We previously reported that overexpression of cytochrome P450 family 24 subfamily A member 1 (CYP24A1) increases lung cancer cell proliferation by activating RAS signaling and that CYP24A1 knockdown inhibits tumor growth. However, the mechanism of CYP24A1-mediated cancer cell proliferation remains unclear. Here, we conducted cell synchronization and biochemical experiments in lung adenocarcinoma cells, revealing a link between CYP24A1 and anaphase-promoting complex (APC), a key cell cycle regulator. We demonstrate that CYP24A1 expression is cell cycle–dependent; it was higher in the G2-M phase and diminished upon G1 entry. CYP24A1 has a functional destruction box (D-box) motif that allows binding with two APC adaptors, CDC20-homologue 1 (CDH1) and cell division cycle 20 (CDC20). Unlike other APC substrates, however, CYP24A1 acted as a pseudo-substrate, inhibiting CDH1 activity and promoting mitotic progression. Conversely, overexpression of a CYP24A1 D-box mutant compromised CDH1 binding, allowing CDH1 hyperactivation, thereby hastening degradation of its substrates cyclin B1 and CDC20, and accumulation of the CDC20 substrate p21, prolonging mitotic exit. These activities also occurred with a CYP24A1 isoform 2 lacking the catalytic cysteine (Cys-462), suggesting that CYP24A1's oncogenic potential is independent of its catalytic activity. CYP24A1 degradation reduced clonogenic survival of mutant KRAS-driven lung cancer cells, and calcitriol treatment increased CYP24A1 levels and tumor burden in Lsl-KRASG12D mice. These results disclose a catalytic activity-independent growth-promoting role of CYP24A1 in mutant KRAS-driven lung cancer. This suggests that CYP24A1 could be therapeutically targeted in lung cancers in which its expression is high.

Arlene Smaldone
Jan 1, 2008; 21:46-49
Evidence-Based Clinical Decision Making

Lucía Trilla-Fuertes
Apr 1, 2020; 19:690-700
Research

Quentin Perraud
Apr 1, 2020; 19:589-607
Research

Elena Lorente
Apr 7, 2020; 0:RA120.002014v1-mcp.RA120.002014
Research

Liye Chen
May 1, 2020; 19:871-883
Research

26 February 2020

Over the past two decades, China has increased its presence in North Africa in terms of trade and investment. This paper looks at China’s policy within the context of its Africa and Middle East policies to better understand its approach to Morocco and Tunisia.

Introduction: To use positron emission tomography coupled with computed tomography (¹⁸FDG-PET/CT) to identify a high-risk subgroup requiring therapeutic intensification among patients with locally advanced cervical cancer (LACC) and para-aortic lymph node (PALN) involvement. Methods: In this retrospective multicentric study, patients with LACC and PALN involvement concurrently treated with chemoradiotherapy and extended-field radiotherapy (EFR) between 2006 and 2016 were included. A senior nuclear medicine specialist in PET for gynaecologic oncology reviewed all ¹⁸FDG-PET/CT scans. Metabolic parameters including maximum standardised uptake value (SUV_max), metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were determined for the primary tumour, pelvic lymph nodes and PALN. Associations between these parameters and overall survival (OS) were assessed with Cox's proportional hazards model. Results: Sixty-eight patients were enrolled in the study. Three-year OS was 55.5% (95% CI (40.8-68.0)). When adjusted for age, stage and histology, pelvic lymph node TLG, PALN TLG and PALN SUV_max were significantly associated with OS (p<0.005). Conclusion: FDG-PET/CT was able to identify predictors of survival in the homogeneous subgroup of patients with LACC and PALN involvement, thus allowing therapeutic intensification to be proposed.

In randomized clinical trials (RCTs), no survival benefit has been observed for selective internal radiotherapy (SIRT) over sorafenib in patients with advanced hepatocellular carcinoma (aHCC). This study aimed to assess by means of a meta-analysis whether overall survival (OS) with SIRT, as monotherapy or followed by sorafenib, is non-inferior to sorafenib, and compare safety profiles for patients with aHCC. Methods: We searched MEDLINE, EMBASE, and the Cochrane Library up to February 2019 to identify RCTs comparing SIRT as monotherapy, or followed by sorafenib, to sorafenib monotherapy among patients with aHCC. The main outcomes were OS and frequency of treatment-related severe adverse events (AEs grade ≥3). The per-protocol population was the primary analysis population. A non-inferiority margin of 1.08 in terms of hazard ratio (HR) was pre-specified for the upper boundary of 95% confidence interval (CI) for OS. Pre-specified subgroup analyses were performed. Results: Three RCTs, involving 1,243 patients, comparing sorafenib with SIRT (SIRveNIB and SARAH) or SIRT followed by sorafenib (SORAMIC), were included. After randomization, 411/635 (64.7%) patients allocated to SIRT and 522/608 (85.8%) allocated to sorafenib completed the studies without major protocol deviations. Median OS with SIRT, whether or not followed by sorafenib, was non-inferior to sorafenib (10.2 and 9.2 months, [HR 0.91, 95% CI 0.78–1.05]). Treatment-related severe adverse events were reported in 149/515 patients (28.9%) who received SIRT and 249/575 (43.3%) who received sorafenib only (p<0.01). Conclusion: SIRT as initial therapy for aHCC is non-inferior to sorafenib in terms of OS, and offers a better safety profile.

