Acidosis Acts through HSP90 in a PHD/VHL-Independent Manner to Promote HIF Function and Stem Cell Maintenance in Glioma

Hypoxia is a common feature of solid tumors, which controls multiple aspects of cancer progression. One important function of hypoxia and the hypoxia-inducible factors (HIF) is the maintenance of cancer stem-like cells (CSC), a population of tumor cells that possess stem cell-like properties and drives tumor growth. Among the changes promoted by hypoxia is a metabolic shift resulting in acidification of the tumor microenvironment. Here, we show that glioma hypoxia and acidosis functionally cooperate in inducing HIF transcription factors and CSC maintenance. We found that these effects did not involve the classical PHD/VHL pathway for HIF upregulation, but instead involved the stress-induced chaperone protein HSP90. Genetic or pharmacologic inactivation of HSP90 inhibited the increase in HIF levels and abolished the self-renewal and tumorigenic properties of CSCs induced by acidosis. In clinical specimens of glioma, HSP90 was upregulated in the hypoxic niche and was correlated with a CSC phenotype. Our findings highlight the role of tumor acidification within the hypoxic niche in the regulation of HIF and CSC function through HSP90, with implications for therapeutic strategies to target CSC in gliomas and other hypoxic tumors. Cancer Res; 76(19); 5845-56. ©2016 AACR.

Loss of PHD3 allows tumours to overcome hypoxic growth inhibition and sustain proliferation through EGFR

Solid tumours are exposed to microenvironmental factors such as hypoxia that normally inhibit cell growth. However, tumour cells are capable of counteracting these signals through mechanisms that are largely unknown. Here we show that the prolyl hydroxylase PHD3 restrains tumour growth in response to microenvironmental cues through the control of EGFR. PHD3 silencing in human gliomas or genetic deletion in a murine high-grade astrocytoma model markedly promotes tumour growth and the ability of tumours to continue growing under unfavourable conditions. The growth-suppressive function of PHD3 is independent of the established PHD3 targets HIF and NF-κB and its hydroxylase activity. Instead, loss of PHD3 results in hyperphosphorylation of epidermal growth factor receptor (EGFR). Importantly, epigenetic/genetic silencing of PHD3 preferentially occurs in gliomas without EGFR amplification. Our findings reveal that PHD3 inactivation provides an alternative route of EGFR activation through which tumour cells sustain proliferative signalling even under conditions of limited oxygen availability.

Little is known on how solid tumours overcome growth inhibitory signals within its hypoxic microenvironment. Here Henze et al. show that oxygen sensor PHD3 is frequently lost in gliomas, and that this loss hyperactivates EGFR signaling to sustain tumour cell proliferation and survival in hypoxia.

Protein kinase D2 is a novel regulator of glioblastoma growth and tumor formation

Glioblastoma multiforme, a highly aggressive tumor of the central nervous system, has a dismal prognosis that is due in part to its resistance to radio- and chemotherapy. The protein kinase C (PKC) family of serine threonine kinases has been implicated in the formation and proliferation of glioblastoma multiforme. Members of the protein kinase D (PKD) family, which consists of PKD1, -2 and, -3, are prominent downstream targets of PKCs and could play a major role in glioblastoma growth. PKD2 was highly expressed in both low-grade and high-grade human gliomas. The number of PKD2-positive tumor cells increased with glioma grading (P < .001). PKD2 was also expressed in CD133-positive glioblastoma stem cells and various glioblastoma cell lines in which the kinase was found to be constitutively active. Inhibition of PKDs by pharmacological inhibitors resulted in substantial inhibition of glioblastoma proliferation. Furthermore, specific depletion of PKD2 by siRNA resulted in a marked inhibition of anchorage-dependent and -independent proliferation and an accumulation of glioblastoma cells in G0/G1, accompanied by a down-regulation of cyclin D1 expression. In addition, PKD2-depleted glioblastoma cells exhibited substantially reduced tumor formation in vivo on chicken chorioallantoic membranes. These findings identify PKD2 as a novel mediator of glioblastoma cell growth in vitro and in vivo and thereby as a potential therapeutic target for this devastating disease.

