Gorka Larrinaga

Distribution of prolyl endopeptidase activities in rat and human brain

Prolyl endopeptidase is a proteolytic enzyme which could have a neuropeptide catabolising role in the central nervous system. Although prolyl endopeptidase has been described as a cytosolic enzyme, it has become clear that it can also be found in particulate form. The regional and subcellular distribution of this enzyme was evaluated in rat and human brain. The activity of the enzyme was higher in the human than in the rat brain. In the human brain, the activity levels of both soluble and particulate prolyl endopeptidase were the highest in frontal, parietal and occipital cortices and the lowest in the cerebellum. In the rat brain, the regional distribution of the enzyme was more homogeneous. The activity in all the areas of the central nervous system is higher than in peripheral tissues. Subcellular distribution of the enzyme in the brain indicates that prolyl endopeptidase was higher in the cytosolic fraction than in the particulate fractions. The particulate form was enriched in the synaptosomal and the myelinic membranes. The high activity of prolyl endopeptidase in the human cortex suggests that prolyl endopeptidase could play a role in the functions of this brain area.

Targeted next-generation sequencing and non-coding RNA expression analysis of clear cell papillary renal cell carcinoma suggests distinct pathological mechanisms from other renal tumour subtypes

Clear cell tubulopapillary renal cell carcinoma (CCPRCC) is a recently described rare renal malignancy that displays characteristic gross, microscopic and immunohistochemical differences from other renal tumour types. However, CCPRCC remains a very poorly understood entity. We therefore sought to elucidate some of the molecular mechanisms involved in this neoplasm by carrying out targeted next‐generation sequencing (NGS) to identify associated mutations, and in addition examined the expression of non‐coding (nc) RNAs. We identified multiple somatic mutations in CCPRCC cases, including a recurrent [3/14 cases (21%)] non‐synonymous T992I mutation in the MET proto‐oncogene, a gene associated with epithelial‐to‐mesenchymal transition (EMT). Using a microarray approach, we found that the expression of mature (n = 1105) and pre‐miRNAs (n = 1105), as well as snoRNA and scaRNAs (n = 2214), in CCPRCC cases differed from that of clear cell renal cell carcinoma (CCRCC) or papillary renal cell carcinoma (PRCC) tumours. Surprisingly, and unlike other renal tumour subtypes, we found that all five members of the miR‐200 family were over‐expressed in CCPRCC cases. As these miRNAs are intimately involved with EMT, we stained CCPRCC cases for E‐cadherin, vimentin and β‐catenin and found that the tumour cells of all cases were positive for all three markers, a combination rarely reported in other renal tumours that could have diagnostic implications. Taken together with the mutational analysis, these data suggest that EMT in CCPRCC tumour cells is incomplete or blocked, consistent with the indolent clinical course typical of this malignancy. In summary, as well as describing a novel pathological mechanism in renal carcinomas, this study adds to the mounting evidence that CCPRCC should be formally considered a distinct entity. Microarray data have been deposited in the GEO database [GEO accession number (GSE51554)]. Copyright

Increased APN/CD13 and acid aminopeptidase activities in head and neck squamous cell carcinoma.

Involvement of peptidases in carcinogenic processes of several tumor types has been investigated in recent years. Head and neck squamous cell carcinoma (HNSCC) is one of the most common cancers worldwide and accounts for more than 90% of all head and neck cancers. Increased understanding of its pathophysiology has led to implication of several proteinases, specially matrix metalloproteinases, in its genesis, growth, and dissemination. However, very little is known about involvement of peptidases in this neoplasm.

Expression and activity profiles of DPP IV/CD26 and NEP/CD10 glycoproteins in the human renal cancer are tumor-type dependent

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.

Increased prolyl endopeptidase activity in human neoplasia.

Prolyl endopeptidase (EC 3.4.21.26) (PEP) is a serine peptidase that converts several biologically active peptides. This enzyme has been linked to several neurological, digestive, cardiovascular and infectous disorders. However, little is known about its involvement in neoplastic processes. This study analyzes fluorimetrically cytosolic and membrane-bound PEP activity in a large series (n=122) of normal and neoplastic tissues from the kidney, colon, oral cavity, larynx, thyroid gland and testis. Cytosolic PEP activity significantly increased in clear cell renal cell carcinoma, urothelial carcinoma of the renal pelvis and head and neck squamous cell carcinoma. Both cytosolic and membrane-bound PEP activity were also increased in colorectal adenomatous polyps. These data suggest the involvement of PEP in some mechanisms that underlie neoplastic processes.

Acid, basic, and neutral peptidases present different profiles in chromophobe renal cell carcinoma and in oncocytoma

Renal cell carcinomas (RCCs) are neoplasias with high prevalence and mortality. We previously reported that several peptidases may be involved in the pathophysiology of clear cell renal cell carcinoma (CCRCC). Now, to gain insight into the reasons that lead the various RCC types to behave very differently with regard to aggressiveness and response to anticancer treatments, we analyzed subsets of chromophobe renal cell carcinoma (ChRCC), and renal oncocytoma (RO), a benign tumor; as well as different grades and stages of CCRCCs. Particulate APN, APB, and APA activities were decreased in both ChRCC and RO (tumor vs. nontumor tissues). Interestingly, activities were downregulated in a tumor-type specific way and the intensities of the decreases were stronger in the benign tumor than in the malignant type. Moreover, when two key histopathological parameters for tumor prognosis (high vs. low stage and grade) were analyzed, increases of activity were also observed in several of these cell surface peptidases (APN, APB). Some soluble activities (APB, Asp-AP) were also downregulated in the RCCs. With respect to genetic expression, PSA and APN were in a positive correlation related to their activities in both ChRCC and RO; but not APB, Asp-AP, APA, and PGI. These results may suggest an involvement of several peptidases in the pathophysiology of renal cancer, since they presented different patterns of activity and expression in tumors with different behaviors.