Anal squamous cell carcinoma is a rare tumor. Chemo-radiotherapy yields a 50% 3-year relapse-free survival rate in advanced anal cancer, so improved predictive markers and therapeutic options are needed. High-throughput proteomics and whole-exome sequencing were performed in 46 paraffin samples from anal squamous cell carcinoma patients. Hierarchical clustering was used to establish groups de novo. Then, probabilistic graphical models were used to study the differences between groups of patients at the biological process level. A molecular classification into two groups of patients was established, one group with increased expression of proteins related to adhesion, T lymphocytes and glycolysis; and the other group with increased expression of proteins related to translation and ribosomes. The functional analysis by the probabilistic graphical model showed that these two groups presented differences in metabolism, mitochondria, translation, splicing and adhesion processes. Additionally, these groups showed different frequencies of genetic variants in some genes, such as ATM, SLFN11 and DST. Finally, genetic and proteomic characteristics of these groups suggested the use of some possible targeted therapies, such as PARP inhibitors or immunotherapy.

Bacteria secrete siderophores to access iron, a key nutrient poorly bioavailable and the source of strong competition between microorganisms in most biotopes. Many bacteria also use siderophores produced by other microorganisms (exosiderophores) in a piracy strategy. Pseudomonas aeruginosa, an opportunistic pathogen, produces two siderophores, pyoverdine and pyochelin, and is also able to use a panel of exosiderophores. We first investigated expression of the various iron-uptake pathways of P. aeruginosa in three different growth media using proteomic and RT-qPCR approaches and observed three different phenotypic patterns, indicating complex phenotypic plasticity in the expression of the various iron-uptake pathways. We then investigated the phenotypic plasticity of iron-uptake pathway expression in the presence of various exosiderophores (present individually or as a mixture) under planktonic growth conditions, as well as in an epithelial cell infection assay. In all growth conditions tested, catechol-type exosiderophores were clearly more efficient in inducing the expression of their corresponding transporters than the others, showing that bacteria opt for the use of catechol siderophores to access iron when they are present in the environment. In parallel, expression of the proteins of the pyochelin pathway was significantly repressed under most conditions tested, as well as that of proteins of the pyoverdine pathway, but to a lesser extent. There was no effect on the expression of the heme and ferrous uptake pathways. Overall, these data provide precise insights on how P. aeruginosa adjusts the expression of its various iron-uptake pathways (phenotypic plasticity and switching) to match varying levels of iron and competition.

Human leukocyte antigen (HLA) B*51:01 and endoplasmic reticulum aminopeptidase 1 (ERAP1) are strongly genetically associated with Behcet's disease (BD). Previous studies have defined two subgroups of HLA-B*51 peptidome containing proline (Pro) or alanine (Ala) at position 2 (P2). Little is known about the unconventional non-Pro/Ala2 HLA-B*51-bound peptides. We aimed to study the features of this novel subpeptidome, and investigate its regulation by ERAP1. CRISPR-Cas9 was used to generate an HLA-ABC-triple knockout HeLa cell line (HeLa.ABC-KO), which was subsequently transduced to express HLA-B*51:01 (HeLa.ABC-KO.B51). ERAP1 was silenced using lentiviral shRNA. Peptides bound to HLA-B*51:01 were eluted and analyzed by mass spectrometry. The characteristics of non-Pro/Ala2, Pro2, and Ala2 peptides and their alteration by ERAP1 silencing were investigated. Effects of ERAP1 silencing on cell surface expression of HLA-B*51:01 were studied using flow cytometry. More than 20% of peptides eluted from HLA-B*51:01 lacked Pro or Ala at P2. This unconventional group of HLA-B*51:01-bound peptides was relatively enriched for 8-mers (with relatively fewer 9-mers) compared with the Pro2 and Ala2 subpeptidomes and had similar N-terminal and C-terminal residue usages to Ala2 peptides (with the exception of the less abundant leucine at position ). Knockdown of ERAP1 increased the percentage of non-Pro/Ala2 from 20% to ~40%, increased the percentage of longer (10-mer and 11-mer) peptides eluted from HLA-B*51:01 complexes, and abrogated the predominance of leucine at P1. Interestingly knockdown of ERAP1 altered the length and N-terminal residue usage of non-Ala2&Pro2 and Ala2 but not the Pro2 peptides. Finally, ERAP1 silencing regulated the expression levels of cell surface HLA-B*51 in a cell-type-dependent manner. In conclusion, we have used a novel methodology to identify an unconventional but surprisingly abundant non-Pro/Ala2 HLA-B*51:01 subpeptidome. It is increased by knockdown of ERAP1, a gene affecting the risk of developing BD. This has implications for theories of disease pathogenesis.

