p16(INK4a) expression in urinary bladder carcinoma.

: The most common genetic damage in urothelial carcinoma is partial loss of chromosome 9. The area around 9p21 where the CDKN2A/ARF gene is located is one of the major sites for deletion. This gene encodes for p16 protein which impedes the cell cycle. Specific binding of the p16 product to the cyclin-dependent protein kinases cdk4 or cdk6 inhibits the catalytic activity of the cyclin D-cdk complex, and consequently arrests the cell cycle at the G1/G2 phase. This study aims to immunohistochemically assess p16 expression in urothelial carcinoma in order to evaluate the correlation of this biological marker with tumour stage and/or grade. We studied specimens of transurethral resection (TURB) from 17 cases of non-invasive papillary urothelial carcinoma and from 22 cases of invasive urothelial carcinoma of the bladder. We observed strong p16 immunoreactivity in 11 cases (28.2%), while 28 cases (71.8%) did not show p16 staining. The expression of p16 was statistically associated with disease stage (p = 0.026, according to the chi-square test), but not with either tumour grade or disease progression. These observations call for further studies to focus the importance of p16 expression in bladder cancer development and/or progression. Additional data may provide insight into treatment guided by molecular changes.