The impact of peptidase activity on clear cell renal cell carcinoma survival

Several studies have proposed that protease expression and activity may have a predictive value in the survival of clear cell renal cell carcinoma (CCRCC). Most efforts on this issue have been focused on the analysis of matrix metalloproteinases (MMP) and very little on the role of other proteases, such as peptidases. The catalytic activity of 9 peptidases (APN, APB, ASP, CAP, DPP-IV, NEP/CD10, PEP, PGI, and PSA) was quantified by fluorometric methods in a series of 79 CCRCC patients, and the results obtained were analyzed for survival (Kaplan-Meier curves, log-rank test, and Cox multivariate analysis). CCRCC patients with higher activity levels of membrane-bound APN and soluble APN, DPP-IV, and CAP had significantly shorter 5-yr survival rates than those with lower levels. By contrast, higher soluble APB activity significantly correlated with longer survival. Our data suggest the involvement of peptidases in the biological aggressiveness of CCRCC and support the usefulness of measuring these proteases to assess the prognosis of patients with CCRCC.

Aminopeptidase activity in the postmortem brain of human heroin addicts

Several studies have reported that the chronic administration of opioids induces changes in the biosynthesis of endogenous opioid peptides or their precursors in specific brain regions of the adult central nervous system. However, little is known about the catabolic regulation of opioid peptides and its contribution to neuroadaptative changes underlying drug addiction. In the present study, we have analyzed the activity of two enkephalin-degrading enzymes (puromycin-sensitive aminopeptidase or PSA and aminopeptidase N or APN) and two functionally different, soluble aminopeptidases (aminopeptidase B and aspartyl-aminopeptidase) in postmortem samples of prefrontal cortex and caudate nucleus of eight human heroin addict brains and eight matched-controls. Enzyme activities were fluorimetrically measured using beta-naphthylamide derivatives. An increase in the activity of soluble PSA in the prefrontal cortex of heroin abusers was observed (heroin addict group: 51,452+/-3892 UAP/mg protein versus control group: 42,003+/-2597 UAP/mg protein; P<0.05), while the activity of the other peptidases in both brain regions remained unaltered. This result agrees with previous findings in morphine-tolerant rats, and indicates that soluble PSA may be involved in neurobiological processes which underlie heroin addiction.

Effects of morphine administration and its withdrawal on rat brain aminopeptidase activities

The endogenous opioid neuropeptide system seems to be involved in the neural processes which underlie drug addiction. Several studies have reported that the administration of morphine induces changes in the levels and/or activity of endogenous opioid peptides (enkephalin, dynorphin) and their precursors in specific brain regions of the adult CNS. The aim of this work was to study the effects of chronic morphine exposure and its withdrawal on certain aminopeptidases capable of degrading opioid peptides in brain areas including the amygdala, hypothalamus, hippocampus, striatum and brain cortices. In animals treated with morphine, aminopeptidase N presented higher enzyme activity levels in the striatum, the hypothalamus and the amygdala compared to control animals, although statistically significant differences were observed only in the case of the striatum. In addition, the activity of soluble puromycin-sensitive aminopeptidase (PSA) was found to be higher in the frontal cortex of these rats. In contrast, rats experiencing withdrawal symptoms presented decreased levels of aminopeptidase activity in certain brain areas. Thus, the activity of aminopeptidase N in the hippocampus and soluble puromycin-sensitive aminopeptidase in the frontal cortex were found to be lower in rats experiencing naloxone precipitated withdrawal symptoms, compared to the corresponding controls. Finally, the activity of the three studied aminopeptidases in vitro was unaltered by incubation with morphine, suggesting that the observed effects are not due to a direct action of this opioid upon the aminopeptidases. The results of the present report indicate that aminopeptidases may play an important role in the processes of tolerance and withdrawal associated with morphine administration.

Cannabinoid CB1 Receptor Is Downregulated in Clear Cell Renal Cell Carcinoma

Several studies in cell cultures and in animal models have demonstrated that cannabinoids have important antitumoral properties. Because many of these effects are mediated through cannabinoid (CB) receptors CB1 and CB2, the study of their expression in human neoplasms has become of great interest in recent years. Fresh and formalin-fixed tissue samples of 20 consecutive clear cell renal cell carcinomas (CCRCCs) were collected prospectively and analyzed for the expression of both CB receptors by using RT–PCR, Western blot (WB), and immunohistochemical techniques. RT-PCR assays demonstrated the expression of mRNA encoding the CB1 in tumor tissue and in adjacent non-neoplastic kidney. Conversely, WB and IHC revealed a marked downregulation of CB1 protein in tumor tissue; CB2 was not expressed. The obtained data suggest a possible implication of the endocannabinoid system in renal carcinogenesis. A posttranscriptional downregulation of CB1 and the absence of expression of CB2 characterize CCRCC. (J Histochem Cytochem 58:1129–1134, 2010)