the existence of a novel inhibitory element in the MUC4 promoter and characterize some of its binding proteins. By luciferase reporter assay, we located the inhibitory element between nucleotides -2530 and -2521 in the MUC4 promoter using a series of deletion and mutant reporter constructs. Electrophoretic mobility shift assay (EMSA) with Bxpc-3 cell nuclear extracts revealed that one protein or protein complex bind to this element. The proteins binding to this element were purified and identified as Yin Yang 1 (YY1) by mass spectrometry. Supershift assay and chromatin immunoprecipitation (ChIP) assay confirmed that YY1 binds to this element in vitro and in vivo. Moreover, transient YY1 overexpression significantly inhibited MUC4 promoter activity and endogenous MUC4 protein expression. In conclusion, we reported here a novel inhibitory element in the human MUC4 promoter. This provides additional data on MUC4 gene regulation and indicates that YY1 may be a potential target for abnormal MUC4 expression.

Clinical significance of expression of hTERT and MUC4 mRNAs in peripheral blood of patients with pancreatic cancer

AIM: To analyze the clinical significance of expression of human telomerase reverse transcriptase (hTERT) and mucin 4 (MUC4) mRNAs in peripheral blood of patients with pancreatic cancer.

METHODS: Real-time fluorescence quantitative RT-PCR was applied to investigate the quantitative expression of hTERT and MUC4 mRNAs in peripheral blood of patients with pancreatic cancer and healthy controls.

RESULTS: The expression levels of hTERT and MUC4 mRNAs in peripheral blood of patients with pancreatic cancer were significantly higher than those in normal controls (7.95 ± 5.46 vs 0.92 ± 1.07, P < 0.01; 38.25 ± 25.07 vs 4.37 ± 5.96, P < 0.05). The expression of both hTERT and MUC4 mRNAs was associated with lymph node metastasis, surrounding organ infiltration, distant metastasis, and TNM stage (hP = 0.036, 0.027, 0.019; MP = 0.041, 0.022, 0.017).

CONCLUSION: Abnormal expression of hTERT and MUC4 mRNAs closely correlates with invasion and metastasis of pancreatic cancer, and hTERT and MUC4 mRNAs in peripheral blood cells might be useful markers for pancreatic caner.

Mutant K-Ras increases GSK-3β gene expression via an ETS-p300 transcriptional complex in pancreatic cancer

Glycogen synthase kinase-3 beta (GSK-3β) is overexpressed in a number of human malignancies and has been shown to contribute to tumor cell proliferation and survival. Although regulation of GSK-3β activity has been extensively studied, the mechanisms governing GSK-3β gene expression are still unknown. Using pancreatic cancer as a model, we find that constitutively active Ras signaling increases GSK-3β gene expression via the canonical mitogen-activated protein kinase signaling pathway. Analysis of the mechanism revealed that K-Ras regulates the expression of this kinase through two highly conserved E-twenty six (ETS) binding elements within the proximal region. Furthermore, we demonstrate that mutant K-Ras enhances ETS2 loading onto the promoter, and ETS requires its transcriptional activity to increase GSK-3β gene transcription in pancreatic cancer cells. Lastly, we show that ETS2 cooperates with p300 histone acetyltransferase to remodel chromatin and promote GSK-3β expression. Taken together, these results provide a general mechanism for increased expression of GSK-3β in pancreatic cancer and perhaps other cancers, where Ras signaling is deregulated.

Mucins and pancreatic cancer

Pancreatic cancer is characterized by an often dramatic outcome (five year survival < 5%) related to a late diagnosis and a lack of efficient therapy. Therefore, clinicians desperately need new biomarkers and new therapeutic tools to develop new efficient therapies. Mucins belong to an ever increasing family of O-glycoproteins. Secreted mucins are the main component of mucus protecting the epithelia whereas membrane-bound mucins are thought to play important biological roles in cell-cell and cell-matrix interactions, in cell signaling and in modulating biological properties of cancer cells. In this review, we will focus on the altered expression pattern of mucins in pancreatic cancer, from the early neoplastic lesion Pancreatic Intraepithelial Neoplasia (PanIN) to invasive pancreatic carcinomas, and the molecular mechanisms (including genetic and epigenetic regulation) and signaling pathways known to control their expression. Moreover, we will discuss the recent advances about the biology of both secreted and membrane-bound mucins and their key roles in pancreatic carcinogenesis and resistance to therapy. Finally, we will discuss exciting opportunities that mucins offer as potential therapeutic targets in pancreatic cancer.

