Molecular basis of aberrant expression of alkaline phosphatase in renal brush border membrane from renal cell carcinoma patients

Abstract

Abstract The incidence of renal cell carcinoma (RCC) has been increasing worldwide. It continues to present a diagnostic and therapeutic challenge. It accounts for approximately 3% of adult malignancies and 90-95% of neoplasm arising from kidney. RCC originates from proximal tubular epithelium of adult kidney. Alkaline phosphatase is abundantly expressed on the BBM and serves as an excellent marker for its integrity. Earlier reports have demonstrated that the activities of brush border membrane (BBM) enzymes are altered in cancer cells. The present study was conducted to find out the molecular basis of altered expression/activity of ALP in BBM from RCC in comparison to normal renal BBM. Total 30 histopathologically confirmed cases of RCC were included in the present study. The specific activity of ALP was drastically reduced in homogenate as well as in BBM from RCC as compared to BBM from adjacent normal kidney parenchyma. SDS-PAGE study showed that the BBM proteins of higher molecular weights were poorly expressed in BBM from RCC as compare to BBM from adjacent normal kidney parenchyma. Incubation of gel with BCIP/NBT dye showed that the expression of ALP in BBM from RCC was reduced as compared to adjacent normal kidney BBM. Western blot analysis using anti ALP antibody also confirmed the reduced expression of ALP in RCC BBM. Further, to check whether this reduced expression of ALP occurs at mRNA level, a semi quantitative RT-PCR was done, which showed markedly reduced expression of ALP mRNA in RCC as compared to adjacent normal kidney.