Edward A Dennis
Apr 28, 2020; 0:jlr.T120000868v1-jlr.T120000868
Tribute

Niemann-Pick disease, type C1 (NPC1) is a lipid storage disorder in which cholesterol and glycosphingolipids accumulate in late endosomal/lysosomal compartments because of mutations in the NPC1 gene. A hallmark of NPC1 is progressive neurodegeneration of the cerebellum as well as visceral organ damage; however, the mechanisms driving this disease pathology are not fully understood. Phosphoinositides are phospholipids that play distinct roles in signal transduction and vesicle trafficking. Here, we utilized consensus spectra analysis of MS imaging datasets and orthogonal LC–MS analyses to evaluate the spatial distribution of phosphoinositides and quantify them in cerebellar tissue from Npc1-null mice. Our results suggest significant depletion of multiple phosphoinositide species, including phosphatidylinositol (PI), phosphatidylinositol monophosphate (PIP), and bisphosphate (PIP2), in the cerebellum of the Npc1-null mice in both whole-tissue lysates and myelin-enriched fractions. Additionally, we observed altered levels of the regulatory enzyme phosphatidylinositol 4-kinase type 2 α (PI4K2A) in Npc1-null mice. In contrast, the levels of related kinases, phosphatases, and transfer proteins were unaltered in the Npc1-null mouse model as observed by Western blot analysis. Our discovery of phosphoinositide lipid biomarkers for NPC1 opens new perspectives on the pathophysiology underlying this fatal neurodegenerative disease.

Vitamin A aldehyde covalently bound to opsin protein is embedded in a phospholipid-rich membrane that supports photon absorption and phototransduction in photoreceptor cell outer segments. Following absorption of a photon, the 11-cis-retinal chromophore of visual pigment in photoreceptor cells isomerizes to all-trans-retinal. To maintain photosensitivity 11-cis-retinal must be replaced. At the same time, however, all-trans-retinal has to be handled so as to prevent nonspecific aldehyde activity. Some molecules of retinaldehyde upon release from opsin are efficiently reduced to retinol. Other molecules are released into the lipid phase of the disc membrane where they form a conjugate (N-retinylidene-PE, NRPE) through a Schiff base linkage with phosphatidylethanolamine (PE). The reversible formation of NRPE serves as a transient sink for retinaldehyde that is intended to return retinaldehyde to the visual cycle. However, if instead of hydrolyzing to PE and retinaldehyde, NRPE reacts with a second molecule of retinaldehyde a synthetic pathway is initiated that leads to the formation of multiple species of unwanted bisretinoid fluorophores. We report on recently identified members of the bisretinoid family some of which differ with respect to the acyl chains associated with the glycerol backbone. We discuss processing of the lipid moieties of these fluorophores in lysosomes of retinal pigment epithelial (RPE) cells, their fluorescence characters and new findings related to light and iron-associated oxidation of bisretinoids.

The human leucocyte antigen (HLA)-B*27:05 allele and the endoplasmic reticulum-resident aminopeptidases are strongly associated with ankylosing spondylitis (AS), a chronic inflammatory spondyloarthropathy. This study examined the effect of endoplasmic reticulum aminopeptidase 2 (ERAP2) in the generation of the natural HLA-B*27:05 ligandome in live cells. Complexes of HLA-B*27:05-bound peptide pools were isolated from human ERAP2-edited cell clones and the peptides were identified using high throughput mass spectrometry analyses. The relative abundance of thousand ligands was established by quantitative tandem mass spectrometry and bioinformatics analysis. The residue frequencies at different peptide position, identified in presence or absence of ERAP2, determined structural features of ligands and their interactions with specific pockets of antigen binding site of HLA-B*27:05 molecule. Sequence alignment of ligands identified with species of bacteria associated with HLA-B*27-dependent reactive arthritis was performed. In the absence of ERAP2, peptides with N-terminal basic residues, and minority canonical P2 residues are enriched in the natural ligandome. Further, alterations of residue frequencies and hydrophobicity profile at P3, P7, and P positions were detected. In addition, several ERAP2-dependent cellular peptides were highly similar to protein sequences of arthritogenic bacteria, including one human HLA-B*27:05 ligand fully conserved in a protein from Campylobacter jejuni. These findings highlight the pathogenic role of this aminopeptidase in the triggering of AS autoimmune disease.

Plasma lipoprotein (a) [Lp(a)] levels are largely determined by variation in the LPA gene, which codes for apo(a). Genome-wide association studies (GWASs) have identified nonsynonymous variants in LPA that associate with low Lp(a) levels, although their effect on apo(a) function is unknown. We investigated two such variants, R990Q and R1771C, which were present in four null Lp(a) individuals, for structural and functional effects. Sequence alignments showed the R990 and R1771 residues to be highly conserved and homologous to each other and to residues associated with plasminogen deficiency. Structural modeling showed both residues to make several polar contacts with neighboring residues that would be ablated on substitution. Recombinant expression of the WT and R1771C apo(a) in liver and kidney cells showed an abundance of an immature form for both apo(a) proteins. A mature form of apo(a) was only seen with the WT protein. Imaging of the recombinant apo(a) proteins in conjunction with markers of the secretory pathway indicated a poor transit of R1771C into the Golgi. Furthermore, the R1771C mutant displayed a glycosylation pattern consistent with ER, but not Golgi, glycosylation. We conclude that R1771 and the equivalent R990 residue facilitate correct folding of the apo(a) kringle structure and mutations at these positions prevent the proper folding required for full maturation and secretion. To our knowledge, this is the first example of nonsynonymous variants in LPA being causative of a null Lp(a) phenotype.

