Expression of Engrailed-2 (EN2) protein in bladder cancer and its potential utility as a urinary diagnostic biomarker

Despite significant advances in our understanding of the molecular pathology of bladder cancer, it remains a significant health problem with high morbidity and mortality associated with muscle-invasive bladder cancer (stages T2+), and high costs associated with the surveillance of non-muscle-invasive bladder cancer (NMIBC, stages Ta/T1/Tis). Moreover, current diagnostic biomarkers are suboptimal and of poor utility for low grade disease and surveillance. In this study, we show that the Engrailed-2 (EN2) transcription factor is expressed in, and secreted by, bladder cancer cell lines and patient tumour specimens, justifying an evaluation of urinary EN2 as a diagnostic biomarker in bladder cancer using archived samples from an established biospecimen collection. In patients with NMIBC, urinary EN2 was detected in most cases with an overall sensitivity of 82% and specificity of 75%. The sensitivity for stage Ta and T1 tumours was 71% and 76%, respectively, and 94% for stage T2+ tumours. This compares favourably with existing markers. The sensitivity for tumour grades 1, 2 and 3 was 69%, 78% and 87%, respectively. Thus urinary EN2 has the potential to be a more sensitive and specific protein biomarker for NMIBC than currently available tests.