Prognostic significance of Klotho expression in patients with renal cell carcinoma

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).

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.

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.

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