P1-03-01: ECM Stiffness and Breast Tumor Histology and Treatment Phenotype.
Authors: Acerbi I , Au A , Chen Y-Y , Park C , Hwang S , Weaver V 
Published: June 2012

Currently, the extent of local surgery and radiation for breast cancer is not guided by biological or anatomical principles, and the optimal volume of treatment is not defined. Local tumor progression is strongly influenced by a dynamic interplay between the genetically-modified epithelium and the associated cellular and non-cellular stroma (Butcher, 2009; Levental, 2009). The extracellular matrix (ECM) is modified in breast tumors and data indicate that the ECM stiffens progressively as mammary tumors evolve and enhancing ECM stiffness promotes mammary tumorigenesis while inhibiting ECM stiffening reduces tumor progression. However, the degree and extent of local stromal changes, and their clinical impact in breast cancer evolution and treatment remain unclear. This has led us to predict that the desmoplastic stroma surrounding breast tumors reflects tumor phenotype and behavior and can be characterized by biophysical metrics of the ECM stroma and molecular signatures of the breast epithelium. Accordingly, we hypothesize that these features may be integrated into a stromal phenotype that can be developed as a predictive tool. To test this concept we used a rigorous biomechanical and biochemical analysis of mastectomy specimens from women with various stages and histology phenotypes of treated and non-treated breast cancer to explore the relationship between ECM stiffness, mechanotransduction and tumor behavior. The goal of the study was to characterize stromal changes as a function of tumor stage and histology phenotype as well as before and after chemotherapy by measuring biophysical and topological features of the ECM and biochemical and molecular signatures of the mammary epithelium. The objective was to determine if there is a significant association with tumor histology phenotype that could be integrated to generate a stromal phenotype. Egan sections of were acquired from breast tissue containing benign and invasive ER positive and negative carcinoma and from treated and non-treated patients. All tissues were subjected to IHC histological and mechanosignaling analysis (H&E; 397FAK; Lysyl Oxidase; phosphomyosin) and biomechanical assessment (Atomic Force Microscopy; Structured Illumination Polarized Imaging; Two Photon Imaging). Preliminary data were consistent with prior in vitro and in vivo studies and showed that there was a significant increase in ECM stiffness as the tissues transitioned from normal to an invasive lesion with the highest stiffness being located at the tumor edge (∼2-4 folds greater). Intriguingly, we observed that ER negative tumors were substantially stiffer than ER positive tumors (50% increase in upper 10-percentile) and that there were tracks of ECM stiffness that correlated with orientated parallel collagen fibers and ECM birefringence. Moreover, we quantified a significant decrease in ECM stiffness following treatment (40% lower) with the most striking reduction in ECM tension being noted in ER negative patient tissues who demonstrated the most robust response. This study should lead to a deeper understanding of the nature of breast cancer stroma and its role in tumor phenotype and response to therapy.

Supported by: NCI SPORE P50 CA058207 to VMW, CP, & SH; U01 ES019458-02 to ZW; NCI R01 CA138818-01A1 to VMW; & U54 CA143836-01 to VMW & JL.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-03-01.