Abstract
BackgroundCell-surface glycoproteins play critical roles in cell-to-cell recognition, signal transduction and regulation, thus being crucial in cell proliferation and cancer etiogenesis and development. DPP IV and NEP are ubiquitous glycopeptidases closely linked to tumor pathogenesis and development, and they are used as markers in some cancers. In the present study, the activity and protein and mRNA expression of these glycoproteins were analysed in a subset of clear-cell (CCRCC) and chromophobe (ChRCC) renal cell carcinomas, and in renal oncocytomas (RO).MethodsPeptidase activities were measured by conventional enzymatic assays with fluorogen-derived substrates. Gene expression was quantitatively determined by qRT-PCR and membrane-bound protein expression and distribution analysis was performed by specific immunostaining.ResultsThe activity of both glycoproteins was sharply decreased in the three histological types of renal tumors. Protein and mRNA expression was strongly downregulated in tumors from distal nephron (ChRCC and RO). Moreover, soluble DPP IV activity positively correlated with the aggressiveness of CCRCCs (higher activities in high grade tumors).ConclusionsThese results support the pivotal role for DPP IV and NEP in the malignant transformation pathways and point to these peptidases as potential diagnostic markers.
Highlights
Cell-surface glycoproteins play critical roles in cell-to-cell recognition, signal transduction and regulation, being crucial in cell proliferation and cancer etiogenesis and development
dipeptidyl peptidase IV (DPP IV) and neutral endopeptidase (NEP) activity profile in renal tumors Data obtained in the activity assays of both glycoproteins across the different tumor types and in stratified CCRCC are given in Figures 1 and 2
Loss of activity was slight in CCRCC, whereas it drastically decreased in the ChRCC and, in a lesser intensity, in the renal oncocytomas (RO)
Summary
The NEP assay was carried out by incubating samples with a saturating concentration of N-Dansyl-D-Ala-Gly-pNOH2-Phe-Gly ([D]AG (pN)PG, a Dansyl derivative), following the method of Florentin et al (1984) [18] These assays are based on the fluorescence of products generated from the hydrolysis of the substrate by the enzyme. Total RNA of tumor and non-tumor tissue samples from 26 CCRCC (21 male, 5 female; mean age: 63 years), 6 ChRCC (2 male, 4 female; mean age: 63 years) and 4 RO (4 male, 0 female; mean age: 63 years) patients was isolated following a standard protocol as previously described [19]. As was for the enzymatic activities, an additional assay-set was performed to compare expression levels of MME and DPP4 between different grades and stages in CCRCC samples. Significant differences were considered at p < 0.05
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