Abstract 4087: Mammary fibroblasts exert divergent effects on the survival of invasive breast cancer cells

Abstract

Abstract Cancer development and progression are inherently inefficient processes riddled with anti-tumorigenic obstacles. Anoikis, or apoptosis induced by detachment from the extracellular matrix (ECM), represents one prominent hindrance to cancer progression that transformed cells must overcome in order to survive, particularly during the ECM-bereft metastatic cascade. Far from acting in isolation, we report that one mechanisms of anoikis evasion by invasive breast cancer cells involves the exploitation of carcinoma-associated fibroblasts (CAFs) from the surrounding tumor microenvironment. CAFs secrete insulin-like growth factor-binding proteins (IGFBPs) that facilitate non-canonical activation of integrin-linked kinase (ILK), activation of ERK/MAPK, and ultimately stabilization of the anti-apoptotic protein Mcl-1 to promote cancer cell survival during ECM detachment. Further investigation into the influence of the tumor microenvironment on cancer cell survival revealed that, contrary to the role of CAFs, normal mammary fibroblasts (NMFs) appear to exert anti-tumorigenic effects on ECM attached cancer cells. Utilizing conditioned media from NMFs, we have found that NMFs secrete factors that increase caspase activation in multiple cancer cell lines, suggestive of NMF-mediated cancer cell death. Because cancer progression necessitates the intermingling of cancer cells with normal stromal cells, particularly at early time points in primary tumor and metastases formation, we hypothesize that this NMFs pose yet another obstacle to disease progression that may compliment the process of anoikis by capping the metastatic cascade with environments that are inhospitable to cancer cell survival. Similar to anoikis evasion, our data suggests that cancer cells must evade NMF-induced death stimuli in order to survive, possibly through the accrual of CAFs in the tumor microenvironment to combat or replace the pro-apoptotic NMFs. Using traditional and 3D mammalian cell culture in combination with in vivo studies, we aim to delineate the roles of both CAFs and NMFs on cancer cell survival under conditions of differential ECM availability. A more complete understanding of the nuances dictating cancer cell-fibroblast interactions could yield informative data relevant to chemotherapeutic research and development. Citation Format: Kimberly Hagel, Kelsey Weigel, Meaghan Boyd, Luke McCormack, Matthew Champion, Zachary Schafer. Mammary fibroblasts exert divergent effects on the survival of invasive breast cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4087.