Methyl-CpG binding domain protein 1 regulates localization and activity of Tet1 in a CXXC3 domain-dependent manner

Cytosine modifications diversify and structure the genome thereby controlling proper development and differentiation. Here, we focus on the interplay of the 5-methylcytosine reader Mbd1 and modifier Tet1 by analyzing their dynamic subcellular localization and the formation of the Tet oxidation product 5-hydroxymethylcytosine in mammalian cells. Our results demonstrate that Mbd1 enhances Tet1-mediated 5-methylcytosine oxidation. We show that this is due to enhancing the localization of Tet1, but not of Tet2 and Tet3 at heterochromatic DNA. We find that the recruitment of Tet1 and concomitantly its catalytic activity eventually leads to the displacement of Mbd1 from methylated DNA. Finally, we demonstrate that increased Tet1 heterochromatin localization and 5-methylcytosine oxidation are dependent on the CXXC3 domain of Mbd1, which recognizes unmethylated CpG dinucleotides. The Mbd1 CXXC3 domain deletion isoform, which retains only binding to methylated CpGs, on the other hand, blocks Tet1-mediated 5-methylcytosine to 5-hydroxymethylcytosine conversion, indicating opposite biological effects of Mbd1 isoforms. Our study provides new insights on how cytosine modifications, their modifiers and readers cross-regulate themselves.

Mutations in SMARCB1 and in other Coffin-Siris syndrome genes lead to various brain midline defects

Mutations in genes encoding components of BAF (BRG1/BRM-associated factor) chromatin remodeling complexes cause neurodevelopmental disorders and tumors. The mechanisms leading to the development of these two disease entities alone or in combination remain unclear. We generated mice with a heterozygous nervous system-specific partial loss-of-function mutation in a BAF core component gene, Smarcb1. These Smarcb1 mutant mice show various brain midline abnormalities that are also found in individuals with Coffin–Siris syndrome (CSS) caused by SMARCB1, SMARCE1, and ARID1B mutations and in SMARCB1-related intellectual disability (ID) with choroid plexus hyperplasia (CPH). Analyses of the Smarcb1 mutant animals indicate that one prominent midline abnormality, corpus callosum agenesis, is due to midline glia aberrations. Our results establish a novel role of Smarcb1 in the development of the brain midline and have important clinical implications for BAF complex-related ID/neurodevelopmental disorders.

Why and how mutations in genes encoding BAF complex components lead to distinct disease entitites remains unresolved. In this study, authors establish the first Smarcb1 mutant mouse model with multiple brain abnormalities recapitulating human Coffin–Siris syndrome and show that one prominent midline abnormality, corpus callosum agenesis, is due to midline glia aberrations.

Novel shuttling domain in a regulator (RSC1A1) of transporter SGLT1 steers cell cycle-dependent nuclear location

The gene product of RSC1A1, RS1, participates in the regulation of the Na(+)-D-glucose cotransporter SGLT1. RS1 inhibits release of SGLT1 from the trans Golgi network. In subconfluent LLC-PK(1) cells, RS1 migrates into the nucleus and modulates transcription of SGLT1, whereas most confluent cells do not contain RS1 in the nuclei. We showed that confluence-dependent nuclear location of RS1 is because of different phases of the cell cycle and identified a RS1 nuclear shuttling domain (RNS) with an associated protein kinase C (PKC) phosphorylation site (RNS-PKC) that mediates cell cycle-dependent nuclear location. RNS-PKC contains a novel non-conventional nuclear localization signal interacting with importin beta1, a nuclear export signal mediating export via protein CRM1 and a Ca(2+)-dependent calmodulin binding site. PKC and calmodulin compete for binding to RNS-PKC. Mutagenesis experiments and analyses of the phosphorylation status suggest the following sequences of events. Subconfluent cells without and with synchronization to the G2/M phase contain non-phosphorylated RNS-PKC that mediates nuclear import of RS1 but not its export. During confluence or synchronization of subconfluent cells to the G2/M phase, phosphorylation of RNS-PKC mediates rapid nuclear export of RS1.

