Oxygen enhancement ratios of cancer cells after exposure to intensity modulated x-ray fields: DNA damage and cell survival

Alpha-ketoglutarate-dependent dioxygenase (ALKBH) is a DNA repair gene involved in the repair of alkylating DNA damage. There are nine types of ALKBH (ALKBH1-8 and FTO) identified in humans. In particular, certain types of ALKBH enzymes are dioxygenases that directly reverse DNA methylation damage via transfer of a methyl group from the DNA adduct onto α-ketoglutarate and release of metabolic products including succinate and formaldehyde. Here, we tested whether ALKBH6 plays a significant role in preventing alkylating DNA damage and decreasing genomic instability in pancreatic cancer cells. Using an E. coli strain deficient with ALKB, we found that ALKBH6 complements ALKB deficiency and increases resistance after alkylating agent treatment. In particular, the loss of ALKBH6 in human pancreatic cancer cells increases alkylating agent-induced DNA damage and significantly decreases cell survival. Furthermore, in silico analysis from The Cancer Genome Atlas (TCGA) database suggests that overexpression of ALKBH6 provides better survival outcomes in patients with pancreatic cancer. Overall, our data suggest that ALKBH6 is required to maintain the integrity of the genome and promote cell survival of pancreatic cancer cells.

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Abstract 5482: Constitutive overexpression of nrf2 in esophageal adenocarcinoma protects cancer cells from bile salts-induced DNA damage and favors cancer cell survival

10.1158/1538-7445.am2017-5482 ◽

2017 ◽

Author(s):

Dunfa Peng ◽

Tianling Hu ◽

Shoumin Zhu ◽

Wael El-Rifai

Keyword(s):

Dna Damage ◽

Cell Survival ◽

Cancer Cells ◽

Esophageal Adenocarcinoma ◽

Cancer Cell ◽

Bile Salts ◽

Cancer Cell Survival ◽

Constitutive Overexpression

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G9a coordinates with the RPA complex to promote DNA damage repair and cell survival

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1700694114 ◽

2017 ◽

Vol 114 (30) ◽

pp. E6054-E6063 ◽

Cited By ~ 24

Author(s):

Qiaoyan Yang ◽

Qian Zhu ◽

Xiaopeng Lu ◽

Yipeng Du ◽

Linlin Cao ◽

...

Keyword(s):

Dna Damage ◽

Cell Survival ◽

Cancer Cells ◽

Dna Damage Repair ◽

Protein A ◽

Dna Double Strand Breaks ◽

Gene Suppression ◽

Cancer Cell Growth ◽

Strand Breaks ◽

Damage Repair

Histone methyltransferase G9a has critical roles in promoting cancer-cell growth and gene suppression, but whether it is also associated with the DNA damage response is rarely studied. Here, we report that loss of G9a impairs DNA damage repair and enhances the sensitivity of cancer cells to radiation and chemotherapeutics. In response to DNA double-strand breaks (DSBs), G9a is phosphorylated at serine 211 by casein kinase 2 (CK2) and recruited to chromatin. The chromatin-enriched G9a can then directly interact with replication protein A (RPA) and promote loading of the RPA and Rad51 recombinase to DSBs. This mechanism facilitates homologous recombination (HR) and cell survival. We confirmed the interaction between RPA and G9a to be critical for RPA foci formation and HR upon DNA damage. Collectively, our findings demonstrate a regulatory pathway based on CK2–G9a–RPA that permits HR in cancer cells and provide further rationale for the use of G9a inhibitors as a cancer therapeutic.

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Comparison of clonogenic cell survival and DNA damage induced by 188Re and X-rays in rat thyroid cells

Nuklearmedizin ◽

10.3413/nukmed-0842-16-08 ◽

2017 ◽

Vol 56 (01) ◽

pp. 47-54

Author(s):

Jana Arlt ◽

Liane Oehme ◽

Robert Freudenberg ◽

Jörg Kotzerke ◽

Roswitha Runge

Keyword(s):

