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Uracil DNA glycosylase (UNG) loss enhances DNA double strand break formation in human cancer cells exposed to pemetrexed

ABSTRACT: To test the effects of uracil DNA glycosylase (UNG) loss on the formation of double strand breaks (DSBs) by the anti-cancer agent pemetrexed, we performed ChIP-seq for serine 139-phosphorylated H2AX (gammaH2AX), a marker of DSBs, in human cells wild-type or deficient for UNG in combination with pemetrexed treatment. UNG deficiency results in an increase in DSBs upon pemetrexed treatment, and we found that pemetrexed treatment induces DSBs at different genomic locations in UNG wild-type and knockout cells. Similar results were observed upon cisplatin treatment of UNG wild-type and knockout cells, and the genomic locations of DSBs were distinct between pemetrexed-treated and cisplatin-treated samples. Taken together, our results suggest differential mechanisms for DSB formation in UNG-competent and UNG-deficient cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE50692 | GEO | 2013/10/28

SECONDARY ACCESSION(S): PRJNA218536

REPOSITORIES: GEO

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Uracil DNA glycosylase (UNG) loss enhances DNA double strand break formation in human cancer cells exposed to pemetrexed

Project description:To test the effects of uracil DNA glycosylase (UNG) loss on the formation of double strand breaks (DSBs) by the anti-cancer agent pemetrexed, we performed ChIP-seq for serine 139-phosphorylated H2AX (gammaH2AX), a marker of DSBs, in human cells wild-type or deficient for UNG in combination with pemetrexed treatment. UNG deficiency results in an increase in DSBs upon pemetrexed treatment, and we found that pemetrexed treatment induces DSBs at different genomic locations in UNG wild-type and knockout cells. Similar results were observed upon cisplatin treatment of UNG wild-type and knockout cells, and the genomic locations of DSBs were distinct between pemetrexed-treated and cisplatin-treated samples. Taken together, our results suggst differential mechanisms for DSB formation in UNG-competent and UNG-deficient cells. The genomic distribution of gammaH2AX in UNG WT and KO cells treated with pemetrexed or cisplatin was determined by ChIP-seq

2013-10-28 | E-GEOD-50692 | biostudies-arrayexpress

Loss of Caenorhabditis elegans UNG-1 uracil-DNA glycosylase affects apoptosis in response to DNA damaging agents.

Project description:The nematode Caenorhabditis elegans has been used extensively to study responses to DNA damage. In contrast, little is known about DNA repair in this organism. C. elegans is unusual in that it encodes few DNA glycosylases and the uracil-DNA glycosylase (UDG) encoded by the ung-1 gene is the only known UDG. C. elegans could therefore become a valuable model organism for studies of the genetic interaction networks involving base excision repair (BER). As a first step towards characterization of BER in C. elegans, we show that the UNG-1 protein is an active uracil-DNA glycosylase. We demonstrate that an ung-1 mutant has reduced ability to repair uracil-containing DNA but that an alternative Ugi-inhibited activity is present in ung-1 nuclear extracts. Finally, we demonstrate that ung-1 mutants show altered levels of apoptotic cell corpses formed in response to DNA damaging agents. Increased apoptosis in the ung-1 mutant in response to ionizing radiation (IR) suggests that UNG-1 contributes to repair of IR-induced DNA base damage in vivo. Following treatment with paraquat however, the apoptotic corpse-formation was reduced. Gene expression profiling suggests that this phenotype is a consequence of compensatory transcriptomic shifts that modulate oxidative stress responses in the mutant and not an effect of reduced DNA damage signaling.

2010-05-26 | GSE21467 | GEO

Loss of Caenorhabditis elegans UNG-1 uracil-DNA glycosylase affects apoptosis in response to DNA damaging agents.

2010-06-08 | E-GEOD-21467 | biostudies-arrayexpress

Uracil DNA glycosylase (UNG) loss enhances DNA double strand break formation in human cancer cells exposed to pemetrexed.

Project description:Misincorporation of genomic uracil and formation of DNA double strand breaks (DSBs) are known consequences of exposure to TS inhibitors such as pemetrexed. Uracil DNA glycosylase (UNG) catalyzes the excision of uracil from DNA and initiates DNA base excision repair (BER). To better define the relationship between UNG activity and pemetrexed anticancer activity, we have investigated DNA damage, DSB formation, DSB repair capacity, and replication fork stability in UNG(+/+) and UNG(-/-) cells. We report that despite identical growth rates and DSB repair capacities, UNG(-/-) cells accumulated significantly greater uracil and DSBs compared with UNG(+/+) cells when exposed to pemetrexed. ChIP-seq analysis of γ-H2AX enrichment confirmed fewer DSBs in UNG(+/+) cells. Furthermore, DSBs in UNG(+/+) and UNG(-/-) cells occur at distinct genomic loci, supporting differential mechanisms of DSB formation in UNG-competent and UNG-deficient cells. UNG(-/-) cells also showed increased evidence of replication fork instability (PCNA dispersal) when exposed to pemetrexed. Thymidine co-treatment rescues S-phase arrest in both UNG(+/+) and UNG(-/-) cells treated with IC50-level pemetrexed. However, following pemetrexed exposure, UNG(-/-) but not UNG(+/+) cells are refractory to thymidine rescue, suggesting that deficient uracil excision rather than dTTP depletion is the barrier to cell cycle progression in UNG(-/-) cells. Based on these findings we propose that pemetrexed-induced uracil misincorporation is genotoxic, contributing to replication fork instability, DSB formation and ultimately cell death.

| S-EPMC3944228 | biostudies-literature

Pemetrexed alters inflammatory profile in EA.hy 926 cells grown under low-folate conditions.

