High glucose exposure promotes activation of protein phosphatase 2A in rodent islets and INS-1 832/13 β-cells by increasing the posttranslational carboxylmethylation of its catalytic subunit

Existing evidence implicates regulatory roles for protein phosphatase 2A (PP2A) in a variety of cellular functions, including cytoskeletal remodeling, hormone secretion, and apoptosis. We report here activation of PP2A in normal rat islets and insulin-secreting INS-1 832/13 cells under the duress of hyperglycemic (HG) conditions. Small interfering RNA-mediated knockdown of the catalytic subunit of PP2A (PP2Ac) markedly attenuated glucose-induced activation of PP2A. HG, but not nonmetabolizable 3-O-methyl glucose or mannitol (osmotic control), significantly stimulated the methylation of PP2Ac at its C-terminal Leu-309, suggesting a novel role for this posttranslational modification in glucose-induced activation of PP2A. Moreover, knockdown of the cytosolic leucine carboxymethyl transferase 1 (LCMT1), which carboxymethylates PP2Ac, significantly attenuated PP2A activation under HG conditions. In addition, HG conditions, but not 3-O-methyl glucose or mannitol, markedly increased the expression of LCMT1. Furthermore, HG conditions significantly increased the expression of B55α, a regulatory subunit of PP2A, which has been implicated in islet dysfunction under conditions of oxidative stress and diabetes. Thapsigargin, a known inducer of endoplasmic reticulum stress, failed to exert any discernible effects on the carboxymethylation of PP2Ac, expression of LCMT1 and B55α, or PP2A activity, suggesting no clear role for endoplasmic reticulum stress in HG-induced activation of PP2A. Based on these findings, we conclude that exposure of the islet β-cell to HG leads to accelerated PP2A signaling pathway, leading to loss in glucose-induced insulin secretion.

Protein farnesylation is requisite for mitochondrial fuel-induced insulin release: further evidence to link reactive oxygen species generation to insulin secretion in pancreatic β-cells

Several lines of recent evidence implicate regulatory roles for reactive oxygen species (ROS) in islet function and insulin secretion. The phagocyte-like NADPH oxidase (Nox2) has recently been shown to be one of the sources of ROS in the signaling events leading to glucose stimulated insulin secretion (GSIS). We recently reported inhibition of glucose- or mitochondrial fuel-induced Nox2-derived ROS by a specific inhibitor of protein farnesyl transferse (FTase; FTI-277), suggesting that activation of FTase might represent one of the upstream signaling events to Nox2 activation. Furthermore, FTase inhibitors (FTI-277 and FTI-2628) have also been shown to attenuate GSIS in INS 832/13 cells and normal rodent islets. Herein, we provide further evidence to suggest that inhibition of FTase either by pharmacological (e.g., FTI-277) or gene silencing (siRNA-FTase) approaches markedly attenuates mitochondrial fuel-stimulated insulin secretion (MSIS) in INS 832/13 cells. Together, our findings further establish a link between nutrient-induced Nox2 activation, ROS generation and insulin secretion in the pancreatic β-cell.

Interpretation of 11C-choline PET/CT for the diagnosis of local relapse in radically treated prostate cancer

Purpose

11C–choline PET/CT is a widely-used tool for the diagnostic of prostate cancer (PCa). In literature, a great variability of local relapse (LR) detection rate is reported. The aim of this study is to provide positivity criteria for 11C–choline PET/CT detection of LR in patients who had surgery for PCa and presented prostate specific antigen (PSA) failure.

Methods

Sixty patients radically treated for PCa and presenting PSA failure were retrospectively analysed. Two Nuclear Medicine Physicians revised the 11C–choline PET/CT scans and defined by consensus if even mild focal uptake was present in the prostate bed (PB) and bladder-urethral junction (BUJ) along midline, regardless the previous report results.

The results were subsequently correlated with a clinical and radiological follow up (FU) of 1 to 2 year and with TNM staging, Gleason score (GS), PSA level at relapse, radiotherapy (RT) and hormone therapy (HT) after surgery.

Results

There was focal uptake in 22/60 patients; 11 of them were true positive and 11 false positive. The PSA level showed a tight connection with the true positivity/negativity of Choline scan. Most of true positive cases (10/11 patients) presented a PSA ≥ 1 ng/ml, while approximately half of the false positive cases (5/11 patients) presented PSA below 1 ng/ml. The other variables were not correlated to Choline detection rate for LR.

Conclusions

This study shows that an even mild focal uptake of Choline in the PB and BUJ along midline must be considered suspicious for LR in patients radically treated for PCa, especially if they are presenting with PSA level > 1 ng/ml.

18F-FDG PET/CT scan confirmed by pathology findings in a singular case of squamous cell carcinoma of the epiglottis

Background

Only about 1% of all head and neck lateral or paramedian cancers described in the scientific literature shows, in staging, contralateral cervical adenopathy without ipsilateral pathological involvement of lymph nodes.

