Phenotypic manifestation of α-synuclein strains derived from Parkinson's disease and multiple system atrophy in human dopaminergic neurons

α-Synuclein is critical in the pathogenesis of Parkinson's disease and related disorders, yet it remains unclear how its aggregation causes degeneration of human dopaminergic neurons. In this study, we induced α-synuclein aggregation in human iPSC-derived dopaminergic neurons using fibrils generated de novo or amplified in the presence of brain homogenates from Parkinson's disease or multiple system atrophy. Increased α-synuclein monomer levels promote seeded aggregation in a dose and time-dependent manner, which is associated with a further increase in α-synuclein gene expression. Progressive neuronal death is observed with brain-amplified fibrils and reversed by reduction of intraneuronal α-synuclein abundance. We identified 56 proteins differentially interacting with aggregates triggered by brain-amplified fibrils, including evasion of Parkinson's disease-associated deglycase DJ-1. Knockout of DJ-1 in iPSC-derived dopaminergic neurons enhance fibril-induced aggregation and neuronal death. Taken together, our results show that the toxicity of α-synuclein strains depends on aggregate burden, which is determined by monomer levels and conformation which dictates differential interactomes. Our study demonstrates how Parkinson's disease-associated genes influence the phenotypic manifestation of strains in human neurons.

Abstract 3563: Fatty acid binding protein 7 regulates beige fat-like differentiation of breast cancer cells and thermogenesis

Cancer cells alter the metabolism in their microenvironment to sustain their survival, growth and progression. Heat is an essential factor that can affect metabolism. However, it is unclear whether cancer cells can alter their temperature by regulating heat production. Non-shivering thermogenesis is known to takes place in inducible beige adipocytes expressing the mitochondrial thermogenic protein, uncoupling protein 1 (UCP1). UCP1 dissipates the proton gradient of the mitochondrial inner membrane and converts its energy into heat. We found that the inhibition of a hypoxia-inducible protein, fatty acid binding protein 7 (FABP7), triggered beige fat-like differentiation and induced thermogenesis in breast cancer cells. We established the breast cancer cell line with a stable knockdown of FAPB7, using lentivirus transduction particles. UCP1-expressing cells were found in 21 ± 5% of the knockdown cells while they were found in only 4 ± 1.7% of the control cells: p = 0.004). UCP1 expression was maximized in the knockdown cells when cultured in hypoxia. A novel thermo-sensitive fluorescent probe confirmed that the cellular temperature of the knockdown cells was 2°C higher than the controls. In addition, the knockdown cells exhibited the increased mitochondrial depolarization, increased proton leak and increased respiration rate compared to controls, suggesting they had the similar energy profile with beige adipocytes. The knockdown cells became more sensitive to hypoxia and radiation, and the clinical manifestation of breast cancer patients differed depending on the expression levels of both UCP1 and FABP7. These observations suggested a missing link between hypoxia-related fatty acid metabolism and cellular thermogenesis which might be a novel therapeutic target for breast cancer.

Citation Format: Masahiro Kawashima, Karim Bensaad, Christos Zois, Alessandro Barberis, Esther Bridges, Christoffer Lagerholm, Ruslan I. Dmitriev, Masakazu Toi, Dmitri B. Papkovsky, Francesca Buffa, Adrian L. Harris. Fatty acid binding protein 7 regulates beige fat-like differentiation of breast cancer cells and thermogenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3563.

RHOQ is induced by DLL4 and regulates angiogenesis by determining the intracellular route of the Notch intracellular domain

Angiogenesis, the formation of new blood vessels by endothelial cells, is a finely tuned process relying on the balance between promoting and repressing signalling pathways. Among these, Notch signalling is critical in ensuring appropriate response of endothelial cells to pro-angiogenic stimuli. However, the downstream targets and pathways effected by Delta-like 4 (DLL4)/Notch signalling and their subsequent contribution to angiogenesis are not fully understood. We found that the Rho GTPase, RHOQ, is induced by DLL4 signalling and that silencing RHOQ results in abnormal sprouting and blood vessel formation both in vitro and in vivo. Loss of RHOQ greatly decreased the level of Notch signalling, conversely overexpression of RHOQ promoted Notch signalling. We describe a new feed-forward mechanism regulating DLL4/Notch signalling, whereby RHOQ is induced by DLL4/Notch and is essential for the NICD nuclear translocation. In the absence of RHOQ, Notch1 becomes targeted for degradation in the autophagy pathway and NICD is sequestered from the nucleus and targeted for degradation in lysosomes.

