Renin-angiotensin system-regulating aminopeptidases in tumor growth of rat C6 gliomas implanted at the subcutaneous region.

BACKGROUND Angiotensin peptides play roles in brain tumor infiltration and associated angiogenesis. MATERIALS AND METHODS We explored the roles of soluble and membrane-bound forms of renin-angiotensin system-regulating aminopeptidase N (APN)-, aminopeptidase B (APB)-, glutamate aminopeptidase- and aspartate aminopeptidase (AspAP)-specific activities on tumor growth in the rat C6 glioma model with implantation into the subcutaneous abdomen of Wistar rats, evaluating these activities as biological markers. The tumor volume was assessed for three weeks and a sample of tumor was obtained every seven days to obtain the soluble and membrane-bound fraction, in order to assay enzyme activities fluorometrically using their corresponding aminoacyl-β-naphthylamide as substrates. RESULTS We found a time-dependent decrease in soluble and membrane-bound APN and APB. Soluble AspAP increases with tumor growth in a time-dependent manner. CONCLUSION Although gliomas are heterogeneous tissues, angiotensin peptides are involved in this model of tumor growth and their role could be analyzed through their corresponding regulatory proteolytic enzymes.