Estudo molecular da transição epitelial mesenquimal em carcinomas micropapilares invasivos da glândula mamária canina

Abstract

The epithelial mesenchymal transition (EMT) is a process whereby neoplastic epithelial cells lost E-cadherin expression, mediated by the transcription factors SNAIL, ZEB1, ZEB2 and TWIST, afterwards acquiring a mesenchymal phenotype and increasing its migratory behavior. Some transcription factors, such as ZEB1 and ZEB2, have showed relationship with the prognosis and metastatisation process in different locations of the human cancer. Hence, the aim of this study was to evaluate protein expression of molecules related to EMT, such as E-cadherin and its transcriptional repressors, and the prognostic value of ZEB1 and ZEB2 ininvasive micropapillary carcinomas (IMPC), which are aggressive and metastasising neoplasms of the canine mammary gland. Through immunohistochemistry we have observed that E-cadherin expression decrease from carcinoma in situ to invasive progression and waslikely to increase in lymph node metastasis of IMPCs. SNAIL expression decreased gradually from carcinoma in situ to invasive areas and to metastatic focus in lymph nodes. However, in ZEB1 analysis we have observed increase of immunoexpression from in situ and invasiveareas to lymph node metastasis. ZEB2 expression was observed in 52%, 38% and 33% of carcinoma in situ areas, invasive areas and lymph node metastases, respectively. TWIST expression was observed in 41%, 28% and 0% of carcinoma in situ areas, invasive areas and lymph node metastases, respectively. In invasive areas, E-cadherin downregulation correlated significantly with SNAIL and TWIST upregulation. Additionally, in infiltrating components of IMPCs, E-cadherin-negative SNAIL-positive neoplastic epithelial cells were observed by immunofluorescence. In the study related to tumour prognostic behavior the specificity for anti-ZEB1 and ZEB2 antibodies was confirmed by western blot technique. The positivity for cytoplasmic ZEB2 showed direct relation to poor overall survival of dogs showing IMPC; and was more frequently observed in in situ areas than in invasive areas of this neoplasm. ZEB1 positivity was associated with a decrease of histological grade. Thus, we concluded that the metastatic progression of canine IMPC is related to the loss of E-cadherin expression, induced by the transcription factor SNAIL, and for ZEB2 expression. The ZEB2 protein appears to be an important prognostic factor in bitches with mammary IMPCs.