Transcript profiling of Elf5+/- mammary glands during pregnancy identifies novel targets of Elf5

Background

Elf5, an epithelial specific Ets transcription factor, plays a crucial role in the pregnancy-associated development of the mouse mammary gland. Elf5^−/− embryos do not survive, however the Elf5^+/− mammary gland displays a severe pregnancy-associated developmental defect. While it is known that Elf5 is crucial for correct mammary development and lactation, the molecular mechanisms employed by Elf5 to exert its effects on the mammary gland are largely unknown.

Principal Findings

Transcript profiling was used to investigate the transcriptional changes that occur as a result of Elf5 haploinsufficiency in the Elf5^+/− mouse model. We show that the development of the mouse Elf5^+/− mammary gland is delayed at a transcriptional and morphological level, due to the delayed increase in Elf5 protein in these glands. We also identify a number of potential Elf5 target genes, including Mucin 4, whose expression, is directly regulated by the binding of Elf5 to an Ets binding site within its promoter.

Conclusion

We identify novel transcriptional targets of Elf5 and show that Muc4 is a direct target of Elf5, further elucidating the mechanisms through which Elf5 regulates proliferation and differentiation in the mammary gland.

Muc4/MUC4 functions and regulation in cancer

The membrane mucin MUC4 (human) is abundantly expressed in many epithelia, where it is proposed to play a protective role, and is overexpressed in some epithelial tumors. Studies on the rat homologue, Muc4, indicate that it acts through anti-adhesive or signaling mechanisms. In particular, Muc4/MUC4 can serve as a ligand/modulator of the receptor tyrosine kinase ErbB2, regulating its phosphorylation and the phosphorylation of its partner ErbB3, with or without the involvement of the ErbB3 ligand neuregulin. Muc4/MUC4 can also modulate cell apoptosis via multiple mechanisms, both ErbB2 dependent and independent. Muc4/MUC4 expression is regulated by multiple mechanisms, ranging from transcriptional to post-translational. The roles of MUC4 in tumors suggest that it may be valuable as a tumor marker or target for therapy.

The membrane-bound mucins: From cell signalling to transcriptional regulation and expression in epithelial cancers

The membrane-bound mucins belong to an ever-increasing family of O-glycoproteins. Based on their structure and localization at the cell surface they are thought to play important biological roles in cell-cell and cell-matrix interactions, in cell signalling and in modulating biological properties of cancer cells. Among them, MUC1 and MUC4 mucins are best characterized. Their altered expression in cancer (overexpression in the respiratory, gastro-intestinal, urogenital and hepato-biliary tracts) indicates an important role for these membrane-bound mucins in tumour progression, metastasis, cancer cell resistance to chemotherapeutics drugs and as specific markers of epithelial cancer cells. Some mechanisms responsible for MUC1 and MUC4 role in tumour cell properties have been deciphered recently. However, much remains to be done in order to understand the molecular mechanisms and signalling pathways that control the expression of membrane-bound mucins during the different steps of tumour progression toward adenocarcinoma and evaluate their potential as prognostic/diagnostic markers and as therapeutic tools. In this review we focus on the molecular mechanisms and signalling pathways known to control the expression of membrane-bound mucins in cancer. We will discuss the mechanisms of regulation at the promoter level (including genetic and epigenetic modifications) that may be responsible for the mucin altered pattern of expression in epithelial cancers.

Tumour growth and resistance to gemcitabine of pancreatic cancer cells are decreased by AP-2alpha overexpression

Background:

Activator protein-2α (AP-2α) is a transcription factor that belongs to the family of AP-2 proteins that have essential roles in tumorigenesis. Indeed, AP-2α is considered as a tumour-suppressor gene in different tissues such as colonic, prostatic or breast epithelial cells. Moreover, AP-2α also participates in the control of colon and breast cancer cells sensitivity towards chemotherapeutic drugs. Despite its potential interest, very few data are available regarding the roles of AP-2α in pancreatic cancer.

Methods:

We have developed a stable pancreatic CAPAN-1 cell line overexpressing AP-2α. Consequences of overexpression were studied in terms of in vivo cell growth, gene expression, migration capacity and chemosensitivity.

