IL-8 Pathway in Gastric Cancer
MH Ryu, P Fordjour, L Ostrom, J Monahan, Y Yao, J Gu, G Yang, J Meltzer, Y Shim, R Meyer, R Mosher. Novartis Institutes for BioMedical Research, Inc., Cambridge, MA
Background: IL-8 is a chemotactic factor for neutrophils, and has two receptors, CXCR1 and CXCR2. There have been several reports that the IL-8 pathway has a role in tumorigenesis of some cancer types. This study was conducted to determine the expression levels of IL-8 and its receptors, the relationship of IL-8 expression with inflammatory cells, and IL-8 polymorphism in gastric cancer.
Design: RNA and DNA were extracted from 70 pairs of gastric cancer and adjacent normal gastric tissues, 8 gastric cancer cell lines (AZ-521, FU-97, GTL-16, KATO-III, MKN-45, NUGC-3, OCUM-1, and SNU-1), 1 endothelial cell line (HuVEC), and a buffy coat from a healthy volunteer. Multiplex real time RT-PCR and genomic qPCR were performed to detect mRNA expression levels of IL-8, CXCR1, and CXCR2, and to identify IL-8 polymorphisms. 18S rRNA was used to normalize target mRNA. The cell proliferation assay was conducted with exogenous IL-8 and IL-8 blockers in gastric cancer cell lines.
Results: Among seventy pairs of gastric tissues, many showed high tumor vs. normal mRNA ratios of IL-8 and its two receptors; the IL-8 mRNA expression levels of tumor tissues were median 40-fold (range, 0.4857) compared to those of adjacent normal tissues, and 50 out of 70 pairs (71%) showed over 10-fold IL-8 mRNA tumor/normal ratio. The tumor/normal ratios of IL-8 mRNA showed a close correlation with those of its two receptors, i.e, CXCR1 (r2=0.54, P<0.001) and CXCR2 (r2=0.47, P<0.0001), and a tendency to correlate with clinical stage. Seven out of 8 gastric cancer cell lines showed IL-8 mRNA expression. However, mRNA of CXCR1 or CXCR2 was not detectable in 8 gastric cancer cell lines and the endothelial HuVEC cell line, while mRNA of IL-8 receptors was highly expressed in a buffy coat. Neither exogenous IL-8 nor IL-8 blockers had an effect on cell proliferation of gastric cancer cell lines. Thirty nine (55.7%) out of 70 gastric tumors had AA (n=13) or AT (n=26) polymorphisms at IL-8-251, and showed a high expression level of IL-8 mRNA compared to a TT polymorphism (P=0.052).
Conclusions: Most gastric cancer tumor tissues express high levels of IL-8 and its two receptors. The IL-8-251 T>A polymorphism correlates with high expression of IL-8. Most gastric cancer cell lines showed IL-8 expression, but there is little or no expression of IL-8 receptors in those cell lines, which suggests that in vivo IL-8 may be working through a paracrine mechanism rather than an autocrine mechanism.
Tuesday, March 10, 2009 1:00 PM
Poster Session IV # 107, Tuesday Afternoon