TβR2 is a ligand-binding receptor for transforming growth factor β – a major regulator of epithelial-mesenchymal transition (EMT). EMT can be defined in cancers by the expression of several markers, E- and N-cadherins being ones of the most widely used. Previously we have shown that N-cad neoexpression can be considered a better EMT marker than E-cadherin downregulation, so N-cad was used as a surrogate of EMT. The aim was to study associations of expression of TβR2 as an EMT regulating molecule and EMT marker in PCa.
28 clinical radical prostatectomy samples were studied. Double immunofluorescence was used to assess proteins expression, with primary mouse monoclonal antibodies to E-cad (1:100) and rabbit polyclonal to N-cad (1:2000) and TβR2 (1:100), secondary antibodies labeled with Alexa Fluor 488 and 555 dyes. Cadherins staining was assessed in the whole slide, while TβR2 in 3-15 separate high power (x40) fields (HPF) (n=277). For very heterogeneously expressed N-cad weighed staining index (WSI) was calculated (combining semiquantitative evaluations of proportion of cells with stained membranes and relative numbers of cells with weak, moderate and strong staining) and for TβR2 – total staining score (TSS) for membranous staining (multiplying of scores for proportion of stained cells and intensity) for each HPF with further median TSS per case.
Median N-cad WSI was 12 (range 3-55). TβR2 membranous expression was generally low with median TSS per case 0.11 (0-4.01) and was completely absent in 11 (39.3%) of cases. No significant correlation was found between N-cad WSI and TβR2 TSS (pSpearman>0.05). When TβR2 TSS was compared in cases with N-cad presence in more (n=10, 35.7%) and less (n=18, 64.3%) than 10% of cells, also no significant differences were seen (0.17 vs. 0.73, pMann-Whitney>0.05).
In this cohort there were no significant associations between expression levels of EMT marker N-cad and EMT regulator receptor TβR2. This may be due to a small sample size, but also a sign of other (including androgen and estrogen) receptors and EMT regulators being crucial for EMT development in PCa with TβR2 alone not defining the result. A study in a larger sample cohort is currently ongoing.
M. Puchinskaya.
Belarusian Republican Foundation for Fundamental Research, Grant No. M14M-143, M19M-123.
M. Puchinskaya: Financial Interests, Personal, Invited Speaker: Roche.