Abstract PR011: DCIS-associated myoepithelial cells drive tumor progressive inflammation through up-regulation of integrin αvβ6

Abstract

Abstract Background: Ductal carcinoma in-situ (DCIS) is a pre-invasive stage of breast cancer, however <50% will progress to invasion. A key component in promoting tumor invasion is inflammation, though its role in DCIS progression is unclear. We previously, showed αvβ6 expression on DCIS myoepithelial cells promotes tumor cell invasion. We hypothesized that altered myoepithelial phenotype in DCIS may modulate periductal inflammation to contribute to disease progression. Methods: The inflammatory infiltrate in DCIS cases (20 αvβ6+ and 20 αvβ6-) was characterized by immunohistochemistry (IHC) and immunofluorescence-IHC, focusing on Tumor Associated Macrophages (TAM) and Regulatory T cell markers. A myoepithelial cell line over-expressing αvβ6 (β6-1089) and a control counterpart (N-1089) were analyzed for cytokine and signaling molecule expression with proteome profilers and western blotting. The monocyte cell line (THP-1) was exposed to conditioned media from β6-1089 or N-1089 followed by qPCR for TAM markers (IL4, IL10 and IL8), MTS proliferation assay and western blotting for NFkB and STAT6 activation (involved in macrophage differentiation). 3D models were used to examine if the in vivo changes to macrophages can be modelled in vitro. Results: IHC analysis revealed a significant association between myoepithelial αvβ6 expression and increased T-reg cell infiltrate (p< 0.0001). Similarly, αvβ6 expression associated with increased presence of TAM (p=0.0026), αvβ6 positive DCIS with exhibited a microenvironment comprising 15% TAMs compared to 3% in αvβ6 negative DCIS cases. This shift in macrophage phenotype was recapitulated in 3D organotypic assays incorporating macrophages and myoepithelial cells. Proteome profiler analysis of THP-1 cells grown with conditioned media from αvβ6 positive myoepithelial cells demonstrated increased expression of CCL5 while all other proteins analyzed where generally suppressed. Nuclear and cytoplasmic western blotting of THP-1s demonstrated NfκB and STAT activation were altered by CM from myoepithelial cells +/- avb6. Conclusion: DCIS myoepithelial cells upregulate αvβ6 and exhibit changes in the periductal inflammatory infiltrate indicating a switch to a tumor promoting phenotype. Further investigation is required to determine the prognostic value and underlying mechanisms of this change. Citation Format: Michael D. Allen, M. Reza Roozitalab, Stephen Murtough, Eleni Maniati, J. Louise Jones. DCIS-associated myoepithelial cells drive tumor progressive inflammation through up-regulation of integrin αvβ6 [abstract]. In: Proceedings of the AACR Special Conference on Rethinking DCIS: An Opportunity for Prevention?; 2022 Sep 8-11; Philadelphia, PA. Philadelphia (PA): AACR; Can Prev Res 2022;15(12 Suppl_1): Abstract nr PR011.