Prolyl endopeptidase activity is correlated with colorectal cancer prognosis

Abstract

Background and objective: Prolyl endopeptidase (PEP) (EC 3.4.21.26) is a serine peptidase involved in differentiation, development and proliferation processes of several tissues. Recent studies have demonstrated the increased expression and activity of this cytosolic enzyme in colorectal cancer (CRC). However, there are no available data about the impact of this peptidase in the biological aggressiveness of this tumor in patient survival.

Methods: The activity of PEP in tissue (n=80) and plasma (n=40) of patients with CRC was prospectively analyzed by fluorimetric methods. Results were correlated with the most important classic pathological data related to aggressiveness, with 5-year survival rates and other clinical variables.

Results: 1) PEP is more active in early phases of CRC; 2) Lower levels of the enzyme in tumors were located in the rectum and this decrease could be related with preoperative chemo-radiotherapy; 3) PEP activity in tissue was higher in patients with better overall and disease-free survival (log-rank p<0.01, Cox analysis p<0.01); 4) Plasmatic PEP activity was significantly higher in CRC patients than in healthy individuals and this was associated with distant metastases and with worse overall and disease-free survivals (log-rank p<0.05, Cox analysis p<0.05).

Conclusions: PEP activity in tissue and plasma from CRC patients is an independent prognostic factor in survival. The determination of PEP activity in the plasma may be a safe, minimally invasive and inexpensive way to define the aggressiveness of CRC in daily practice.

Keywords: PEP; Prolyl endopeptidase; colorectal cancer; prognosis; survival..

Figure 1

A. Topographic distribution of PEP activity in CRC tissue. Columns compare PEP activity of tumor tissues from right hemicolon (between cecum and the end of transverse colon), left hemicolon (between the splenic flexure and the end of sigmoid colon) and rectum. Values are means ± SE of peptidase activity recorded as pmol of units of peptidase (UP) per milligram of protein. One-way ANOVA p<0.05. (*) Scheffé Test, p<0.05, when comparing left hemicolon and rectum. B. PEP activity in rectal cancer in response to preoperative chemo-radiotherapy. Columns compare PEP activity in neoplastic tissue from rectal cancer patients without and with preoperative chemo-radiotherapy. Values are means ± SE of peptidase activity recorded as pmol of units of peptidase (UP) per milligram of protein. (*) Student's T test, p<0.05.

Figure 1

A. Topographic distribution of PEP activity in CRC tissue. Columns compare PEP activity of tumor tissues from right hemicolon (between cecum and the end of transverse colon), left hemicolon (between the splenic flexure and the end of sigmoid colon) and rectum. Values are means ± SE of peptidase activity recorded as pmol of units of peptidase (UP) per milligram of protein. One-way ANOVA p<0.05. (*) Scheffé Test, p<0.05, when comparing left hemicolon and rectum. B. PEP activity in rectal cancer in response to preoperative chemo-radiotherapy. Columns compare PEP activity in neoplastic tissue from rectal cancer patients without and with preoperative chemo-radiotherapy. Values are means ± SE of peptidase activity recorded as pmol of units of peptidase (UP) per milligram of protein. (*) Student's T test, p<0.05.

Figure 2

Kaplan-Meier curves and Multivariate Analysis (Cox regression model) with PEP activity in CRC tissues. Overall survival (A) and disease-free survival (C) of 80 CRC patients according to their tumor PEP activity pattern. Multivariate analysis of clinicopathologic variables and tumor PEP activity in predicting overall survival (B) and disease-free survival (D) of patients with CRC.

Figure 2

Kaplan-Meier curves and Multivariate Analysis (Cox regression model) with PEP activity in CRC tissues. Overall survival (A) and disease-free survival (C) of 80 CRC patients according to their tumor PEP activity pattern. Multivariate analysis of clinicopathologic variables and tumor PEP activity in predicting overall survival (B) and disease-free survival (D) of patients with CRC.

Figure 3

Plasmatic PEP activity in CRC patients and healthy subjects (controls). Values are means ± SE of units of peptidase per liter of plasma (UP/L). (*) Student's T test, p<0.05.

Figure 4

Receiver-operating characteristic (ROC) curves for plasmatic PEP activity. Optimal sensitivity and specificity ratios were observed using the following cut-off value: 11 UP/L, both for overall survival (A) and disease-free survival (B).

Figure 4

Receiver-operating characteristic (ROC) curves for plasmatic PEP activity. Optimal sensitivity and specificity ratios were observed using the following cut-off value: 11 UP/L, both for overall survival (A) and disease-free survival (B).

Figure 5

Kaplan-Meier curves and Multivariate Analysis (Cox regression model) with PEP activity in plasma from CRC patients. Overall survival (A) and disease-free survival (C) of 40 CRC patients according to their plasmatic PEP activity pattern. Multivariate analysis of clinicopathologic variables and plasmatic PEP activity in predicting overall survival (B) and disease-free survival (D) of patients with CR.

Figure 5

Kaplan-Meier curves and Multivariate Analysis (Cox regression model) with PEP activity in plasma from CRC patients. Overall survival (A) and disease-free survival (C) of 40 CRC patients according to their plasmatic PEP activity pattern. Multivariate analysis of clinicopathologic variables and plasmatic PEP activity in predicting overall survival (B) and disease-free survival (D) of patients with CR.