Investigating the epithelial to mesenchymal transition in prostate cancer invasion and metastasis

Introduction The majority of prostate cancer (PCa) deaths occur due to the metastatic spread of tumour cells to distant organs and the establishment of secondary tumours. The epithelial to mesenchymal transition (EMT) is an important developmental pathway that becomes re-activated in many cancers and has been shown to play pivotal roles in cancer progression and metastasis. However the role of EMT in PCa has not been fully characterised. We previously engineered an inducible cell model with the inducible expression of known EMT inducer Snail, whereby EMT induction could be controlled and temporally studied. Here we have engineered a second model with the EMT inducer Slug, which we have used in combination with Snail to derive a PCa specific EMT signature. Methods We developed doxycycline inducible cell models whereby the induction and reversal of EMT can be tightly regulated with the inducible expression of Snail or Slug. Protein, RNA and morphological changes were recorded, in two dimensional tissue culture experiments and three dimensional (3D) Matrigel assays following EMT induction. We have a custom designed Agilent 180K probe microarray to identify a temporal transcriptional signature of EMT induction in LNCaP PCa cells. A number of candidate genes identified in our microarray studies have been validated using quantitative real time PCR (qRT-PCR) and western blotting. Results qRT-PCR and western blot analysis demonstrated robust expression of Snail and Slug when doxycycline was added to the culture media, resulting in a decrease in E-cadherin expression (a hallmark event of EMT). In 3D Matrigel cultures, LNCaP cells acquired a highly invasive phenotype upon induction of Slug or Snail expression. Biostatistical analysis of the microarray data revealed a common EMT-Invasion signature induced by both Snail and Slug models during 3D Matrigel invasion. Interrogation of multiple clinical PCa datasets has identified a number of these EMT-Invasion candidate genes to be dysregulated in metastatic and therapy resistant tumour tissue. Conclusion This study reports that for the first time a PCa specific EMT signature using novel inducible PCa models. Future studies will focus on determining the functional relevance of identified candidate genes on EMT and PCa metastasis using both in vitro and in vivo models