Cytoplasmic expression of ß-catenin is an independent predictor of progression of conventional renal cell carcinoma: a simple immunostaining score.

AIMS: The aims of this study were to investigate the potential of ß-catenin as a biomarker for predicting cancer-specific survival, and to find a reproducible mode of evaluation of immunohistochemistry. METHODS AND RESULTS: ß-Catenin expression was analysed by immunohistochemistry in a cohort of 488 patients with conventional renal cell carcinoma (RCC) operated on between 2000 and 2010. The association between ß-catenin expression and cancer-specific survival was assessed with univariate and multivariate Cox regression models in relation to conventional clinical pathological prognostic factors, and by Kaplan-Meier survival analysis with the log rank test. The univariate Cox regression model revealed an association of cytoplasmic ß-catenin positivity and pathological variables with cancer-specific death. The multivariate Cox regression model analysis of tumours without metastatic disease at the first presentation identified the T-classification (P < 0.001) and cytoplasmic ß-catenin positivity as risk factors for postoperative tumour progression. Specifically, cytoplasmic ß-catenin expression was an independent factor indicating an unfavourable prognosis, with a four-fold higher risk of cancer-specific death (relative risk 4.017; 95% confidence interval 2.489-6.482; P < 0.001). The median survival time for patients with tumours showing cytoplasmic accumulation of ß-catenin was 48 months, whereas the overall survival time was 166 months. CONCLUSIONS: Cytoplasmic ß-catenin expression is an independent prognostic factor for conventional RCC, and may help to identify patients with a high risk of cancer-specific death and to direct optimized active surveillance or adjuvant therapy.

Absence of Canonical WNT Signaling in Adult Renal Cell Tumors of Embryonal Origin.

BACKGROUND/AIM: The canonical ß-catenin pathway is involved in the development of Wilms' tumor, but its role in adult renal cell tumors (RCT) of embryonal origin is not yet known. MATERIALS AND METHODS: We sequenced the catenin beta 1 (CTNNB1) gene in papillary RCTs, applied the TOPflash/FOPflash reporter plasmid system on cell lines, and examined the ß-catenin protein expression by immunohistochemistry. RESULTS: The absence of mutations in CTNNB1 and low TOPflash/FOPflash ratio in tumor cell lines indicated the absence of active Wingless-type MMTV integration site family (WNT) signaling in RCTs. The weakly cytoplasmic tending towards membranous expression of ß-catenin in RCT is analogous to cellular differentiation in the embryonal kidney rather than tumorigenic activation of WNT signaling. CONCLUSION: The localization of ß-catenin in papillary RCT, metanephric adenoma and mucinous tubular and spindle-cell carcinoma corresponds to that of emerging tubules of kidney at distinct stage of maturation, indicating their embryonal origin.