PTEN Deletions Are Associated With Tumor Progression But Unrelated to Patient Prognosis in Muscle-Invasive Urothelial Bladder Carcinomas: A Large Multi-Center Validation Study on 2710 Urothelial Bladder Carcinomas

The tumor suppressor gene PTEN plays an important role in many cancer types. Mechanism of PTEN inactivation includes gene mutations and deletions. In this large multi-center study, we analyzed the impact of PTEN deletions on tumor aggressiveness, patient prognosis, and p53 and p16 alterations, especially in muscle-invasive urothelial bladder carcinomas to expand the results from our previous study on 686 pTa to pT4 urothelial bladder carcinomas. The PTEN copy number status was analyzed by fluorescence in situ hybridization (FISH) on more than 2700 urothelial bladder carcinomas in a tissue microarray format. PTEN deletion data were compared with clinico-pathological parameters in pTa and pT2-4 carcinomas and clinical outcomes in pT2-4 carcinomas, immunohistochemical p16 and p53 expression, and TP53 copy number status measured by FISH from previous studies. PTEN deletions occurred in 18.8% of 1854 analyzable carcinomas, including 17.6% heterozygous and 1.2% homozygous deleted tumors. The PTEN deletion rate increased markedly from pTaG2 low-grade (3.1%), to pTaG2 high-grade (4.5%) and pTaG3 (20.7%, p < 0.0001) carcinomas, and was 23.8% in pT2-4 carcinomas (p < 0.0001 for pTa vs. pT2-4). In pT2-4 cancers, PTEN deletions were unrelated to histopathological parameters of tumor aggressiveness and patient outcome. PTEN deletions were significantly associated with parameters of p53 alterations and p16 overexpression. It is concluded that PTEN deletions accumulate with grade progression in non-invasive urothelial carcinomas of the urinary bladder. The absence of a prognostic role of PTEN deletions in pT2-4 urothelial carcinomas is in line with our notorious inability to predict the clinical course of these tumors by only one morphological or molecular feature.