Differential ectonucleotidase expression in human bladder cancer cell lines

Abstract

Bladder cancer is the most prevalent tumor in the genitourinary tract. Nucleotides are important molecules that regulate many pathophysiological functions in the extracellular space. Studies have revealed evidence of a relationship between purinergic signaling and urothelial malignancies. Nucleotide-mediated signaling is controlled by a highly efficient enzymatic cascade, which includes the members of the ectonucleoside triphosphate diphosphohydrolase (E-NTPDases), ectonucleotide pyrophosphatase/phosphodiesterase (E-NPPs), ecto-alkaline phosphatases, and ecto-5'-nucleotidase/CD73. In an attempt to identify possible differential expression of ectonucleotidases during bladder cancer progression, a comparative analysis between RT4 (grade 1) and T24 (grade 3) bladder cancer cell lines was performed. In RT4 cells, the hydrolysis of tri- and diphosphate nucleosides was higher than monophosphonucleosides. T24 cells, however, presented the opposite profile, a low level of hydrolysis of tri- and diphosphate nucleosides and a high level of hydrolysis of monophosphates. Phosphodiesterase activity was negligible in both cell lines at physiological pH, indicating that these enzymes are not active under our assay conditions, although they are expressed in both cell lines. The T24 cells expressed NTPDase5 mRNA, while the RT4 cells expressed NTPDase3 and NTPDase5 mRNA. Both cell lines expressed ecto-5'-nucleotidase/CD73 mRNA. The present work describes, for the first time, the differential pattern of ectonucleotidases in the more malignant bladder cancer cells compared with cells derived from an early stage of bladder cancer. Our results open new avenues for research into the physiological roles of this family of enzymes and their possible therapeutic potential in bladder cancer.