Abstract LB-B18: Epithelial to mesenchymal transition in human tumor biopsies: Quantitative, histopathological proof of the existence of EMT in vivo by immunofluorescence microscopy

Abstract

Abstract Epithelial-mesenchymal transition (EMT) is a dynamic process whereby epithelial cells acquire mesenchymal properties. Despite the clinical significance of the acquired mesenchymal properties for metastasis and drug resistance, histopathological evidence of transitional cells in patient samples is lacking and EMT remains an unproven clinical hypothesis. We previously developed and validated a multiplex immunofluorescence assay (IFA) that quantifies the levels of EMT biomarkers (E-Cadherin, Vimentin, β-catenin) in snap-frozen, formalin-fixed, paraffin-embedded (FFPE) tumor tissue (Navas et al, AACR 2013). Building upon that method, we now report a precise, quantitative and unbiased IFA method of tissue analysis (EMT-IFA) using Definiens® software to quantify co-expression of the epithelial marker E-cadherin (E) and mesenchymal marker Vimentin (V) at the cellular level in FFPE clinical biopsies. FFPE human tumor xenografts and cell lines serve as calibrators and reference materials for establishing initial image acquisition parameters for segmented tumor regions of interest. Flanking H&E sections of the clinical biopsies are initially annotated by an anatomic pathologist to identify regions of tumor tissue, non-tumor related areas (including normal or stromal tissues), inflammatory and/or necrotic regions, and freeze artifacts. Adjacent sections are used for the EMT-IFA, and further tumor segmentation from stroma is applied to extracted regions of interests (fields) using the β-catenin layer. Within segmented tumor regions, E-cadherin (E) and Vimentin (V) sub-cellular pixel areas are measured using predetermined thresholds for each biomarker and reported as Log10 (V:E). High resolution images confirmed the co-localization of plasma membrane E-cadherin and cytoplasmic Vimentin to individual transitional tumor cells, and the co-localization of E and V within individual tumor cells of the segmented regions of interest was key for distinguishing EMT from tumor heterogeneity in which adjacent tumor cells can be exclusively E+ or V+. Quantitative analysis of a clinical biopsy series of various histologies revealed all possible phenotypes: epithelial (E+V- colorectal carcinoma), mesenchymal (E-V+ sarcomas), heterogeneous mixtures of E+V- and E-V+ subpopulations, and EMT. Importantly, using the EMT-IFA, we discovered that pharmacological targeting of VEGFR/FGFR/PDGFR signaling with the multi-kinase inhibitor pazopanib stimulated EMT in a preclinical xenograft model of gastric carcinoma (MKN45), as revealed by the significant increase in the V:E ratio (P = 0.0023) coupled with an increase in the EMT phenotype (co-localized V+E+ at the individual cell level) (P = 0.0070) in biopsy specimens. Thus, the EMT-IFA has potential value for investigating EMT in the clinic and its ramifications for drug response and other clinical endpoints. Funded by NCI Contract No. HHSN261200800001E. Citation Format: Tony Navas, Robert J. Kinders, Scott M. Lawrence, Katherine Ferry-Galow, Thomas D. Pfister, Apurva K. Srivastava, Sergio Y. Alcoser, Melinda G. Hollingshead, Lindsay M. Dutko, Brad A. Gouker, Donna O. Butcher, Hala Makhlouf, Rodrigo Chuaqui, Donald P. Bottaro, Shivaani Kummar, Alice Chen, James H. Doroshow, Ralph E. Parchment. Epithelial to mesenchymal transition in human tumor biopsies: Quantitative, histopathological proof of the existence of EMT in vivo by immunofluorescence microscopy. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-B18.