Notch signaling pathway: dual role in tumour progression and therapeutic opportunities for bladder cancer

During cancer progression Notch signaling pathway and its components could demonstrate oncogenic and tumor-suppressive properties depending on tissue type and cellular microenvironment. However, until recently, very little was known about Notch role in bladder cancer (BC). According to recent studies it was revealed that loss of copy number and decreased expression of NOTCH1 is the hallmark of BC cell lines; and NOTCH1 activation in vitro reduces cell proliferation, suggesting that NOTCH1 acts as a tumor suppressor in BC. Furthermore, BC could be promoted by bladder-specific inactivation of a component of gamma-secretase complex, which is directly involved in Notch signaling, in vivo. By contrast, further studies have demonstrated that NOTCH2 acts as an oncogene which could promote cell proliferation and metastasis through induction of epithelial-to-mesenchymal transition and maintaining stemness. Studies indicating that NOTCH1 and NOTCH2 have opposite effects on BC progression could give rise to novel therapeutic approaches aimed at impact on Notch activity.