Glucagon secretion is regulated by circulating glucose, but it has turned out that amino acids also play an important role, and that hepatic amino acid metabolism and glucagon are linked in a mutual feed-back cycle, the liver-alpha cell axis. On this background, we hypothesized that hepatic steatosis might impair glucagon’s action on hepatic amino acid metabolism and lead to hyperaminoacidemia and hyperglucagonemia.

We subjected 15 healthy lean and 15 obese steatotic male participants to a pancreatic clamp with somatostatin and evaluated hepatic glucose and amino acid metabolism during basal and high physiological levels of glucagon. The degree of steatosis was evaluated from liver biopsies.

Total RNA sequencing of liver biopsies revealed perturbations in the expression of genes predominantly involved in amino acid metabolism in the obese steatotic individuals. This group was also characterized by fasting hyperglucagonemia, hyperaminoacidemia and an absent lowering of amino acid levels in response to high levels of glucagon. Endogenous glucose production was similar between lean and obese individuals.

Our results suggest that hepatic steatosis causes resistance to the effect of glucagon on amino acid metabolism resulting in increased amino acid concentrations as well as increased glucagon secretion providing a likely explanation of fatty liver-associated hyperglucagonemia.

Diabetic retinopathy (DR) is diagnosed clinically by directly viewing retinal vascular changes during ophthalmoscopy or through fundus photographs. However, electroretinography (ERG) studies in humans and rodents have revealed that retinal dysfunction is demonstrable prior to the development of visible vascular defects. Specifically, delays in dark-adapted ERG oscillatory potential (OP) implicit times in response to dim flash stimuli (<-1.8 log cd·s/m²) occur prior to clinically-recognized diabetic retinopathy. Animal studies suggest that retinal dopamine deficiency underlies these early functional deficits. Here, we randomized persons with diabetes, without clinically detectable retinopathy, to treatment with either low or high dose Sinemet (levodopa plus carbidopa) for 2 weeks and compared their ERG findings with those of control (no DM) subjects. We assessed dim flash stimulated OP delays using a novel hand-held ERG system (RETeval) at baseline, 2 and 4 weeks. RETeval recordings identified significant OP implicit-time delays in persons with diabetes without retinopathy compared to age-matched controls (p<0.001). After two weeks of Sinemet treatment, OP implicit times were restored to control values, and these improvements persisted even after a two-week washout. We conclude that detection of dim flash OP delays could provide early detection of DR, and that Sinemet treatment may reverse retinal dysfunction.

Branched chain amino acids (BCAAs) are associated with the progression of obesity-related metabolic disorders, including T2DM and non-alcoholic fatty liver disease. However, whether BCAAs disrupt the homeostasis of hepatic glucose and lipid metabolism remains unknown. In this study, we observed that BCAAs supplementation significantly reduced high-fat (HF) diet-induced hepatic lipid accumulation while increasing the plasma lipid levels and promoting muscular and renal lipid accumulation. Further studies demonstrated that BCAAs supplementation significantly increased hepatic gluconeogenesis and suppressed hepatic lipogenesis in HF diet-induced obese (DIO) mice. These phenotypes resulted from severe attenuation of Akt2 signaling via mTORC1- and mTORC2-dependent pathways. BCAAs/branched-chain α-keto acids (BCKAs) chronically suppressed Akt2 activation through mTORC1 and mTORC2 signaling and promoted Akt2 ubiquitin-proteasome-dependent degradation through the mTORC2 pathway. Moreover, the E3 ligase Mul1 played an essential role in BCAAs/BCKAs-mTORC2-induced Akt2 ubiquitin-dependent degradation. We also demonstrated that BCAAs inhibited hepatic lipogenesis by blocking Akt2/SREBP1/INSIG2a signaling and increased hepatic glycogenesis by regulating Akt2/Foxo1 signaling. Collectively, these data demonstrate that in DIO mice, BCAAs supplementation resulted in serious hepatic metabolic disorder and severe liver insulin resistance: insulin failed to not only suppress gluconeogenesis but also activate lipogenesis. Intervening BCAA metabolism is a potential therapeutic target for severe insulin-resistant disease.

