P4-02-05: The Regulation of Artemin Signalling by IGF-1 in Mammary Carcinoma Cells.

Abstract

Abstract Artemin is a neurotrophic signalling factor which belongs to the glial-derived neurotrophic factor (GDNF) family of ligands. Artemin acts as a survival, proliferation and migration factor for a number of neurological cell types, by signalling through the RET (rearranged during transfection) receptor and, in most cases, the GDNF receptor (GFR)-a3 co-receptor. Recently, a number of published studies have implicated Artemin as a potential oncogene in several cell types, including mammary carcinoma cells. Other studies further indicate that Artemin may influence cancer progression and tamoxifen resistance in some breast cancers. Available clinical data has demonstrated that increased Artemin expression is correlated with decreased overall patient survival in breast cancer patients and a poor outcome in tamoxifen treated breast cancer patients. Here we investigate interaction between the Artemin and the insulin-like growth factor-1 (IGF-1) signal transduction pathways. Using mammary carcinoma cell lines, we demonstrate that IGF-1 treatment increases the endogenous expression of both Artemin and its endogenous receptors, RET and GFRa3. Semi-quantitative RT-PCR assays demonstrated that IGF-1 stimulated mRNA expression of Artemin as well as RET and GFRa3 in wild-type MCF-7 and ZR-75-1 cells in a time-dependent and dose-dependent manner. The same effect was not observed in wild-type T47D cells where IGF-1 did not increase Artemin mRNA expression. We also demonstrated that forced expression of Artemin in MCF-7 cells consistently enhanced the response of these cells to IGF-1 in a number of cell function assays. Forced expression of Artemin significantly enhanced IGF-1-mediated stimulation of total cell number in MCF-7 cells. Consistent with this, Artemin enhanced IGF-1-mediated stimulation of S-phase entry and cell survival. In a soft agar assay, forced expression of Artemin also enhanced IGF-1-mediated stimulation of colony formation. Conversely, depletion of Artemin expression using siRNA abrogated the response to IGF-1 stimulation in MCF-7 cells. Artemin depletion significantly decreased IGF-1-stimulated increase in total cell number by decreasing IGF-1-stimulated cell proliferation and protection from apoptotic cell death. In addition, forced expression of Artemin in MCF-7 cells reduced cell sensitivity to the IGF-1 receptor small molecule inhibitor, AG1024. In conclusion, we have demonstrated that IGF-1 increases Artemin mRNA and protein expression in the breast cancer cell lines MCF-7 and ZR-75-1 and have identified potential cross-talk between the Artemin and IGF-1 signalling pathways in MCF-7 cells. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-02-05.