Patient adherence to statin therapy within 12 months after coronary stenting depending on regular or remote monitoring

Funding Acknowledgements

Type of funding sources: Other. Main funding source(s): Russian Ministry of Health

Background. Low adherence to statins remains a challenge in the treatment of patients with cardiovascular diseases. Some patients who underwent coronary stenting (CS) are unavailable for regular follow-up with outpatient visits. The ability to remotely monitor patients after CS may facilitate adherence to treatment, achieve target low density lipoprotein (LDL) cholesterol levels and early detection of adverse events. We aimed to evaluate the adherence to statin therapy in patients after CS receiving remote monitoring or care with outpatient visits.

Methods. We enrolled 279 consecutive stable CAD/silent myocardial ischemia patients (61.5 ± 9.5 years) who underwent CS. The patients were randomized into groups of regular outpatient visits (group 1, n = 96), remote monitoring (group 2, n = 95) and control group (group 3, n = 88). The visits (cardio exam and blood testing) and remote monitoring (videoconference, telephone care and blood tests interpretation) were performed at 1, 3, 6 and 12 months after CS for groups 1 and 2. Patients in the control group were cared by a physician at the residence place, the contact with the study coordinator was performed at baseline and 12 months after CS. Adherence to the prescribed medical therapy based on the four-item Morisky Green Levine Medication Adherence Scale was assessed at each contact with the study coordinator.

Results. Patient adherence to statin therapy 12 months after CS was 53.6% for group 1, 55.8% for group 2 and 24.4% for group 3 (p &lt; 0.05 for group 3 versus groups 1 and 2). In group 1 26.9/36.5/31.7/37.4*/41.3*% of patients achieved target LDL level at baseline/1mo/3mo/6mo/12mo, respectively (р&lt;0.05 vs. baseline). In group 2 - 35.8/36.8/40.0/51.6*/57.9*% of patients (р&lt;0.05 vs. baseline). In group 3 25.5/28.2% of patients achieved target LDL level at baseline/12mo, respectively. The significant decrease in LDL cholesterol levels between baseline and 12mo values was observed in groups 1 and 2 (p &lt; 0.05). No differences were observed in group 3.

Conclusion. The groups of patients receiving remote monitoring or care with outpatient visits demonstrate the same increase in the proportion of patients that achieved target LDL cholesterol levels within 12 months after CS. The remote monitoring is a safe strategy for improving and maintaining the adherence to statins in patients after CS.

Enrichment of FGF8-expressing cells from neurally induced human pluripotent stem cell cultures

In early vertebrate development, organizer regions-groups of cells that signal to and thereby influence neighboring cells by secreted morphogens-play pivotal roles in the establishment and maintenance of cell identities within defined tissue territories. The midbrain-hindbrain organizer drives regionalization of neural tissue into midbrain and hindbrain territories with fibroblast growth factor 8 (FGF8) acting as a key morphogen. This organizer has been extensively studied in chicken, mouse, and zebrafish. Here, we demonstrate the enrichment of FGF8-expressing cells from human pluripotent stem cells (hPSCs), cultured as attached embryoid bodies using antibodies that recognize "Similar Expression to Fgf" (SEF) and Frizzled proteins. The arrangement of cells in embryoid body subsets of these cultures and the gene expression profile of the FGF8-expressing population show certain similarities to the midbrain-hindbrain organizer in animal models. In the embryonic chick brain, the enriched cell population induces formation of midbrain structures, consistent with FGF8-organizing capability.

