Growth Arrest And DNA Damage-inducible 45 Alpha Research Articles

Gene Expression Alterations Associated with Sanguinarine‐Induced Antiproliferative effects and Apoptosis in Triple‐Negative Breast Cancer Cells

Sanguinarine (SAN) is a plant alkaloid found in various plants, mainly Sanguinaria canadensis. SAN has various pharmacological properties, including anti-bacterial, anti-fungal, anti-inflammatory, and anti-cancer effects. The current study investigated the mechanisms that mediated the anti-cancer effects of SAN in two triple-negative breast cancer (TNBC) cell lines; MDA-MB-231 and MDA-MB-468 cells. The data obtained suggested SAN is a potent compound in reducing cell viability and proliferation. Moreover, the results show that MDA-MB-468 cells were more sensitive than MDA-MB-231 cells to SAN. Also, SAN induced apoptosis in both cell lines by arresting cell growth. The compound arrested MDA-MB-231 cells at the Sub-G1 phase and MDA-MB-468 cells at the G2/M phase. Gene expression profiling indicated that MDA-MB-468 cells had significant transcription activation (2-4-fold) in eighteen genes. The genes activated include two members of the caspase family (caspase 1 and caspase 10), seven members of the TNF receptor superfamily (TNFRSF) such as TNFRSF10A, TNFRSF10B, TNFRSF11B, TNFRSF21, and TNFRSF25), in addition to TNFRSF1A Associated Via Death Domain (TRADD) and Fas-associated via death domain (FADD). On the other hand, in MDA-MB-231 cells, SAN was found to alter twelve five genes. The upregulated genes include Lymphotoxin Alpha (LTA; 15-fold), growth arrest and DNA damage-inducible 45 alpha (GADD45A), BCL2 Related Protein A1 (BCL2A1), BCL2-Like 11 (BCL2L11), and Bcl-2-Binding Protein Bis (BAG3). These results provide evidence that genetically different cells may respond differently to treatments, explaining the inadequate therapeutic response of some patients with advanced TNBC. The data also suggest that this plant alkaloid SAN could have therapeutic potential for TNBC patients.

Gene Expression Alterations Associated with Oleuropein-Induced Antiproliferative Effects and S-Phase Cell Cycle Arrest in Triple-Negative Breast Cancer Cells.

It is known that the Mediterranean diet is effective in reducing the risk of several chronic diseases, including cancer. A critical component of the Mediterranean diet is olive oil, and the relationship between olive oil consumption and the reduced risk of cancer has been established. Oleuropein (OL) is the most prominent polyphenol component of olive fruits and leaves. This compound has been shown to have potent properties in various types of cancers, including breast cancer. In the present study, the molecular mechanism of OL was examined in two racially different triple-negative breast cancer (TNBC) cell lines—African American (AA, MDA-MB-468) and Caucasian American (CA, MDA-MB-231). The data obtained showed that OL effectively inhibits cell growth in both cell lines, concomitant with S-phase cell cycle arrest-mediated apoptosis. The results also showed that OL-treated MDA-MB-468 cells were two-fold more sensitive to OL antiproliferative effect than MDA-MB-231 cells were. At lower concentrations, OL modified the expression of many apoptosis-involved genes. OL was more effective in MDA-MB-468, compared to MDA-MB-231 cells, in terms of the number and the fold-change of the altered genes. In MDA-MB-468 cells, OL induced a noticeable transcription activation in fourteen genes, including two members of the caspase family: caspase 1 (CASP1) and caspase 14 (CASP14); two members of the TNF receptor superfamily: Fas-associated via death domain (FADD) and TNF receptor superfamily 21 (TNFRSF21); six other proapoptotic genes: growth arrest and DNA damage-inducible 45 alpha (GADD45A), cytochrome c somatic (CYCS), BCL-2 interacting protein 2 (BNIP2), BCL-2 interacting protein 3 (BNIP3), BH3 interacting domain death agonist (BID), and B-cell lymphoma/leukemia 10 (BCL10); and the CASP8 and FADD-like apoptosis regulator (CFLAR) gene. Moreover, in MDA-MB-468 cells, OL induced a significant upregulation in two antiapoptotic genes: bifunctional apoptosis regulator (BFAR) and B-Raf proto-oncogene (BRAF) and a baculoviral inhibitor of apoptosis (IAP) repeat-containing 3 (BIRC3). On the contrary, in MDA-MB-231 cells, OL showed mixed impacts on gene expression. OL significantly upregulated the mRNA expression of four genes: BIRC3, receptor-interacting serine/threonine kinase 2 (RIPK2), TNF receptor superfamily 10A (TNFRSF10A), and caspase 4 (CASP4). Additionally, another four genes were repressed, including caspase 6 (CASP6), pyrin domain (PYD), and caspase recruitment domain (CARD)-containing (PAYCARD), baculoviral IAP repeat-containing 5 (BIRC5), and the most downregulated TNF receptor superfamily member 11B (TNFRSF11B, 16.34-fold). In conclusion, the data obtained indicate that the two cell lines were markedly different in the anticancer effect and mechanisms of oleuropein’s ability to alter apoptosis-related gene expressions. The results obtained from this study should also guide the potential utilization of oleuropein as an adjunct therapy for TNBC to increase chemotherapy effectiveness and prevent cancer progression.

