What's known on the subject? and What does the study add? Epithelial-mesenchymal 
transition (EMT) is involved in tumor progression where the underlying cellular 
changes associated with EMT have been identified in in vitro models and 
confirmed in a limited number of in vivo studies. ZEB1, which targets E-cadherin 
repression, is a transcriptional regulator that has been implicated in EMT, and 
is associated with uterine and colorectal cancers. Regulation of ZEB1 expression 
has been shown to involve different microRNAs (miRNAs), identifying a potential 
role for miRNA in EMT. In the present study we have identified novel expression 
of ZEB1 in bladder tumours and shown a role for ZEB1 in enhanced migration and 
invasion potential in in vitro assays. Confirmation of ZEB1 expression in 
bladder tumours was shown in tissue microarrays (TMAs).
OBJECTIVE: To evaluate ZEB1 expression in bladder tumorigenesis and define a 
possible role for this transcription factor in urothelial carcinomas of the 
bladder (UCBs).
MATERIALS AND METHODS: Five hundred and fifty-eight samples were assembled in 10 
tissue microarrays (TMAs; 263 non-muscle-invasive Ta/T1/Tis, 295 muscle-invasive 
T2-T4). All tumours were transitional cell carcinomas (TCCs) and processed for 
immunohistochemistry to assess nuclear ZEB1 expression. Expression levels of 
ZEB1 were modulated in bladder carcinoma cell lines CUBIII or UM-UC-3 after 
forced expression or shRNA knockdown, respectively. Protein expression levels 
were determined using western blot analysis and transfectants were assessed for 
migration and invasion potential in standard in vitro assays.
RESULTS: Nuclear ZEB1 expression was recorded in 22.8% of non-muscle-invasive 
UCBs and 21.7% of muscle-invasive UCBs, including 24.1% grade I/II and 21.1% 
grade III tumours, and absent in normal bladder mucosa. No significant 
correlation was observed for tumour stage and grade, nodal involvement, vascular 
invasion, metastasis and overall or cancer-specific survival. The introduction 
or knockdown of ZEB1 expression in bladder carcinoma cell lines showed enhanced 
or reduced migration and invasive potential, respectively. Changes in ZEB1 
expression were accompanied by altered microRNA (miRNA) expression underlying 
events linked to epithelial-mesenchymal transition (EMT).
CONCLUSION: The results in the present study showed novel expression of ZEB1 in 
bladder cancer in the absence of a link to clinical variables of change, 
including metastasis and survival. However, in vitro assays showed enhanced or 
reduced migration and invasion after the introduction or reduction of ZEB1, 
respectively, in transfected bladder cell lines. Modulation in expression of 
ZEB1 was closely linked to changes in the miR-200 family along with alternative 
known prognostic indicators of bladder tumour progression.