Speckle-type POZ protein as a diagnostic biomarker in renal cell carcinoma

Background: Renal cell carcinoma (RCC) is the most common kidney neoplasm and requires an early diagnosis because of poor response to conventional cancer treatments. However, till date, there is no reliable tumor marker available for the diagnosis of RCC. Objective: The aim of the study was to evaluate the expression of speckle-type POZ protein (SPOP) as a biomarker in patients with RCC. Materials and Methods: Blood samples were collected from fifty patients with RCC and ten healthy controls. Tumor tissue samples were obtained from nephrectomy specimen. Adjoining normal renal parenchyma of these fifty patients and eight normal renal tissue samples from normal kidney served as controls. Reverse transcriptase-polymerase chain reaction assay was performed for SPOP and mammalian target of rapamycin expression. Results: SPOP was significantly increased in blood of patients with RCC as compared to controls (0.754 +/- 0.32 vs. 0.224 +/- 0.14; P < 0.001). Twenty-two patients (44%) had SPOP value more than mean + 2 standard deviation (SD) of controls. In RCC tissue, 42 (84%) patients had increased expression of SPOP more than 0.523 (mean + 2 SD value of SPOP expression in controls). SPOP expression was high in blood of 60% patients and in tumor tissue of 90% patients with clear cell RCC. SPOP was higher in high grade and high stage of RCC. Conclusions: Our result suggests that SPOP expression in blood might have a sensitivity that is low for routine diagnostic use and for screening for RCC. However, SPOP could be a potential tissue diagnostic biomarker in RCC.