NT5DC2 promotes tumor cell proliferation by stabilizing EGFR in hepatocellular carcinoma.

Most hepatocellular carcinoma (HCC) patients are diagnosed at an advanced stage; however, the effect of systemic therapy on advanced HCC remains undetermined. Therefore, new treatment targets must be identified. We analyzed Gene Expression Omnibus datasets from two HCC patient cohorts and found that NT5DC2 was associated with vascular invasion and poor survival. In two hepatoma cell lines, NT5DC2 overexpression promoted HCC cell proliferation and clone formation in vitro and promoted tumor growth in vivo. Coimmunoprecipitation assays and liquid chromatography with tandem mass spectrometry analysis revealed that NT5DC2 bound directly to epidermal growth factor receptor (EGFR). NT5DC2 upregulated EGFR expression by downregulating EGFR ubiquitination and preventing its degradation via the ubiquitin-proteasome pathway but did not upregulate its transcription. EGFR upregulation activated downstream signal transduction, which played a critical role in the protumor effects of NT5DC2. Erlotinib, a small-molecule inhibitor of EGFR, blocked the effect of NT5DC2 in promoting HCC cell proliferation. In a cohort of 79 patients who underwent curative resection for HCC, NT5DC2 expression in the tumors was associated with larger tumors and microvascular invasion. NT5DC2 expression was also independently associated with recurrence-free survival. The present study demonstrated for the first time that NT5DC2 promotes tumor cell proliferation in HCC and may serve as a potential molecular target for treating HCC. EGFR blockage could be used to treat selected patients with NT5DC2 upregulation.

HMGB1 correlates with angiogenesis and poor prognosis of perihilar cholangiocarcinoma via elevating VEGFR2 of vessel endothelium.

Perihilar cholangiocarcinoma (PHCCA) is the most common type of cholangiocarcinoma with low resection rate and high morbidity. The study of PHCCA biomarkers made progresses slowly compared with intrahepatic cholangiocarcinoma because of surgical complexity and low possibility of radical surgery, which resulted in the difficulty of specimen obtainment. To screen and identify new biomarkers in PHCCA, we constructed a retrospective cohort with 121 PHCCA patients and a prospective cohort consisting of 64 PHCCA patients, and screened the candidate biomarkers by immunohistochemistry and quantified PCR. In our study, expression of high mobility group box 1 (HMGB1) was demonstrated to be significantly associated with microvascular density (MVD) and unfavorable prognosis of PHCCA in both retrospective and prospective study. Moreover, HMGB1 concentrations in bile and serum of PHCCA patients and healthy controls were detected and compared. Postoperative serum HMGB1 and reflux cholangitis indicated recurrence and unfavorable prognosis of PHCCA. With experiments in vitro and in vivo, we demonstrated that intracellular HMGB1 could be released from PHCCA cells and induce invasion and angiogenesis with LPS stimulation. VEGFR2 expression in vessel endothelial cells was upregulated by the released HMGB1 from PHCCA, resulting in the ectopic angiogenesis. In conclusion, intracellular HMGB1 could be released from PHCCA cells and promote angiogenesis via elevating VEGFR2 in vessel endothelial cells. High expression of HMGB1 was associated with MVD and poor prognosis in clinical analyzation. Postoperative serum HMGB1 and cholangitis could predict high recurrence and unfavorable prognosis.

Crystal structure and catalytic activity of the PPM1K N94K mutant.

Protein Phosphatase Mg2+ /Mn2+ -Dependent 1K (PPM1K),also named as PP2Cm or branched-chain α-ketoacid dehydrogenase complex phosphatase, is a member of the metal-dependent phosphatase family and an important metabolic regulator. Single nucleotide polymorphisms (SNPs) in PPM1K contributing to protein functional defects have been found to be associated with numerous human diseases, such as cardiovascular disease, maple syrup urine disease, type 2 diabetes, and neurological disease. PPM1K N94K is an identified missense mutant produced by one of the SNPs in the human PPM1K coding sequence. However, the effects of the N94K mutant on its activity and structural property have not been defined. Here, we performed a detailed enzymological study using steady-state kinetics in the presence of pNPP or phospho-peptide substrates and crystallographic analyses of the wild-type and N94K PPM1K. The PPM1K-N94K significantly impaired its Mg2+ -dependent catalytic activity and structural analysis demonstrated that the N94K mutation induced a conformational change in the key residue in coordinating the Mg2+ in the active site. Specifically, three Mg2+ were located in the active site of the PPM1K N94K instead of two Mg2+ in the PPM1K wild type. Therefore, our results provide a structure basis for the metal ion-dependent PPM1K-N94K phosphatase activity.

Sprouty2 suppresses progression and correlates to favourable prognosis of intrahepatic cholangiocarcinoma via antagonizing FGFR2 signalling.

