Carboxypeptidase 4 gene variants and early-onset intermediate-to-high risk prostate cancer

Enhanced proteomic profiling of human plasma-derived extracellular vesicles through charge-based fractionation to advance biomarker discovery potential

The study introduces a charge-based fractionation method for fractionating plasma-derived extracellular vesicles (EVs) into sub-populations aimed at the improved purification from free plasma proteins to enhance the diagnostic potential of EV sub-populations for specific pathophysiological states. Here, we present a novel approach for EV fractionation that leverages EVs' inherent surface charges, differentiating them from other plasma components and, thus, reducing the sample complexity and increasing the purity of EVs. The developed method was optimized and thoroughly evaluated using proteomic analysis, transmission electron microscopy, nanoparticle tracking, and western blotting of isolated EVs from healthy donors. Subsequently, we pilot-tested the developed technique for its applicability to real-world specimens using a small set of clinical prostate cancer samples and matched controls. The presented technique demonstrates the effective isolation and fractionation of EV sub-populations based on their surface charge, which may potentially help enhance EV-based diagnostics, biomarker discovery, and basic biology research. The method is designed to be straightforward, scalable, easy-to-use, and it does not require specialized skills or equipment.

CPA4 as a biomarker promotes the proliferation, migration and metastasis of clear cell renal cell carcinoma cells

Clear cell renal cell carcinoma (ccRCC) is a commonly occurring and highly aggressive urological malignancy characterized by a significant mortality rate. Current therapeutic options for advanced ccRCC are limited, necessitating the discovery of novel biomarkers and therapeutic targets. Carboxypeptidase A4 (CPA4) is a zinc-containing metallocarboxypeptidase with implications in various cancer types, but its role in ccRCC remains unexplored. The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases were utilized in order to investigate the differential expression patterns of CPA4. The expression of CPA4 in ccRCC patients was further verified using immunohistochemical (IHC) examination of 24 clinical specimens. A network of protein-protein interactions (PPI) was established, incorporating CPA4 and its genes that were expressed differentially. Functional enrichment analyses were conducted to anticipate the contribution of CPA4 in the development of ccRCC. To validate our earlier study, we conducted real-time PCR and cell functional tests on ccRCC cell lines. Our findings revealed that CPA4 is overexpressed in ccRCC, and the higher the expression of CPA4, the worse the clinical outcomes such as TNM stage, pathological stage, histological grade, etc. Moreover, patients with high CPA4 expression had worse overall survival, disease-specific survival and progress-free interval than patients with low expression. The PPI network analysis highlighted potential interactions contributing to ccRCC progression. Functional enrichment analysis indicated the involvement of CPA4 in the regulation of key pathways associated with ccRCC development. Additionally, immune infiltration analysis suggested a potential link between CPA4 expression and immune response in the tumour microenvironment. Finally, cell functional studies in ccRCC cell lines shed light on the molecular mechanisms underlying the role of CPA4 in promoting ccRCC formation. Overall, our study unveils CPA4 as a promising biomarker with prognostic potential in ccRCC. The identified interactions and pathways provide valuable insights into its implications in ccRCC development and offer a foundation for future research on targeted therapies. Further investigation of CPA4's involvement in immune responses may contribute to the development of immunotherapeutic strategies for ccRCC treatment.

Carboxypeptidase A4 negatively regulates HGS-ETR1/2-induced pyroptosis by forming a positive feedback loop with the AKT signalling pathway

Pyroptosis, a mode of inflammatory cell death, has recently gained significant attention. However, the underlying mechanism remains poorly understood. HGS-ETR1/2 is a humanized monoclonal antibody that can bind to DR4/5 on the cell membrane and induce cell apoptosis by activating the death receptor signalling pathway. In this study, by using morphological observation, fluorescence double staining, LDH release and immunoblot detection, we confirmed for the first time that HGS-ETR1/2 can induce GSDME-mediated pyroptosis in hepatocellular carcinoma cells. Our study found that both inhibition of the AKT signalling pathway and silencing of CPA4 promote pyroptosis, while the overexpression of CPA4 inhibits it. Furthermore, we identified a positive regulatory feedback loop is formed between CPA4 and AKT phosphorylation. Specifically, CPA4 modulates AKT phosphorylation by regulating the expression of the AKT phosphatase PP2A, while inhibition of the AKT signalling pathway leads to a decreased transcription and translation levels of CPA4. Our study reveals a novel mechanism of pyroptosis induced by HGS-ETR1/2, which may provide a crucial foundation for future investigations into cancer immunotherapy.

Increased copy number of imprinted genes in the chromosomal region 20q11-q13.32 is associated with resistance to antitumor agents in cancer cell lines

BACKGROUND

Parent of origin-specific allelic expression of imprinted genes is epigenetically controlled. In cancer, imprinted genes undergo both genomic and epigenomic alterations, including frequent copy number changes. We investigated whether copy number loss or gain of imprinted genes in cancer cell lines is associated with response to chemotherapy treatment.

RESULTS

We analyzed 198 human imprinted genes including protein-coding genes and noncoding RNA genes using data from tumor cell lines from the Cancer Cell Line Encyclopedia and Genomics of Drug Sensitivity in Cancer datasets. We examined whether copy number of the imprinted genes in 35 different genome locations was associated with response to cancer drug treatment. We also analyzed associations of pretreatment expression and DNA methylation of imprinted genes with drug response. Higher copy number of BLCAP, GNAS, NNAT, GNAS-AS1, HM13, MIR296, MIR298, and PSIMCT-1 in the chromosomal region 20q11-q13.32 was associated with resistance to multiple antitumor agents. Increased expression of BLCAP and HM13 was also associated with drug resistance, whereas higher methylation of gene regions of BLCAP, NNAT, SGK2, and GNAS was associated with drug sensitivity. While expression and methylation of imprinted genes in several other chromosomal regions was also associated with drug response and many imprinted genes in different chromosomal locations showed a considerable copy number variation, only imprinted genes at 20q11-q13.32 had a consistent association of their copy number with drug response. Copy number values among the imprinted genes in the 20q11-q13.32 region were strongly correlated. They were also correlated with the copy number of cancer-related non-imprinted genes MYBL2, AURKA, and ZNF217 in that chromosomal region. Expression of genes at 20q11-q13.32 was associated with ex vivo drug response in primary tumor samples from the Beat AML 1.0 acute myeloid leukemia patient cohort. Association of the increased copy number of the 20q11-q13.32 region with drug resistance may be complex and could involve multiple genes.

CONCLUSIONS

Copy number of imprinted and non-imprinted genes in the chromosomal region 20q11-q13.32 was associated with cancer drug resistance. The genes in this chromosomal region may have a modulating effect on tumor response to chemotherapy.