HLA-DQA1 and -DQB1 are strongly associated with type 1 diabetes (T1D), and DQ8.1 and DQ2.5 are major risk haplotypes. Next generation targeted sequencing of HLA-DQA1 and -DQB1 in Swedish newly diagnosed 1-18 year-old patients (n=962) and controls (n=636) was used to construct abbreviated DQ haplotypes, converted into amino acid (AA) residues, and assessed for their associations with T1D. A hierarchically-organized haplotype (HOH) association analysis, allowed 45 unique DQ haplotypes to be categorized into seven clusters. The DQ8/9 cluster included two DQ8.1 risk and the DQ9 resistant haplotypes, and the DQ2 cluster, included the DQ2.5 risk and DQ2.2 resistant haplotypes. Within each cluster, HOH found residues α44Q (OR 3.29, p=2.38*10^-85 ) and β57A (OR 3.44, p=3.80*10^-84) to be associated with T1D in the DQ8/9 cluster representing all ten residues (α22, α23, α44, α49, α51, α53, α54, α73, α184, β57) due to complete linkage-disequilibrium (LD) of α44 with eight such residues. Within the DQ2 cluster and due to LD, HOH analysis found α44C and β135D to share the risk for T1D (OR 2.10, p=1.96*10^-20). The motif "QAD" of α44, β57, and β135 captured the T1D risk association of DQ8.1 (OR 3.44, p=3.80*10^-84), the corresponding motif "CAD" captured the risk association of DQ2.5 (OR 2.10, p=1.96*10^-20). Two risk associations were related to GADA and IA-2A, but in opposite directions. "CAD" was positively associated with GADA (OR 1.56; p=6.35*10^-8) but negatively with IA-2A (OR 0.59, p= 6.55*10^-11). "QAD" was negatively associated with GADA (OR 0.88; p= 3.70*10^-3) but positively with IA-2A (OR 1.64; p= 2.40*10^-14), despite a single difference at α44. The residues are found in and around anchor pockets 1 and 9, as potential TCR contacts, in the areas for CD4 binding and putative homodimer formation. The identification of three HLA-DQ AA (α44, β57, β135) conferring T1D risk should sharpen functional and translational studies.

Conceivably, upregulation of myo-inositol oxygenase (MIOX) is associated with altered cellular redox. Its promoter includes oxidant-response elements, and we also discovered binding sites for XBP-1, a transcription factor of ER stress response. Previous studies indicate that MIOX’s upregulation in acute tubular injury is mediated by oxidant and ER stress. Here, we investigated if hyperglycemia leads to accentuation of oxidant and ER stress, while boosting each other’s activities and thereby augmenting tubulo-interstitial injury/fibrosis. We generated MIOX-overexpressing transgenic (MIOX-TG) and -knockout (MIOX-KO) mice. A diabetic state was induced by streptozotocin administration. Also, MIOX-KO were crossbred with Ins2^Akita to generate Ins2^Akita/KO mice. MIOX-TG mice had worsening renal functions with kidneys having increased oxidant/ER stress, as reflected by DCF/DHE staining, perturbed NAD/NADH and GSH/GSSG ratios, increased NOX-4 expression, apoptosis and its executionary molecules, accentuation of TGF-β signaling, Smads and XBP-1 nuclear translocation, expression of GRP78 and XBP1 (ER stress markers) and accelerated tubulo-interstitial fibrosis. These changes were not seen in MIOX-KO mice. Interestingly, such changes were remarkably reduced in Ins2^Akita/KO mice, and likewise in vitro experiments with XBP1-siRNA. These findings suggest that MIOX expression accentuates while its deficiency shields kidneys from tubulo-interstitial injury by dampening oxidant and ER stress, which mutually enhance each other’s activity.

The transcription factor forkhead box P3 (FOXP3) is a biomarker for regulatory T cells and can also be expressed in cancer cells, but its function in cancer appears to be divergent. The role of hepatocyte-expressed FOXP3 in hepatocellular carcinoma (HCC) is unknown. Here, we collected tumor samples and clinical information from 115 HCC patients and used five human cancer cell lines. We examined FOXP3 mRNA sequences for mutations, used a luciferase assay to assess promoter activities of FOXP3's target genes, and employed mouse tumor models to confirm in vitro results. We detected mutations in the FKH domain of FOXP3 mRNAs in 33% of the HCC tumor tissues, but in none of the adjacent nontumor tissues. None of the mutations occurred at high frequency, indicating that they occurred randomly. Notably, the mutations were not detected in the corresponding regions of FOXP3 genomic DNA, and many of them resulted in amino acid substitutions in the FKH region, altering FOXP3's subcellular localization. FOXP3 delocalization from the nucleus to the cytoplasm caused loss of transcriptional regulation of its target genes, inactivated its tumor-inhibitory capability, and changed cellular responses to histone deacetylase (HDAC) inhibitors. More complex FKH mutations appeared to be associated with worse prognosis in HCC patients. We conclude that mutations in the FKH domain of FOXP3 mRNA frequently occur in HCC and that these mutations are caused by errors in transcription and are not derived from genomic DNA mutations. Our results suggest that transcriptional mutagenesis of FOXP3 plays a role in HCC.

The actin cytoskeleton is extremely dynamic and supports diverse cellular functions in many physiological and pathological processes, including tumorigenesis. However, the mechanisms that regulate the actin-related protein 2/3 (ARP2/3) complex and thereby promote actin polymerization and organization in cancer cells are not well-understood. We previously implicated the proline-rich 11 (PRR11) protein in lung cancer development. In this study, using immunofluorescence staining, actin polymerization assays, and siRNA-mediated gene silencing, we uncovered that cytoplasmic PRR11 is involved in F-actin polymerization and organization. We found that dysregulation of PRR11 expression results in F-actin rearrangement and nuclear instability in non-small cell lung cancer cells. Results from molecular mechanistic experiments indicated that PRR11 associates with and recruits the ARP2/3 complex, facilitates F-actin polymerization, and thereby disrupts the F-actin cytoskeleton, leading to abnormal nuclear lamina assembly and chromatin reorganization. Inhibition of the ARP2/3 complex activity abolished irregular F-actin polymerization, lamina assembly, and chromatin reorganization due to PRR11 overexpression. Notably, experiments with truncated PRR11 variants revealed that PRR11 regulates F-actin through different regions. We found that deletion of either the N or C terminus of PRR11 abrogates its effects on F-actin polymerization and nuclear instability and that deletion of amino acid residues 100–184 or 100–200 strongly induces an F-actin structure called the actin comet tail, not observed with WT PRR11. Our findings indicate that cytoplasmic PRR11 plays an essential role in regulating F-actin assembly and nuclear stability by recruiting the ARP2/3 complex in human non-small cell lung carcinoma cells.