Fibroblast growth factor receptor 2 (FGFR2) was demonstrated to correlate to the progression and prognosis of intrahepatic cholangiocarcinoma (ICC) by numerous evidences. However, as a well-recognized suppressor of FGFR2 signalling, the clinical significance of Sprouty (SPRY) family of ICC has not been investigated. In our study, the expressions of SPRY1-4 in 20 pairs of fresh tumour tissues were detected with qPCR, and in 108 cases of paraffin-embedded tissues with immunohistochemistry. The prognostic value of SPRY family in ICC was estimated with univariate analysis and multivariate analysis. As a result, SPRY2 was identified as an independent prognostic biomarker predicting favourable prognosis of ICC. High SPRY2 expression was correlated with good differentiation of ICC. With silencing SPRY2 expression, we demonstrated that SPRY2 could suppress FGFR2-induced ERK phosphorylation, migration, invasion and epithelial-mesenchymal transition (EMT) under FGF1 stimulation. By overexpressing SPRY2-wide type or SPRY2-Y55F, the tyrosine-55 of SPRY2 was demonstrated to be essential in suppressing ERK phosphorylation, tumour invasion and EMT of ICC cells. In conclusion, SPRY2 was correlated with favourable prognosis of ICC via suppressing FGFR2-induced ERK phosphorylation, invasion and EMT. The phosphorylation of SPRY2-Y55 was required in this tumour-suppressing function of SPRY2.

Identification of a benzo imidazole thiazole derivative as the specific irreversible inhibitor of protein tyrosine phosphatase.

Protein tyrosine phosphatases (PTPs) play key roles in many physiological processes, including cell proliferation, differentiation, immune responses and neural activities. Inappropriate regulation of the PTP activity could lead to human diseases, such as cancer or diabetes. Functional studies of PTP can be greatly facilitated by chemical probes that covalently label the active site of a PTP through an activity-dependent chemical reaction. Here, we characterize compound E4 as a new class of PTP activity probes. Compound E4 inactivate STEP in a time- and concentration-dependent fashion. Further study showed that compound E4 inhibits a series of PTPs in a time dependent manner, whereas it shows little or no inhibition toward metal dependent protein phosphatases. Collectively, this new identified covalent inhibitor of PTPs has the potential to be developed to an active site Cys directed PTP probes to study the active properties of the PTPs in cell signaling.

Identification of para-Substituted Benzoic Acid Derivatives as Potent Inhibitors of the Protein Phosphatase Slingshot.

Slingshot proteins form a small group of dual-specific phosphatases that modulate cytoskeleton dynamics through dephosphorylation of cofilin and Lim kinases (LIMK). Small chemical compounds with Slingshot-inhibiting activities have therapeutic potential against cancers or infectious diseases. However, only a few Slingshot inhibitors have been investigated and reported, and their cellular activities have not been examined. In this study, we identified two rhodanine-scaffold-based para-substituted benzoic acid derivatives as competitive Slingshot inhibitors. The top compound, (Z)-4-((4-((4-oxo-2-thioxo-3-(o-tolyl)thiazolidin-5-ylidene)methyl)phenoxy)methyl)benzoic acid (D3) had an inhibition constant (Ki) of around 4 µm and displayed selectivity over a panel of other phosphatases. Moreover, compound D3 inhibited cell migration and cofilin dephosphorylation after nerve growth factor (NGF) or angiotensin II stimulation. Therefore, our newly identified Slingshot inhibitors provide a starting point for developing Slingshot-targeted therapies.

Phospho-selective mechanisms of arrestin conformations and functions revealed by unnatural amino acid incorporation and (19)F-NMR.

Specific arrestin conformations are coupled to distinct downstream effectors, which underlie the functions of many G-protein-coupled receptors (GPCRs). Here, using unnatural amino acid incorporation and fluorine-19 nuclear magnetic resonance ((19)F-NMR) spectroscopy, we demonstrate that distinct receptor phospho-barcodes are translated to specific ß-arrestin-1 conformations and direct selective signalling. With its phosphate-binding concave surface, ß-arrestin-1 'reads' the message in the receptor phospho-C-tails and distinct phospho-interaction patterns are revealed by (19)F-NMR. Whereas all functional phosphopeptides interact with a common phosphate binding site and induce the movements of finger and middle loops, different phospho-interaction patterns induce distinct structural states of ß-arrestin-1 that are coupled to distinct arrestin functions. Only clathrin recognizes and stabilizes GRK2-specific ß-arrestin-1 conformations. The identified receptor-phospho-selective mechanism for arrestin conformation and the spacing of the multiple phosphate-binding sites in the arrestin enable arrestin to recognize plethora phosphorylation states of numerous GPCRs, contributing to the functional diversity of receptors.

FFA4 receptor (GPR120): A hot target for the development of anti-diabetic therapies.