Results:

In vivo tumour growth of CAPAN-1 cells overexpressing AP-2α was significantly decreased by comparison to control cells. An altered expression pattern of cell cycle-controlling factors (CDK-4, CDK-6, cyclin-G1, p27^kip1 and p57^kip2) was observed in AP-2α-overexpressing clones by microarrays and western blot analysis. Promoter activity and ChIP analysis indicated that AP-2α induces p27^kip1 protein levels by direct binding to and transactivation of its promoter. Moreover, AP-2α overexpression increased the chemosensitivity of CAPAN-1 cells to low doses of gemcitabine and reduced their in vitro migration capacity.

Conclusion:

Our data suggested that AP-2α overexpression could be exploited to decrease in vivo tumour growth of pancreatic cancer cells and to increase their sensitivity to gemcitabine.

Transglutaminase 3 as a prognostic biomarker in esophageal cancer revealed by proteomics

To develop a prognostic biomarker for esophageal squamous cell carcinoma (ESCC), we examined the proteomic profile of ESCC using two-dimensional difference gel electrophoresis (2D-DIGE), and identified proteins associated with prognosis by mass spectrometry. The prognostic performance of the identified proteins was examined by immunohistochemistry in additional cases. We identified 22 protein spots whose intensity was statistically different between ESCC cases with good (N = 9; survived more than 5 years without evidence of recurrence) and poor (N = 24; died within 2 years postsurgery) prognosis, within the patient group that had two or more lymph node metastases. Mass spectrometric protein identification resulted in 18 distinct gene products from the 22 protein spots. Transglutaminase 3 (TGM3) was inversely correlated with shorter patient survival. The prognostic performance of TGM3 was further examined by immunohistochemistry in 76 ESCC cases. The 5-year disease-specific survival rate was 64.5% and 32.1% for patients with TGM3-positive and TGM3-negative tumors, respectively (p = 0.0033). Univariate and multivariate analyses revealed that TGM3 expression was an independent prognostic factor among the clinicopathologic variables examined. It is noteworthy that the prognostic value of TGM3 was shown to be higher than those of the lymph node metastasis, intramural metastasis and vascular invasion status. These results establish TGM3 as a novel prognostic biomarker for ESCC for the first time. Examination of TGM3 expression may provide novel therapeutic strategies to prevent recurrence of ESCC.

Reduced tumorigenesis in mouse mammary cancer cells following inhibition of Pea3- or Erm-dependent transcription

Pea3 and Erm are transcription factors expressed in normal developing branching organs such as the mammary gland. Deregulation of their expression is generally associated with tumorigenesis and particularly breast cancer. By using RNA interference (RNAi) to downregulate the expression of Pea3 and/or Erm in a mammary cancer cell line, we present evidence for a role of these factors in proliferation, migration and invasion capacity of cancer cells. We have used different small interfering RNAs (siRNAs) targeting pea3 and erm transcripts in transiently or stably transfected cells, and assessed the physiological behavior of these cells in in vitro assays. We also identified an in vivo alteration of tumor progression after injection of cells that overexpress pea3 and/or erm short hairpin RNAs (shRNAs) in immunodeficient mice. Using transcriptome profiling in Pea3- or Erm-targeted cells, two largely independent gene expression programs were identified on the basis of their shared phenotypic modifications. A statistically highly significant part of both sets of target genes had previously been already associated with the cellular signaling pathways of the ;proliferation, migration, invasion' class. These data provide the first evidence, by using endogenous knockdown, for pivotal and complementary roles of Pea3 and Erm transcription factors in events crucial to mammary tumorigenesis, and identify sets of downstream target genes whose expression during tumorigenesis is regulated by these transcription factors.

Epigenetic regulation of the human mucin gene MUC4 in epithelial cancer cell lines involves both DNA methylation and histone modifications mediated by DNA methyltransferases and histone deacetylases

The human gene MUC4 encodes a transmembrane mucin, ligand of ErbB2, that is associated with pancreatic tumor progression. In the normal pancreas, MUC4 is not expressed, whereas activation of its expression is observed in the early steps of pancreatic carcinogenesis. The molecular mechanisms responsible for MUC4 gene activation are however still unknown. The MUC4 5'-flanking region being GC-rich and including two CpG islands, we hypothesized that epigenetic regulation may be involved and undertook to decipher the molecular phenomenons implied. By treating cancer cell lines with 5-aza-2'-deoxycytidine (5-aza) and trichostatin A (TSA), we were able to restore MUC4 expression in a cell-specific manner. We showed by bisulfite-treated genomic DNA sequencing and chromatin immunoprecipitation that methylation of five CpG sites and establishment of a repressive histone code at the 5'-untranslated region were associated with MUC4 silencing and impaired its activation by Sp1. Direct involvement of DNMT3A, DNMT3B, HDAC1, and HDAC3 was demonstrated by RNA interference and chromatin immunoprecipitation. Moreover, inhibition of histone deacetylation by TSA was associated with strong MUC4 repression in high-expressing cells. In conclusion, this work shows for the first time the importance of epigenetics in regulating MUC4 expression and may represent a new strategy to inhibit its expression in epithelial tumors.

