Clinicopathological examination of dipeptidase 1 expression in colorectal cancer

Dipeptidase 1 (DPEP1) is a zinc-dependent metalloproteinase that is fundamental in glutathione and leukotriene metabolism. DPEP1 was initially considered as a tumor suppressor gene in Wilms' tumor and breast cancer. However, it has been reported that DPEP1 is upregulated in colorectal cancers (CRCs) and high DPEP1 expression levels are associated with poorer patient survival. The role of DPEP1 genes in CRC, as well as their expression, requires investigation. Therefore, the present study investigated DPEP1 expression using reverse transcription-quantitative polymerase chain reaction or immunohistochemistry on surgically resected samples from CRC cases, and further examined the biological significance of DPEP1 by comparing the expression of the epithelial to mesenchymal transition (EMT) markers, including epithelial cadherin and Vimentin to clarify the function of DPEP1 in CRC, particularly in metastasis. The level of DPEP1 expression was identified to be significantly increased in tumorous tissue samples compared with that in non-tumorous tissue samples. In addition, increased DPEP1 mRNA expression levels were associated with positive lymph node metastasis in the included cohort. However, no positive correlations were observed between DPEP1 and EMT markers in the cohort. The results indiciates that further investigations into the upregulation of DPEP1 in colorectal carcinogenesis and the role of therapeutic or prognostic biomarkers are required.