Knockdown of carboxypeptidase A4 (CPA4) inhibits gastric cancer cell progression via cell cycle arrest and apoptosis

Background

Gastric cancer is one of the most prevalent cancers, with a low survival rate at the later stages. Carboxypeptidase A4 (CPA4) is associated with the aggressiveness and growth in cancer. However, its regulatory role in gastric cancer remains unknown. Therefore, we investigated the role of CPA4 in gastric cancer progression in vitro.

Methods

The human gastric adenocarcinoma cell line (AGS cell line) was used in the present study. CPA4 knockdown lentiviruses were constructed. Western blot analysis was performed to evaluate the protein expression levels of epithelial-mesenchymal transition (EMT) transcription factors, EMT biomarkers, and proteins involved in the Wnt signaling pathway, mitogen-activated protein kinase (MAPK) signaling pathway, and phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway. Quantitative real-time polymerase chain reaction (qRT-PCR) analysis was carried out to evaluate the mRNA expression level of CPA4. The String database was employed for protein-protein interaction (PPI) network analysis. Cell colony formation, proliferation, migration, invasion, apoptosis, and cell cycle analyses were performed using corresponding kits.

Results

CPA4 is highly expressed in gastric cancer cell lines. Overexpressed CPA4 was associated with the induction of EMT. Knockdown of CPA4 inhibited cell colony formation, proliferation, migration, and invasion of gastric cancer cells. Knockdown of CPA4 also promoted cell apoptosis of gastric cancer cells.

Conclusions

Knockdown of CPA4 inhibited cell progression via arresting the cell cycle and inducing EMT in gastric cancer.

Carboxypeptidase N2 as a Novel Diagnostic and Prognostic Biomarker for Lung Adenocarcinoma

Carboxypeptidase N2 (CPN2) is a plasma metallo-protease that cleaves basic amino acids from the C-terminal of peptides and proteins. Emerging evidence showed that carboxypeptidases perform many diverse functions in the body and play key roles in tumorigenesis. However, the clinical significance and biological functions of CPN2 in lung adenocarcinoma remain unclear. Our study aimed to explore the potential role and functions of CPN2 in lung adenocarcinoma. The results showed that the transcription level of CPN2 was significantly increased in the tumor tissues of lung adenocarcinoma patients compared to the adjacent normal tissues in The Cancer Genome Atlas cohort (P < 0.05). The survival plots showed that the overall survival of patients with a high expression of CPN2 was significantly lower than that of patients with a low expression of CPN2, both in the Kaplan-Meier database and the clinical sample cohort (P < 0.05). The tissue microarray analysis found that CPN2 protein expression was significantly positively correlated with node status and tumor stage as well as tumor malignancy (P < 0.05). Further univariate and multivariate Cox regression analyses showed that CPN2 may act as an independent prognostic factor in patients with lung adenocarcinoma (P < 0.05). In addition, the analysis of co-expression genes from LinkedOmics showed that CPN2 was positively associated with many genes of fibrillar collagen family members and the PI3K-Akt pathway. The gene set enrichment analysis showed that a higher expression of CPN2 may participate in mTOR, TGF-BETA, NOTCH, TOLL-like-receptor, WNT, and MAPK signaling pathway in lung adenocarcinoma. Notably, the knockdown of CPN2 significantly inhibited the ability of cell proliferation, clone formation, invasion, and migration. Our findings suggested that the upregulation of CPN2 is associated with a worse clinical outcome in lung adenocarcinoma and cancer-related pathways, which laid the foundation for further research on CPN2 during carcinogenesis.

Recent advances in the application of metallomics in diagnosis and prognosis of human cancer

Metals play a critical role in human health and diseases. In recent years, metallomics has been introduced and extensively applied to investigate the distribution, regulation, function, and crosstalk of metal(loid) ions in various physiological and pathological processes. Based on high-throughput multielemental analytical techniques and bioinformatics methods, it is possible to elucidate the correlation between the metabolism and homeostasis of diverse metals and complex diseases, in particular for cancer. This review aims to provide an overview of recent progress made in the application of metallomics in cancer research. We mainly focuses on the studies about metallomic profiling of different human biological samples for several major types of cancer, which reveal distinct and dynamic patterns of metal ion contents and the potential benefits of using such information in the detection and prognosis of these malignancies. Elevated levels of copper appear to be a significant risk factor for various cancers, and each type of cancer has a unique distribution of metals in biofluids, hair/nails, and tumor-affected tissues. Furthermore, associations between genetic variations in representative metalloprotein genes and cancer susceptibility have also been demonstrated. Overall, metallomics not only offers a better understanding of the relationship between metal dyshomeostasis and the development of cancer but also facilitates the discovery of new diagnostic and prognostic markers for cancer translational medicine.

Comprehensive Analysis of CPA4 as a Poor Prognostic Biomarker Correlated with Immune Cells Infiltration in Bladder Cancer

Simple Summary

The overexpression of Carboxypeptidase A4 (CPA4) has been observed in plenty of types of cancer and has been elucidated to promote tumor growth and invasion; however, its role in bladder urothelial carcinoma (BLCA) is still unclear. Therefore, we aimed to show the prognostic role of CPA4 and its relationship with immune infiltrates in BLCA. We confirmed that the overexpression of CPA4 is associated with shorter overall survival, disease-specific survival, progress-free intervals, and higher dead events. Moreover, we found that several infiltrating immune cells (Th1cell, Th2 cell, T cell exhaustion, and Tumor-associated macrophage) were correlated with the expression of CPA4 in bladder cancer using TIMER2 and GEPIA2. In conclusion, CPA4 may be a novel and great prognostic biomarker based on bioinformation analysis in BLCA.

Abstract

Carboxypeptidase A4 (CPA4) has shown the potential to be a biomarker in the early diagnosis of certain cancers. However, no previous research has linked CPA4 to therapeutic or prognostic significance in bladder cancer. Using data from The Cancer Genome Atlas (TCGA) database, we set out to determine the full extent of the link between CPA4 and BLCA. We further analyzed the interacting proteins of CPA4 and infiltrated immune cells via the TIMER2, STRING, and GEPIA2 databases. The expression of CPA4 in tumor and normal tissues was compared using the TCGA + GETx database. The connection between CPA4 expression and clinicopathologic characteristics and overall survival (OS) was investigated using multivariate methods and Kaplan–Meier survival curves. The potential functions and pathways were investigated via gene set enrichment analysis. Furthermore, we analyze the associations between CPA4 expression and infiltrated immune cells with their respective gene marker sets using the ssGSEA, TIMER2, and GEPIA2 databases. Compared with matching normal tissues, human CPA4 was found to be substantially expressed. We confirmed that the overexpression of CPA4 is linked with shorter OS, DSF(Disease-specific survival), PFI(Progression-free interval), and increased diagnostic potential using Kaplan–Meier and ROC analysis. The expression of CPA4 is related to T-bet, IL12RB2, CTLA4, and LAG3, among which T-bet and IL12RB2 are Th1 marker genes while CTLA4 and LAG3 are related to T cell exhaustion, which may be used to guide the application of checkpoint blockade and the adoption of T cell transfer therapy.

