Clinical impact of aspartyl aminopeptidase expression and activity in colorectal cancer

Aspartyl aminopeptidase (ASP; EC 3.4.11.21) is a widely distributed and abundant cytosolic enzyme that regulates bioactive peptides such as angiotensin II. It has been demonstrated that the expression and activity of this enzyme is modified in tissue and serum of patients with several types of cancer. However, the involvement of ASP in the neoplastic development and survival of patients with colorectal cancer (CRC) has not been analyzed to date. The activity and messenger RNA expression of ASP in tumor tissue (n = 71) and plasma (n = 40) of patients with CRC was analyzed prospectively using fluorometric and quantitative real-time polymerase chain reaction methods. Data obtained from tumor tissue were compared with those from the surrounding normal mucosa. Classic pathologic parameters (grade, stage, nodal invasion, distant metastases and perineural, lymphatic, and vascular invasion) were stratified following ASP data and analyzed for 5-year survival. ASP was upregulated in CRC tissues, and greater activity correlated significantly with the absence of lymph node metastases and with better overall survival. Inversely, greater plasmatic ASP activity was associated with worse overall and disease-free survival. Data suggest that ASP is involved in colorectal neoplasia and point to this enzyme as a potential useful diagnostic tool in clinical practice.