cAMP-responding element-binding protein and c-Ets1 interact in the regulation of ATP-dependent MUC5AC gene expression

Exogenous ATP activates purinoreceptors on the cell surface that regulate diverse cellular functions, including mucous cell secretion in the respiratory epithelium. In this study, ATP increased MUC5AC mRNA in primary human nasal epithelial cells and in NCI-H292 pulmonary adenocarcinoma cells in vitro. ATP-induced MUC5AC mRNA was mediated by phospholipase Cbeta3. A dominant-negative mutation in the PDZ binding domain of PLCbeta3 inhibited ATP-induced MUC5AC gene expression. ATP sequentially activated the phosphorylation of Akt, ERK1/2, p38, RSK1, and cAMP-responding element-binding protein (CREB) in a protein kinase C-independent manner. ATP-induced MUC5AC mRNA levels were regulated by CREB via direct interaction with c-Ets1 on the MUC5AC gene promoter (located -938 to -930). Effects of CREB and c-Ets1 were additive. Inhibition of either CREB or c-Ets1 inhibited ATP-induced MUC5AC gene expression. Stimulation with ATP caused the direct binding of CREB and c-Ets1 to the MUC5AC promoter, increasing the phosphorylation of c-Ets1. Chromatin immunoprecipitation assays demonstrated that in the presence of ATP, both c-Ets1 and CREB bound to the MUC5AC promoter. The effects of exogenous ATP on MUC5AC gene expression are mediated by a complex regulatory cascade controlling interactions between CREB and c-Ets1 that bind to a promoter element in the MUC5AC gene enhancing MUC5AC gene transcription. ATP-dependent activation of MUC5AC gene expression via CREB-c-Ets1 may contribute to mucous cell hypersecretion associated with common respiratory disorders.

Differential regulation of ErbB2 expression by cAMP-dependent protein kinase in tamoxifen-resistant breast cancer cells

Acquired resistance to tamoxifen (TAM) is a serious therapeutic problem in breast cancer patients, and Her-2/ErbB2 expression is associated with decreased sensitivity to TAM. We previously reported that cAMP-dependent protein kinase (PKA)-mediated activator protein-2 (AP-2) activation was responsible for the expression of Her-2/ErbB2 in p53-inactivated mammary epithelial cells (Yang et al., 2006). In the present study, we tested the hypothesis that PKA plays a role in the expression of ErbB2 in tamoxifen-resistant breast cancer cells. Treatment with H-89, a specific PKA inhibitor, suppressed 4-hydroxytamoxifen-induced ErbB2 expression in control MCF-7 cells. In contrast, PKA inhibition by H-89 or cAMP-dependent protein kinase inhibitor l gamma overexpression increased the expression levels of ErbB2 in TAM-resistant MCF-7 (TAMR-MCF-7) cells. Transcriptional regulation of the erbB2 gene depends on two transcription factors, AP-2 and polyomavirus enhancer activator3 (PEA3). H-89 decreased nuclear or total levels of PEA3 in TAMR-MCF-7 cells. Chromatin immunoprecipitation assay results revealed that H-89 treatment reduced PEA3 binding to the proximal Ets binding site of the erbB2 gene promoter. Reporter gene analyses using human erbB2 gene promoter supported the critical role of PEA3 in the overexpression of ErbB2 in TAMR-MCF-7 cells treated with H-89. This deregulated PKA signaling cascades required for the ErbB2 expression may be important for the differential response of TAM-resistant breast cancer cells to EGF/ErbB2 stimuli.

