Serum procarboxypeptidase A and carboxypeptidase A levels in pancreatic disease

CPXM1 correlates to poor prognosis and immune cell infiltration in gastric cancer

Background

Gastric cancer (GC) is the fourth most common cause of cancer-related death and the fifth most frequent malignant cancer, especially advanced GC. Carboxypeptidase X member 1 (CPXM1) is an epigenetic factor involved in many physiological processes, including osteoclast differentiation and adipogenesis. Several studies have shown the association of CPXM1 with multiple tumors; however, the mechanism of CPXM1 involvement in the progression of GC is yet to be characterized.

Method

CPXM1 expression data were obtained from the Tumor Immune Estimation Resource. The Cancer Genome Atlas and the Gene Expression Omnibus databases were used to obtain patient-matched clinicopathological information, and the Kaplan-Meier plot database was utilized for the prognosis analysis of GC patients. The Catalog of Somatic Mutations in Cancer and cBioportal databases were adopted to study CPXM1 mutations in tumors. Next, we utilized the Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Gene Set Enrichment Analysis for mechanism research. Furthermore, we performed tumor microenvironment and immune infiltration analysis based on CPXM1. Finally, we predicted sensitivity to several targeted drugs in GC patients based on CPXM1.CPXM1 is upregulated in GC and is correlated with poor prognosis, gender, and tumor stage in GC patients. Gene enrichment analysis suggested that CPXM1 may regulate the occurrence and progression of GC via the PI3K-AKT and TGF-β pathway. Moreover, CPXM1 expression results in an increase in the proportion of immune and stromal cells. Additionally, the proportion of plasma cells was inversely related to the expression of CPXM1, whereas macrophage M2 expression was proportionate to CPXM1 expression. Finally, six small-molecule drugs that showed notable variations in IC50 between two groups were screened.

Conclusion

These results suggested that CPXM1 regulates the progression of GC and may represent a novel target for the detection and treatment of GC.

Novel Insights Into Immunohistochemical Analysis For Acinar Cell Neoplasm of The Pancreas: Carboxypeptidase A2, Carboxypeptidase A1, and Glycoprotein 2

Acinar cell carcinoma (ACC) is a rare and highly malignant pancreatic tumor. Owing to histologic similarity, ACC is often difficult to distinguish from other solid medullary pancreatic tumors, particularly neuroendocrine neoplasm (NEN) and intraductal tubulopapillary neoplasm (ITPN). We aimed to identify new immunohistochemical markers commonly expressed in tumor cells with acinar cell differentiation and useful for both surgical and small biopsy specimens. Candidate molecules exclusively expressed in neoplastic or non-neoplastic acinar cells in pancreatic tissues with specific and available antibodies suitable for immunohistochemistry were selected. We selected carboxypeptidase A1 (CPA1), carboxypeptidase A2 (CPA2), and glycoprotein 2 (GP2), which were expressed in 100%, 100%, and 96% of cases, respectively, in ACC (n=27) or neoplasia with acinar cell differentiation, including mixed acinar-neuroendocrine carcinoma (n=9), mixed acinar-ductal carcinoma (n=3), pancreatoblastoma (n=4), and acinar cystic transformation (n=2), in the cytoplasm of tumor cells with a granular pattern. Both CPA2 and CPA1 were not expressed in any other tumors without acinar cell differentiation, including NEN (n=44), pancreatic ductal adenocarcinoma (n=44), and ITPN (n=4). GP2 was not expressed in these tumors except in rare cases, including 14% of NEN, 15% of intraductal papillary-mucinous neoplasm, 25% of intraductal oncocytic papillary neoplasm, 25% of ITPN, and 7% of pancreatic ductal adenocarcinoma, wherein a small proportion of tumor cells expressed GP2 in their apical cell membrane. NEN cases also showed cytoplasmic GP2 expression. Therefore, CPA2, CPA1, and potentially GP2 may act as ACC markers.

Screening of Therapeutic Targets for Pancreatic Cancer by Bioinformatics Methods

Pancreatic cancer (PC) has the lowest survival rate and the highest mortality rate among all cancers due to lack of effective treatments. The objective of the current study was to identify potential therapeutic targets in PC. Three transcriptome datasets, namely GSE62452, GSE46234, and GSE101448, were analyzed for differentially expressed genes (DEGs) between cancer and normal samples. Several bioinformatics methods, including functional analysis, pathway enrichment, hub genes, and drugs were used to screen therapeutic targets for PC. Fisher's exact test was used to analyze functional enrichments. To screen DEGs, the paired t-test was employed. The statistical significance was considered at p <0.05. Overall, 60 DEGs were detected. Functional enrichment analysis revealed enrichment of the DEGs in "multicellular organismal process", "metabolic process", "cell communication", and "enzyme regulator activity". Pathway analysis demonstrated that the DEGs were primarily related to "Glycolipid metabolism", "ECM-receptor interaction", and "pathways in cancer". Five hub genes were examined using the protein-protein interaction (PPI) network. Among these hub genes, 10 known drugs targeted to the CPA1 gene and CLPS gene were found. Overall, CPA1 and CLPS genes, as well as candidate drugs, may be useful for PC in the future.

