Molecular regulation of constitutive expression of interleukin-8 in human pancreatic adenocarcinoma.
Recent studies have shown that interleukin-8 (IL-8) plays an important role in the growth and metastasis of human pancreatic cancer. In the present study, we determined the molecular regulation of constitutive IL-8 expression in human pancreatic cancer cells. Various human pancreatic cancer cell lines were incubated in vitro. Sixty-seven percent of the cell lines constitutively secreted high levels of IL-8, as determined using enzyme-linked immunosorbent assay. Consistently, these cells constitutively expressed high levels of IL-8 mRNA, as determined using Northern blot analysis. To determine the mechanisms of the high steady-state levels of IL-8 mRNA, the IL-8 half-life and transcription rate were measured. There was no significant difference in IL-8 half-life between cells expressing high and low levels of IL-8. However, higher transcription rates and increased IL-8 promoter activity were observed in the cells constitutively expressing high levels of IL-8. Detailed IL-8 promoter analysis using deletion mutation revealed that the region from -85 to -133 bp was essential for the constitutive IL-8 promoter activity. Also, point-mutation analysis indicated that mutation of NF-kappaB, AP-1, or NF-IL-6 binding sites significantly reduced or eliminated the constitutive IL-8 promoter activity. Consistent with the constitutive IL-8 transcription activity, high levels of constitutive NF-kappaB and AP-1 activity were detected in the cells overexpressing IL-8, as determined using electrophoretic mobility shift assay. In addition, transfection of a dominant-negative I-kappaBalpha expression vector (I-kappaBalphaM) inhibited constitutive NF-kappaB activity and IL-8 expression in pancreatic cancer cells. Collectively, our data demonstrated that constitutive NF-kappaB and AP-1 activation contributes to the overexpression of IL-8, which in turn plays an important role in tumor angiogenesis and contributes to the aggressive biology of human pancreatic cancer.
Le
X
X
Department of Gastrointestinal Medical Oncology and Digestive Diseases, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA.
Shi
Q
Q
Wang
B
B
Xiong
Q
Q
Qian
C
C
Peng
Z
Z
Li
X C
XC
Tang
H
H
Abbruzzese
J L
JL
Xie
K
K
D000230:Adenocarcinoma / Q000378:metabolism*; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000378:metabolism; D006801:Humans; D016209:Interleukin-8 / Q000235:genetics* / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism; D010190:Pancreatic Neoplasms / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D020871:RNA Stability; D018808:Transcription Factor AP-1 / Q000378:metabolism; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured
D022782:CCAAT-Enhancer-Binding Protein-beta; D016209:Interleukin-8; D016328:NF-kappa B; D018808:Transcription Factor AP-1