Dna Damage ◽

Cell Survival ◽

Pearson Correlation ◽

Dna Lesions ◽

X Rays ◽

Dsb Repair ◽

Thyroid Cells ◽

X Ray ◽

Rat Thyroid ◽

Spearman Test

Summary Aim: Ionizing radiation produces DNA lesions among which DNA double strand breaks (DSB) are the most critical events. Radiation of various energy types might differ in their biological effectiveness. Here, we compared cell survival and DNA damage induced by 188Re and X-rays using YH2AX foci as a measure of DSB. The correlation between survival and residual foci was also analyzed. Methods: PCCl3 cells were irradiated with 200 kV X-rays (1.2 Gy/min) or 0.5-25 MBq/ml 188Re (1 h irradiation) achieving doses up to 10 Gy. By blocking of sodium iodide sym- porter (NIS) essentially extracellular activity could be guaranteed. Survival fractions (SF) were detected by colony forming assay. Initial and residual YH2AX foci (15 min and 24 h after irradiation) were assessed by immunos- taining. The relationship between SF and residual radiation induced YH2AX foci (RIF) was evaluated by Spearman and Pearson correlation tests. Results: We did not find significant differences between the survival curves in terms of the radiation quality. The D37 values were 4.6 Gy and 4.2 Gy for 188Re or X-ray, respectively. The initial foci numbers were in the same range for 188Re and X-ray, but higher levels of residual foci persisted after X-rays in comparison to 188Re (1 GyX-ray 6.5 ± 0.2; 1 GyRe-188 4.8 ± 0.2 RIF). Accordingly, for 188Re a higher extent of DSB repair was found. The Spearman test revealed a significant (p < 0.01) correlation between SF and residual RIF for both radiation modalities. Conclusion: No differences in terms of radiation were found for SF and initial foci. However, residual foci were lower for 188Re than for X-rays. A prediction of SF by residual foci should consider the properties of the radiation qualities that influence foci removal and DSB repair.

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ATM Is Required for the Prolactin-Induced HSP90-Mediated Increase in Cellular Viability and Clonogenic Growth After DNA Damage

Endocrinology ◽

10.1210/en.2017-00652 ◽

2017 ◽

Vol 159 (2) ◽

pp. 907-930 ◽

Cited By ~ 4

Author(s):

Ödül Karayazi Atici ◽

Anna Urbanska ◽

Sesha Gopal Gopinathan ◽

Florence Boutillon ◽

Vincent Goffin ◽

...

Keyword(s):

Breast Cancer ◽

Dna Damage ◽

Cell Viability ◽

Cell Survival ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Janus Kinase ◽

Drug Synergism ◽

Cellular Resistance ◽

Atm Protein

Abstract Prolactin (PRL) acts as a survival factor for breast cancer cells, but the PRL signaling pathway and the mechanism are unknown. Previously, we identified the master chaperone, heat shock protein 90 (HSP90) α, as a prolactin–Janus kinase 2 (JAK2)–signal transducer and activator of transcription 5 (STAT5) target gene involved in survival, and here we investigated the role of HSP90 in the mechanism of PRL-induced viability in response to DNA damage. The ataxia–telangiectasia mutated kinase (ATM) protein plays a critical role in the cellular response to double-strand DNA damage. We observed that PRL increased viability of breast cancer cells treated with doxorubicin or etoposide. The increase in cellular resistance is specific to the PRL receptor, because the PRL receptor antagonist, Δ1-9-G129R-hPRL, prevented the increase in viability. Two different HSP90 inhibitors, 17-allylamino-17-demethoxygeldanamycin and BIIB021, reduced the PRL-mediated increase in cell viability of doxorubicin-treated cells and led to a decrease in JAK2, ATM, and phosphorylated ATM protein levels. Inhibitors of JAK2 (G6) and ATM (KU55933) abolished the PRL-mediated increase in cell viability of DNA-damaged cells, supporting the involvement of each, as well as the crosstalk of ATM with the PRL pathway in the context of DNA damage. Drug synergism was detected between the ATM inhibitor (KU55933) and doxorubicin and between the HSP90 inhibitor (BIIB021) and doxorubicin. Short interfering RNA directed against ATM prevented the PRL-mediated increase in cell survival in two-dimensional cell culture, three-dimensional collagen gel cultures, and clonogenic cell survival, after doxorubicin treatment. Our results indicate that ATM contributes to the PRL–JAK2–STAT5–HSP90 pathway in mediating cellular resistance to DNA-damaging agents.

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