Unknown,Transcriptomics,Genomics,Proteomics

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HLA peptides derived from tumor antigens induced by inhibition of DNA methylation for development of drug-facilitated immunotherapy

ABSTRACT: Treatment of cancer cells with anti-cancer drugs often fails to achieve complete remission. Yet, such drug treatments may induce alteration in the tumorâs gene expression patterns, including those of Cancer/Testis Antigens (CTA). The degradation products of such antigens can be presented as HLA peptides on the surface of the tumor cells and be developed into anti-cancer immunotherapeutics. For example, the DNA methyl transferase inhibitor, 5-aza-2'-deoxycytidine (Decitabine) has limited anti-tumor efficacy, yet it induces the expression of many genes, including CTAs that are normally silenced in the healthy adult tissues. In this study, the presentation of many new HLA peptides derived from CTAs and induced by Decitabine was demonstrated in three human Glioblastoma cell lines. Such presentation of CTA-derived HLA peptides can be exploited for development of new treatment modalities, combining drug treatment with anti-CTA targeted immunotherapy. The Decitabine-induced HLA peptidomes include many CTAs that are not normally detected in healthy tissues or in cancer cells, unless treated with the drug. In addition, the study included large-scale analyses of the simultaneous effects of Decitabine on the transcriptomes, proteomes and HLA peptidomes of the human Glioblastoma cells. It demonstrates the poor correlations between these three levels of gene expression, both in their total levels and in their response to the drug. The transcriptomes, proteomes and HLA peptidomes of the U-87, T98G and LNT-229 GBM human cell lines were analyzed before and after treatment with Decitabine. Overall, the RNA-Seq transcriptome analyses resulted in the identification of above 26000 transcripts, the proteome analyses identified about 7500 proteins and the HLA class I peptidome analyses resulted in above 25000 identified HLA peptides. Two biological repetitions of the transcriptome, three of the proteome and three of the HLA peptidome were performed with each of the cell lines and treatment, resulting in highly reproducible datasets.

ORGANISM(S): Homo sapiens

SUBMITTER: Arie Admon

PROVIDER: E-GEOD-80137 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: Epigenetic modifications such as methylation silencing of genes with CpG-island-associated promoters is frequently observed in cancer. Studies regarding the implications of epigenetic modifications in osteosarcoma (OS) have been limited. The epigenetic drug decitabine is a potential re-activator of silenced genes through de-methylation, and is currently undergoing clinical trials for cancer treatment. No study to date has utilized decitabine to modify gene expression in OS-derived cells to identify gene-specific methylation targets that may have therapeutic importance. The objective of this study was to measure the response of the OS cell line, U-2OS, to decitabine treatment both in vitro and in vivo. Results: Genome-wide screening was used to distinguish decitabine-dependent changes in gene expression in U-2OS and to identify responsive loci with de-methylated CpG regions. U-2OS xenografts were established in the sub-renal capsule of immune-deficient mice to study the effect of decitabine in vivo on tumor growth and differentiation. Genome-wide screening of U-2OS cells in vitro revealed that decitabine treatment at low-dosage (1 ÂµM) caused a significant induction (p<0.0025) in the expression of 88 genes, 13 had a â?¥2-fold change, 11 of which had CpG-island-associated promoters. Interestingly, 6 of these 11 were pro-apoptotic genes. 1 ÂµM decitabine resulted in a significant induction of cell death in U-2OS cells in vitro (p<0.05). Decitabine treatment also reduced tumor volume size significantly (p<0.05) in U-2OS in vivo at a 2.5 mg/kg dose. Histological analysis of U-2OS xenograft sections revealed a lower mitotic activity (p<0.0001), a higher bone matrix production (p<0.0001), and higher apoptosis (p = 0.0329) after treatment. The 6 pro-apoptotic genes were also induced to â?¥2-fold in vivo. Quantitative Methylation Pyrosequencing (Pyro Q-CpG) showed that 4 pro-apoptotic genes had CpG-island DNA de-methylation as a result of treatment in vitro and in vivo. Conclusion: Our data provide new insights regarding the use of epigenetic modifiers in OS, and have important implications for therapeutic trials involving demethylation drugs. The findings of this study suggest an epigenetic mechanism, whereby OS tumor cells silence expression of pro-apoptotic genes through promoter-CpG methylation, to maintain high proliferation capacity and continuous growth. Experiment Overall Design: Total RNA was extracted using the RNeasy kit (Qiagen, Germany) from duplicate experiments of U-2OS cells at Day3 after treatment with 1 ÂµM decitabine or medium alone (control). In each experiment RNA yields were pooled from two independent cultures per treatment arm to minimize experimental noise. For each case, 10 Âµg of RNA was labeled and hybridized to the Affymetrix HG-U133A GeneChips using the manufacturerâ??s protocol (Affymetrix, Santa Clara, CA) by the Center of Applied Genomics at the Hospital for Sick Children (Toronto, Canada). Data were extracted using the Microarray Suite (MAS) version 5.0 (Affymetrix) and linearly scaled to achieve an average intensity of 150 across each chip. The candidate gene list obtained from the MAS 5.0-extracted data was selected by eliminating genes that were not present in at least one experiment. The arrays were subjected to a pair wise comparison using MAS 5.0, with signal intensities from the no-treatment cells as the baseline. The statistical significance for the change of expression for each probe set between the decitabine treated and control was calculated by the MAS5.0 software. The criteria for gene selection for real-time expression validation analysis was based on the statistically significant up-regulation (p<0.0025) and fold change of â?¥ 2 for expression after decitabine treatment. The gene list was annotated based on the NetAffx data-base (http://www.affymetrix.com/analysis /index.affx) and further verified using the Human Genome Browser data base (http://genome.ucsc.edu/)

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HLA peptides derived from tumor antigens induced by inhibition of DNA methylation for development of drug-facilitated immunotherapy

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