Pathological Significance of Kidney and Brain Expressed Protein (KIBRA) in Clear Cell Renal Cell Carcinoma

Background/Aim: Kidney and brain expressed protein (KIBRA), a member of the WW domain-containing protein family, has an important role in tumour growth and progression in various cancers. However, the pathological significance of KIBRA expression in clear cell renal cell carcinoma (ccRCC) tissues is not fully understood. The aim of this study was to clarify the pathological significance and prognostic roles of KIBRA expression in patients with ccRCC. Materials and Methods: KIBRA immunoreactivity, proliferation index (PI; with anti-Ki-67 antibody), apoptotic index (AI; using anti-cleaved caspase-3), and large tumour suppressor kinases (LATS-2) were evaluated in 157 ccRCC specimens by immunohistochemistry. Fifty normal kidney tissues were also evaluated as controls. The relationships between KIBRA expression and these cancer-related variables as well as clinicopathological features and survival were analysed. Results: Moderate to strong immunoreactivity of KIBRA was identified in all normal kidney tissues; however, ccRCC cells with strong KIBRA expression was rare. The immunoreactivity score (IRS) of KIBRA was negatively associated with grade, T stage, tumour diameter, and metastasis. Kaplan–Meier survival curves showed that high KIBRA expression was a favourite predictor for overall survival. KIBRA IRS was negatively associated with PI and positively associated with the IRS of LATS-2 by univariate analysis. In addition, multivariate analysis showed that KIBRA was significantly associated with PI. Conclusion: KIBRA demonstrated important roles as a tumour suppressor in ccRCC. In addition, its expression was significantly associated with survival in these patients. Several such KIBRA-related functions were speculated to be modulated by cancer cell proliferation and LATS-2.