A new method of double immunofluorescent staining for flow cytometry has been created to evaluate quantitative expression of mesenchymal protein vimentin only in epithelial cells of a solid tumor that is a mix of different origin cells. De novo vimentin expression is strongly associated with epithelial-mesenchymal transition and therefore is a metastatic potential marker of epithelial tumor cells. In comparison with semiquantitative available methods, the proposed one has several advantages, such as the accurate measurement of the marker's expression, and minimization of spatial and temporal tumor heterogeneity. Clinical validation of the method has revealed inverse correlation between the quantitative index of epithelial-mesenchymal transition level and progression-free survival using Kaplan-Meier curves and the COX proportional hazards ratio in 32 ovarian cancer patients.
Keywords: cytokeratins; epithelial–mesenchymal transition; flow cytometry; immunofluorescent assay; ovarian cancer; prognostic value; solid tumors; vimentin.