We previously reported that overexpression of cytochrome P450 family 24 subfamily A member 1 (CYP24A1) increases lung cancer cell proliferation by activating RAS signaling and that CYP24A1 knockdown inhibits tumor growth. However, the mechanism of CYP24A1-mediated cancer cell proliferation remains unclear. Here, we conducted cell synchronization and biochemical experiments in lung adenocarcinoma cells, revealing a link between CYP24A1 and anaphase-promoting complex (APC), a key cell cycle regulator. We demonstrate that CYP24A1 expression is cell cycle–dependent; it was higher in the G2-M phase and diminished upon G1 entry. CYP24A1 has a functional destruction box (D-box) motif that allows binding with two APC adaptors, CDC20-homologue 1 (CDH1) and cell division cycle 20 (CDC20). Unlike other APC substrates, however, CYP24A1 acted as a pseudo-substrate, inhibiting CDH1 activity and promoting mitotic progression. Conversely, overexpression of a CYP24A1 D-box mutant compromised CDH1 binding, allowing CDH1 hyperactivation, thereby hastening degradation of its substrates cyclin B1 and CDC20, and accumulation of the CDC20 substrate p21, prolonging mitotic exit. These activities also occurred with a CYP24A1 isoform 2 lacking the catalytic cysteine (Cys-462), suggesting that CYP24A1's oncogenic potential is independent of its catalytic activity. CYP24A1 degradation reduced clonogenic survival of mutant KRAS-driven lung cancer cells, and calcitriol treatment increased CYP24A1 levels and tumor burden in Lsl-KRASG12D mice. These results disclose a catalytic activity-independent growth-promoting role of CYP24A1 in mutant KRAS-driven lung cancer. This suggests that CYP24A1 could be therapeutically targeted in lung cancers in which its expression is high.

The transfer of a phosphate from ATP to a protein substrate, a modification known as protein phosphorylation, is catalyzed by protein kinases. Protein kinases play a crucial role in virtually every cellular activity. Recent studies of atypical protein kinases have highlighted the structural similarity of the kinase superfamily despite notable differences in primary amino acid sequence. Here, using a bioinformatics screen, we searched for putative protein kinases in the intracellular bacterial pathogen Legionella pneumophila and identified the type 4 secretion system effector Lpg2603 as a remote member of the protein kinase superfamily. Employing an array of biochemical and structural biology approaches, including in vitro kinase assays and isothermal titration calorimetry, we show that Lpg2603 is an active protein kinase with several atypical structural features. Importantly, we found that the eukaryote-specific host signaling molecule inositol hexakisphosphate (IP6) is required for Lpg2603 kinase activity. Crystal structures of Lpg2603 in the apo-form and when bound to IP6 revealed an active-site rearrangement that allows for ATP binding and catalysis. Our results on the structure and activity of Lpg2603 reveal a unique mode of regulation of a protein kinase, provide the first example of a bacterial kinase that requires IP6 for its activation, and may aid future work on the function of this effector during Legionella pathogenesis.

Philip Newsholme
Dec 1, 2006; 55:S39-S47
Section II: The Muscle and Liver Connections

Ralph A. DeFronzo
Apr 1, 2009; 58:773-795
Banting Lecture

The Earthquake Unit at the University of the West Indies is reporting that a minor quake hit a section of Portland this morning. The unit says the 2.8 quake occurred about 9:13 and had an epicentre near Spring Garden. It had a focal depth of five...

The Orioles' crowded outfield mix gained another member on Monday when the team signed veteran Eric Young Jr. to a Minor League contract with an invitation to Spring Training.

Patients who experience chronic rhinosinusitis may way for a considerable period of time before presenting, because they believe the condition to be trivial. In this podcast, Alam Hannan, ENT Consultant at the Royal Throat Nose and Ear Hospital in London, explains why that belief is not founded, and describes which treatments can be effective at...

Cannabinoid hyperemesis syndrome is a relatively newly recognised condition - but, according to one study, can account for up to 6% of patients presenting to emergency departments. The causal mechanism is as yet unclear - but currently the only known way to prevent the syndrome is for the patient to stop their cannabis use. Yaniv Chocron, chief...

Ralph A. DeFronzo
Apr 1, 2009; 58:773-795
Banting Lecture

Andreas Festa
Apr 1, 2002; 51:1131-1137
Complications

The Diabetes Control and Complications Trial Research Group
Aug 1, 1995; 44:968-983
Original Article

Upon the passing of his physical on Tuesday, the Reds signed infielder/outfielder Derek Dietrich to a Minor League contract with an invitation to big league camp for Spring Training.

