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Tumor circulating DNA profiling in xenografted mice exposed to intermittent hypoxia

ABSTRACT: Intermittent hypoxia (IH) is a hallmark of obstructive sleep apnea (OSA), which has been proposed as the major determinant of processes involving tumor invasion and metastasis. To study whether circulating DNA (cirDNA) in blood plasma reflects the changes that the tumor cells undergo under IH conditions, we used a xenografted murine model. Mice engrafted with TC1 epithelial lung and controls were exposed to IH or room air (RA) conditions. Plasma cirDNA amounts were significantly increased in mice exposed to IH (p<0.05). We found a significant correlation between plasma cirDNA concentration and tumor size, weight and invasiveness (p<0.05). Using a microarray-based approach, we identified 2,094 regions showing significant differential cirDNA modifications. System biology analysis revealed an association with molecular pathways misregulated in cancer progression and with distal and TSS-associated transcription factor binding sites. We detected clusters of highly variable regions in chromosomes 7, 13, 14 and X, which may highlight hotspots for DNA deletions. Single locus displayed high intragroup variation, suggesting cellular heterogeneity within the tissue may be associated to cirDNA release. Our result showed that exposure to IH increases the shedding of cirDNA into circulation, which carries epigenetic modifications that may characterize cell populations within the tumor that preferentially release their DNA upon IH exposure.

ORGANISM(S): Mus musculus

PROVIDER: GSE61070 | GEO | 2015/02/24

SECONDARY ACCESSION(S): PRJNA260179

REPOSITORIES: GEO

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Project description:The long-term effects of neonatal intermittent hypoxia (IH), an accepted model of apnea-induced hypoxia, are unclear. We have previously shown lasting âprogrammingâ effects on the HPA axis in adult rats exposed to neonatal IH. We hypothesized that neonatal rat exposure to IH will subsequently result in a heightened inflammatory state in the adult. Rat pups were exposed to normoxia (control) or six cycles of 5% IH or 10% IH over one hour daily from postnatal day 2 â 6. Plasma samples from blood obtained at 114 days of age were analyzed by assessing the capacity to induce transcription in a healthy peripheral blood mononuclear cell (PBMC) population and read using a high-density microarray. The analysis of plasma from adult rats previously exposed to neonatal 5% IH vs. 10% IH resulted in 2,579 significantly regulated genes including increased expression of Cxcl1, Cxcl2, Ccl3, Il1a, and Il1b. We conclude that neonatal exposure to intermittent hypoxia elicits a long-lasting programming effect in the adult resulting in an upregulation of inflammatory-related genes. Apnea is the most common cause of neonatal hypoxia affecting about 50% of preterm births (30 Ã¢ÂÂ 31 weeks), usually due to immature respiratory development. Upregulation of inflammatory genes and pathways in children 7 Ã¢ÂÂ 10 years of age has been shown, and there is a known increased risk of insulin resistance in adulthood when the fetus is exposed to maternal hypoxia, but the mechanism is unclear. The long-term metabolic, endocrine, and immunological effects of neonatal intermittent hypoxia (IH) exposure, an accepted model of apnea-induced hypoxia, have not been thoroughly evaluated. Recent studies in rats have shown that perinatal IH exposure can result in oxidative stress, causing a permanent immune response subsequently resulting in features of diabetes mellitus. We have previously examined adult rats exposed to neonatal intermittent hypoxia and perinatal continuous hypoxia, and have found lasting Ã¢ÂÂprogrammingÃ¢ÂÂ effects on the HPA axis. We now assess the long term effects of an accepted model of apnea-induced hypoxia using a validated transcriptional bioassay to study the extracellular milieu of adult rats exposed to neonatal intermittent hypoxia. We hypothesize that exposure to neonatal intermittent hypoxia will result in an increased inflammatory state in the adult as a result of long-lasting programming. Sprague-Dawley (SD) rat pups were treated with neonatal normoxia (21% O2, control), 5% intermittent hypoxia (IH), or 10% IH on postnatal days (PD) 2-6, daily over 1 hr. They were reared normally by birth dams and weaned at PD22. Males were allowed to mature and sacrificed at age PD114 after an overnight fast. Whole blood collected by decapitation into tubes with EDTA, and plasma saved for further analysis. Two adult (~180 day) male Brown Norway (BN) rats served as PBMC donors. Cells were incubated with 20% plasma that was either autologous BN (self-control), or one of 3 pools: a) SD normoxic N=8, b) SD 5% IH treated N=5, and c) SD 10% IH N=3.

