[The clinico-pathological significance of protein expression of PAK1 in bladder transitional cell carcinoma]

To investigate the protein expression of p21-activated kinase 1 gene (PAK1) in bladder transitional cell carcinoma (BTCC) and its clinico-pathological significance.

Immunohistochemistry and TUNEL were used, in combination with tissue microarray technique, to examine the protein expression of PAK1 and status of cell apoptosis in 100 BTCC tissue specimens obtained during operation and 30 specimens of adjacent normal bladder mucosa.

All adjacent normal bladder mucosa specimens were negative in PAK1 protein expression or only with a low-level expression of PAK1 protein, while 58% of the BTCC specimens showed over-expression of PAK1. PAK1 expression was significantly associated with tumor pathological grade and tumor size (both P < 0.05). The PAK1 overexpression rate of the poorly-differentiated BTCC specimens (at the G3 stage) was 78%, significantly higher than that of the well-differentiated specimens (at the stage G1/G2, 47%, P = 0.05). The PAK1 overexpression rate of the large-sized BTCC specimens (>or= 3 cm in diameter) was 73%, significantly higher than that of the small-sized BTCC specimens (< 3 cm in diameter, P = 0.034). The PAK1 protein expression was negatively correlated with the apoptotic index of the cells (P < 0.05).

Overexpression of PAK1 protein may via its anti-apoptotic function to play an important role in the development and progression of BTCC. Overexpression of PAK1 in BTCC is associated closely with tumor malignant histological phenotype and it may be used as a molecular marker to predicate the malignant potential of BTCC.