Insufficient ablation promotes the metastasis of residual non-small cell lung cancer (NSCLC) cells via upregulating carboxypeptidase A4

BACKGROUND

Thermal ablation is a potentially curative therapy for early-stage non-small cell lung cancer (NSCLC). Early recurrence after thermal ablation necessitates our attention.

METHODS

The invasion and migration abilities of NSCLC after sublethal heat stimulus were observed in vitro and in vivo. Sublethal thermal stimulus molecular changes were identified by RNA sequencing. A xenograft model of NSCLC with insufficient ablation was established to explore the epithelial-to-mesenchymal transition (EMT) and metastasis-related phenotypes alteration of residual tumors.

RESULTS

In vitro, the invasion and migration abilities of NSCLC cells were enhanced 72 h after 44 °C and 46 °C thermal stimulus. Epithelial-mesenchymal transition (EMT) phenotypes were also upregulated under these conditions. RNA sequencing revealed that the expression of carboxypeptidase A4 (CPA4) was significantly upregulated after thermal stimulus. Significant upregulation of CPA4 and EMT phenotypes was also found in the xenograft model of insufficient NSCLC ablation. The EMT process and invasion and migration abilities can be reversed by silencing CPA4.

CONCLUSIONS

This study demonstrates that sublethal heat stimulus caused by insufficient ablation can promote EMT and enhance the metastatic capacity of NSCLC. CPA4 plays an important role in these biological processes. Inhibition of CPA4 might be of great significance for improving early-stage NSCLC survival after ablation.

Reviewing the experimental and mathematical factors involved in tight binding inhibitors Ki values determination: The bi-functional protease inhibitor SmCI as a test model

Different methodologies for determining the dissociation equilibrium constant (K_i) of protein tight binding inhibitors are frequently found in the scientific literature. Taking into account that the K_i value is the main parameter characterizing the inhibition strength, its determination often represents the first step during the characterization of a potential drug. The purpose of this review is to summarize the current information related to tight binding inhibitors K_i values determination and discuss about the importance of different factors as the enzyme concentration, the inhibitor concentration dilution series, the enzyme-inhibitor incubation time and the dose-response data mathematical fitting. For this aim, the bi-functional SmCI protease inhibitor is used as a tool for exemplifying the experimental and mathematical steps performed during tight binding inhibitors K_i values determination. In addition, the natural and the different recombinant forms of SmCI were used to go deeply into the comparison of some mathematic approaches that are frequently used in the literature. Finally, other biochemical techniques that could be potentially used for tight binding inhibitors K_i values determination are also commented.

CPA4 Promotes EMT in Pancreatic Cancer via Stimulating PI3K-AKT-mTOR Signaling

Background

Carboxypeptidase A4 (CPA4), as a novel tumor biomarker, is prevalently observed in various cancers. However, the potential role of CPA4 in pancreatic cancer (PC), to our knowledge, has not been fully clarified.

Materials and Methods

We systematically explored the detailed function of CPA4 in epithelial to mesenchymal transition (EMT) stimulated PC in human clinical samples and in vitro.

Results

CPA4 was overexpressed in clinical PC samples that was positively related with tumor size (P=0.026), T stage (P=0.011), lymph-node metastasis (P=0.026) and a worse prognosis for PC patients (P=0.001). Interestingly, CPA4 was inversely correlated with E-cadherin (r=−0.372, P=0.003) in clinical samples and PC cell lines which cooperatively contributed to a worse prognosis (P=0.005) for PC patients. CPA4 overexpression enhanced EMT in AsPC-1 and Capan-2 cells, which promoted EMT-like cellular morphology and cell invasion and migration. Meanwhile, CPA4 overexpression activated EMT and PI3K-AKT-mTOR signaling, following with the downregulation of E-cadherin and β-catenin, and the upregulation of N-cadherin, vimentin, p-PI3K (Tyr458), p-AKT (Ser473) and p-mTOR (Ser2448). However, PI3K inhibitor LY294002 reversed CPA4 overexpression-stimulated EMT in vitro. Moreover, CPA4 was co-immunoprecipitated with AKT in two PC cells with CPA4 high expression. Conversely, CPA4 silencing inhibited EMT in PANC-1 cells. CPA4 overexpression or silencing promoted or inhibited cell proliferation and drug resistance in Capan-2 and PANC-1 cells via regulating Bcl2/Bax and cleaved-caspase3 signaling. However, LY294002 reversed CPA4 overexpression-stimulated cell proliferation and drug resistance in vitro in Bcl2/Bax and caspase3-dependent apoptosis.

Conclusion

CPA4 overexpression contributes to aggressive clinical stage of PC patients and promotes EMT in vitro via activation of PI3K-AKT-mTOR signaling.

Development and External Validation of a Novel 12-Gene Signature for Prediction of Overall Survival in Muscle-Invasive Bladder Cancer

Purpose: We aimed to develop and validate a novel gene signature from published data and improve the prediction of survival in muscle-invasive bladder cancer (MIBC).

Methods: We searched the published gene signatures associated with the overall survival (OS) of MIBC and compiled all 274 genes to develop a novel gene signature. RNAseq data of TCGA (the Cancer Genome Atlas) bladder cohort were downloaded. All genes were included in a univariate Cox hazard ratio model. We then used a reduced multivariate Cox regression model, which included only genes achieving P < 0.05 in the univariate model. A total of 172 patients at Fudan University Shanghai Cancer Center (FUSCC) and 61 patients from GEO datasets were used as an external validation set.

Results: A total of 327 patients in the TCGA cohort were enrolled. We identified 274 genes from eight published papers on the OS of MIBC. Using the TCGA database, we identified 12 genes that correlated with OS (P < 0.05 in both univariate and multivariate analyses). By integrating these genes with the RT-qPCR data in our validation dataset and GEO datasets, we confirmed that the power for predicting OS of the 12-gene panel (AUC of 0.741 and 0.727, respectively) was higher than just clinical data (including gender, age, T stage, grade, and N stage) alone in the TCGA and FUSCC cohort (AUC of 0.667 and 0.631, respectively). Additionally, upon combining the clinical data and 12-gene panel together, the AUC increased to 0.768, 0.757, and 0.88 in the TCGA, FUSCC and GSE13507 cohorts, respectively.

