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RNA sequencing of MDA-MB231 and U2OS cancer cell lines exposed to the alkylating agent methyl methanesufonate (MMS) and classical chemotherapeutics

ABSTRACT: Understanding the mechanisms by which cells respond to chemotherapeutics is key to identifying means to improve therapy effiicacy while reducing systemic toxicity of these widely used classes of drugs. While determining the role of NRF2-GSH and ER stress in cells exposed to alkylating compounds such as methyl-methanesulfonate (MMS), we asked if these pathways could also be a general cell damage response relevant to other clinically used chemotherapeutics or if it is an alkylation specific response. With this intent, we performed RNA sequencing of MDA-MB231 breast cancer and U2OS osteosarcoma cells lines treated for 8 hours with a topoisomerase II inhibitor etoposide (20 µM), the antimitotic beta-tubulin-interacting drug paclitaxel (0.2 µM), doxorubicin (1 µM) and compared to MMS (40 µg/mL) treated cells. Doses represent IC50 level after 72 hours exposure. We observed that even though non-alkylating drugs, especially etoposide, caused an increase in the mRNA expression of some NRF2 and ER stress signaling markers, the number and magnitude of upregulation of genes markers in either pathway was more pronounced in alkylation treatments compared to other drugs. This indicates that alterations in NRF2 and ER stress pathways could be more likely associated with differential sensitivity to alkylating chemotherapies.

ORGANISM(S): Homo sapiens

PROVIDER: GSE84863 | GEO | 2017/02/13

SECONDARY ACCESSION(S): PRJNA335388

REPOSITORIES: GEO

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Project description:Alkylation damage to DNA occurs when cells encounter alkylating agents in the environment or when active alkylators are generated by nitrosation of amino acids in metabolic pathways. To cope with DNA alkylation damage, cells have evolved genes that encode proteins with alkylation-specific DNA repair activities. It is notable that these repair systems are conserved from bacteria to humans. In Escherichia coli, cells exposed to a low concentration of an alkylating agent, such as N-methyl-Nâ-nitro-N-nitrosoguanidine (MNNG) or methyl methanesulfonate (MMS), show a remarkable increase in resistance to both the lethal and mutagenic effects of subsequent high-level challenge treatments with the same or other alkylating agents. This increased resistance has been known as âadaptive responseâ to alkylation damage in DNA. To date, four genes have been identified as components of this response, ada, alkA, alkB and aidB. The ada gene encodes the Ada protein, which has the dual function of a transcriptional regulator for the genes involved in the adaptive response, and a methyltransferase that demethylates two methylated bases (O6meG and O4meT) and methylphosphotriesters produced by methylating agents in the sugar phosphate backbone. The differences between the wild-type and mutant strains were characterized at transcriptome levels. In addition, the global changes in gene expressions in response to alkylating agents (MMS), in E. coli K-12 W3110 and ada mutant strains were also analyzed. The analysis of time- and strain-dependent adaptive responses revealed the regulatory and physiological characteristics of the Ada-dependent adaptive response in E. coli. In order to examine the intracellular changes that are induced by the ada gene deletion in the MMS-untreated, normal growth condition, the expression levels of genes of ada mutant cells were compared with those of wild-type cells at the mid-log growth phase (at 0.5 h sampling point). Cells were cultivated at 37oC and 250 rpm in 100 mL of Luria-Bertani (LB) medium (10 g/L tryptone, 5 g/L yeast extract, and 5 g/L NaCl) in 250-mL Erlenmeyer flasks. Transcriptome analysis were also performed for the samples (E. coli wildtype and ada mutant strains) taken at 0.5, 1.5 and 3.9 h following MMS treatment for both MMS-treated and -untreated control cultures, and the expression levels were compared.

Project description:Drug-induced liver injury (DILI) is an important clinical problem. Here we used a genomics approach to establish the critical drug-induced toxicity pathways that act in synergy with the pro-inflammatory cytokine tumor necrosis factor (TNF) to cause cell death of liver HepG2 cells. Transcriptomics of the cell injury stress response pathways initiated by two hepatoxicants, diclofenac and carbamazepine, revealed the endoplasmic reticulum (ER) stress/translational initiation signaling and Nrf2 antioxidant signaling as two major affected pathways, which was similar to that observed for the majority of ~80 DILI compounds in primary human hepatocytes. The ER stress was primarily related to PERK and ATF4 activation and subsequent expression of CHOP, which was all independent of TNFÎ± signaling. Identical ATF4 dependent transcriptional programs were observed in primary human hepatocytes as well as primary precision cut human liver slices. Targeted RNA interference studies revealed that while ER stress signaling through IRE1Î± and ATF6 acted cytoprotective, activation of the ER stress protein kinase PERK and subsequent expression of CHOP was pivotal for the onset of drug/TNF-induced apoptosis. While inhibition of the Nrf2-dependent adaptive oxidative stress response enhanced the drug/TNF cytotoxicity, Nrf2 signaling did not affect CHOP expression. Both hepatotoxic drugs enhanced expression of the translational initiation factor EIF4A1, which was essential for CHOP expression and drug/TNF-mediated cell killing. Our data support a model in which enhanced drug-induced translation initiates PERK-mediated CHOP signaling in an EIF4A1 dependent manner, thereby sensitizing towards caspase-8-dependent TNF induced apoptosis. We sought to determine the effect of co-exposure of certain drugs associated with idiosyncratic DILI with the cytokine TNFalpha to mimic drug exposure with inflammation signaling in HepG2 cells Human hepatoma HepG2 cells were obtained from American Type Culture Collection (ATCC, Wesel, Germany), cultured in DMEM supplemented with 10% (v/v) FBS, 25 U/mL penicillin and 25 Âµg/mL streptomycin and used for experiments between passage 5 and 20.

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RNA sequencing of MDA-MB231 and U2OS cancer cell lines exposed to the alkylating agent methyl methanesufonate (MMS) and classical chemotherapeutics

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