Abstract 521: Downregulation of type I IFN response in hypoxia as a possible mechanism of immune escape

Introduction: Hypoxia is a common phenomenon in solid tumors and is considered a hallmark of cancer. Increasing evidence shows that tumor hypoxia promotes local immune suppression and inhibits immune cell killing functions. However, there is little information about the relationship between hypoxia and the type I interferon (IFN) pathway, which comprises the sensing double-stranded RNA and DNA (dsRNA/dsDNA) in the tumor microenvironment, followed by IFNα/β secretion. The aim of this study is to determine the effect of hypoxia on the type I IFN pathway in breast cancer and the consequences for tumor survival.

Methods: A panel of breast cancer cell lines [MCF7, T47D, BT474, SKBR3, MDA231, MDA453, MDA468] were analyzed by Western blot and RT-qPCR in normoxia and acute hypoxia (0.1% O2) for 24 hours, using medium containing 5mM glucose. Cells were stimulated with the dsRNA mimic poly I:C [10ng/ml to 20ug/ml] to activate the IFN type I pathway.

Results: An overall 50% decrease in expression of the dsRNA-sensing branch (sensors: RIG-I, MDA5; adaptor: MAVS; effectors: IRF3, IRF7, STAT1, STAT2; interferon stimulated genes (ISGs): PKR, ADAR1) was observed in all breast cancer cell lines studied when they were treated with 0.1% O2 for 24h both at RNA and protein levels. Moreover, when the pathway was stimulated using poly I:C, hypoxia also showed a decrease in the stimulation and in the activation of pIRF3 and pSTAT1. Different IFN bioassays were performed using HEK293 cells expressing (i) the IFN stimulated response element (ISRE), which were cultured for 24h with supernatant from MCF7 previously treated with normoxia/hypoxia and different concentration of poly I:C, and (ii) the IFNβ promoter, which were transfected with total RNA from normoxic/hypoxic cells. Consistent with reduced expression of factors involved in the IFN pathway, there was lower activation of the ISRE by supernatants from hypoxic cells compared to samples from normoxic cells, indicating lower IFN production in hypoxia. In addition, RNA from hypoxic cells showed much lower activation of the IFNβ promoter pointing to lower IFNβ transcription in hypoxic cells.

HIF1α and/or HIF2α downregulation using siRNAs partially upregulated the expression of some ISGs (i.e. RIG-I, ADAR1), but this treatment did not completely reverse the effect of hypoxia, suggesting that the effect observed in hypoxia does not fully depend on HIF1α and HIF2α. Further studies on how chromatin conformation under hypoxia could affect the expression of genes in the type I IFN pathway are on going.

Conclusions: Hypoxia downregulates the dsRNA-sensing branch of the type I IFN system in breast cancer, thus favoring an immunosuppressive status that could help immune evasiveness.

Note: This abstract was not presented at the meeting.

Citation Format: Ana Miar, Jan Rehwinkel, Christos Zois, Adrian L. Harris. Downregulation of type I IFN response in hypoxia as a possible mechanism of immune escape [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 521.

Integrated Pharmacodynamic Analysis Identifies Two Metabolic Adaption Pathways to Metformin in Breast Cancer

Late-phase clinical trials investigating metformin as a cancer therapy are underway. However, there remains controversy as to the mode of action of metformin in tumors at clinical doses. We conducted a clinical study integrating measurement of markers of systemic metabolism, dynamic FDG-PET-CT, transcriptomics, and metabolomics at paired time points to profile the bioactivity of metformin in primary breast cancer. We show metformin reduces the levels of mitochondrial metabolites, activates multiple mitochondrial metabolic pathways, and increases 18-FDG flux in tumors. Two tumor groups are identified with distinct metabolic responses, an OXPHOS transcriptional response (OTR) group for which there is an increase in OXPHOS gene transcription and an FDG response group with increased 18-FDG uptake. Increase in proliferation, as measured by a validated proliferation signature, suggested that patients in the OTR group were resistant to metformin treatment. We conclude that mitochondrial response to metformin in primary breast cancer may define anti-tumor effect.