Conclusions: Applying published gene signatures and TCGA data, we successfully built and externally validated a novel 12-gene signature for the survival of MIBC.

circCPA4 acts as a prognostic factor and regulates the proliferation and metastasis of glioma

Circular RNAs (circRNAs) are reported to play vital roles in tumour process and might be potential prognostic biomarkers and therapeutic targets for tumours. But the expression and function of circRNAs in glioma remain unclear. Here, we performed circRNA microarray analysis of glioma tissues and matched normal brain tissue samples to explore the circRNA profile in glioma. GO analysis, KEGG and Reactom pathway analysis of linear mRNA transcripts corresponding to circRNAs were performed to study the involved biological process and pathways. The clinical significance of the selected circRNA was investigated by Kaplan‐Meier survival analysis. Relevant biological function, such as cell proliferation and metastasis, was detected in vitro and in vivo. And possible mechanism of the regulatory function of the selected circRNA in glioma was explored. We found that circCPA4 (hsa_circ_0082374) up‐regulated the most in glioma tissues and high levels of circCPA4 were positively related to poor outcome of glioma. And knockdown of circCPA4 suppresses cell proliferation and metastasis in glioma. Moreover, circCPA4 interacts with let‐7 and serves as a sponge for let‐7. Through the competitive endogenous RNA (ceRNA) mechanism, circCPA4 sponges let‐7 to regulate the expression of CPA4 and glioma progression. The circCPA4/let‐7/CPA4 axis regulates glioma progression by ceRNA mechanism, and circCPA4 could be a novel prognostic biomarker and target for glioma treatment.

Downregulation of CPA4 inhibits non small-cell lung cancer growth by suppressing the AKT/c-MYC pathway

Carboxypeptidase A4 (CPA4) is a member of the metallocarboxypeptidase family. A previous study indicated that CPA4 may participate in the modulation of peptide hormone activity and hormone-regulated tissue growth and differentiation. However, the role of CPA4 in lung tumorigenesis remains unclear. Our study revealed that CPA4 expression was higher in both lung cancer cells and tumor tissues. We performed 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assays, colony-formation assays, and Cellomics ArrayScan Infinity analysis to demonstrate that CPA4 knockdown inhibited non small-cell lung cancer (NSCLC) cell proliferation. Conversely, ectopic expression of CPA4 enhanced lung cancer cell proliferation. Consistent with these observations, we generated xenograft tumor models to confirm that CPA4 downregulation suppressed NSCLC cell growth. Mechanistically, we revealed that CPA4 downregulation may induce apoptosis and G1-S arrest by suppressing the protein kinase B/c-MYC pathway. These results suggest that CPA4 has an oncogenic effect on lung cancer growth. Taken together, we identified a novel gene in lung cancer that might provide a basis for new therapeutic targets.

Carboxypeptidase A4 promotes cell growth via activating STAT3 and ERK signaling pathways and predicts a poor prognosis in colorectal cancer

Carboxypeptidase A4 (CPA4) is a novel cancer-related gene that is aberrantly expressed in various malignant tumors. However, the roles and mechanisms of CPA4 have not been explored in colorectal cancer (CRC). In this study, we investigated the functions and mechanisms by which CPA4 promotes CRC progression. Quantitative real-time PCR (qRT-PCR) and western blot showed that CPA4 mRNA and CPA4 protein levels were up-regulated in CRC compared to levels in adjacent normal tissue. Immunohistochemistry (IHC) results indicating high CPA4 levels were positively associated with poor prognoses. In addition, Cell Counting Kit-8 (CCK-8), colony formation, flow cytometry, and transwell assays demonstrated that CPA4 overexpression facilitated the growth of CRC cells, whereas CPA4 knockdown resulted in decreased proliferation, G1/S phase transition arrest, and apoptosis. Subcutaneous tumorigenesis was performed in nude mice to confirm the tumor-promoting effects of CPA4 in vivo. Western blot revealed that activation of the STAT3 and ERK pathways is one of the oncogenic functions of CPA4 in CRC. Accordingly, CPA4 promotes CRC cell growth via activating the STAT3 and ERK pathways and may be a prognostic factor or therapeutic target for CRC.

Carboxypeptidase A4 promotes proliferation and stem cell characteristics of hepatocellular carcinoma

Carboxypeptidase A4 (CPA4), a member of the metallo-carboxypeptidase family, is overexpressed in liver cancer and is associated with cancer progression. The role of CPA4 in hepatocellular carcinoma (HCC) remains unclear. In this study, we aimed to evaluate the relevance of CPA4 to the proliferation and expression of stem cell characteristics of hepatocellular carcinoma cells. Western blot analysis showed high CPA4 expression in the liver cancer cell line Bel7402 and low expression in HepG2 cells. Knock-down of CPA4 decreased cancer cell proliferation as detected by MTT and clone formation assays. The serum-free culture system revealed that downregulated CPA4 suppressed the sphere formation capacities of tumour cells. However, upregulated CPA4 increased the proliferation and sphere formation capacity. In addition, the protein expression of CD133, ALDH1 and CD44 also increased in cells with upregulated CPA4. In vivo, the overexpression of CPA4 in tumour cells that were subcutaneously injected into nude mice markedly increased the growth of the tumours. These data suggest that CPA4 expression leads to poor prognoses by regulating tumour proliferation and the expression of stem cell characteristics and may therefore serve as a potential therapeutic target of HCC.

Diagnostic and Prognostic Significance of Carboxypeptidase A4 (CPA4) in Breast Cancer

Recent research focused on prolonged survival has suggested that carboxypeptidase A4 (CPA4) plays a role in both tumor microenvironment formation and distant metastasis in cancer. In some patients, serum and expression (mRNA) levels of CPA4 have been found to be correlated with the aggressiveness and progression of the disease. Accordingly, we conducted a first study to investigate the diagnostic and prognostic significance of CPA4 in the case of breast cancer (BC), the most common form of malignancy in women. The study included a total of 50 patients with BC and 20 healthy women as the control group. The participants’ serum CPA4 levels were determined by the ELISA test, and, for assessment of CPA4 mRNA, we used the PCR method. The serum CPA4 (p = 0.001) and CPA4 mRNA (p = 0.015) levels were found to be statistically significantly higher in the controls, compared to the patient group. When the results of patient group were statistically analyzed based on subgrouping by tumor characteristics, the measured CPA4 mRNA levels showed significant difference with respect to the molecular subtype (p = 0.006), pN status (p = 0.023), and pathological stage (p = 0.039), while the serum CPA4 measurements differed significantly in terms of pathological type only (p = 0.024). We conclude that CPA4 is diagnostically and prognostically not futile when used in combination with the other considerations and measurements in breast cancer.

Distribution of a Single Nucleotide Polymorphism of Insulin-Like Growth Factor-1 in Colorectal Cancer Patients and Its Association with Mucinous Adenocarcinoma

Purpose

To analyze the difference in the distribution of an insulin growth factor-1 (IGF-1) polymorphism (-2995 C/A) between young and old colorectal cancer (CRC) patients.

Methods

Information from 950 CRC patients undergoing surgery at the Taipei Veterans General Hospital between 2000 and 2005 was collected. The IGF-1 polymorphism was analyzed in patients in extreme age ranges at the time of CRC onset (i.e., under the 20th and above the 80th percentiles, respectively). Associations between clinicopathological variables and the IGF-1 polymorphism were analyzed.

