Polycystins Expression in Astrocytic Gliomas

Background: Polycystin 1 (PC1) and polycystin 2 (PC2) proteins are members of the transient receptor potential (TRP) channels family and are encoded from PKD1 and PKD2 genes, respectively. Until recently, the role of PKD1 and PKD2 has been associated with the pathogenesis of the kidney since mutations in these genes cause autosomal dominant polycystic kidney disease (ADPKD). Recent data implicates polycystins in the pathogenesis of solid tumors. In this aspect, the expression of PKD1 and PKD2 in human astrocytomas is largely unknown. The aim of the present research study was to investigate the expression of PKD1 and PKD2 in astrocytic tumors and correlate it with clinicopathological characteristics such as the grade of malignancy, age, and gender of the patients. Methods: A total of 70 cases—corresponding to 8 grade II (diffuse fibrillary astrocytomas), 12 grade III (anaplastic astrocytomas), and 50 grade IV (glioblastomas multiforme)—were examined. The mRNA expression levels of PKD1 and PKD2 were determined through molecular qRT-PCR analysis using the relative quantification ΔΔCt method and the expression of PC1 and PC2 was detected through immunohistochemistry using the semi-quantitative H-score system. Results: Increased levels of PKD1 and PKD2 in astrocytomas were found compared with that of a normal brain (p < 0.05). Glioblastomas demonstrated the greatest increase in PKD1 and PKD2 expression compared to other grades of malignancy (p < 0.05). The same pattern of expression showed PC1 and PC2 proteins. A significant correlation between PKD1 and PKD2 as well as PC1 and PC2 expressions was found (p < 0.05). Although no association was detected between PC1 or PC2 and Ki67 expression (p > 0.05), a significant correlation between PC1 and p53 immunoexpressions, in grade III and between PC2 and p53 immunoexpressions, in grade II astrocytomas (p < 0.01) has emerged. PC1 expression was correlated with age of the patients (p < 0.05). PKD1 and PKD2 expression were negatively correlated with the prognosis of glioma patients. Conclusions: The results of this study indicate the potential involvement of polycystins in the pathogenesis of astrocytomas. However, further research is required to fully understand the mechanisms that these molecules are implicated.