Project description:Pemetrexed is an antifolate drug used in the treatment of lung cancer. EA.hy 926 cells grown under low (Lo) and normal (Hi) folate conditions were treated with PMX. Microarray analysis was used to examine changes in gene expression due to PMX treatment.

2012-10-03 | GSE31986 | GEO

Cytotoxic mechanisms of pemetrexed and HDAC inhibition in non-small cell lung cancer cells

Project description:The cytotoxic effects of thymidylate synthase (TYMS) inhibitors, such as the multitarget antifolate pemetrexed (PMX), are not fully understood. Recent studies suggest that the combination of PMX with histone deacetylase inhibitors may be effective in the treatment of non- small cell lung cancer (NSCLC). To investigate this further, A549 NSCLC cells were exposed to various combinations of PMX and the HDAC inhibitor MS275 (entinostat) and Vorinostat (SAHA) and monitored for cell survival, cell cycle alterations and genotoxic markers. MS275 increased PMX sensitivity in A549 cells when added after preincubation with PMX. Both HeLa (p53 negative) and A549 (p53-naïve) exhibited robust activation of γH2AX upon treatment with the combination. Interestingly, CRISPR-Cas9 UNG knockout did not affect γH2AX activation or sensitivity to PMX. Proteomic analysis revealed that MS275 altered expression of known PMX targets, several proteins involved in pyrimidine metabolism, and several DNA repair proteins (RNaseH2, TOP1, RAD51C, PCNA). Contra to the prevailing model of antifolate toxicity mediated by uracil excision and repeated futile repair cycles caused by reincorporation of uracil, we propose that ribonucleotide incorporation in nuclear and mitochondrial DNA is a major contributor to cytotoxicity antifolates such as PMX, and likely also for fluorinated pyrimidine analogs. The DNA lesions induced by these agents and how their processing can be modulated by HDAC inhibition to potentiate cytotoxicity, warrants further investigation in clinical models.

2024-12-18 | PXD051824 | Pride

UNG shapes the specifity of AID-induced somatic hypermutation in B cells

Project description:Secondary diversification of antibodies through somatic hypermutation (SHM) and class switch recombination (CSR) is a critical component of the immune response. Activation-induced deaminase (AID) initiates both processes by deaminating cytosine residues in immunoglobulin genes. The resulting U:G mismatch can be processed by alternative pathways to give rise to a mutation (SHM) or a DNA double-strand break (CSR). Central to this processing is the activity of uracil-N-glycosylase (UNG), an enzyme normally involved in error-free base excision repair. We used next generation sequencing to analyze the contribution of UNG to the resolution of AID-induced lesions. Loss- and gain-of-function experiments showed that UNG activity can promote both error-prone and high fidelity repair of U:G lesions. Unexpectedly, the balance between these alternative outcomes was influenced by the sequence context of the deaminated cytosine, with individual hotspots exhibiting higher susceptibility to UNG-triggered error-free or error-prone resolution. These results reveal UNG as a new molecular layer that shapes the specificity of AID-induced mutations and may provide new insights into the role of AID in cancer development.

2012-07-05 | GSE39114 | GEO

Transcription profiling by array of mesothelioma pre- and post-resistance biopsies in order to determine a resistance signature to pemetrexed/carboplatin treatment

Project description:Pemetrexed, a multi-folate inhibitor combined with a platinum compound is the first-line treatment of malignant mesothelioma, but median survival is still one year. Innate and acquired resistance to pemetrexed is common, but its biological basis is obscure. Here we report for the first time a genome-wide profile of acquired resistance in the tumour from an exceptional case with advanced pleural mesothelioma and almost six years survival after 39 cycles of second-line pemetrexed/carboplatin treatment.

2012-10-01 | E-MTAB-1109 | biostudies-arrayexpress

UNG shapes the specifity of AID-induced somatic hypermutation in non B cells

2012-07-05 | GSE39108 | GEO

Sorafenib, Pemetrexed, and Cisplatin in Treating Patients With Advanced Solid Tumors

Project description:RATIONALE: Sorafenib and pemetrexed may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. Sorafenib may also stop the growth of tumor cells by blocking blood flow to the tumor. Drugs used in chemotherapy, such as cisplatin, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing. Giving sorafenib together with pemetrexed and cisplatin may kill more tumor cells. PURPOSE: This phase I trial is studying the side effects and best dose of sorafenib when given together with pemetrexed and cisplatin in treating patients with advanced solid tumors.

| 2057338 | ecrin-mdr-crc

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