Results

Young CRC patients had a higher frequency of advanced disease (58.7%) and mucinous adenocarcinoma (20%) than old CRC patients. Among old CRC patients, the frequency of the AA genotype of IGF-1 was 12.7% (24/189), which was significantly higher than in young patients (4.2%). Other clinicopathological factors including tumor location, differentiation, lymphovascular invasion, and TNM stage were not associated with the AA genotype of IGF-1. Mucinous differentiation (but not the other clinicopathological factors) was significantly associated with the CA/AA genotype of IGF-1 (39/195).

Conclusions

Older patients had a higher frequency of the AA genotype of IGF-1(-2995 C/A), while younger patients more often had advanced disease and mucinous adenocarcinoma.

Serum carboxypeptidaseA4 levels predict liver metastasis in colorectal carcinoma

Hepatic metastasis is the most critical prognostic factor for colorectal cancer (CRC), and early detection of CRC liver metastasis can significantly improve cancer patient outcomes. In this study, we examined the levels of CPA4 in CRC samples, and assessed the potential of serum CPA4 as a biomarker for predicting CRC liver metastasis. CPA4 positivity was observed in 68.4% (130/190) colorectal cancer tissues, and significantly correlated with Depth of invasion, Lymph node metastasis, Distant metastasis and Stage. In addition, high CPA4 expression was associated with poor overall survival, and was an independent prognostic marker in patients with CRC. In CRC serum samples, serum CPA4 concentrations in CRC-M1(S) patients (3717.89 ± 375.98 pg/mL) were significantly increased as compared to in CRC-M1(H) patients (3692.12 ± 261.51 pg/mL), CRC patients without liver metastasis (2480.47 ± 507.90 pg/mL) or healthy controls (2183.7 ± 621.7 pg/mL) (P < 0.05). Furthermore, high CPA4 concentration was significantly correlated with Distant metastasis, Lymph node involvement, Stage and poor overall survival of the patients with CRC. Logistic regression analysis revealed that serum CPA4 level and Lymph node metastasis were the significant parameters for predicting CRC liver metastasis. In leave-one-out-cross-validation, these two markers resulted in sensitivity (90.0%) and specificity (93.8%) for hepatic metastasis detection. Moreover, this combination could correctly classify 49 cases of the 50 CRC patients with heterochronous liver metastasis in an independent test set. Therefore, our results suggest that CPA4 is closely associated with CRC liver metastasis, and serum CPA4 concentration combined with lymph node involvement may be used as accurate predictors of liver metastasis in colorectal cancer.

Associations of carboxypeptidase 4 with ALDH1A1 expression and their prognostic value in esophageal squamous cell carcinoma

Esophageal cancer is an aggressive disease with poor prognosis because of early metastasis when diagnosed and recurrence after surgery. This study is aimed at investigating the expression of carboxypeptidaseA4 (CPA4) and aldehyde dehydrogenase 1A1 (ALDH1A1) in esophageal squamous cell carcinoma (ESCC) tumor tissues and analyzed their association and clinical significance. The expression of CPA4 and ALDH1A1 was determined by immunohistochemistry using the corresponding primary antibodies on two commercial tissue arrays. High level of CPA4 was observed in 87/150 (58%) ESCC samples and was significantly associated with histologic grade, lymph node metastasis, and TNM Classification of Esophageal cancer stage. The expression level of ALDH1A1 was much higher in ESCC than their corresponding normal epithelial tissues, with 66% positive rate. And, high levels of ALDH1A1 were significantly associated with lymph nodes metastasis (P < 0.05) and TNM stage (P < 0.05). Correlation analysis showed the expression level of CPA4 positively correlated with that of ALDH1A1 (r = 0.416, P < 0.01). In Kaplan-Meier survival analysis, either CPA4 or ALDH1A1 was significantly correlated with poor overall survival of ESCC patients. Multivariate Cox regression model showed that high expression of CPA4 was an independent prognostic factor for ESCC patients. In conclusion, our present study demonstrated for the first time that CPA4 might be used as an independent poor prognostic factor in ESCC. This study demonstrated for the first time that CPA4 was aberrantly expressed in ESCC tissues. Overexpression of CPA4 was closely associated with the putative cancer stem cell marker ALDH1A1 and might be used as an independent prognostic factor in ESCC.

Multiple effects of ellagic acid on human colorectal carcinoma cells identified by gene expression profile analysis

Colorectal carcinoma (CRC) is the third most commonly diagnosed cancer in the world. Phytochemicals have become a research hotspot in recent years as cancer prevention and treatment agents due to their low toxicity and limited side-effects. Ellagic acid (EA), a natural phenolic constituent, displays various biological activities, including anticancer effects. However, the detailed anticancer mechanisms of EA remain unclear. In the present study, we found that EA inhibited the growth of HCT-116 colon cancer cells. Moreover, we identified differentially expressed genes (DEGs) by microarray profiling of HCT-116 cells treated with EA. A total of 857 DEGs (363 upregulated and 494 downregulated) were identified with a >1.5-fold change in expression after treatment with EA for 72 h. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that a large number of cellular functions were modified by EA including proliferation, apoptosis, cell cycle and angiogenesis. Interaction network analysis using DEGs provided details of their interactions and predicted the key target pathways of EA. To verify the result of cDNA microarray, 10 selected DEGs related to proliferation, apoptosis or cell cycle were further confirmed by real-time RT-PCR. Based on microarray data, we identified several crucial functions of EA. These results provide important new data for EA in anti-CRC research.

Association between expression of Carboxypeptidase 4 and stem cell markers and their clinical significance in liver cancer development

The development of liver cancer would undergo a sequential progression from chronic inflammatory liver disease, cirrhosis to neoplasia. During these pathophysiological changes, abnormal liver microenvironment might induce the hepatocytes to die, abnormally proliferate and initiate cancer stem cells. Metallocarboxypeptidases (MCPs) involved in multiple biological functions including inflammation, fibrosis and stem cell niche formation. This study aimed to evaluate the expression of carboxypeptidase 4 (CPA4) in hepatitis, liver cirrhosis and liver cancer tissues, and revealed its clinical significance in liver cancer progression. We firstly found that the CPA4 levels in tissues were significantly higher in liver cancer patients than those in other three groups. Then, elevated levels of CPA4 was observed in 57/100 (57%) liver cancer samples, and significantly correlated with Grade and Stage. We also identified a significant positive correlation between aberrant elevation of CPA4 and overexpression of stem cell markers including CD90, AFP and CD34 with follow-up data (n=100). Further Kaplan-Meier analysis confirmed that high levels of CPA4 and CD90 were significant predictors of poor overall survival. Multivariate Cox regression model showed that CPA4 was an independent prognostic factor for patients with liver cancer. This study demonstrated for the first time that high CPA4 expression was closely correlated with hepatocarcinogenesis, and might be used as an independent poor prognostic factor in liver cancer.

