Abstract 4009: CCL25-CCR9 axis mediates pancreatic cancer progression through beta-catenin activation.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Background: Expression of the chemokine receptor CCR9 is elevated in select solid organ cancers; and may contribute to drug resistance. However, there is no data for the role of CCR9 in GI cancers, aside from our prior work which demonstrated elevated expression in pancreatic cancer. Our current studies have uncovered activation of a novel CCR9-mediated molecular pathway and suggest that CCR9 may play a critical role in cancer progression through the aberrant activation of β-catenin. Methods: Immunohistochemistry and western blotting were used to assess CCR9 expression. We exposed human pancreatic cancer cell lines to CCL25 and evaluated levels of activated β-catenin and phosphorylated AKT via western blot. Proliferation and invasion were measured using an ATP-based assay and a Boyden chamber assay, respectively. IC50 of gemcitabine was determined using an acid phosphatase assay. Results: We have previously shown that CCR9 is expressed in human and murine PanIN lesions and in a human pancreatic cancer cell line. Here we expand upon these findings to show CCR9 expression in human pancreatic cancer tissue samples and in multiple cell lines. We determined that stimulation of CCR9 by its ligand, CCL25, signals through AKT and β-catenin to increase cell proliferation and invasion in pancreatic cancer cell lines. Following treatment with CCL25, cell proliferation was increased by an average of 20% across all cell lines (p<0.01). Pre-treatment with the PI3K inhibitor, LY294002, inhibited the CCL25-mediated increase in proliferation. We further show a CCL25-mediated increase in invasion. Using a modified Boyden chamber matrigel invasion assay, we determined that CCL25 as a chemoattractant heightened the invasive abilities of our pancreatic cancer cell lines by 3-fold. Inhibiting PI3K activation blocked this increase. In addition, exposure to CCL25 led to reduced gemcitabine sensitivity. Pre-treatment with CCL25 increased the IC50 of gemcitabine by 7-fold in PANC-1 cells, from 0.1μM to 0.77μM (p=0.005) and 5.5-fold in AsPC-1 cells from 17.7μM to 96.7μM (p=0.008), indicating a drastic decrease in the effectiveness of gemcitabine when CCL25 is present. Conclusions: The current paucity of effective therapies for pancreatic cancer presents a significant clinical challenge. This highlights the need to identify and study mechanisms and pathways involved in pancreatic cancer progression. Determining the role of CC9R in pancreatic cancer and targeting the CCL25-CCR9-β-catenin pathway may therefore present an innovative, clinically significant therapeutic target for pancreatic cancer. Citation Format: Eileen L. Heinrich, Jianming Lu, Wendy Lee, Carrie Luu, Joseph Kim. CCL25-CCR9 axis mediates pancreatic cancer progression through beta-catenin activation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4009. doi:10.1158/1538-7445.AM2013-4009