Immortalisation of normal XXXX urothelial cells compromises differentiation capacity.

@entity1 @entity5 @entity2557 @entity189 @entity1799 @entity2215
BACKGROUND: The development of @entity5 is not solely a consequence of loss of proliferation constraints but also involves loss of cellular differentiation, defined histopathologically as grade. Although @entity5 grade is an independent prognostic marker for @entity189 ( @entity189 ), the molecular events underpinning the loss of urothelial differentiation are poorly understood. OBJECTIVE: To examine the effect of gene alterations implicated in @entity189 development on the ability of @entity1 urothelial cells to undergo molecular differentiation and form a functional urothelial barrier. DESIGN, SETTING, AND @entity1 : Laboratory study. INTERVENTION: Normal @entity1 urothelial (NHU) cell cultures were transduced with recombinant retroviruses to produce stable sublines overexpressing wild-type or oncogenic mutated @entity2557 or @entity1 telomerase reverse transcriptase ( @entity2215 ). Previously generated NHU sublines carrying dominant-negative CDK4 and p53 mutant genes or immortalised with the @entity1799 E6 oncoprotein were included. MEASUREMENTS: The activity of introduced transgenes was demonstrated by comparing phenotypes of transgene-expressing and isogenic control NHU cells. Modified and control sublines were compared for changes in generational potential (life span) and capacity to respond to differentiation-inducing signals by transcript expression of uroplakins 2 and 3. The ability to form a barrier epithelium was assessed by measuring the transepithelial electrical resistance. RESULTS AND LIMITATIONS: By contrast to @entity5 suppressor loss of function or oncogene overactivation, @entity2215 overexpression alone led to life span extension and immortalisation. The @entity2215 immortalised cells carried no gross genomic alterations but became progressively insensitive to differentiation signals and lost the ability to form an epithelial barrier. Further characterisation of @entity2215 cells revealed a downregulation of p16 cyclin-dependent kinase inhibitor expression and loss of responsiveness to peroxisome proliferator-activated receptor y, providing mechanistic explanations for the subjugation of senescence constraints and the abrogation of differentiation capability, respectively. Although immortalised urothelial cell lines without karyotypic aberrations may be generated, such cell lines are compromised in terms of differentiation and functional capacity. CONCLUSIONS: Overexpression of @entity2215 promotes development of an immortalised differentiation-insensitive urothelial cell phenotype. Although such cells offer a useful insight into the grade/stage paradigm of @entity189 , they have limited value for investigating normal urothelial cell/tissue biology and physiology.