Abstract 2439: The importance of cellular oxygenation measurements in the analysis of hypoxia-induced signaling and related metabolic adaptation

There is a growing appreciation that typical cell culture conditions reflect a hyperoxic condition for the majority of cell types. In an effort to more accurately reflect the in vivo condition, a growing number of researchers are conducting in vitro measurements at what are deemed to be more physiologically relevant oxygen concentrations (1-8% O2). The importance of oxygen concentration in in vitro model design is underscored by observations that O2 levels influence a wide range of cellular phenomena, including metabolic poise, differentiation and senescence while the development of localised hypoxic environments are implicated in a variety of diseases including stroke, and cancer. Impaired O2 supply can reduce O2 concentrations to below normal physiological levels, initiating a graded series of complex interconnected adaptive responses mediated by regulators including the hypoxia-inducible factor (HIF). These processes are particularly relevant within solid tumours, where oncogene-driven proliferation causes nutrient and oxygen deprivation, aberrant angiogenesis, and the activation of O2-sensitive survival pathways.

Despite the importance of cellular oxygenation, research using in vitro models makes the assumption that oxygenation can be defined by simply altering the oxygen condition applied to the in vitro model. To test this key assumption, cellular oxygenation measurements are performed using a nanoparticulate intracellular oxygen probe (MitoXpress®-Intra), while tumour hypoxia/oygenation is modelled on a fluorescence plate reader equipped with an atmospheric control unit (CLARIOstar®). Data is presented illustrating that the depth of hypoxia experienced by the cell model is impacted significantly by respiratory activity, and that this additional oxygen deprivation is a dynamic process, effected by respiratory substrate availability and related metabolic poise. Data is also presented demonstrating that, in in vitro models, additional respiration-induced hypoxia directly impacts glycolytic flux and other relevant metabolic pathways. Together these data invalidate the assumption that cellular oxygenation can be inferred from ambient oxygen measurements. If ignored, the significant and dynamic deviations between ambient O2 and oxygenation at the cellular level leads to erroneous collusions regarding the relationship between oxygen concentration, HIF stabilisation and related metabolic adaptations. This in turn can impair the physiological relevance of experimental observations.

Citation Format: Michelle Potter, James Hynes, Anke Nijhuis, Conn Carey, Christos Zois, Adrian Harris, Hector Keun, Karl Morten. The importance of cellular oxygenation measurements in the analysis of hypoxia-induced signaling and related metabolic adaptation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2439.

The "stone-like" pattern of autophagy in human epithelial tumors and tumor-like lesions: an approach to the clinical outcome

Cancer cells survive the adverse conditions of the extracellular milieu, i.e., hypoxia and nutrient deprivation, through angiogenesis and anaerobic glycolysis. Yet, continuously proliferating malignant cells, having high metabolic needs, may not be fully covered by these processes and seek additional sources of energy. An alternative metabolic pathway for providing energy in tumor cells is autophagy-a self-degradation mechanism by which cells recycle their own cytoplasmic constituents. Given that the clinical impact of this phenomenon on human malignancies remains by and large unexplored, we investigated morphological patterns of autophagy primarily in breast carcinomas and, subsequently, in a series of other epithelial tumors and tumor-like lesions from various organs and cell types. The microtubule-associated protein 1 light chain 3A (MAP1-LC3A) antibody and a standard immunohistochemical technique were used. Three main patterns of autophagic activity were recognized: diffuse cytoplasmic, cytoplasmic/juxta-nuclear and "stone-like" structures (SLS); the latter are dense, spheroidal, amorphous structures, of 5 microm average size, typically enclosed within cytosolic vacuoles. Normal tissues, in the proximity of malignant tumors, and tumorlike lesions expressed with remarkable consistency the cytoplasmic and the juxta-nuclear pattern, but were deprived of SLS. Interestingly, tumors having a substantial number of SLS were of high grade and unfavorable prognosis, whereas those with juxta-nuclear accumulation of LC3A protein were associated with an improved survival. Prognosis was unaffected by the diffuse cytoplasmic pattern. It is concluded that immunohistochemical staining for LC3A is a suitable method for detecting autophagy in human tissues by light microscopy, but the significance of the various patterns described needs further evaluation.