Project description:The long-term effects of neonatal intermittent hypoxia (IH), an accepted model of apnea-induced hypoxia, are unclear. We have previously shown lasting “programming” effects on the HPA axis in adult rats exposed to neonatal IH. We hypothesized that neonatal rat exposure to IH will subsequently result in a heightened inflammatory state in the adult. Rat pups were exposed to normoxia (control) or six cycles of 5% IH or 10% IH over one hour daily from postnatal day 2 – 6. Plasma samples from blood obtained at 114 days of age were analyzed by assessing the capacity to induce transcription in a healthy peripheral blood mononuclear cell (PBMC) population and read using a high-density microarray. The analysis of plasma from adult rats previously exposed to neonatal 5% IH vs. 10% IH resulted in 2,579 significantly regulated genes including increased expression of Cxcl1, Cxcl2, Ccl3, Il1a, and Il1b. We conclude that neonatal exposure to intermittent hypoxia elicits a long-lasting programming effect in the adult resulting in an upregulation of inflammatory-related genes. Apnea is the most common cause of neonatal hypoxia affecting about 50% of preterm births (30 – 31 weeks), usually due to immature respiratory development. Upregulation of inflammatory genes and pathways in children 7 – 10 years of age has been shown, and there is a known increased risk of insulin resistance in adulthood when the fetus is exposed to maternal hypoxia, but the mechanism is unclear. The long-term metabolic, endocrine, and immunological effects of neonatal intermittent hypoxia (IH) exposure, an accepted model of apnea-induced hypoxia, have not been thoroughly evaluated. Recent studies in rats have shown that perinatal IH exposure can result in oxidative stress, causing a permanent immune response subsequently resulting in features of diabetes mellitus. We have previously examined adult rats exposed to neonatal intermittent hypoxia and perinatal continuous hypoxia, and have found lasting “programming” effects on the HPA axis. We now assess the long term effects of an accepted model of apnea-induced hypoxia using a validated transcriptional bioassay to study the extracellular milieu of adult rats exposed to neonatal intermittent hypoxia. We hypothesize that exposure to neonatal intermittent hypoxia will result in an increased inflammatory state in the adult as a result of long-lasting programming.

Project description:This study compared the circRNA expression levels in plasma samples from patients with IH and control individuals. The circRNA expression profiles were determined using microarray in three pairs of plasma samples from patients with proliferative IH and healthy control individuals. Expression of the identified circRNAs was verified using quantitative reverse transcription polymerase chain reaction (RT-qPCR), and bioinformatic analysis was performed to predict the microRNAs targeted by the validated circRNAs. In the circRNA expression profiles in the plasma of patients with IHs, we found 128 differentially expressed circRNAs, of which 72 were upregulated and 56 were downregulated. The downregulated expression of three circRNAs (hsa_circRNA_101566, hsa_circRNA_103546, and hsa_circRNA_103573) was verified using RT-qPCR. Circular RNAs (circRNAs) are noncoding RNAs that play important roles in tumor progression. Few studies have examined the circRNAs involved in infantile hemangioma (IH) progression. This study compared the circRNA expression levels in plasma samples from patients with IH and control individuals. The circRNA expression profiles were determined using microarray in three pairs of plasma samples from patients with proliferative IH and healthy control individuals. Expression of the identified circRNAs was verified using quantitative reverse transcription polymerase chain reaction (RT-qPCR), and bioinformatic analysis was performed to predict the microRNAs targeted by the validated circRNAs. In the circRNA expression profiles in the plasma of patients with IHs, we found 128 differentially expressed circRNAs, of which 72 were upregulated and 56 were downregulated. The downregulated expression of three circRNAs (hsa_circRNA_101566, hsa_circRNA_103546, and hsa_circRNA_103573) was verified using RT-qPCR. Gene ontology term and Kyoto Encyclopedia of Genes and Genomes pathway analyses showed that all identified networks participated in angiogenesis and tumor formation and progression. We found that hsa_circRNA_101566, which can regulate the mammalian target of rapamycin signaling pathway, may be an important regulatory molecule in IH development and that targeting of hsa_miR_520c can indirectly regulate the vascular endothelial growth factor signaling pathway. Further studies are needed to clarify these effects and the underlying mechanisms.

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Tumor circulating DNA profiling in xenografted mice exposed to intermittent hypoxia

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