The S100 proteins for screening and prognostic grading of bladder cancer

The S100 gene family, which is composed of at least 24 members carrying the Ca2+ binding EF-hand motif, has been implicated in both intracellular and extracellular functions, including enzyme activities, immune responses, cytoskeleton dynamics, Ca2+ homeostasis, cell growth and cell differentiation. Altered S100 protein levels are associated with a broad range of diseases, including cardiomyopathy, inflammatory and immune disorders, neurodegenerative disorders and cancer. Although the precise role of S100 protein in carcinogenesis is poorly understood, it seems that formation of homo- and hetero-dimers, binding of Ca2+ and interaction with effector molecules are essential for the development and progression of many cancers. Several studies have suggested that S100 proteins promote cancer progression and metastasis through cell survival and apoptosis pathways. In animal models of bladder cancer, several S100 proteins are differentially expressed in bladder tumors relative to normal urothelium. In human bladder cancer, overexpression of S100A4, S100A8 or S100A11 are associated with stage progression, invasion, metastasis and poor survival. This review summarizes these findings and evaluates their implications for human bladder cancer management.