Impaired Delta Np63 Expression is Associated with Poor Tumor Development in Transitional Cell Carcinoma of the Bladder

The oncogenic isoform of the p63 protein, delta Np63 (delta Np63), plays an important role in the pathogenesis of many epithelial carcinomas, and emerging evidences suggest that delta Np63 is a promising drug target. However, the functions of delta Np63 in transitional cell carcinoma of bladder (TCCB) are poorly defined. In this study, a delta Np63 shRNA expression vector was transfected into TCCB cell line 5637 and cell cycling, cell proliferation and protein expression were assessed by flow cytometry and 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-dimethyl tetrazolium bromide (MTT) assay, and immunohistochemistry, respectively. The delta Np63 shRNA expression vector was also injected into 5637 cell xenograft tumors in nude mice, and tumor size was measured, tumor tissue morphology was assessed by immunohistopathology and transmission electron microscopy. In the in vitro study, delta Np63 shRNA transfection caused successful delta Np63 gene silencing and resulted in significant arrest of cell cycling and cellular proliferation (p<0.05) as well as cyclin D1 expression. In the nude mouse xenograft model, delta Np63 shRNA greatly inhibited tumor growth, induced tumor cell apoptosis (p<0.05) and resulted in cyclin D1 downregulation. Our data suggest that delta Np63 may play an oncogenic role in TCCB progression through promoting cell survival and proliferation. Intratumoral administration of delta Np63-specific shRNA suppressed tumor delta Np63 expression and cellular proliferation while promoted tumor cellular apoptosis, and therefore inhibited tumor growth and improved survival of xenograft-bearing mice, which was not accompanied by significant signs of systemic toxicity.