Transcriptional regulation of human mucin MUC4 by bile acids in oesophageal cancer cells is promoter-dependent and involves activation of the phosphatidylinositol 3-kinase signalling pathway.
Abnormal gastro-oesophageal reflux and bile acids have been linked to the presence of Barrett's oesophageal premalignant lesion associated with an increase in mucin-producing goblet cells and MUC4 mucin gene overexpression. However, the molecular mechanisms underlying the regulation of MUC4 by bile acids are unknown. Since total bile is a complex mixture, we undertook to identify which bile acids are responsible for MUC4 up-regulation by using a wide panel of bile acids and their conjugates. MUC4 apomucin expression was studied by immunohistochemistry both in patient biopsies and OE33 oesophageal cancer cell line. MUC4 mRNA levels and promoter regulation were studied by reverse transcriptase-PCR and transient transfection assays respectively. We show that among the bile acids tested, taurocholic, taurodeoxycholic, taurochenodeoxycholic and glycocholic acids and sodium glycocholate are strong activators of MUC4 expression and that this regulation occurs at the transcriptional level. By using specific pharmacological inhibitors of mitogen-activated protein kinase, phosphatidylinositol 3-kinase, protein kinase A and protein kinase C, we demonstrate that bile acid-mediated up-regulation of MUC4 is promoter-specific and mainly involves activation of phosphatidylinositol 3-kinase. This new mechanism of regulation of MUC4 mucin gene points out an important role for bile acids as key molecules in targeting MUC4 overexpression in early stages of oesophageal carcinogenesis.
Unité INSERM 560, Place de Verdun, 59045 Lille Cedex, France.
Christophe
C
Mariette
Michaël
M
Perrais
Emmanuelle
E
Leteurtre
Nicolas
N
Jonckheere
Brigitte
B
Hémon
Pascal
P
Pigny
Surinder
S
Batra
Jean-Pierre
JP
Aubert
Jean-Pierre
JP
Triboulet
Isabelle
I
Van Seuningen
D000230:Adenocarcinoma / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D001647:Bile Acids and Salts / Q000494:pharmacology / Q000502:physiology*; D014408:Biomarkers, Tumor / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor; D004789:Enzyme Activation / Q000502:physiology; D004938:Esophageal Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D005752:Gastric Mucins / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D006801:Humans; D018396:Mucin-1 / Q000096:biosynthesis; D055264:Mucin-4; D009077:Mucins / Q000096:biosynthesis / Q000235:genetics*; D009092:Mucous Membrane / Q000737:chemistry / Q000378:metabolism; D010446:Peptide Fragments / Q000096:biosynthesis; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013274:Stomach Neoplasms / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D001647:Bile Acids and Salts; D014408:Biomarkers, Tumor; D005752:Gastric Mucins; C116055:MUC1 tandem repeat peptide; C524658:MUC4 protein, human; D018396:Mucin-1; D055264:Mucin-4; D009077:Mucins; D010446:Peptide Fragments; D012333:RNA, Messenger; C053366:apomucin; D019869:Phosphatidylinositol 3-Kinases