Abstract PO-132: Rosmarinic acid-induced apoptosis and cell cycle arrest in triple-negative breast cancer cells

Abstract Rosmarinic acid (RA) is a polyphenolic compound with various pharmacological properties, including anti-inflammatory, immunomodulatory, anti-mutagenic, antioxidant, and anticancer activities. This study evaluated the effects of RA in two racially different triple-negative breast cancer (TNBC) cell lines. One cell line was derived from Caucasian origin (MDA-MB-231), and another one was derived from an African American origin (MDA-MB-468). The apoptotic effect of RA was performed using An Annexin V-FITC Apoptosis Detection Kit, while the Propidium Iodide Flow Cytometry Kit was used to detect the cell cycle distribution. Gene expression profiling was established using Human Apoptosis PCR array. The results obtained show that RA significantly caused cytotoxic and antiproliferative effects in both cell lines in a dose- and time-dependent manner. It was noted that RA induced cell cycle arrest-related apoptosis and altered the expression of many apoptosis-involved genes differently. In MDA-MB-231 cells, RA arrested the cells in the G0/G1 phase. In contrast, RA causes S-phase arrest in MDA-MB-468 cells, leading to a 2-fold increase in the apoptotic effect compared to MDA-MB-231 cells. Furthermore, in MDA-MB- 231 cells, RA significantly upregulated the mRNA expression of three genes: Harakiri (HRK), tumor necrosis factor receptor superfamily 25 (TNFRSF25), and BCL-2 interacting protein 3 (BNIP3). In contrast, in the MDA-MB-468 cell line, RA induced a significant transcription activation in three genes, including TNF, growth arrest, and DNA damage-inducible 45 alpha (GADD45A), and BNIP3. Furthermore, RA repressed the expression of TNF receptor superfamily 11B (TNFRSF11B) in MDA-MB-231 cells in comparison to the ligand TNF superfamily member 10 (TNFSF10) and baculoviral IAP repeat-containing 5 (BIRC5) in MDA-MB-468 cells. In conclusion, the data suggest that the polyphenol RA may have a potential role in TNBC therapies, particularly in African American cells. Citation Format: Karam F.A. Soliman, Samia S. Messeha, Najla O. Zarmouh, Abrar Asiri. Rosmarinic acid-induced apoptosis and cell cycle arrest in triple-negative breast cancer cells [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-132.

Liquiritigenin decreases tumorigenesis by inhibiting DNMT activity and increasing BRCA1 transcriptional activity in triple-negative breast cancer.