Aging is accompanied by a decrease in the number of naive Tregs

Funding Acknowledgements

Type of funding sources: None.

Background. Age-related changes in the immune system are an important factor contributing to the maintenance of chronic inflammatory status. There are undoubted data on the decrease of the number of T-lymphocytes with age caused by thymus involution, but there are currently no unambiguous data on changes of minor T-cell subpopulations, in particular, regulatory T-cells (Treg). The aim of this study was to analyze the content of effector and regulatory CD4+ T cell subsets in patients with coronary and/or carotid atherosclerosis depending on age.

Methods. 111 patients (men, median age 63 (55;69)) with coronary and/or carotid atherosclerosis, without smoking anamnesis, were enrolled.  Mononuclear leuocytes were isolated from blood by gradient centrifugation, and CD4 + CD25high and CD4 + Foxp3+ Treg, CD4 + IL17+ T-helpers (Th) 17 and CD4 + INFγ Th1 were evaluated by direct immunofluorescence and flow cytometry. For intracellular cytokine detection cells were pre-activated in vitro in the presence of PMA/ionomycin/brefeldin A. In 74 patients cells were additionally stained with CD39, CD278, CD45RA Mabs to reveal naïve and primed T-cells.

Results. According to age the patients formed three groups: I – &lt;55 y.o. (n = 23), II – 55-64 y.o. (n = 42), III - ≥65 y.o. (n = 46). All patients were taking statins at baseline. The groups were comparable in traditional risk factors of CVD (BMI, arterial hypertension, diabetes mellitus, previous myocardial infarction anamnesis). The absolute content of CD4+ T cells was lower in group III (646.3 (516.0;806.4)) compared to groups I (903.0 (585.6;1113.8), p = 0.03) and II (745.4 (502.2;924.0), p = 0.06). The absolute content of CD4 + CD25high Treg was lower in group III (24.2 (18.4;35.2)) compared to groups I (35.0 (28.7;54.4), p = 0.01) and II (31.0 (21.1;43.6), p = 0.03). There were no differences in Th1, Th17, CD39 + CD45RA- and CD278+ Treg content between groups. A negative correlation was found between age and the content of CD4+ T cells (r= -0.28), CD4 + CD25high Treg (r= -0.27), p &lt; 0.05. A negative correlation was found between age and CD4 + CD25highCD45RA+ Treg (r= -0.24) and CD4 + CD45RA+ T cells (r= -0.36), CD4 + CD45RA+/CD4 + CD45RA- T-cells ratio (r= -0.24), p &lt; 0.05.

Conclusion. Here we demonstrate an age-dependent decrease of total CD4+ T cell population and Treg subset in patients with atherosclerosis. The changes observed were primary due to the deficiency of CD45RA+ naïve T cells. The effector cell Th1 and Th17 quantities were at the same levels. Future research will show whether the identified immunological patterns can contribute to the progression of atherosclerosis and other chronic inflammatory diseases.

Surfactant-driven optimization of iron-based nanoparticle synthesis: a study on magnetic hyperthermia and endothelial cell uptake

