1973P Membranous vimentin (Vim) expression as a possible surrogate of cell surface vimentin in prostate cancer (PCa)

Abstract

Vimentin (Vim) up-regulation is an important marker of epithelial-mesenchymal transition (EMT) in cancer cells. At the same time cell surface Vim has been shown to be a possible marker of cells with cancer stem cell (CSC) characteristics. Regarding this, membranous expression of Vim in tumor tissue may be considered as a surrogate marker of EMT and CSC in the tumor, and show a possible link between these two processes. In the present work we aimed to evaluate membranous Vim expression in prostate cancer (PCa). 36 cases of PCa (radical prostatectomy specimens, 1 representative block from each case) were analyzed. 4 μm thick sections were immunohistochemically stained with polyclonal rabbit anti-Vimentin antibodies (1:1000 dilution, ThermoFischer Scientific). For visualization of staining peroxidase method with diaminobenzidine as a chromogen was used. Staining was evaluated semiquantitatively with x20 magnification. Membranous Vim staining was present in 29 (80.6%) of cases, but was notably less frequent than cytoplasmic one. Staining was mostly patchy, but the entire cell membrane was stained. In most cases (n=20, 69.0% of cases with staining) only up to 5% of tumor cells were stained, in 5 (17.2%) – 5-20%, in 1 (3.4%) case -- 20-50%, more than 50% of tumor cells were stained also in 1 (3.4%) case. When staining intensity was considered, in most cases cells with moderate (present in 19 (65.5%) of cases) or strong (n=15, 51.7%) membranous Vim staining were present. Weighed staining index (WSI) was calculated for membranous Vim, the median of which being 6 (range 0-16) for all cases and 9 (3-16) for stained ones. When amount of stained cells was considered, median WSI was 6 (0-48) and 9 (3-16), respectively. No significant correlations were found with tumor stage and grade, as well as preoperative androgen deprivation therapy. Membranous Vim staining was present in most cases, but usually only occasional cells stained positively, that may correspond to data about low prevalence of cells with CSC phenotype in tumors. However, in some cases strong staining was present. Further assessment of membranous Vim correlation with CSC markers CD44 and CD133 expression in the same cohort is planned.