LAUSR

Abstract Background Vimentin (Vim) is one of the mesenchymal markers, that are often upregulated in cancer cells during epithelial-mesenchymal transition (EMT) – a process endowing tumor cells with invasiveness, pro-metastatic potential and, arguably, cancer stem cells (CSC) properties. It is normally seen in cytoplasm, but cell surface Vim was also detected on cells with CSC characteristics. Vim expression may be used as a surrogate marker of EMT in tumor tissue samples from patients and aid in prognosis evaluation. We aimed to characterize Vim expression in prostate cancer (PCa) using our method of semiquantitative staining assessment. Methods Vim expression was assessed in 48 cases of PCa using immunohistochemistry with primary rabbit polyclonal antibodies (ThermoFischer, 1:1000). UnoView Rabbit Detection Kit was used for visualization. Specificity of staining was confirmed by another antibody (mouse monoclonal, DAKO, 1:200) in selected cases. To assess Vim expression semiquantitatively we proposed a weighed staining index (WSI) that takes into account the proportion of stained cells as well as the ratios of staining intensities and can be applied to different cellular compartments staining separately. It combines advantages of simple ad oculus semiquantitative staining evaluation and obtaining numerical characteristics of marker expression. Results Median WSI for membranous staining was 5 (0 – 52) (7, if cases without expression were excluded), for cytoplasmic – 20.5 (0 – 64) (22.5, if cases without expression were excluded). In 2 (4.2%) cases marker expression was absent in both membrane and cytoplasm. WSI in PCa was significantly higher for cytoplasmic staining. However, in 3 (6.25%) cases WSI for membranous staining was higher than that for cytoplasmic. Significant correlation was found between WSI for cytoplasmic and membranous staining (Spearman test, r = 0.51, p  Conclusions Vim expression as a sign of EMT in the tumor is present in 95.8% cases of PCa and is more prevalent in cytoplasm. WSI is a useful tool to assess Vim (and possibly other markers) expression. Legal entity responsible for the study M. Puchinskaya. Funding Belarusian Republican Foundation for Fundamental Research. Disclosure All authors have declared no conflicts of interest.