Abstract P4-06-01: Epiregulin-induced matrix metalloproteinase-1 contributes to early stages of breast tumorigenesis
Authors: Schwertfeger Kathryn L , Farooqui Mariya , Bohrer Laura R , Nelson Andrew C 
Published: May 2015

The earliest stages of malignant transformation require the acquisition of multiple phenotypes, such as proliferation, survival and migration, which contribute to tumor growth and progression. Identifying the key cellular and molecular factors that drive the formation of early breast cancer lesions will ultimately result in the development of preventive approaches for patients that are at high risk for developing invasive breast cancer. The epidermal growth factor (EGF) family of ligands has been implicated in promoting breast cancer growth and progression. The contributions of EGF family ligands and their receptors to breast cancer are complex, and the specific mechanisms through which different ligands regulate different stages of breast tumor initiation and growth are not well-defined. These studies focus on the EGF family member epiregulin (EREG) as a mediator of early stages of breast tumorigenesis. In comparison with other EGF family members, EREG was found to be highly expressed in MCF10DCIS.com cells compared with the non-transformed MCF10A cells. Increased EREG expression was also found in significantly more patient samples of human ductal carcinoma in situ (DCIS) than in samples of normal epithelium (64.5% vs. 29.4%, p&lt;0.05). Therefore, further studies were performed to identify mechanisms through which EREG promotes the formation of DCIS lesions.

Experimental studies demonstrated that treatment of MCF10A cells with exogenous EREG enhanced multiple tumorigenic phenotypes, including proliferation, migration and survival. Examination of EREG-induced signaling pathways demonstrated that EREG promotes survival of MCF10A cells primarily through activation of the signal transducer and activator of transcription 5 (STAT5) pathway. Analysis of potential STAT5 target genes revealed that the EREG-STAT5 pathway induces expression of matrix metalloproteinase-1 (MMP-1), a novel STAT5 target gene that was subsequently found to promote survival in response to EREG treatment. To assess the consequences of loss of EREG expression on tumor formation, EREG was knocked down in MCF10DCIS.com cells using shRNA strategies. Loss of EREG led to decreased tumor growth in vivo, which corresponded with decreased cell survival and decreased MMP-1 expression. To determine the relevance of these findings in human tumors, samples of DCIS were analyzed for both EREG and MMP-1 expression. MMP-1 was significantly induced in DCIS lesions in comparison with normal breast epithelium, and EREG and MMP-1 were significantly correlated in a subset of DCIS samples (p=0.011). Together, these studies suggest that EREG contributes to early stages of breast tumorigenesis through regulation of MMP-1. Based on these studies, we propose that EREG contributes to the formation of preneoplastic lesions in a subset of breast cancers and further studies are focused on characterizing the mechanisms through which the EREG-MMP-1 pathway contributes to tumor initiation and growth. Understanding these mechanisms will ultimately lead to the identification of biomarkers of aggressive disease and novel targets for therapeutic strategies for breast cancer patients.

Citation Format: Kathryn L Schwertfeger, Mariya Farooqui, Laura R Bohrer, Andrew C Nelson. Epiregulin-induced matrix metalloproteinase-1 contributes to early stages of breast tumorigenesis [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-06-01.