Oxygen: a master regulator of pancreatic development?

Beyond its role as an electron acceptor in aerobic respiration, oxygen is also a key effector of many developmental events. The oxygen‐sensing machinery and the very fabric of cell identity and function have been shown to be deeply intertwined. Here we take a first look at how oxygen might lie at the crossroads of at least two of the major molecular pathways that shape pancreatic development. Based on recent evidence and a thorough review of the literature, we present a theoretical model whereby evolving oxygen tensions might choreograph to a large extent the sequence of molecular events resulting in the development of the organ. In particular, we propose that lower oxygenation prior to the expansion of the vasculature may favour HIF (hypoxia inducible factor)‐mediated activation of Notch and repression of Wnt/β‐catenin signalling, limiting endocrine cell differentiation. With the development of vasculature and improved oxygen delivery to the developing organ, HIF‐mediated support for Notch signalling may decline while the β‐catenin‐directed Wnt signalling is favoured, which would support endocrine cell differentiation and perhaps exocrine cell proliferation/differentiation.     

Immobilization of enzymes on Spheron: 2. β-Amylase — The development of a column reactor—separator

The titanium-chelation method has been used to immobilize β-amylase (1,4-α-d-glucan maltohydrolase, EC 3.2.1.2) on to Spheron. On various grades of Spheron, protein coupling yields of 56–76% were obtained with barley and sweet-potato β-amylases. The specific enzymic activities of the immobilized enzymes fell in the range 3.7–7.6% of those of the soluble enzymes. The immobilized enzymes were more stable than the soluble, especially in the presence of l-cysteine and serum albumin. The presence of cysteine and serum albumin brought about increases in activity in the preparations, presumably by regenerating essential thiol groups in the enzyme which had been oxidized during the operations. Maltose could be separated from amylopectin and other large polysaccharides by chromatography on Spheron P100, and a system was developed in which maltose, produced by hydrolysis of amylopectin applied in pulses to a column of immobilized β-amylase, was separated from starting material and by-products on a second column of Spheron P100.     

Proteins in Tumor-Derived Plasma Extracellular Vesicles Indicate Tumor Origin

Cancer-derived extracellular vesicles (EVs) promote tumorigenesis, premetastatic niche formation, and metastasis via their protein cargo. However, the proteins packaged by patient tumors into EVs cannot be determined in vivo because of the presence of EVs derived from other tissues. We therefore developed a cross-species proteomic method to quantify the human tumor-derived proteome of plasma EVs produced by patient-derived xenografts of four cancer types. Proteomic profiling revealed individualized packaging of novel protein cargo, and machine learning accurately classified the type of the underlying tumor.     

Simultaneous Binding of Basic Peptides at Intracellular Sites on a Large Conductance Ca2+-activated K+ Channel : Equilibrium and Kinetic Basis of Negatively Coupled Ligand Interactions

The homologous Kunitz inhibitor proteins, bovine pancreatic trypsin inhibitor (BPTI) and dendrotoxin I (DTX-I), interact with large conductance Ca²⁺-activated K⁺ channels (maxi-K_Ca) by binding to an intracellular site outside of the pore to produce discrete substate events. In contrast, certain homologues of the Shaker ball peptide produce discrete blocking events by binding within the ion conduction pathway. In this study, we investigated ligand interactions of these positively charged peptide molecules by analysis of single maxi-K_Ca channels in planar bilayers recorded in the presence of DTX-I and BPTI, or DTX-I and a high-affinity homologue of ball peptide. Both DTX-I (K _d, 16.5 nM) and BPTI (K _d, 1,490 nM) exhibit one-site binding kinetics when studied alone; however, records in the presence of DTX-I plus BPTI demonstrate simultaneous binding of these two molecules. The affinity of BPTI (net charge, +6) decreases by 11.7-fold (K _d, 17,500 nM) when DTX-I (net charge, +10) is bound and, conversely, the affinity of DTX-I decreases by 10.8-fold (K _d, 178 nM) when BPTI is bound. The ball peptide homologue (BP; net charge, +6) exhibits high blocking affinity (K _d, 7.2 nM) at a single site when studied alone, but has 8.0-fold lower affinity (K _d, 57 nM) for blocking the DTX-occupied channel. The affinity of DTX-I likewise decreases by 8.4-fold (K _d, 139 nM) when BP is bound. These results identify two types of negatively coupled ligand–ligand interactions at distinct sites on the intracellular surface of maxi-K_Ca channels. Such antagonistic ligand interactions explain how the binding of BPTI or DTX-I to four potentially available sites on a tetrameric channel protein can exhibit apparent one-site kinetics. We hypothesize that negatively coupled binding equilibria and asymmetric changes in transition state energies for the interaction between DTX-I and BP originate from repulsive electrostatic interactions between positively charged peptide ligands on the channel surface. In contrast, there is no detectable binding interaction between DTX-I on the inside and tetraethylammonium or charybdotoxin on the outside of the maxi-K_Ca channel.     

