Abstract 555: CCL2 promotes pancreatic tumor growth and is upregulated in tumor-stroma models
Authors: Shi Frank F. , Campion Liam , Kaiser Elizabeth , Ferrante Catherine , Wiley Diana , McCabe Frank , Doshi Parul , Snyder Linda 
Published: February 2011

CCL2 (C-C chemokine ligand 2; also known as MCP-1) is a pleiotropic chemokine overexpressed by many types of tumors. CCL2 is believed to promote tumor growth by increasing macrophage infiltration, angiogenesis, tumor proliferation/survival, and metastasis. The purpose of these studies was to assess potential mechanisms of action associated with the efficacy of neutralizing CCL2 in human pancreatic xenograft models.

Cell lines included BxPC-3, PANC-1 and AsPC-1 human pancreatic carcinoma, all of which are p53mut/krasmut, but each differentially expresses CCL2 and its receptor, CCR2. The three tumor cell lines were implanted subcutaneously in immunocompromised mice. When tumors reached ∼50-100 mm3, a cocktail of neutralizing antibodies to human CCL2, mouse MCP-1 and mouse MCP-5 (termed CCL2 blockade) was administered i.p. at 10 mg/kg each, twice a week for the study duration, either alone or in combination with gemcitabine i.p. at 120 mg/kg q3dx4. CCL2 blockade alone significantly inhibited primary tumor growth for BxPC-3 (66-78% tumor growth inhibition (TGI); P&lt;0.001) or prolonged survival for PANC-1 (by seven days; P&lt;0.004). CCL2 in combination with gemcitabine significantly inhibited AsPC-1 tumor growth compared to either therapy alone (55% TGI; P&lt;0.034). By IHC analysis, macrophage infiltration in AsPC-1 tumors was reduced significantly by CCL2 blockade (P=0.049).

In vitro studies were conducted to further understand the mechanism of action. Recombinant huCCL2 had no effect on pancreatic tumor cell proliferation in vitro, suggesting that the in vivo anti-tumor effect by CCL2 blockade may be through CCL2 neutralization within the host stroma. Co-culture studies to mimic the tumor-stroma interaction were conducted, using pancreatic tumor cells and normal human lung fibroblasts (NHLF). Secretion of CCL2, as well as IL-5, IL-6, IL-6R, IL-8 and GRO, was significantly enhanced 2-10-fold during co-culture of BxPC3 with NHLF (P&lt;0.001), while only CCL2 was enhanced 2-fold during PANC-1/NHLF co-culture (P&lt;0.001).

Furthermore, cell-cell contact was not required for cytokine induction for both BxPC-3 and PANC-1 with NHLF. Tumor cell conditioned medium (CM) stimulated NHLF to produce cytokines, not vice versa, suggesting that a factor(s) in tumor CM is responsible for cytokine induction. Neutralizing antibodies to either CCL2 or IL-6 did not abolish induction of other cytokines in the BxPC-3/NHLF model. The inducers of chemokines/cytokines as well as in vitro migration and in vivo gene profiling studies are underway to better understand the impact of CCL2 blockade on pancreatic tumor growth. These results demonstrate the significant effect of CCL2 blockade on pancreatic tumor growth in vivo, and suggest that the tumor cell/fibroblast interaction may be an important source of CCL2 at the tumor site.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 555.