Abstract
Angiogenesis is a key step in the progression toward and maintenance of a malignant phenotype. Interaction between CXC ligands and CXC receptors are associated with specific angiogenic or angiostatic activity. CXCL5 [epithelial neutrophil activating peptide-78], a CXC ligand, shares the same receptor (CXCR2) with the known angiogenic CXC chemokine, CXCL8 [Interleukin-8]. The precise role of CXCL5 in pancreatic cancer has yet to be defined. The mRNA and protein levels of CXCL5 were analyzed by real time PCR and immunohistochemistry in six human pancreatic cancer cell lines, and 17 human pancreatic cancers with matched normal pancreas. CXCL5 mRNA and protein were detectable in all six human pancreatic cancer cell lines, and CXCL5 mRNA level was increased in cancer tissue compared to normal pancreas tissue in 14 out of 17 (82.4%) patients. A majority (66.7%) of the high CXCL5 mRNA expression cancers were poorly differentiated. Tumors with elevated CXCL5 mRNA were two-fold larger by volume. Immunohistochemistry confirmed most of cancer specimens (77.3%) overexpressed CXCL5 compared to normal tissue. The microvascular density was significantly higher in tumors with high CXCL5 levels compared to low CXCL5 expressing tumors (p=0.02). For In Vitro functional analysis of CXCL5, human umbilical vascular endothelial cells (HUVEC) were treated with exogenous recombinant human (rh) CXCL5[ENA-78]. We observed a dose dependent increase in HUVEC growth in response to rhCXCL5[ENA-78] treatment (p<0.02). This response was specific to the ligand given that rhCXCL5[ENA-78] in combination with antibody to CXCL5[ENA-78] or its receptor, CXCR2, blocked HUVEC growth (IgG served as control) (p<0.02). Conditioned media from pancreatic cancer cells (ASPC-1, BxPC-3 and Capan-2) significantly stimulated HUVEC growth (p<0.01). The induction of HUVEC growth by pancreatic cancer cell media was blocked by antibody treatment to CXCL5[ENA-78] or CXCR2 (p<0.03). Finally, pancreatic cancer cell conditioned media and rhCXCL5[ENA-78] both stimulated capillary tube formation, and tubule formation was inhibited by antibody treatment to CXCL5[ENA-78] or CXCR2. These findings indicate that CXCL5 is constitutively expressed in the majority of human pancreatic cancers. The expression correlates with microvascular density, tumor volume, and differentiation. CXCL5 potently stimulated endothelial cell growth and tube formation. Specific blockade of CXCL5 may be a novel and effective therapeutic option in patients with pancreatic cancer.
Published Version
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