PO-245 Vimentin expression as a sign of epithelial-mesenchymal transition in prostate cancer

Abstract

IntroductionEpithelial-mesenchymal transition (EMT) is an important mechanism of tumour metastasis and treatment resistance. It is also linked to cancer stem cell (CSC) phenotype. Vimentin is a mesenchymal marker up-regulated during EMT and cell surface vimentin was shown in CSC. The present study aimed to evaluate vimentin expression in prostate cancer (PCa).Material and methods36 cases of PCa were immunohistochemically stained with rabbit polyclonal antibodies to vimentin (ThermoScientific). Membranous and cytoplasmic expression was evaluated separately semiquantitevely in PCa as well as in the adjacent non-cancerous glands (NCG) with calculation of weighed staining index (WSI).Results and discussionsIn the present study vimentin exhibited membranous and cytoplasmic expression. The pattern of staining varied in NCG and PCa. In the former membranous staining prevailed and was especially evident in benign prostatic hyperplasia, mainly in basolateral membranes. In NCG cytoplasmic vimentin expression was generally weaker than membranous and seen mostly in basal part of the cell. Conversely, in PCa vimentin was much more often expressed in cytoplasm, but staining was usually weak or moderate, and it was seen mostly in apical part of cytoplasm, while membranous staining was seen on the whole cell membrane. There was a patchy distribution of cell groups with membranous vimentin. We propose that such membranous expression may correspond to cell-surface vimentin. Membranous staining in PCa was absent in 32.3% of cases, present in <5% of cells in 45.2%, 5%–20% in 16.1%, 20%–50% in 3.2% and in >50% of cells in 3.2%. For cytoplasmic staining the corresponding numbers were 0%, 6.5%, 32.3%, 16.1% and 32.3%. When WSI was counted, it was significantly higher for cytoplasmic staining in PCa and for membranous in NCG (p<0,05). In PCa, cytoplasmic vimentin was higher and membranous lower than in NCG (p<0,05). No significant associations were found between vimentin expression and Gleason score or pT category (p>0,05). Previously we studied E- and N-cadherin expression in the same cases, but they didn’t correlate significantly with vimentin (p>0,05). This may be due to a relatively small number of cases.ConclusionVimentin neoexpression is seen in PCa as a sign of tumour EMT, and membranous vimentin seen in 67.7% of cases may also mark CSCs. We are planning to confirm the results of the present study in a larger series and the specificity of membranous staining with another antibody.