Interleukin 6 upregulates myeloid cell leukemia-1 expression through a STAT3 pathway in cholangiocarcinoma cells.
Interleukin 6 (IL-6) contributes to the pathogenesis of cholangiocarcinoma by upregulating myeloid cell leukemia-1 (Mcl-1), a key antiapoptotic Bcl-2 family member protein. IL-6 can alter gene transcription via Janus kinases (JAK) and signal transducer and activator of transcription (STAT) signal cascade. We examined this cascade in IL-6 regulation of Mcl-1 transcription in human cholangiocarcinoma cell lines. STAT3 was constitutively activated (i.e., tyrosine-phosphorylated) in cholangiocarcinoma cells but not in nonmalignant cholangiocytes. Treatment with anti-IL-6 antisera or the JAK inhibitor AG490 or transfection with dominant negative STAT3 diminished Mcl-1 messenger RNA and protein levels. Likewise, these attempts to interrupt the STAT3 cascade also reduced Mcl-1 promoter activity. Site-directed mutagenesis of a putative STAT3 consensus binding sequence decreased Mcl-1 promoter activity. Chromatin immunoprecipitation analysis demonstrated a direct binding of STAT3 to the putative STAT3 binding sequences in the Mcl-1 promoter. Downregulation of Mcl-1 by AG490 sensitized the cells to apoptosis mediated by tumor necrosis factor-related apoptosis-inducing ligand. In conclusion, we have directly demonstrated a STAT3 regulatory element in the Mcl-1 promoter. Downregulation of Mcl-1 transcription by inhibiting this cascade is a potential strategy for the treatment of this cancer.
Isomoto
Hajime
H
Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
Kobayashi
Shogo
S
Werneburg
Nathan W
NW
Bronk
Steve F
SF
Guicciardi
Maria Eugenia
ME
Frank
David A
DA
Gores
Gregory J
GJ
D017209:Apoptosis; D001650:Bile Duct Neoplasms / Q000378:metabolism* / Q000473:pathology; D001653:Bile Ducts, Intrahepatic; D001665:Binding Sites; D045744:Cell Line, Tumor; D018281:Cholangiocarcinoma / Q000378:metabolism* / Q000473:pathology; D004742:Enhancer Elements, Genetic; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015850:Interleukin-6 / Q000502:physiology*; D053613:Janus Kinase 1; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics*; D050796:STAT3 Transcription Factor / Q000502:physiology*; D015854:Up-Regulation
D015850:Interleukin-6; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D009363:Neoplasm Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D050796:STAT3 Transcription Factor; D011505:Protein-Tyrosine Kinases; C507904:JAK1 protein, human; D053613:Janus Kinase 1