Carboxypeptidase A1 (CPA1) Immunohistochemistry Is Highly Sensitive and Specific for Acinar Cell Carcinoma (ACC) of the Pancreas

Carboxypeptidase A1 (CPA1) is a zinc metalloprotease that is produced in pancreatic acinar cells and plays a role in cleaving C-terminal branched-chain and aromatic amino acids from dietary proteins. This study assessed the utility of immunohistochemical CPA1 staining for diagnosing pancreatic acinar cell carcinoma (ACC). A total of 12,274 tumor samples from 132 different tumor types and subtypes as well as 8 samples each of 76 different normal tissue types were interpretable by immunohistochemistry in a tissue microarray format. CPA1 was strongly expressed in acinar cells of all normal pancreas samples but not in any other normal tissues. CPA1 immunostaining was detected in 100% of 11 pancreatic ACCs and 1 mixed acinar endocrine carcinoma, but absent in 449 pancreatic ductal adenocarcinomas, 75 adenocarcinomas of the ampulla Vateri, and 11,739 other evaluable cancers from 128 different tumor entities. A weak to moderate diffuse staining of epithelial and stromal cells of cancer tissues immediately adjacent to non-neoplastic pancreatic acinar cells often occurred and was considered to be caused by the diffusion of the highly abundant CPA1 from normal acinar cells that may have suffered some autolytic cell damage. In conclusion, our data show that CPA1 is a highly sensitive and largely specific marker for normal and neoplastic pancreatic acinar cells. CPA1 immunohistochemistry greatly facilitates the otherwise often difficult diagnosis of pancreatic ACC.

Carboxypeptidase A1 and regenerating islet-derived 1α as new markers for pancreatic acinar cell carcinoma

Acinar cell carcinoma (ACC) is a rare tumor that differentiates toward pancreatic acinar cells and shows evidence of pancreatic enzyme production. Mixed acinar-neuroendocrine carcinoma (MANC) is defined as having more than 30% of both acinar and neuroendocrine cell types as per immunohistochemistry analysis. Trypsin is currently the most commonly used stain for acinar differentiation. In this study, we investigate the utility of two novel markers, carboxypeptidase A1 (CPA1) and regenerating islet-derived 1α (REG1a), in diagnosing ACC/MANC. Immunohistochemical staining for CPA1 and REG1a was performed on 14 cases of ACC and 5 cases of MANC as well as on 80 other pancreatic tumors including 20 cases each of ductal adenocarcinoma, well-differentiated neuroendocrine tumor, mucinous cystic neoplasm, and solid pseudopapillary tumor. All ACCs and MANCs were positive for CPA1 (all diffuse) and REG1a (12 diffuse, 4 patchy, and 3 focal). A diffuse or patchy staining pattern was significantly more common in ACC/MANC cases (100% diffuse/patchy for CPA1 and 84% for REG1a) than in other pancreatic tumors (5% diffuse/patchy for CPA1 and 7.5% for REG1a), with a P-value of <0.0001 for both CPA1 and REG1a. The sensitivity and specificity of diffuse/patchy staining for CPA1 and REG1a in diagnosing pancreatic ACC/MANC were 100% and 95% for CPA1 and 84% and 93% for REG1a, respectively. In conclusion, CPA1 and REG1a are sensitive markers for ACC that can be used as additional acinar cell differentiation markers to help in the diagnosis of pancreatic ACC and MANC. A negative result for CPA1 virtually excludes ACC/MANC.

An intact C-terminal end of albumin is required for its long half-life in humans

Albumin has an average plasma half-life of three weeks and is thus an attractive carrier to improve the pharmacokinetics of fused therapeutics. The half-life is regulated by FcRn, a cellular receptor that protects against intracellular degradation. To tailor-design the therapeutic use of albumin, it is crucial to understand how structural alterations in albumin affect FcRn binding and transport properties. In the blood, the last C-terminal residue (L585) of albumin may be enzymatically cleaved. Here we demonstrate that removal of the L585 residue causes structural stabilization in regions of the principal FcRn binding domain and reduces receptor binding. In line with this, a short half-life of only 3.5 days was measured for cleaved albumin lacking L585 in a patient with acute pancreatitis. Thus, we reveal the structural requirement of an intact C-terminal end of albumin for a long plasma half-life, which has implications for design of albumin-based therapeutics.

Nilsen et al. show that structural alterations in the last C-terminal α-helix of albumin strongly reduce its binding to the neonatal Fc receptor, decreasing the half-life of albumin in humans. This study suggests the structural requirement of the C-terminal of albumin for its long plasma half-life, providing insights into the design of albumin used to carry drugs.

