Characterization of cancer stem-like cells by detecting chromosomal aberrations in bladder cancer

Th e capability of a tumor to grow and propagate seems to depend on a small sub-population of cells, called cancer stem cells (CSCs) [1]. We isolated and characterized putative bladder CSCs populations from primary Transitional Cell Carcinomas (TCCs). Th ese cells proliferated as urospheres and had abilities for extensive proliferation and self-renewal. Their positivity for stem cell markers and their potential to diff erentiate were assessed. Urospheres gradually showed loss of proliferation, adherence to the substrate, and morphological changes, which might refl ect their progressive loss of self-renewal ability. Conventional cytogenetic analysis was carried out on fresh chromosome spreads immediately aft er the isolation and aft er one week of culture. Th e data indicated important karyotype selection and the loss of complexity present in fresh tumors. Another purpose was to evaluate the performance of a targeted test (UroVysion assay) widely used for the detection of TCCs [2], on Formalin Fixed Paraffi n Embedded (FFPE) tissues and interphasic nuclei of urospheres: comparing tissue and aft er-culture data, we observed a great heterogeneity also among samples with the same histotype. The comparison between array-CGH and UroVysion assay evidenced the same heterogeneity on two different types of material derived from the same tumor: FFPE and Freshly Isolated interphasic Nuclei (FIN). Our results confi rmed the importance of use complementary techniques such array-CGH and FISH, as the former is able to detect alterations at the genome level, but the latter is able to maintain the individual data at the level of single cells, even if it focuses on few genomic regions.