Case Presentation

This case is one of them, in which 18F–FDG PET/CT scan is confirmed by pathology findings, and has correctly identified all metastatic disease foci.

Conclusions

To date, PET/CT is not recommended in head and neck cancer staging. However, the use of PET/CT in head and neck cancer staging can define possible metastatic disease foci, clarify c.e. CT suspicious findings and, in some cases, change the TNM stage, with a strong prognostic and therapeutic impact.

OP0337 DIFFERENTIAL METHYLATION OF PERIPHERAL BLOOD ADAPTIVE IMMUNE CELLS IN INDIVIDUALS AT HIGH RISK FOR RA AND WITH EARLY RA COMPARED WITH CONTROLS IDENTIFIES PATHWAYS IMPORTANT IN TRANSITION TO ARTHRITIS

Background:

The “Targeting Immune Responses for Prevention of RA” (TIP-RA) collaboration studies individuals at high risk for developing RA because of serum anti-citrullinated protein antibody positivity in absence of arthritis, and is focused on defining how they transition from at-risk to classifiable disease. One potential mechanism is through alterations in epigenetics patterns in adaptive immune cells.

Objectives:

Previous studies showed that DNA methylation patterns of early RA (ERA) synoviocytes differ from long-standing RA, suggesting that abnormal methylation occurs early in synovium and evolves over time. To extend these observations, we performed a cross-sectional analysis in TIP-RA of DNA methylation signatures in peripheral blood cells in ERA, at-risk anti-CCP3+ individuals and demographically matched CCP- controls.

Methods:

Genomic DNA was isolated from two independent cohorts of CCP- (cohorts 1 and 2, respectively: B cell: n = 17/34; memory T cell: n = 21/34; and naïve T cell: n = 21/33), CCP3+ (B cell: n = 18/37; memory T cell: n = 20/36; and naïve T cell: n = 20/35), and CCP3+ ERA (B cell: n = 4/18; memory T cell: n = 5/18; and naïve T cell: n = 5/18) after separating PBMCs using antibodies and magnetic beads. Methylation was measured by Illumina Infinium MethylationEPIC chip. Differentially methylated loci (DMLs) were identified using Welch’s t-test and mapped to gene promoter regions to define DM genes (DMGs). Principal component analysis (PCA) was used to represent relationship among groups. Pathway analysis was applied by Reactome.

Results:

For the initial cohort, 1494, 1097 and 1330 DMLs were identified among CCP+, CCP- and ERA in B cells, memory T cells and naïve T cells, respectively. For the confirmatory cohort, 523, 793 and 548 DMLs were found in corresponding cell populations. The DML overlap between the 2 cohorts was highly significant (p= 2.48E-77). The DMLs were combined for both groups and corresponded to 411, 412, and 351 DMGs in B cells, memory T cells and naïve T cells. Of these, we found 246, 198 and 195 DMGs between CCP3+ and ERA in each peripheral blood cell population, respectively. PCA showed separation of CCP+, CCP- and ERA in each of the three blood cell types by DMLs (Fig. 1). DMGs were mapped to biological pathways to identify DM pathways. Although most were not significant, there were several highly significant differences comparing CCP+, ERA and CCP- in memory T cells involving pathways, including “Interferon gamma signaling” (FDR 7.48E-14), “PD-1 signaling” (FDR 8.71E-10), “Translocation of ZAP-70 to Immunological synapse” (FDR 4.75E-10), and “Phosphorylation of CD3 and TCR zeta chains” (FDR 8.71E-10).

Figure 1.

PCA shows the separation of CCP+, CCP- and ERA patients in memory T cells in confirmatory cohort.

Conclusion:

We identified reproducible methylation signatures of CCP-, CCP+, and ERA in peripheral blood B cells, memory T cells and naïve T cells in initial and confirmatory cohorts. The methylome of ERA also demonstrated a distinctive pattern from CCP+, indicating that progression to RA is accompanied by epigenetic remodeling, especially in T cell signaling and interferon responses. These signatures identify critical pathways in CCP positivity and classifiable RA and could provide the basis of novel interventions to prevent disease.

Disclosure of Interests:

Rizi Ai: None declared, David Boyle: None declared, Deepa Hammaker: None declared, Kevin Deane Grant/research support from: Janssen, Consultant of: Inova, ThermoFisher, Janseen, BMS and Microdrop, V. Michael Holers Grant/research support from: Janssen, Celgene, and BMS, Andre Matti: None declared, William Robinson: None declared, Jane Buckner Grant/research support from: Bristol-Myers Squibb, Janssen, Navin Rao Shareholder of: Janssen Pharmaceuticals, Employee of: Janssen Pharmaceuticals, Frederic Baribaud Shareholder of: Janssen Research & Development, LLC, Employee of: Janssen Research & Development, LLC, Alyssa Johnsen Employee of: Janssen, Sunil Nagpal Shareholder of: Janssen Pharmaceuticals, Employee of: Janssen Pharmaceuticals, Wei Wang: None declared, Gary Firestein Grant/research support from: Lilly, Janssen, Abbvie