Paraneoplastic Cast Nephropathy Associated With Pancreatic Mixed Acinar-Neuroendocrine Carcinoma: A Case Report

Acute kidney injury is common in patients with cancer and may result from sepsis, obstruction, radiotherapy, chemotherapeutic agents, and nonsteroidal anti-inflammatory drugs. Rare reports of acute kidney injury due to cast nephropathy in patients with pancreatic acinar cell carcinoma have been described, but a pathogenetic link between cast nephropathy and carcinoma was not established. We report a patient with pancreatic mixed acinar-neuroendocrine carcinoma who developed severe acute kidney injury. Kidney biopsy showed cast nephropathy characterized by fractured periodic acid-Schiff-negative casts, associated with mononuclear and giant cell reaction. The patient did not have multiple myeloma and casts did not show immunoglobulin light chain restriction on immunofluorescence. Analysis using liquid chromatography-tandem mass spectrometry and immunohistochemistry identified 2 acinar cell-specific proteins, regenerating islet-derived 1α and carboxypeptidase A1, in both tubular casts and tumor cells. Thus, this case demonstrates that solid tumor-specific proteins can be nephropathic by obstructing renal tubules, resulting in acute kidney injury, a previously proposed but not characterized pathophysiologic mechanism for paraneoplastic nephropathy associated with carcinoma.

Label-Free Quantitative Proteomics Unravels Carboxypeptidases as the Novel Biomarker in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers, with a high mortality rate and poor prognosis. However, little is known concerning the molecular mechanism of PDAC at the proteomics level. Here we report a proteomics analysis of PDAC tumor and adjacent tissues by shotgun proteomics followed by label-free quantification, and in total, 3031 and 3306 proteins were identified in three pairs of PDAC tumor and adjacent tissues, respectively; 40 of them were differentially expressed for at least three-fold in PDAC tumor tissues. Ontological and interaction network analysis highlighted the dysregulation of a set of four proteins in the carboxypeptidase family: carboxypeptidase A1 (CPA1), A2 (CPA2), B1 (CPB1), and chymotrypsin C (CTRC). Western blotting confirmed the downregulation of the carboxypeptidase network in PDAC. Immunohistochemistry of tissue microarray from 90 PDAC patients demonstrated that CPB1 was downregulated 7.07-fold (P < .0001, n = 81) in tumor comparing with the peritumor tissue. Further 208 pancreatic tissues from PDAC tumor, peritumor, and pancreatis confirmed the downregulation of CPB1 in the PDAC patients. In summary, our results displayed that the expression of carboxypeptidase is significantly downregulated in PDAC tumor tissues and may be novel biomarker in the patient with PDAC.

The proteome of postsurgical pancreatic juice

OBJECTIVE

This study aimed to evaluate the proteome of the pancreatic juice after pancreatectomy.

METHODS

Pancreatic juice samples were obtained during surgery and the postoperative period. Proteins were identified by mass spectrometry-based protein quantification technology and compared with published data of the nonoperated pancreas. Subgroup analyses were done in patients with pancreatic ductal adenocarcinoma (PDAC) receiving neoadjuvant chemotherapy and in smokers.

RESULTS

Five hundred eighteen proteins were identified in the postoperative pancreatic juice, encompassing all of the main organ functions. Sixty-seven of these were also present in the published data of the nonoperated pancreas and 7 of these had significant variation of concentration after surgery. Growth factors that have been described in postsurgical regeneration of the liver were not found to be overexpressed, whereas clusterin did, confirming the finding of previous experimental studies on pancreatic regeneration. Several proteins involved in immunomodulation and organ functions were differently expressed, depending on PDAC, neoadjuvant therapy, and smoking.

CONCLUSIONS

The proteome of the pancreas after surgical resection contains factors related to all main organ functions, changes over time, and is different in patients with PDAC receiving neoadjuvant therapy and in smokers. The pancreas reacts to the surgical trauma by producing proteins that protect the organ and stimulate the restoration of its function.

Relative quantification of albumin and fibrinogen modifications by liquid chromatography tandem mass spectrometry in the diagnosis and monitoring of acute pancreatitis

The increasing availability of liquid chromatography tandem mass spectrometry (LC-MS/MS) in clinical laboratories provides the opportunity to replace or complement present underperforming immuno- and chemometric assays. Amylase and lipase show limited specificity and sensitivity for pancreatic inflammation and lack the capacity of monitoring the disease due to their short half-lives. Previous findings suggested that cleavage products of the pancreatic enzyme carboxypeptidase A could be a more suitable indicator for defining and classifying pancreatic inflammation. The plasma proteins albumin and β-fibrinogen were digested with trypsin and truncated forms (des-Leu-albumin, and des-Gln-β-fibrinogen) quantified against their non-truncated forms by LC-MS/MS. Four hundred fifty eight samples from 83 patients were used to evaluate the novel method and affirm its suitability for detecting acute pancreatitis. A robust, selective, precise and accurate LC-MS/MS method was set up to measure the proportion of truncated proteins. Reference ranges for the proportion of the truncated albumin and β-fibrinogen were from 2% to 9% and 3% to 25%, respectively. Acute pancreatitis patients had values above these ranges and were distinctly separated from reference control individuals. The longer circulating half-lives of albumin and fibrinogen compared to pancreatic enzymes themselves provide the potential to diagnose pancreatitis more specifically over a longer time period, to monitor the course of the disease, and to track recurrent complications. The wide range of the proportion and the differential half-life of both truncated proteins could also be used for assessing the severity of pancreatitis.