Abstract 1984: Anisotropy of collagen I matrix influences therapeutic response and secretome of Luminal A cells
Authors: Reyes Ana M. , Almodovar Jorge , Alarid Elaine , Domenech Maribella 
Published: August 2019

Abstract
High degree of collagen I fiber orientation has been associated with guided tumor cell invasion, but little is known about its impact in therapeutic response. Anisotropic substrates have been shown to influence the phenotype of stem cells which suggests that it can influence tumor cell behavior beyond cell migration. We hypothesized that the anisotropy of collagen I matrix impacts therapeutic response by modulating the secretome of breast cancer cells and this effect is mediated by integrin signaling. To test our hypothesis, the cell secretome, response to hormone ablation therapy and integrin inhibitors were evaluated in breast tumor cells cultured in collagen type 1 substrates of defined orientation. The orientation of electrospun collagen I fibrils was regulated by adjusting the syringe flow rate and collector velocity to obtain random (&lt;70%) or aligned (&gt;80%) oriented fibrils. Average porosity (45± 3.4 %), matrix stiffness (0.8 ±0.24 MPa) and fiber diameter (1.6 ± 0.86μm) were kept constant across collagen substrates. Estrogen-dependent Luminal A cells (MCF-7 and T-47D) cells were cultured on collagen substrates in a hormone-deprived environment for 3-6 days. Polycaprolactone (PCL) fibrous substrates of aligned and random orientation were used as negative fibrous controls for integrin signaling. Evaluation of cell growth showed that a fibrillar structure in combination with a high degree of fibril orientation significantly increased cell proliferation (&gt;75%) as compared to gelatin-coated tissue culture plastic (TCP). Collagen fibers significantly supported hormone-independent tumor growth at levels equivalent to or above those observed in the estrogen-treated control. Increased proliferation levels were supported on collagen fibrous substrates treated with Tamoxifen and Fulvestrant, and this effect was enhanced in aligned collagen I. Inhibition of α2β1 integrin resulted in enhanced proliferation rates in random fibers and suppression of cell growth in aligned fibers. PCL aligned substrates where not sufficient to support hormone-independent cell growth. MCF-7 cells on collagen substrates significantly stimulated the growth (&gt;7 fold) of adjacent cells on TCP in a dose-response manner as follows: aligned &gt; random &gt; gelatin. Expression levels of 1000 factors were quantified in conditioned medium to identify differences in the secretome signatures associated with cell-matrix signaling. MCF-7 cells cultured on collagen fibrous substrates displayed secretome signatures that were different across all substrates. Fourteen factors were identified to be upregulated in fibrous substrates by more than ten folds including apoptotic regulators RalA and BCL-2. Our results show for the first time the influence of collagen I fibril orientation in supporting hormone-independent growth and as a novel regulator therapeutic response in luminal A cells.
Citation Format: Ana M. Reyes, Jorge Almodovar, Elaine Alarid, Maribella Domenech. Anisotropy of collagen I matrix influences therapeutic response and secretome of Luminal A cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1984.