Abstract
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-κB, 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-κB 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-κBα expression vector (I-κBαM) inhibited constitutive NF-κB activity and IL-8 expression in pancreatic cancer cells. Collectively, our data demonstrated that constitutive NF-κB 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.
Get full access to this article
View all access options for this article.