Transcription factor AP-2alpha represses both the mucin MUC4 expression and pancreatic cancer cell proliferation

MUC4 is a transmembrane mucin expressed in pancreatic ductal adenocarcinoma (DAC) in contrast to normal pancreas, and is an independent predictor of poor prognosis in patients with invasive DAC. Our aim was therefore to investigate the mechanisms that control MUC4 expression in pancreatic cancer cells. We focused our study on activator protein (AP)-2alpha transcription factor that acts as a tumour suppressor gene in several cancers. In a series of 18 human DAC, using immunohistochemistry, we confirmed that MUC4 was exclusively expressed in cancerous or preneoplastic lesions in 83% of the samples. On the contrary, AP-2 was mainly expressed by non-tumoural ductal cells (61%) or endocrine cells (67%). Moreover, MUC4 and AP-2 were never found co-expressed suggesting an inhibitory role of AP-2alpha in normal ductal cells. In CAPAN-1 and CAPAN-2 cells, transient AP-2alpha over-expression decreased both MUC4 mRNA and apomucin levels by 20-40% by a mechanism involving inhibition of MUC4 promoter. By chromatin immunoprecipitation and gel-shift assays, we demonstrated that this inhibition involved two AP-2 cis-elements located in the -475/-238 region of the promoter. CAPAN-1 clones, which stably over-expressed AP-2alpha, displayed a strong MUC4 down-regulation (-38 to -100%), a significant decrease of both cell proliferation and invasion concomitant to the up-regulation of p27 cyclin-dependent kinase inhibitor. In conclusion, our data provide evidence that AP-2alpha is an important in vivo negative regulator of MUC4 expression in human pancreatic tissue and that AP-2alpha may play a tumour-suppressive role in pancreatic DAC.

ETS transcription factors in endocrine systems

E26 transformation-specific (ETS) transcription factors have become increasingly recognized as key regulators of differentiation, hormone responses and tumorigenesis in endocrine organs and target tissues. The ETS family is highly diverse, consisting of both transcription activators and repressors that mediate growth factor signaling and regulate gene expression through combinatorial interactions with multiple protein partners on composite DNA elements. ETS proteins have a role in the endocrine system in establishing pituitary-specific gene expression, mammary gland development and cancers of the breast, prostate and reproductive organs.

Regulation of the human mucin MUC4 by taurodeoxycholic and taurochenodeoxycholic bile acids in oesophageal cancer cells is mediated by hepatocyte nuclear factor 1alpha

MUC4 (mucin 4) is a membrane-bound mucin overexpressed in the early steps of oesophageal carcinogenesis and implicated in tumour progression. We previously showed that bile acids, main components of gastro-oesophageal reflux and tumour promoters, up-regulate MUC4 expression [Mariette, Perrais, Leteurtre, Jonckheere, Hemon, Pigny, Batra, Aubert, Triboulet and Van Seuningen (2004) Biochem. J. 377, 701-708]. HNF (hepatocyte nuclear factor) 1alpha and HNF4alpha transcription factors are known to mediate bile acid effects, and we previously identified cis-elements for these factors in MUC4 distal promoter. Our aim was to demonstrate that these two transcription factors were directly involved in MUC4 activation by bile acids. MUC4, HNF1alpha and HNF4alpha expressions were evaluated by immunohistochemistry in human oesophageal tissues. Our results indicate that MUC4, HNF1alpha and HNF4alpha were co-expressed in oesophageal metaplastic and adenocarcinomatous tissues. Studies at the mRNA, promoter and protein levels indicated that HNF1alpha regulates endogenous MUC4 expression by binding to two cognate cis-elements respectively located at -3332/-3327 and -3040/-3028 in the distal promoter. We also showed by siRNA (small interfering RNA) approach, co-transfection and site-directed mutagenesis that HNF1alpha mediates taurodeoxycholic and taurochenodeoxycholic bile acid activation of endogenous MUC4 expression and transcription in a dose-dependent manner. In conclusion, these results describe a new mechanism of regulation of MUC4 expression by bile acids, in which HNF1alpha is a key mediator. These results bring new insights into MUC4 up-regulation in oesophageal carcinoma associated with bile reflux.