This work examines the effect of changing the ratio of different surfactants in single-core iron-based nanoparticles with respect to their specific absorption rate in the context of magnetic hyperthermia and cellular uptake by human umbilical vein endothelial cells (HUVEC). Three types of magnetic nanoparticles were synthesized by separately adding oleic acid or oleylamine or a mixture of both (oleic acid/oleylamine) as surfactants. A carefully controlled thermal decomposition synthesis process led to monodispersed nanoparticles with a narrow size distribution. Spherical-shaped nanoparticles were mainly obtained for those synthesized with oleic acid, while the shape changed upon adding oleylamine. The combined use of oleic acid and oleylamine as surfactants in single-core iron-based nanoparticles resulted in a substantial saturation magnetization, reaching up to 140 A m2 kg-1 at room temperature. The interplay between these surfactants played a crucial role in achieving this high magnetic saturation. By modifying the surface of the magnetic nanoparticles using a mixture of two surfactants, the magnetic fluid hyperthermia heating rate was significantly improved compared to using a single surfactant type. This improvement can be attributed to the larger effective anisotropy achieved through the modification with both (oleic acid/oleylamine). The mixture of surfactants enhances the control of interparticle distance and influences the strength of dipolar interactions, ultimately leading to enhanced heating efficiency. Functionalization of the oleic acid-coated nanoparticles with trimethoxysilane results in the formation of a core-shell structure Fe@Fe3O4, showing exchange bias (EB) associated with the exchange anisotropy between the shell and the core. The biomedical relevance of our synthesized Fe@Fe3O4 nanoparticles was demonstrated by their efficient uptake by human umbilical vein endothelial cells (HUVECs) in a concentration-dependent manner. This remarkable cellular uptake highlights the potential of these nanoparticles in biomedical applications.

Association of elevated lipoprotein(a) level and monocyte subsets with the severity of coronary atherosclerosis

Background

Chronic inflammation associated with the uncontrolled activation of innate and acquired immunity plays a fundamental role at all stages of atherogenesis. Monocytes are a heterogeneous population, and each subset contributes differently to the inflammatory process. High level of lipoprotein(a) [Lp(a)] is a proven atherosclerotic cardiovascular disease (ASCVD) risk factor. The aim of the study was to investigate the association between the increased concentration of Lp(a) and monocyte subsets in patients with different severity of coronary atherosclerosis.

Methods

150 patients (124 males (82.6%)), median age 60 (54; 65) years undergoing coronary angiography were enrolled. Lipids, Lp(a) were assessed by enzyme immunoassay. Monocyte subpopulations (classical CD14++CD16-, intermediate CD14++CD16+, non-classical CD14+CD16++) were analyzed by direct immunofluorescence and flow cytometry.

Results

The patients were divided into two groups depending on the Lp(a) concentration: normal Lp(a) &lt;30 mg/dl (n=82) and hyperLp(a) ≥30 mg/dl (n=68). Patients of both groups were comparable in routine ASCVD risk factors (age, BMI, arterial hypertension, previous myocardial infarction, smoking, lipids). In patients with hyperLp(a) the content (absolute and relative) of non-classical CD14+CD16++ monocytes was higher (71.0 (56.6; 105.7 1000/ml vs. 62.2 (45.7; 82.4) 1000/ml and 17.7 (13.0; 23.3) % vs. 15.1 (11.4; 19.4) %, respectively, p&lt;0.05). The association of the relative content of non-classical CD14+CD16++ monocytes with the Lp(a) concentration retained statistical significance when adjusted for gender and age (r=0.18, p=0.03). The severity of coronary atherosclerosis was correlated with the Lp(a) concentration (r=0.20, p&lt;0.05), as well as the relative (r=−0.16, p&lt;0.05) and absolute (r=−0.21, p&lt;0.05) content of classical CD14++CD16- monocytes. The high content of non-classical CD14+CD16++ monocytes (OR=3.5 (95% CI 1.2–10.8), as well as intermediate CD14++CD16+ monocytes (OR=8.7 (95% CI 2.5–30.6) in patients with hyperLp(a) were associated with stenotic three-vessel coronary artery disease.

Conclusion

Here we demonstrate the correlation between the Lp(a) concentration and the blood content of non-classical monocytes, regardless of gender and age. The hyperLp(a) and decreased quantity of classical CD14++CD16- monocytes were associated with the severity of coronary atherosclerosis. The expansion of CD16+ monocytes (intermediate and non-classical) in the presence of hyperLp(a) significantly increased the risk of stenotic three-vessel coronary artery disease. Further studies of the differentiation and functioning of subsets of monocytes in the presence of congenital disorders of lipid metabolism, and especially hyperLp(a), are needed.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): The study was approved by Russian Ministry of Health