Abstract 4053: A label-free spectroscopic signature associated with hormone sensitivity in 3D co-culture models of breast cancer
Authors: Holton Sarah E. , Bergamaschi Anna , Katzenellenbogen Benita S. , Bhargava Rohit 
Published: August 2012

Treatment of estrogen-receptor positive breast cancers relies on endocrine therapies; however, up to 30% of patients become resistant to this treatment. It is beneficial to identify patients who will remain sensitive to endocrine therapy using markers inherent in tissue at the time of diagnosis. Using a three-dimensional (3D) co-culture, we developed a method to determine the chemical signature of hormone sensitivity based on Fourier Transform Infrared (FT-IR) spectroscopic imaging, a highly sensitive label-free method that can detect chemical changes in tissue samples. We used a 3D co-culture model comprised of MCF7 breast cancer cells and MCF7 Tam-resistant cells grown as spheroids on Matrigel™ and different densities of human mammary fibroblasts (HMFs) embedded within collagen. Upon treatment with 17β-estradiol (E2) or tamoxifen (Tam), samples were paraffin embedded for imaging and, in parallel, RNA was isolated to determine hormone sensitivity. MCF7 grown in 3D showed comparable E2 and Tam sensitivity compared to 2D culture as determined through expression of estrogen-responsive genes. Co-culture led to a decrease in the ability of E2 and Tam to regulate known response genes, and this was dependent on fibroblast density. Furthermore, EMT markers were up-regulated after co-culture, showing that this model more closely mimics an early, more invasive tumor stage. FT-IR detection of spectroscopic features identified changes occurring after treatment with Tam in MCF7 grown alone or in co-culture. A significant decrease in a peak associated with nucleic acids (1080 cm-1) was seen compared to untreated or Tam-resistant cells, emphasizing the inhibitory effects of Tam on proliferation of MCF7. Moreover, Tam induced a significant decrease in peaks associated with fatty acid synthesis (2930 cm-1, 2850 cm-1) that have been related to apoptosis. When cells were exposed to E2 in the presence of HMFs, there was a distinct increase in the peak associated with glycosylation (1030 cm-1), suggesting a synergistic metabolic effect between E2 and the surrounding microenvironment. Based on the application of FT-IR, we identified a novel spectroscopic signature that can distinguish between hormone-responsive and non-responsive tumor cell lines. Although there is already considerable insight into molecular signatures of endocrine response in cell culture and in vivo models of breast cancer, FT-IR spectroscopic imaging provides a label-free and global chemical signature that could be used in addition to immunohistochemical analysis of the initial biopsy as a way to predict endocrine sensitivity. (Supported by grants from The Breast Cancer Research Foundation to BSK, DOD postdoctoral fellowship (W81XWH-09-1-0398) to AB, NIH NCI Alliance for Nanotechnology in Cancer ‘Midwest Cancer Nanotechnology Training Center’ (R25 CA154015A) to SEH, and National Institutes of Health (RO1CA138882) to RB.)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4053. doi:1538-7445.AM2012-4053