Incretin hormone dysregulation contributes to reduced insulin secretion and hyperglycemia in patients with type 2 diabetes mellitus (T2DM). Resistance to glucose-dependent insulinotropic polypeptide (GIP) action may occur through desensitization or downregulation of β-cell GIP receptors (GIP-R). Studies in rodents and cell lines show GIP-R expression can be regulated through peroxisome proliferator–activated receptor (PPAR) response elements (PPREs). Whether this occurs in humans is unknown. To test this, we conducted a randomized, double-blind, placebo-controlled trial of pioglitazone therapy on GIP-mediated insulin secretion and adipocyte GIP-R expression in subjects with well-controlled T2DM. Insulin sensitivity improved, but the insulinotropic effect of infused GIP was unchanged following 12 weeks of pioglitazone treatment. In parallel, we observed increased GIP-R mRNA expression in subcutaneous abdominal adipocytes from subjects treated with pioglitazone. Treatment of cultured human adipocytes with troglitazone increased PPAR binding to GIP-R PPREs. These results show PPAR agonists regulate GIP-R expression through PPREs in human adipocytes, but suggest this mechanism is not important for regulation of the insulinotropic effect of GIP in subjects with T2DM. Because GIP has antilipolytic and lipogenic effects in adipocytes, the increased GIP-R expression may mediate accretion of fat in patients with T2DM treated with PPAR agonists.

Diabetic retinopathy (DR) is a widespread vision-threatening disease, and neuroretinal abnormality should be considered as an important problem. Brain-derived neurotrophic factor (BDNF) has recently been considered as a possible treatment to prevent DR-induced neuroretinal damage, but how BDNF is upregulated in DR remains unclear. We found an increase in hydrogen peroxide (H₂O₂) in the vitreous of patients with DR. We confirmed that human retinal endothelial cells secreted H₂O₂ by high glucose, and H₂O₂ reduced cell viability of MIO-M1, Müller glia cell line, PC12D, and the neuronal cell line and lowered BDNF expression in MIO-M1, whereas BDNF administration recovered PC12D cell viability. Streptozocin-induced diabetic rats showed reduced BDNF, which is mainly expressed in the Müller glia cell. Oral intake of eicosapentaenoic acid ethyl ester (EPA-E) ameliorated BDNF reduction and oscillatory potentials (OPs) in electroretinography (ERG) in DR. Mass spectrometry revealed an increase in several EPA metabolites in the eyes of EPA-E–fed rats. In particular, an EPA metabolite, 18-hydroxyeicosapentaenoic acid (18-HEPE), induced BDNF upregulation in Müller glia cells and recovery of OPs in ERG. Our results indicated diabetes-induced oxidative stress attenuates neuroretinal function, but oral EPA-E intake prevents retinal neurodegeneration via BDNF in Müller glia cells by increasing 18-HEPE in the early stages of DR.

Type 2 diabetes accounts for 90% of the population with diabetes, and these patients are generally obese and hyperlipidemic. In addition to hyperglycemia, hyperlipidemia is also closely related with diabetic retinopathy. The aim was to investigate retinopathy in a model closely mimicking the normal progression and metabolic features of the population with type 2 diabetes and elucidate the molecular mechanism. Retinopathy was evaluated in rats fed a 45% kcal as fat diet for 8 weeks before administering streptozotocin, 30 mg/kg body weight (T2D), and compared with age- and duration-matched type 1 diabetic rats (T1D) (60 mg/kg streptozotocin). The role of epigenetic modifications in mitochondrial damage was evaluated in retinal microvasculature. T2D rats were obese and severely hyperlipidemic, with impaired glucose and insulin tolerance compared with age-matched T1D rats. While at 4 months of diabetes, T1D rats had no detectable retinopathy, T2D rats had significant retinopathy, their mitochondrial copy numbers were lower, and mtDNA and Rac1 promoter DNA methylation was exacerbated. At 6 months, retinopathy was comparable in T2D and T1D rats, suggesting that obesity exaggerates hyperglycemia-induced epigenetic modifications, accelerating mitochondrial damage and diabetic retinopathy. Thus, maintenance of good lifestyle and BMI could be beneficial in regulating epigenetic modifications and preventing/retarding retinopathy in patients with diabetes.

