[Truncated] The transcription factor ETS1 is frequently overexpressed in prostate tumours, with its increased expression correlated with disease severity and accelerated progression to castrate resistance. Three structurally and functionally distinct ETS1 isoforms have been identified and in this study, ETS1 isoform mRNA expression was characterised in 45 human prostate tumours and adjacent non-malignant prostate tissue using isoformspecific RT-qPCR. qPCR analysis identified ETS1p51 and ETS1p42 but not ETS1p27 expression in the malignant and nonmalignant prostate specimens and significantly higher ETS1p51 expression compared to ETS1p42 in both malignant and non-malignant prostate (p<0.0001). In addition, the expression of both ETS1p51 and ETS1p42 was reduced in the majority (65-69%) of prostate tumours relative to non-malignant tissue. Western blotting of protein extracts from the same specimens detected only ETS1p51 protein, which was expressed at significantly higher levels in the majority (67%) of prostate tumours examined (p<0.01), while no association was identified between ETS1p51 mRNA and protein expression in either malignant or non-malignant prostate tissues. These findings indicated that ETS1p51 was the predominant isoform expressed in the prostate and overexpressed in prostate tumours.
The rapid growth and spread of ETS1-overexpressing prostate tumours suggested that ETS1 may promote epithelial-to-mesenchymal transition (EMT), a process associated with loss of epithelial and acquisition of mesenchymal marker expression, promotion of migration and invasion, and in tumour cells, metastasis. To examine ETS1p51-induced EMT, the expression of 84 EMT-associated genes was assessed by PCR array in the human prostate cancer cell line LNCaP that had been transiently transfected with an expression construct encoding GFP-tagged ETS1p51. ETS1p51 overexpression in LNCaP cells was found to upregulate expression of 16 EMTassociated genes including MMP3 and MMP9, which encode matrix metalloproteinases that regulate invasion, NODAL and SPARC, which encode factors that facilitate migration, and genes encoding EMT-promoting transcription factors, including ZEB1 and ZEB2. Bioinformatics analysis of PCR array results predicted significant regulation of cell movement, activation of TGF-β signalling (a well-characterised inducer of EMT), SMAD nuclear translocation (a process central to TGF-β signalling) and promotion of EMT.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2014|