Free Fatty Acid 4 receptor (FFA4 receptor or GPR120), a rhodopsin-like G protein coupled receptor (GPCR) subfamily member, is a receptor that senses specific fatty acids such as ω-3 fatty acid in fish oil or the endogenous signaling lipid, PHASA. FFA4 receptor is enriched in lung, colon and adipose tissue but is also detected in many other tissues and cells. The activation of FFA4 receptor has multiple effects, including but not limited to inhibition of inflammation, improving insulin sensitivity and adipogenesis, and regulating hormone secretion from the gastro-intestinal system and pancreatic islets. The important role of FFA4 receptor in maintaining metabolic homeostasis strongly indicates the great potential of selective FFA4 receptor agonizts to treat diabetes and inflammation. In this review, we summarize recent research progress in the physiological and biochemical studies of FFA4 receptor and highlight its underlying signaling mechanisms and ligand identification to assist future research to exploit FFA4 receptor as a drug target.

The catalytic role of the M2 metal ion in PP2Cα.

PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members.

Application of air insufflation to prevent clinical pancreatic fistula after pancreaticoduodenectomy.

AIM: To introduce an air insufflation procedure and to investigate the effectiveness of air insufflation in preventing pancreatic fistula (PF). METHODS: From March 2010 to August 2013, a total of 185 patients underwent pancreaticoduodenectomy (PD) at our institution, and 74 patients were not involved in this study for various reasons. The clinical outcomes of 111 patients were retrospectively analyzed. The air insufflation test was performed in 46 patients to investigate the efficacy of the pancreaticojejunal anastomosis during surgery, and 65 patients who did not receive the air insufflation test served as controls. Preoperative assessments and intraoperative outcomes were compared between the 2 groups. Univariate and multivariate analyses were performed to identify the risk factors for PF. RESULTS: The two patient groups had similar baseline demographics, preoperative assessments, operative factors, pancreatic factors and pathological results. The overall mortality, morbidity, and PF rates were 1.8%, 48.6%, and 26.1%, respectively. No significant differences were observed in either morbidity or mortality between the two groups. The rate of clinical PF (grade B and grade C PF) was significantly lower in the air insufflation test group, compared with the non-air insufflation test group (6.5% vs 23.1%, P = 0.02). Univariate analysis identified the following parameters as risk factors related to clinical PF: estimated blood loss; pancreatic duct diameter ≤ 3 mm; invagination anastomosis technique; and not undergoing air insufflation test. By further analyzing these variables with multivariate logistic regression, estimated blood loss, pancreatic duct diameter ≤ 3 mm and not undergoing air insufflation test were demonstrated to be independent risk factors. CONCLUSION: Performing an air insufflation test could significantly reduce the occurrence of clinical PF after PD. Not performing an air insufflation test was an independent risk factor for clinical PF.

Hepatoma-derived growth factor: a novel prognostic biomarker in intrahepatic cholangiocarcinoma.

Hepatoma-derived growth factor (HDGF) is an acidic heparin-binding protein involved in tumor progression and poor prognosis of kinds of cancers. Aimed at investigating the functions of HDGF in intrahepatic cholangiocarcinoma (IHCC), we detected the expression of HDGF by immunohistochemistry in 83 patients. Associations of HDGF with clinicopathologic features, microvascular density (MVD), and overall survival rates were further analyzed by Chi-square method, univariate or multivariate analysis. HDGF functions in IHCC proliferation, invasion, and angiogenesis were detected by MTT, transwell, and tube formation assays, respectively. As a result, we found that HDGF-positive expression rate in IHCC was 51.8 % (43/83) in IHCC. HDGF expression was significantly correlated to MVD (P = 0.031), lymphatic invasion (P = 0.030), distant metastasis (P = 0.002), and TNM stage (P = 0.037). HDGF was further identified as an independent prognostic factor in IHCC with Kaplan-Meier method (P = 0.003) and Cox-regression model (P = 0.008). Moreover, both intracellular and extracellular HDGF were proved to promote the proliferation, invasion, and angiogenesis of IHCC cell lines. In conclusion, HDGF was identified as an independent prognostic biomarker in IHCC. HDGF can promote IHCC cells progression, including proliferation, invasion, and angiogenesis, indicating HDGF could become a new promising and potential drug target of IHCC.

Cadmium is a potent inhibitor of PPM phosphatases and targets the M1 binding site.

The heavy metal cadmium is a non-degradable pollutant. By screening the effects of a panel of metal ions on the phosphatase activity, we unexpectedly identified cadmium as a potent inhibitor of PPM1A and PPM1G. In contrast, low micromolar concentrations of cadmium did not inhibit PP1 or tyrosine phosphatases. Kinetic studies revealed that cadmium inhibits PPM phosphatases through the M1 metal ion binding site. In particular, the negative charged D441 in PPM1G specific recognized cadmium. Our results suggest that cadmium is likely a potent inhibitor of most PPM family members except for PHLPPs. Furthermore, we demonstrated that cadmium inhibits PPM1A-regulated MAPK signaling and PPM1G-regulated AKT signaling potently in vivo. Cadmium reversed PPM1A-induced cell cycle arrest and cadmium insensitive PPM1A mutant rescued cadmium induced cell death. Taken together, these findings provide a better understanding of the effects of the toxicity of cadmium in the contexts of human physiology and pathology.