Overexpression of carboxypeptidase A4 (CPA4) is associated with poor prognosis in patients with gastric cancer

CarboxypeptidaseA4 (CPA4) is a zinc-containing exopeptidases, and its aberrant expression has been implicated in cancer development and progression. However, few studies have investigated the association between CPA4 over-expression and clinical significance in gastric cancer (GC). In this study, we employed immunohistochemistry to evaluate the expression of CPA4 in gastric cancer tissues, and found that elevated CPA4 expression was detected in 64% (n=100) of primary GCs, but was weak or no staining in the normal mucosa. Clinical relevance analysis showed that positive staining for CPA4 was significantly associated with Tumor size, Stage, Lymph node metastasis, Depth of invasion and Distant metastasis. As tumor markers p53 and Ki67 are closely associated with tumor progression, we further analyzed the correlations between CPA4 levels and these two factors. We found that abnormal expression of CPA4 was positively associated with Ki67 (P=0.002) and reversely correlated with p53 (P=0.035) in GC. In Kaplan-Meier survival analysis, high levels of CPA4 were significantly associated with unfavorable survival in GC patients (P<0.001). Multivariate Cox regression model showed that high expression of CPA4 was an independent prognostic factor for GC patients. In conclusion, our results suggested that CPA4 was highly expressed in gastric cancer tissues. Overexpression of CPA4 can be used as an independent poor prognostic factor in gastric cancer.

Genetic variants in cell cycle control pathway confer susceptibility to aggressive prostate carcinoma

BACKGROUND

Because a significant number of patients with prostate cancer (PCa) are diagnosed with disease unlikely to cause harm, genetic markers associated with clinically aggressive PCa have potential clinical utility. Since cell cycle checkpoint dysregulation is crucial for the development and progression of cancer, we tested the hypothesis that common germ-line variants within cell cycle genes were associated with aggressive PCa.

METHODS

Via a two-stage design, 364 common sequence variants in 88 genes were tested. The initial stage consisted of 258 aggressive PCa patients and 442 controls, and the second stage added 384 aggressive PCa Patients and 463 controls. European-American and African-American samples were analyzed separately. In the first stage, SNPs were typed by Illumina Goldengate assay while in the second stage SNPs were typed by Pyrosequencing assays. Genotype frequencies between cases and controls were compared using logistical regression analysis with additive, dominant and recessive models.

RESULTS

Eleven variants within 10 genes (CCNC, CCND3, CCNG1, CCNT2, CDK6, MDM2, SKP2, WEE1, YWHAB, YWHAH) in the European-American population and nine variants in 7 genes (CCNG1, CDK2, CDK5, MDM2, RB1, SMAD3, TERF2) in the African-American population were found to be associated with aggressive PCa using at least one model. Of particular interest, CCNC (rs3380812) was associated with risk in European-American cohorts from both institutions. CDK2 (rs1045435) and CDK5 (rs2069459) were associated with risk in the African-American cohorts from both institutions. Lastly, variants within MDM2 and CCNG1 were protective for aggressive PCa in both ethnic groups.

CONCLUSIONS

This study confirms that polymorphisms within cell cycle genes are associated with clinically aggressive PCa. Validation of these markers in additional populations is necessary, but these markers may help identify patients at risk for potentially lethal carcinoma.

Identifying the genes regulated by IDH1 via gene-chip in glioma cell U87

Glioma is the most common form of primary brain tumor. Increasing evidence show that IDH1 gene mutation is implicated in glioma. However, the mechanism involved in the progression of glioma remains unclear until now. In the study reported here, we used gene chip to identifying the genes regulated with IDH mutanted at R132. The results showed that IDH1-mutant leads to 1255 up-regulated genes and 1862 down-regulated genes in U87 cell lines. Meanwhile, GO and gene-network was performed and shown IDH1-mutant mainly affect small molecule metabolic process, mitotic cell cycle and apoptosis. This result will lay a foundation for further study of IDH1 gene function in the future.

Insights into the evolution of longevity from the bowhead whale genome

The bowhead whale (Balaena mysticetus) is estimated to live over 200 years and is possibly the longest-living mammal. These animals should possess protective molecular adaptations relevant to age-related diseases, particularly cancer. Here, we report the sequencing and comparative analysis of the bowhead whale genome and two transcriptomes from different populations. Our analysis identifies genes under positive selection and bowhead-specific mutations in genes linked to cancer and aging. In addition, we identify gene gain and loss involving genes associated with DNA repair, cell-cycle regulation, cancer, and aging. Our results expand our understanding of the evolution of mammalian longevity and suggest possible players involved in adaptive genetic changes conferring cancer resistance. We also found potentially relevant changes in genes related to additional processes, including thermoregulation, sensory perception, dietary adaptations, and immune response. Our data are made available online (http://www.bowhead-whale.org) to facilitate research in this long-lived species.

Immune status, strain background, and anatomic site of inoculation affect mouse papillomavirus (MmuPV1) induction of exophytic papillomas or endophytic trichoblastomas

Papillomaviruses (PVs) induce papillomas, premalignant lesions, and carcinomas in a wide variety of species. PVs are classified first based on their host and tissue tropism and then their genomic diversities. A laboratory mouse papillomavirus, MmuPV1 (formerly MusPV), was horizontally transmitted within an inbred colony of NMRI-Foxn1(nu)/Foxn1nu (nude; T cell deficient) mice of an unknown period of time. A ground-up, filtered papilloma inoculum was not capable of infecting C57BL/6J wild-type mice; however, immunocompetent, alopecic, S/RV/Cri-ba/ba (bare) mice developed small papillomas at injection sites that regressed. NMRI-Foxn1(nu) and B6.Cg-Foxn1(nu), but not NU/J-Foxn1(nu), mice were susceptible to MmuPV1 infection. B6 congenic strains, but not other congenic strains carrying the same allelic mutations, lacking B- and T-cells, but not B-cells alone, were susceptible to infection, indicating that mouse strain and T-cell deficiency are critical to tumor formation. Lesions initially observed were exophytic papillomas around the muzzle, exophytic papillomas on the tail, and condylomas of the vaginal lining which could be induced by separate scarification or simultaneous scarification of MmuPV1 at all four sites. On the dorsal skin, locally invasive, poorly differentiated tumors developed with features similar to human trichoblastomas. Transcriptome analysis revealed significant differences between the normal skin in these anatomic sites and in papillomas versus trichoblastomas. The primarily dysregulated genes involved molecular pathways associated with cancer, cellular development, cellular growth and proliferation, cell morphology, and connective tissue development and function. Although trichoepitheliomas are benign, aggressive tumors, few of the genes commonly associated with basal cell carcinoma or squamous cells carcinoma were highly dysregulated.

