Prognostic significance of Klotho expression in patients with renal cell carcinoma.

Introduction: Various molecular markers have been investigated in renal cell carcinoma (RCC) without significant reliability. We analyzed Klotho (tumor suppressive protein) expression in RCC to investigate its association with tumor-stage, grade, disease-free-survival (DFS) and overall-survival (OS).

Methods: Data of histologically confirmed patients of RCC with complete clinical follow-up were retrieved from Medical-Record-Library. Tissue sections of tumor and normal parenchyma were prepared from the blocks. Immunohistochemical studies for Klotho were done with commercially available kit (EPR6856, Ab181373; Abcam, Cambridge MA, USA). Klotho expression was scored between 0-3 and grouped into weak/absent (0, 1) and moderate/strong (2, 3). Tumors stages and grades were grouped into low stage (I and II) and high stage (III and IV) and into low grade (grade 1 and 2) and high grade (grade 3 and 4) according to WHO/ISUP grading. The histopathologists were blinded as to the clinical and follow-up data. Various prognostic factors were analyzed with respect to Klotho expression. Kaplan-Meier curves were created for DFS and OS.

Results: Fifty-four patients of mean age 55.15 ± 13.34 years and M:F ratio of 1.8:1 were included. Normal renal tissue had strong expression of Klotho in all. In tumor tissue 20 (37%) had negative, 7 (13%) had weak, 14 (25.9%) had moderate and 13 (24.1%) had strong Klotho expression. Significantly more patients had absent/weak Klotho expression with higher grade (16/24 (66.7%) vs 7/25 (28%); p = 0.007), higher stage (22/33 (66%) vs 5/21 (23.8%); p = 0.002), LVI (12/14 (85.7%) vs 2/14 (14.3%); p = 0.002), sinus-fat-invasion (16/21 (76.2%) vs 5/21 (23.8%); p = 0.002), renal-vein-involvement (14/18 (77.8%) vs 4/18 (22.2%); p = 0.004), necrosis (17/26 (65.3%) vs 9/26 (34.6%); p = 0.029) and metastasis (8/9 (88.9%) vs 1/9 (11.1%); p = 0.01). Median DFS and OS were significantly lower in patients with weak/absent Klotho expression (12 vs 23 months, p = 0.023 and 15 vs 33 months, p = 0.006 respectively). Kaplan-Meier curves showed lower estimated DFS and OS in patients with weak/absent expression.

Conclusions: We conclude that Klotho expression in renal tumor could be a good prognostic marker in patients with RCC.