Natural course of autoimmune thyroiditis after elimination of iodine deficiency in northwestern Greece

We have previously reported the elimination of iodine deficiency and increasing prevalence of autoimmune thyroiditis (AIT) among schoolchildren in northwestern Greece. This study followed up 29 children (12-18 years old) with AIT for 5 years to track its course in the postiodination era. At diagnosis, thyroid peroxidase autoantibodies (TPOAbs) were positive in 25 children (86%) and became positive in all children during follow-up. Thyroglobulin autoantibodies (TgAbs) were positive in 17 children at diagnosis (59%) and became positive in 3 more children (69%). Both antibody types increased by the end of the observation period (p < 0.005). Regarding thyroid function, 7 children (24%) at diagnosis had subclinical hypothyroidism that persisted and 4 more children developed subclinical hypothyroidism during the study period (38%). Only 5 of these children (45%) had positive TgAbs. There was an increase in thyrotropin (TSH) so that at the end of the study all children had TSH greater than 2.5 mU/L but none developed overt hypothyroidism. Thyroid hypoechogenicity that increased over time was seen in all children, especially in those with subclinical hypothyroidism. In conclusion, both antibody types increased in frequency and level, but TPOAbs were the predominant autoimmunity marker predictive of impending thyroid failure in children with AIT, as was thyroid hypoechogenicity on ultrasound.

Combined estrogen receptor α and estrogen receptor β genotypes influence the age of menarche

BACKGROUND

Age at menarche has a strong genetic influence. We reported recently an association between the XbaI (351A-->C)and PvuII (397T-->C) polymorphisms of the estrogen receptor (ER)alpha gene with the age of menarche in Greek adolescents. In the present study, we examined whether ERbeta genotypes alone, or in combination with ERalpha genotypes, may also influence onset of menarche.

METHODS

We performed genotyping for the single nucleotide polymorphisms 1730A-->G and 1082G-->A of the ERbeta gene and examined their association with the age of menarche in the same cohort of 145 Greek girls. We then looked for a possible effect of combined ERalpha and beta genotypes on the age of menarche.

RESULTS

Menarche occurred 7 months later in girls with the AA genotype of the 1730A-->G polymorphism than in girls with the AG genotype (mean +/- SD: 13.23 +/- 1.24 versus 12.66 +/- 1.26 years, respectively; P = 0.005). The 1082G-->A polymorphism was not detected in any of the girls examined. A significant effect of combined ERalpha and beta genotypes was also apparent. Menarche occurred 11 months later in girls bearing the AA/TT,AA (ERalpha, ERbeta) genotypes compared with girls with the CC/CC,AG genotype (13.30 +/- 1.27 nersus 12.41 +/- 1.28 years; P = 0.042). The difference remained significant after adjusting for body mass index (P = 0.034).

CONCLUSION

Combined ERalpha and ERbeta polymorphisms may influence the age of menarche.

