The phosphatidylinositol‐3 kinase pathway regulates bladder cancer cell invasion

Abstract

Three of the studies described in this section relate to bladder cancer. The first of these concerns the PI‐3 kinase pathway, which has been a topic of interest in cancer in general. The authors from Sacramento suggest that it may regulate cancer cell invasion, and hope that this may lead to translational therapeutic uses. Another study describes the pharmacological characteristics of Ro115‐1240, which is a selective alpha 1A/1L adrenoceptor partial agonist, a compound which may have a future in treating stress urinary incontinence. OBJECTIVES To investigate the role of the phosphatidylinositol (PI)‐3 kinase pathway in the invasion of bladder cancer cell lines, and to assess the activation of this pathway in primary human bladder tumours. MATERIALS AND METHODS Human bladder cancer cells were treated with pathway specific inhibitors or were transfected with PI‐3 kinase pathway components. The invasion of cultured bladder cancer cells was analysed by an invasion assay. Bladder cancer cells lines and primary human bladder tumours were analysed for pathway activation by western blotting. RESULTS A specific inhibitor of PI‐3 kinase enzyme activity, Ly294002, potently suppressed the invasive properties of three highly invasive bladder tumour cell lines. Restoration of the PTEN gene to invasive UM‐UC‐3 bladder tumour cells or expression of a dominant‐negative version of the PI‐3 kinase target, Akt, also potently inhibited invasion, indicating a central role for the PI‐3 kinase/Akt pathway in this process. In addition, 55% of primary tumours from patients with bladder cancer had markedly high levels of phosphorylated Akt. CONCLUSION Pharmacological or biochemical inhibition of the PI‐3 kinase pathway drastically reduced the invasive capacity of bladder cancer cell lines; over half of primary human bladder tumours had high Akt phosphorylation, suggesting that the aberrant activation of this pathway may contribute to the invasion of a significant subset of bladder cancers.