2191

FAP

fibroblast activation protein, alpha;FAP;fibroblast activation protein, alpha

170 kDa melanoma membrane-bound gelatinase|FAPalpha|dipeptidyl peptidase FAP|gelatine degradation protease FAP|integral membrane serine protease|post-proline cleaving enzyme|prolyl endopeptidase FAP|seprase|serine integral membrane protease|surface-expres

2q23

protein-coding

Seprase is a membrane-bound serine proteinase with gelatinase activity, which may be involved in cancer invasion and metastasis. We examined seprase expression in colorectal cancer specimens obtained from 109 patients. Seprase immunoreactivity was found in cancer cells and adjacent stromal cells. Immunoblotting showed higher levels of seprase protein in colorectal cancer tissue than in normal colorectal tissue. A semiquantitative assessment of the immunohistochemistry results revealed a significant correlation between seprase expression and lymph node metastasis. These results suggested that an abundant expression of seprase in colorectal cancer tissue is associated with lymph node metastasis.

Seprase is a membrane-bound serine proteinase with gelatinase activity, which may be involved in cancer invasion and metastasis. We examined seprase expression in colorectal cancer specimens obtained from 109 patients. Seprase immunoreactivity was found in cancer cells and adjacent stromal cells. Immunoblotting showed higher levels of seprase protein in colorectal cancer tissue than in normal colorectal tissue. A semiquantitative assessment of the immunohistochemistry results revealed a significant correlation between seprase expression and lymph node metastasis. These results suggested that an abundant expression of seprase in colorectal cancer tissue is associated with lymph node metastasis.

Seprase (fibroblast activation protein alpha) has been examined as an invasion biomarker for various types of solid tumors. We studied whether plasma levels of seprase and homologous protease, DPP4 in cancer might serve as tumor biomarkers. We developed sensitive and specific Enzyme-Linked Immunosorbent Assays (ELISAs) to measure these proteases. In 747 plasma samples (from 139 healthy volunteers and 561 cancer patients), mean seprase and DPP4 levels were 0.51 +/- 0.30 and 4.65 +/- 6.37 mug/mL, respectively, and they were correlated with each other (R(2) = 0.382). Plasma DPP4 and seprase levels were significantly lower in cancer patients compared with healthy subjects (4.38 versus 5.65 mug/mL, p< 0.001 for DPP4; 0.46 versus 0.66 mug/mL, p< 0.001 for seprase). Higher DPP4 was associated with better survival in all cancers combined (n=346) as well as in head and neck malignancies (n=38). Higher seprase was associated with better survival in all non-metastatic cancers combined (n=151) as well as head and neck malignancies, but worse survival in colorectal cancers (n=47). This study demonstrates that in contrast to the high expression in solid tumors, plasma concentrations of seprase and DPP4 are reduced and correlate inversely with survival in most types of cancer, suggesting that these circulating proteases represent useful tumor markers.

The tumor invasive phenotype driven by seprase expression/activity has been widely examined in an array of malignant tumor cell types; however, very little is known about the transcriptional regulation of this critical protease. Seprase (also named fibroblast activation protein-alpha, antiplasmin-cleaving enzyme, and dipeptidyl prolyl peptidase 5) is expressed at high levels by stromal fibroblast, endothelial, and tumor cells in a variety of invasive tumors but is undetectable in the majority of normal adult tissues. To examine the transcriptional regulation of the gene, we cloned the human seprase promoter and demonstrated that endogenous seprase expression and exogenous seprase promoter activity are high in invasive melanoma cells but not in non-invasive melanoma cells/primary melanocytes. In addition, we identified a crucial TGF-beta-responsive cis-regulatory element in the proximal seprase promoter region that enabled robust transcriptional activation of the gene. Treatment of metastatic but not normal/non-invasive cells with TGF-beta1 caused a rapid and profound up-regulation of endogenous seprase mRNA, which coincided with an abolishment of the negative regulator c-Ski, and an increase in binding of Smad3/4 to the seprase promoter in vivo. Blocking TGF-beta signaling in invasive melanoma cells through overexpression of c-Ski, chemically using SB-431542, or with a neutralizing antibody against TGF-beta significantly reduced seprase mRNA levels. Strikingly, RNAi of seprase in invasive cells greatly diminished their invasive potential in vitro as did blocking TGF-beta signaling using SB-431542. Altogether, we found that seprase is transcriptionally up-regulated in invasive melanoma cells via the canonical TGF-beta signaling pathway, supporting the roles of both TGF-beta and seprase in tumor invasion and metastasis.