Carboxyterminal protein processing in health and disease: key actors and emerging technologies

Carboxypeptidases are important mediators of cellular behavior. Through C-terminal truncations, they alter protein functionality and participate in proteome turnover. Similarly, carboxypeptidases shape the human peptidome by targeting neuroendocrine and vasoactive peptides, thereby regulating signaling pathways in the nervous and cardiovascular systems as well as in embryonic development. Carboxypeptidases are widely connected to various pathological processes such as carcinogenesis and neurodegenerative and cardiovascular diseases. The repertoire of carboxypeptidase in vivo substrates still remains poorly defined, largely due to the lack of suitable experimental approaches. Understanding the precise role of carboxypeptidases is pivotal in the future development of diagnostic/prognostic markers in such diseases. To date, very little attention has been paid to the implication of carboxypeptidases in shaping the proteome as well as the peptidome. This review focuses on the patho-physiological function of carboxypeptidases and highlights the approaches by which proteomics-based technologies can be applied to characterize carboxypeptidases and to quantify the differential regulation of proteins by carboxypeptidases in a proteome-wide manner.

Interleukin-1-induced changes in the glioblastoma secretome suggest its role in tumor progression

The tumor microenvironment including glial cells and their inflammatory products regulates brain tumor development and progression. We have previously established that human glioma cells are exquisitely sensitive to IL-1 stimulation leading us to undertake a comparative analysis of the secretome of unstimulated and cytokine (IL-1)-stimulated glioblastoma cells. We performed label-free quantitative proteomic analysis and detected 190 proteins which included cytokines, chemokines, growth factors, proteases, cell adhesion molecules, extracellular matrix (ECM) and related proteins. Measuring area under the curve (AUC) of peptides for quantitation, the IL-1-induced secretome contained 13 upregulated and 5 downregulated extracellular proteins (p<0.05) compared to controls. Of these, IL-8, CCL2, TNC, Gal-1 and PTX3 were validated as upregulated and SERPINE1, STC2, CTGF and COL4A2 were validated as downregulated factors by immunochemical methods. A major representation of the ECM and related proteins in the glioblastoma secretome and their modulation by IL-1 suggested that IL-1 induces its effect in part by altering TGFβ expression, activity and signaling. These findings enhance our understanding of IL-1-induced modulation of glioma microenvironment, with implications for increased tumor invasion, migration and angiogenesis. They further provide novel targets for the glioblastoma intervention.

BIOLOGICAL SIGNIFICANCE

Present study is on an unbiased screening of the glioblastoma secretome stimulated by IL-1 which triggers neuroinflammatory cascades in the central nervous system. Network of secreted proteins were shown to be regulated revealing their possible contribution to glioma progression. Label free quantitative proteomics has provided unique novel targets for potential glioblastoma intervention.

Genetic polymorphism and prostate cancer aggressiveness: a case-only study of 1,536 GWAS and candidate SNPs in African-Americans and European-Americans

BACKGROUND

Genome-wide association studies have established a number of replicated single nucleotide polymorphisms (SNPs) for susceptibility to prostate cancer (CaP), but it is unclear whether these susceptibility SNPs are also associated with disease aggressiveness. This study evaluates whether such replication SNPs or other candidate SNPs are associated with CaP aggressiveness in African-American (AA) and European-American (EA) men.

METHODS

A 1,536 SNP panel which included 34 genome-wide association study (GWAS) replication SNPs, 38 flanking SNPs, a set of ancestry informative markers, and SNPs in candidate genes and other areas was genotyped in 1,060 AA and 1,087 EA men with incident CaP from the North Carolina-Louisiana Prostate Cancer Project (PCaP). Tests for association were conducted using ordinal logistic regression with a log-additive genotype model and a 3-category CaP aggressiveness variable.

RESULTS

Four GWAS replication SNPs (rs2660753, rs13254738, rs10090154, rs2735839) and seven flanking SNPs were associated with CaP aggressiveness (P < 0.05) in three genomic regions: One at 3p12 (EA), seven at 8q24 (5 AA, 2 EA), and three at 19q13 at the kallilkrein-related peptidase 3 (KLK3) locus (two AA, one AA and EA). The KLK3 SNPs also were associated with serum prostate-specific antigen (PSA) levels in AA (P < 0.001) but not in EA. A number of the other SNPs showed some evidence of association but none met study-wide significance levels after adjusting for multiple comparisons.

CONCLUSIONS

Some replicated GWAS susceptibility SNPs may play a role in CaP aggressiveness. However, like susceptibility, these associations are not consistent between racial groups.

Association of the innate immunity and inflammation pathway with advanced prostate cancer risk

Prostate cancer is the most frequent and second most lethal cancer in men in the United States. Innate immunity and inflammation may increase the risk of prostate cancer. To determine the role of innate immunity and inflammation in advanced prostate cancer, we investigated the association of 320 single nucleotide polymorphisms, located in 46 genes involved in this pathway, with disease risk using 494 cases with advanced disease and 536 controls from Cleveland, Ohio. Taken together, the whole pathway was associated with advanced prostate cancer risk (P = 0.02). Two sub-pathways (intracellular antiviral molecules and extracellular pattern recognition) and four genes in these sub-pathways (TLR1, TLR6, OAS1, and OAS2) were nominally associated with advanced prostate cancer risk and harbor several SNPs nominally associated with advanced prostate cancer risk. Our results suggest that the innate immunity and inflammation pathway may play a modest role in the etiology of advanced prostate cancer through multiple small effects.

Assessing the clinical role of genetic markers of early-onset prostate cancer among high-risk men enrolled in prostate cancer early detection

BACKGROUND

Men with familial prostate cancer and African American men are at risk for developing prostate cancer at younger ages. Genetic markers predicting early-onset prostate cancer may provide clinically useful information to guide screening strategies for high-risk men. We evaluated clinical information from six polymorphisms associated with early-onset prostate cancer in a longitudinal cohort of high-risk men enrolled in prostate cancer early detection with significant African American participation.

METHODS

Eligibility criteria include ages 35 to 69 with a family history of prostate cancer or African American race. Participants undergo screening and biopsy per study criteria. Six markers associated with early-onset prostate cancer [rs2171492 (7q32), rs6983561 (8q24), rs10993994 (10q11), rs4430796 (17q12), rs1799950 (17q21), and rs266849 (19q13)] were genotyped. Cox models were used to evaluate time to prostate cancer diagnosis and prostate-specific antigen (PSA) prediction for prostate cancer by genotype. Harrell's concordance index was used to evaluate predictive accuracy for prostate cancer by PSA and genetic markers.

RESULTS

Four hundred and sixty participants with complete data and ≥ 1 follow-up visit were included. Fifty-six percent were African American. Among African American men, rs6983561 genotype was significantly associated with earlier time to prostate cancer diagnosis (P = 0.005) and influenced prediction for prostate cancer by the PSA (P < 0.001). When combined with PSA, rs6983561 improved predictive accuracy for prostate cancer compared with PSA alone among African American men (PSA = 0.57 vs. PSA + rs6983561 = 0.75, P = 0.03).