High prevalence of autoimmune thyroiditis in schoolchildren after elimination of iodine deficiency in northwestern Greece

The current iodine status and the impact of silent iodine prophylaxis on the prevalence of autoimmune thyroiditis among schoolchildren in a formerly iodine-deficient community in northwestern Greece, were investigated. The findings were compared to those obtained from a similar survey conducted 7 years previously in the same area. A total of 302 schoolchildren (12-18 years of age) from a mountainous area of northwestern Greece were examined for the presence of goiter, and blood and urine samples were collected for assessment of thyroid function, antithyroid antibodies and urinary iodine excretion. In those children (n = 42) with palpable goiter or positive antibodies and/or a thyrotropin (TSH) level greater than 5 mU/L, thyroid ultrasonography was performed to estimate thyroid gland size and morphology. Median urinary iodine concentration in the children was 20.21 microg/dL, indicating sufficient iodine intake. Thyroid function was normal in all but 7 children, who had subclinical hypothyroidism (2.5%). Antithyroid antibodies (antithyroid peroxidase [TPO] and/or antithyroglobulin [Tg]) were positive in 32 children, including those with subclinical hypothyroidism (10.6%). Twenty-nine of these children (9.6%) also had the characteristic echo pattern of thyroiditis on ultrasound and were diagnosed to have autoimmune thyroiditis. In comparison to data from our previous survey 7 years ago, there has been a threefold increase in the prevalence of autoimmune thyroiditis among schoolchildren. In conclusion, silent iodine prophylaxis has resulted in the elimination of iodine deficiency in Greece, and this has been accompanied by an increase in the prevalence of autoimmune thyroiditis.

Association of polymorphisms of the estrogen receptor alpha gene with bone mineral density and fracture risk in women: a meta-analysis

The contribution of genetic polymorphisms to bone mineral density (BMD) and fracture risk in women is a controversial topic. We evaluated the effect of the XbaI and PvuII polymorphisms of the estrogen receptor a to BMD and fracture risk in a meta-analysis, including published data and additional information from investigators. Five thousand eight hundred thirty-four women from 30 study groups were analyzed with fixed and random effects models. The PvuII polymorphism was not associated with BMD at any skeletal site examined and 95% CIs exclude effects over 0.015 g/cm2 for both the femoral neck and the lumbar spine. Conversely, XX homozygotes (women carrying two copies of the gene variant without an XbaI restriction site) consistently had higher BMD than other subjects. The magnitude of the effect was similar in the femoral neck and lumbar spine (0.014 g/cm2 [95% CI, 0.003-0.025] and 0.015 g/cm2 [95% CI, 0.000-0.030], respectively; no between-study heterogeneity for either). Total body BMD was also significantly higher in XX homozygotes (by 0.039 g/cm2 and 0.029 g/cm2 compared with Xx and xx, respectively). Available data on fractures suggested a protective effect for XX (odds ratio [OR], 0.66 [95% CI, 0.47-0.93] among 1591 women), but not PP (OR, 0.93 [95% CI, 0.72-1.18] among 2,229 women). In summary, we have found that XX homozygotes may have higher BMD and also a decreased risk of fractures when compared with carriers of the x allele, whereas the PvuII polymorphism is not associated with either BMD or fracture risk.

Association of polymorphisms of the oestrogen receptor alpha gene with the age of menarche

BACKGROUND

The age of menarche may be subject to hereditary influences, but the specific genetic determinants are largely unknown. We evaluated whether the XbaI and PvuII polymorphisms of the estrogen receptor alpha gene are associated with the age of menarche.

METHODS

We performed genotyping for XbaI and PvuII in a cohort of 145 adolescent females from a closed community in North-Western Greece.

RESULTS

There was strong linkage disequilibrium between the two polymorphisms. Menarche occurred later in girls with the XX genotype than in girls with the Xx or xx genotype (mean +/- SD: 13.36 +/- 1.24 versus 12.80 +/- 1.14 and 12.75 +/- 1.35 years respectively; P = 0.017). Menarche also tended to occur later in PP homozygotes than in Pp and pp subjects, but the difference was not significant (mean +/- SD: 13.09 +/- 1.29 versus 12.80 +/- 1.19 and 12.85 +/- 1.33 years respectively). The strongest effect was seen when the PX haplotype was considered [mean +/- SD: 13.43 +/- 1.18 years for homozygotes versus 12.76 +/- 1.25 years in heterozygotes and in subjects without the PX allele, P = 0.006].

CONCLUSIONS

We document that the XbaI polymorphism, and possibly PvuII, may be genetic determinants of the age of menarche.