Peptidome analysis reveals the involvement of endogenous peptides in mouse pancreatic dysfunction with aging

Type 2 diabetes (T2D) is a glucose regulation disorder that has significantly enhanced mortality and the global disease burden. The prevalence of T2D has increased worldwide and is higher in the elderly. The function of pancreatic islets decreases with age, which is one important reason for the occurrence of diabetes in the elderly. Recently, peptidome analysis has attracted attention. However, the role of age-related peptides in pancreatic dysfunction has not been investigated extensively. Here, we conducted a comparison of endogenous peptides between pancreas from adult and aging mice by liquid chromatography tandem mass spectrometry (LC-MS/MS). A total of 2,089 peptides originating from 1,280 protein precursors were identified, of which 232 were upregulated and 183 were downregulated in the aging mice (fold change ≥ 2 and p < 0.05), suggesting that the expression of pancreatic peptides in mice varied with age. The molecular weight of most peptides was <3.0 kDa, and the isoelectric point distribution had a bimodal characteristic. Further analysis of cleavage site patterns indicated that proteases cleaved pancreatic proteins according to their rules. Moreover, Gene Ontology and pathway analyses showed that the differentially expressed peptides potentially had specific effects on pancreatic dysfunction. Some differential peptides were located within the domains of precursor proteins that were closely associated with the development of diabetes. We believe that our research may advance the current understanding of pancreas-derived peptides and that certain peptides may be involved in the etiology of diabetes.     

Does Microhistology Improve the Cytological Diagnosis of Liver and Pancreatic Tumours?

Guided percutaneous fine needle aspiration cytodiagnosis of the liver, retroperitoneum and pancreas was performed in 197 patients. In 42 cases, material left after the smears were prepared was embedded in paraffin wax for histological examination. Six liver tumours and seven pancreatic tumours were identified in this material. In two cases the diagnosis of liver cell carcinoma was made only after microhistological examination. Re-examination of the cytological material in both cases disclosed features of liver cell carcinoma which were underestimated in the first examination and diagnosed only broadly as cancer cells. On the other hand, in another case cancer cells were present only in the smear and absent in the microhistological preparation. Diagnosis of pancreatic tumours was generally not improved by microhistological examination. In one case cancer cells were present only in the cytological material. In another case a cytological diagnosis of suspected cancer was confirmed as adenocarcinoma by microhistology. The diagnosis of non-neoplastic material in the remaining 29 cases were identical by cytopathology and microhistology. It is concluded that the microhistology of needle aspirate material complements cytological examination and can refine diagnosis although it increases cost.     

CRABP1 provides high malignancy of transformed mesenchymal cells and contributes to the pathogenesis of mesenchymal and neuroendocrine tumors

CRABP1 (cellular retinoic acid binding protein 1) belongs to the family of fatty acid binding proteins. Retinoic acid binding is the only known functional activity of this protein. The role of CRABP1 in human carcinogenesis remains poorly understood. Here, for the first time we demonstrated pro-metastatic and pro-tumorigenic activity of CRABP1 in mesenchymal tumors. Further functional analysis revealed that the pro-tumorigenic effect of CRABP1 does not depend on retinoic acid binding activity. These results suggest that CRABP1 could have an alternative intracellular functional activity that contributes to the high malignancy of transformed mesenchymal cells. Microarray analysis detected CRABP1-mediated alterations in the expression of about 100 genes, including those encoding key regulatory proteins. CRABP1 is ubiquitously expressed in monophasic synovial sarcomas, while in biphasic synovial sarcomas it is expressed uniquely by the spindle cells of the aggressive mesenchymal component. High level of CRABP1 expression is associated with lymph node metastasis and poor differentiation/high grade of pancreatic neuroendocrine tumors (pNETs). Presented data suggest CRABP1 as a promising biomarker of pNETs’ clinical behavior. Our results give the first evidence of pro-tumorigenic and pro-metastatic activity of CRABP1 in mesenchymal and neuroendocrine tumors.     

Parkin deficiency contributes to pancreatic tumorigenesis by inducing spindle multipolarity and misorientation

Parkin, an E3 ubiquitin ligase well known for its role in the pathogenesis of juvenile Parkinson disease, has been considered as a candidate tumor suppressor in certain types of cancer. It remains unknown whether parkin is involved in the development of pancreatic cancer, the fourth leading cause of cancer-related deaths worldwide. Herein, we demonstrate the downregulation and copy number loss of the parkin gene in human pancreatic cancer specimens. The expression of parkin negatively correlates with clinicopathological parameters indicating the malignancy of pancreatic cancer. In addition, knockdown of parkin expression promotes the proliferation and tumorigenic properties of pancreatic cancer cells both in vitro and in mice. We further find that parkin deficiency increases the proportion of cells with spindle multipolarity and multinucleation. Parkin-depleted cells also show a significant increase in spindle misorientation. These findings indicate crucial involvement of parkin deficiency in the pathogenesis of pancreatic cancer.