Treatment of patients with advanced medullary thyroid carcinoma (MTC) is still a challenge. For more than 2 decades, it has been known that the cholecystokinin 2 receptor is a promising target for the treatment of MTC with radiolabeled minigastrin analogs. Unfortunately, kidney toxicity has precluded their therapeutic application so far. In 6 consecutive patients, we evaluated with advanced 3-dimensional dosimetry whether improved minigastrin analog ¹⁷⁷Lu-DOTA-(d-Glu)₆-Ala-Tyr-Gly-Trp-Nle-Asp-PheNH₂ (¹⁷⁷Lu-PP-F11N) is a suitable agent for the treatment of MTC. Methods: Patients received 2 injections of about 1 GBq (~80 μg) of ¹⁷⁷Lu-PP-F11N with and without a solution of succinylated gelatin (SG, a plasma expander used for nephroprotection) in a random crossover sequence to evaluate biodistribution, pharmacokinetics, and tumor and organ dosimetry. An electrocardiogram was obtained and blood count and blood chemistry were measured up to 12 wk after the administration of ¹⁷⁷Lu-PP-F11N to assess safety. Results: In all patients, ¹⁷⁷Lu-PP-F11N accumulation was visible in tumor tissue, stomach, and kidneys. Altogether, 13 tumors were eligible for dosimetry. The median absorbed doses for tumors, stomach, kidneys, and bone marrow were 0.88 (interquartile range [IQR]: 0.85–1.04), 0.42 (IQR: 0.25–1.01), 0.11 (IQR: 0.07–0.13), and 0.028 (IQR: 0.026–0.034) Gy/GBq, respectively. These doses resulted in median tumor-to-kidney dose ratios of 11.6 (IQR: 8.11–14.4) without SG and 13.0 (IQR: 10.2–18.6) with SG; these values were not significantly different (P = 1.0). The median tumor-to-stomach dose ratio was 3.34 (IQR: 1.14–4.70). Adverse reactions (mainly hypotension, flushing, and hypokalemia) were self-limiting and not higher than grade 1. Conclusion: ¹⁷⁷Lu-PP-F11N accumulates specifically in MTC at a dose that is sufficient for a therapeutic approach. With a low kidney and bone marrow radiation dose, ¹⁷⁷Lu-PP-F11N shows a promising biodistribution. The dose-limiting organ is most likely the stomach. Further clinical studies are necessary to evaluate the maximum tolerated dose and the efficacy of ¹⁷⁷Lu-PP-F11N.

The signal peptide of preproinsulin is a major source for HLA class I autoantigen epitopes implicated in CD8 T cell (CTL)–mediated β-cell destruction in type 1 diabetes (T1D). Among them, the 10-mer epitope located at the C-terminal end of the signal peptide was found to be the most prevalent in patients with recent-onset T1D. While the combined action of signal peptide peptidase and endoplasmic reticulum (ER) aminopeptidase 1 (ERAP1) is required for processing of the signal peptide, the mechanisms controlling signal peptide trimming and the contribution of the T1D inflammatory milieu on these mechanisms are unknown. Here, we show in human β-cells that ER stress regulates ERAP1 gene expression at posttranscriptional level via the IRE1α/miR-17-5p axis and demonstrate that inhibition of the IRE1α activity impairs processing of preproinsulin signal peptide antigen and its recognition by specific autoreactive CTLs during inflammation. These results underscore the impact of ER stress in the increased visibility of β-cells to the immune system and position the IRE1α/miR-17 pathway as a central component in β-cell destruction processes and as a potential target for the treatment of autoimmune T1D.

Invitation Only Research Event

Event participants

Professor Keun-Wook Paik, Associate Fellow, Energy, Environment and Resources Department, Chatham House
Chair: John Lough, Associate Fellow, Russia and Eurasia Programme, Chatham House

The actin cytoskeleton is extremely dynamic and supports diverse cellular functions in many physiological and pathological processes, including tumorigenesis. However, the mechanisms that regulate the actin-related protein 2/3 (ARP2/3) complex and thereby promote actin polymerization and organization in cancer cells are not well-understood. We previously implicated the proline-rich 11 (PRR11) protein in lung cancer development. In this study, using immunofluorescence staining, actin polymerization assays, and siRNA-mediated gene silencing, we uncovered that cytoplasmic PRR11 is involved in F-actin polymerization and organization. We found that dysregulation of PRR11 expression results in F-actin rearrangement and nuclear instability in non-small cell lung cancer cells. Results from molecular mechanistic experiments indicated that PRR11 associates with and recruits the ARP2/3 complex, facilitates F-actin polymerization, and thereby disrupts the F-actin cytoskeleton, leading to abnormal nuclear lamina assembly and chromatin reorganization. Inhibition of the ARP2/3 complex activity abolished irregular F-actin polymerization, lamina assembly, and chromatin reorganization due to PRR11 overexpression. Notably, experiments with truncated PRR11 variants revealed that PRR11 regulates F-actin through different regions. We found that deletion of either the N or C terminus of PRR11 abrogates its effects on F-actin polymerization and nuclear instability and that deletion of amino acid residues 100–184 or 100–200 strongly induces an F-actin structure called the actin comet tail, not observed with WT PRR11. Our findings indicate that cytoplasmic PRR11 plays an essential role in regulating F-actin assembly and nuclear stability by recruiting the ARP2/3 complex in human non-small cell lung carcinoma cells.

Faced with a lack of employment opportunities and recurrent poverty, Albanian youth migrate to Italy alone in the hopes of improving their educational prospects or making money for their families. Yet upon arrival, they face many vulnerabilities. While some protections for unaccompanied minors exist in the Italy, the system is greatly fragmented and challenges, including how to return them to Albania, remain persistent.

In his first public address on his inaugural official visit to Washington, DC, IOM Director General António Vitorino discusses his vision for IOM; reforms in the UN system; coordination with other organizations in addressing humanitarian protection; and the operational steps IOM is taking to respond to forced migration and displacement.