Functional and molecular characterization of cancer stem-like cells in bladder cancer: a potential signature for muscle-invasive tumors

// Margarida Ferreira-Teixeira 1, 2 , Belmiro Parada 1, 3 , Paulo Rodrigues-Santos 4, 5, 6 , Vera Alves 5, 6 , Jose S. Ramalho 7 , Francisco Caramelo 8 , Vitor Sousa 9, 10 , Flavio Reis 1, 2, 6 , Celia M. Gomes 1, 2, 6 1 Laboratory of Pharmacology and Experimental Therapeutics, Institute for Biomedical Imaging and Life Sciences (IBILI), Faculty of Medicine, University of Coimbra, Coimbra, Portugal 2 CNC.IBILI, University of Coimbra, Coimbra, Portugal 3 Urology and Renal Transplantation Department, Coimbra University Hospital Centre (CHUC), Coimbra, Portugal 4 Immunology and Oncology Laboratory, Center for Neurosciences and Cell Biology (CNC), University of Coimbra, Coimbra, Portugal 5 Institute of Immunology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal 6 Center of Investigation in Environment, Genetics and Oncobiology (CIMAGO), Faculty of Medicine, University of Coimbra, Coimbra, Portugal 7 CEDOC, Faculty of Medical Sciences, New University of Lisbon, Lisbon, Portugal 8 Laboratory of Biostatistics and Medical Informatics, Faculty of Medicine, University of Coimbra, Coimbra, Portugal 9 Institute of Anatomical and Molecular Pathology, Faculty of Medicine, University of Coimbra, Coimbra, Portugal 10 Service of Anatomical Pathology, Coimbra University Hospital Centre (CHUC), Coimbra, Portugal Correspondence to: Celia M. Gomes, e-mail: cgomes@fmed.uc.pt Keywords: bladder cancer, cancer stem cells, ALDH, stemness markers, chemoresistance Received: May 22, 2015      Accepted: September 24, 2015      Published: October 05, 2015 ABSTRACT Striking evidence associates cancer stem cells (CSCs) to the high recurrence rates and poor survival of patients with muscle-invasive bladder cancer (BC). However, the prognostic implication of those cells in risk stratification is not firmly established, mainly due to the functional and phenotypic heterogeneity of CSCs populations, as well as, to the conflicting data regarding their identification based on a single specific marker. This emphasizes the need to exploit putative CSC-related molecular markers with potential prognostic significance in BC patients. This study aimed to isolate and characterize bladder CSCs making use of different functional and molecular approaches. The data obtained provide strong evidence that muscle-invasive BC is enriched with a heterogeneous stem-like population characterized by enhanced chemoresistance and tumor initiating properties, able to recapitulate the heterogeneity of the original tumor. Additionally, a logistic regression analysis identified a 2-gene stem-like signature (SOX2 and ALDH2) that allows a 93% accurate discrimination between non-muscle-invasive and invasive tumors. Our findings suggest that a stemness-related gene signature, combined with a cluster of markers to more narrowly refine the CSC phenotype, could better identify BC patients that would benefit from a more aggressive therapeutic intervention targeting CSCs population.