CONCLUSIONS

Early-onset marker rs6983561 adds potentially useful clinical information for African American men undergoing prostate cancer risk assessment. Further study is warranted to validate these findings.

IMPACT

Genetic markers of early-onset prostate cancer have potential to refine and personalize prostate cancer early detection for high-risk men.

Structural and Functional Analysis of the Complex between Citrate and the Zinc Peptidase Carboxypeptidase A

A high-resolution carboxypeptidase-Zn(2+)-citrate complex was studied by X-ray diffraction and enzyme kinetics for the first time. The citrate molecule acts as a competitive inhibitor of this benchmark zinc-dependent peptidase, chelating the catalytic zinc ion in the active site of the enzyme and inducing a conformational change such that carboxypeptidase adopts the conformation expected to occur by substrate binding. Citrate adopts an extended conformation with half of the molecule facing the zinc ion, while the other half is docked in the S1' hydrophobic specificity pocket of the enzyme, in contrast with the binding mode expected for a substrate like phenylalanine or a peptidomimetic inhibitor like benzylsuccinic acid. Combined structural and enzymatic analysis describes the characteristics of the binding of this ligand that, acting against physiologically relevant zinc-dependent proteases, may serve as a general model in the design of new drug-protecting molecules for the oral delivery of drugs of peptide origin.

Identification of novel epithelial ovarian cancer biomarkers by cross-laboratory microarray analysis

The purpose of this study was to pool information in epithelial ovarian cancer by combining studies using Affymetrix expression microarray datasets made at different laboratories to identify novel biomarkers. Epithelial microarray expression information across laboratories was screened and combined after preprocessing raw microarray data, then ANOVA and unpaired T test statistical analysis was performed for identifying differentially expressed genes (DEGs), followed by clustering and pathway analysis for these DEGs. In this work, we performed a combination analysis on microarrays from three different laboratories using gene expression data on ovarian cancer and obtained a list of differential expression profiles identified as potential candidate in aggressiveness of ovarian cancer. The clustering and pathway analysis explored the different molecular basis of different ovarian cancer stages and potential important regulatory pathways in ovarian cancer development. Our results showed that combination of microarray data from different laboratories in the same platforms may overcome biases derived from probe design and technical features, thereby accelerating the identification of trustworthy DEGs, and demonstrating the advantage of integrative analysis in gene expression studies on epithelial ovarian cancer research.

Progress in metallocarboxypeptidases and their small molecular weight inhibitors

In what corresponds to a life span, metallocarboxypeptidases (MCPs) have jumped from being mere contaminants in animal pancreas powders (in depression year 1929) to be key players in cellular and molecular processes (in yet-another-depression years 2009-2010). MCPs are unique zinc-dependent enzymes that catalyze the breakdown of the amide bond at the C-terminus of peptide and protein substrates and participate in the recovery of dietary amino acids, tissue organogenesis, neurohormone and cytokine maturation and other important physiological processes. More than 26 genes code for MCPs in the human genome, many of them still waiting to be fully understood in terms of physiological function. A variety of MCPs have been linked to diseases in man: acute pancreatitis and pancreas cancer, type 2 diabetes, Alzheimer's Disease, various types of cancer, and fibrinolysis and inflammation. Many of these discoveries have been made possible thanks to recent advances, as exemplified by plasma carboxypeptidases N and B, known for fifty and twenty years, respectively, which have had their structures released only very recently. Plasma carboxypeptidase B is a biological target for therapy because of its involvement in the coagulation/fibrinolysis processes. Besides, the widespread use of carboxypeptidase A as a benchmark metalloprotease since the early days of Biochemistry has allowed the identification and design of an increasingly vast repertory of small molecular weight inhibitors. With these two examples we wish to emphasize that MCPs have become part of the drug discovery portfolio of pharmaceutical companies and academic research laboratories. This paper will review key developments in the discovery and design of MCP small molecular weight inhibitors, with an emphasis on the discovery of chemically diverse entities. Although encouraging advances have been achieved in the last few years, the specificity and oral bioavailability of the new chemotherapeutic agents seem to pose a challenge to medicinal chemists.

Characterization of the substrate specificity of human carboxypeptidase A4 and implications for a role in extracellular peptide processing

CPA4 (carboxypeptidase A4) is a member of the metallocarboxypeptidase family. CPA4 was originally found in a screen of mRNAs up-regulated by sodium butyrate-induced differentiation of cancer cells. Further studies suggested a relation between CPA4 and prostate cancer aggressiveness. In the present study, we determined that CPA4 is secreted from cells as a soluble proenzyme (pro-CPA4) that can be activated by endoproteases, such as trypsin. Three complementary approaches were used to study the substrate specificity of CPA4; kinetic analysis was performed using a new series of chromogenic substrates and some biologically relevant peptides, the cleavage of synthetic peptides was tested individually, and the cleavage of a mixture of >100 mouse brain peptides was examined using a quantitative peptidomics mass spectrometry-based approach. CPA4 was able to cleave hydrophobic C-terminal residues with a preference for Phe, Leu, Ile, Met, Tyr, and Val. However, not all peptides with C-terminal hydrophobic residues were cleaved, indicating the importance of additional residues within the peptide. Aliphatic, aromatic, and basic residues in the P1 position have a positive influence on the cleavage specificity. In contrast, acidic residues, Pro, and Gly have a negative influence in the P1 position. Some of the peptides identified as CPA4 substrates (such as neurotensin, granins, and opioid peptides) have been previously shown to function in cell proliferation and differentiation, potentially explaining the link between CPA4 and cancer aggressiveness. Taken together, these studies suggest that CPA4 functions in neuropeptide processing and regulation in the extracellular environment.

The X-ray structure of carboxypeptidase A inhibited by a thiirane mechanism-based inhibitor

The three-dimensional X-ray crystal structure of carboxypeptidase A, a zinc-dependent hydrolase, covalently modified by a mechanism-based thiirane inactivator, 2-benzyl-3,4-epithiobutanoic acid, has been solved to 1.38 A resolution. The interaction of the thiirane moiety of the inhibitor with the active site zinc ion promotes its covalent modification of Glu-270 with the attendant opening of the thiirane ring. The crystal structure determination at high resolution allowed for the clear visualization of the covalent ester bond to the glutamate side chain. The newly generated thiol from the inhibitor binds to the catalytic zinc ion in a monodentate manner, inducing a change in the zinc ion geometry and coordination, while its benzyl group fits into the S1' specificity pocket of the enzyme. The inhibitor molecule is distorted at the position of the carbon atom that is involved in the ester bond linkage on one side and the zinc coordination on the other. This particular type of thiirane-based metalloprotease inhibitor is for the first time analyzed in complex to the target protease at high resolution and may be used as a general model for zinc-dependent proteases.