Mucin Genes (MUC2, MUC4, MUC5AC, and MUC6) Detection in Normal and Pathological Endometrial Tissues

Changes in the composition and physical properties of the mucous gel covering the endometrial surface are detected during the menstrual cycle and in pathological conditions. The aim of this study is to analyze the expression patterns of the 11p15 secreted mucins, MUC2, MUC5AC, and MUC6, and the membrane-bound mucin MUC4 in proliferative and secretory normal endometrium, simple and complex hyperplasia, and endometrial adenocarcinoma. A total of 98 samples, 19 of normal endometrium (11 proliferative and 8 secretor), 44 of endometrial hyperplasia (23 simple, 21 complex), and 35 of endometrial endometrioid adenocarcinomas were analyzed by immunohistochemical techniques using specific antimucin antibodies. In the endometrial proliferative glandular epithelium, only MUC4 is detected (36.3% cases). During the secretory phase, increased levels of MUC2 are found (37.5%), whereas MUC4 is less detected (12.5%). In simple hyperplasia, higher levels of mucins are expressed in the endometrial glands: MUC2 is detected in 8.7%, MUC4 in 43.4%, and MUC5AC and MUC6 in 13% of the samples, whereas in complex hyperplasia, decreased levels of mucin expression are found: MUC2 and MUC5AC are not detected, and MUC4 (28.5%) and MUC6 (20.4%) are positive. In endometrial adenocarcinoma, MUC4 is highly detected (77.1%) and increased levels of MUC5AC and MUC6 are found (61.7% and 48.5%), whereas MUC2 is poorly detected (8.5%). These findings suggest that during endometrial neoplasic transformation, increased levels of MUC4, MUC5AC, and MUC6 are detected, whereas MUC2 is only significantly detected in the secretory endometrium.

Expression of PEA3 and lack of correlation between PEA3 and HER-2/neu expression in breast cancer

The ETS protein PEA3 functions as a transcription factor to regulate gene expression. Although members of the ETS family have been reported to be involved in tumor progression, ectopic expression of PEA3 has been shown to suppress tumor formation. Despite several studies demonstrated frequent expression of PEA3 and its high association with HER-2/neu and have suggested a potential role of PEA3 in breast cancer, contradictory result has shown that the PEA3 was associated with better survival rate in breast cancer. In the current study, we address this discrepancy by examining the expression of PEA3 and HER-2/neu on 289 archived breast cancer tumor tissues and their correlation with clinicopathologic factors and prognosis. The staining of PEA3 was further validated by in situ hybridization for PEA3 mRNA. We found PEA3 was positive in 22.2% (64/289) of all cases and only 25.6% (21/82) of HER-2/neu-overexpressing cases showed co-expression of PEA3. In contrast to HER-2/neu, PEA3 expression was not correlated with prognosis or major clinicopathologic factors, except for a negative correlation with lymphovascular permeation ( p=0.007). This study demonstrates that PEA3 expression is not correlated with HER-2/neu expression in breast cancer tumor tissues, nor is it associated with adverse clinicopathologic factors or prognosis.

Disruption of the Y-Box Binding Protein-1 Results in Suppression of the Epidermal Growth Factor Receptor and HER-2

The overexpression of the epidermal growth factor receptor (EGFR) and HER-2 underpin the growth of aggressive breast cancer; still, it is unclear what governs the regulation of these receptors. Our laboratories recently determined that the Y-box binding protein-1 (YB-1), an oncogenic transcription/translation factor, induced breast tumor cell growth in monolayer and in soft agar. Importantly, mutating YB-1 at Ser(102), which resides in the DNA-binding domain, prevented growth induction. We reasoned that the underlying cause for growth attenuation by YB-1(Ser(102)) is through the regulation of EGFR and/or HER-2. The initial link between YB-1 and these receptors was sought by screening primary tumor tissue microarrays. We determined that YB-1 (n = 389 cases) was positively associated with EGFR (P < 0.001, r = 0.213), HER-2 (P = 0.008, r = 0.157), and Ki67 (P < 0.0002, r = 0.219). It was inversely linked to the estrogen receptor (P < 0.001, r = -0.291). Overexpression of YB-1 in a breast cancer cell line increased HER-2 and EGFR. Alternatively, mutation of YB-1 at Ser(102) > Ala(102) prevented the induction of these receptors and rendered the cells less responsive to EGF. The mutant YB-1 protein was also unable to optimally bind to the EGFR and HER-2 promoters based on chromatin immunoprecipitation. Furthermore, knocking down YB-1 with small interfering RNA suppressed the expression of EGFR and HER-2. This was coupled with a decrease in tumor cell growth. In conclusion, YB-1(Ser(102)) is a point of molecular vulnerability for maintaining the expression of EGFR and HER-2. Targeting YB-1 or more specifically YB-1(Ser(102)) are novel approaches to inhibiting the expression of these receptors to ultimately suppress tumor cell growth.