As a selective estrogen receptor β agonist, the natural flavonoid liquiritigenin reportedly inhibits invasiveness of breast cancer cells, but its specific role and mechanism remain largely unclear. In this study, cells from the triple negative breast cancer lines MDA-MB-231 and BT549 were incubated with different concentrations of liquiritigenin. The results indicated that low concentrations had no significant cytotoxic effect, whereas high concentrations decreased viability of both MDA-MB-231 and BT549 cells. Liquiritigenin treatment also resulted in increased apoptosis and enhanced Caspase3 activity. After liquiritigenin treatment, we observed decreased invasive and migratory capacities of cells, as well as upregulated E-cadherin and downregulated N-cadherin, vimentin, and MMP9. Interestingly, liquiritigenin increased the mRNA and protein expression of breast cancer 1 (BRCA1). It also increased p21 and growth arrest and DNA-damage-inducible 45 alpha (GADD45A) levels, accompanied by decreased cellular DNA methyltransferase (DNMT) activity and downregulation of DNMT1, DNMT3a, and DNMT3b. These findings suggest that liquiritigenin can inhibit malignant behavior of triple negative breast cancer cells by inhibiting DNMT activity and increasing BRCA1 expression and its transcriptional activity. Liquiritigenin thus may be a promising candidate for the treatment of breast cancer.

Rosmarinic acid-induced apoptosis and cell cycle arrest in triple-negative breast cancer cells

Rosmarinic acid (RA) is a polyphenolic compound with various pharmacological properties, including, anti-inflammatory, immunomodulatory, and neuroprotective, as well as having antioxidant and anticancer activities. This study evaluated the effects and mechanisms of RA in two racially different triple-negative breast cancer (TNBC) cell lines. Results obtained show that RA significantly caused cytotoxic and antiproliferative effects in both cell lines in a dose- and time-dependent manner. Remarkably, RA induced cell cycle arrest-related apoptosis and altered the expression of many apoptosis-involved genes differently. In MDA-MB-231 cells, RA arrested the cells in the G0/G1 phase. In contrast, the data suggest that RA causes S-phase arrest in MDA-MB-468 cells, leading to a 2-fold increase in the apoptotic effect compared to MDA-MB-231 cells. Further, in MDA-MB-231 cells, RA significantly upregulated the mRNA expression of three genes: harakiri (HRK), tumor necrosis factor receptor superfamily 25 (TNFRSF25), and BCL-2 interacting protein 3 (BNIP3). In contrast, in the MDA-MB-468 cell line, the compound induced a significant transcription activation in three genes, including TNF, growth arrest and DNA damage-inducible 45 alpha (GADD45A), and BNIP3. Furthermore, RA repressed the expression of TNF receptor superfamily 11B (TNFRSF11B) in MDA-MB-231 cells in comparison to the ligand TNF superfamily member 10 (TNFSF10) and baculoviral IAP repeat-containing 5 (BIRC5) in MDA-MB-468 cells. In conclusion, the data suggest that the polyphenol RA may have a potential role in TNBC therapies, particularly in MDA-MB-468 cells.

Rosmarinic Acid‐Induced Apoptosis and Cell Cycle Arrest in Triple‐Negative Breast Cancer Cells

Rosmarinic acid (RA) is one of the potent polyphenolic compounds in rosemary (Rosmarinus officinalis) extract. The compound has shown various bioactive properties, including, anti‐inflammatory, immunomodulatory, anti‐mutagenic, hepatoprotective, and neuroprotective, as well as having antioxidant and anti‐cancer activity. This study evaluated the effects and mechanisms of RA in two triple‐negative breast cancer (TNBC) cell lines; MDA‐MB‐231(MM‐231) and MDA‐MB‐468 (MM‐468); which were derived from a Caucasian and an African American woman, respectively. In this study, RA significantly and similarly inhibited cell viability and proliferation in both cell lines in a dose‐ and time‐dependent manner. The results obtained show that RA differentially affected the two cell lines in cell cycle arrest‐related apoptosis and in the alteration of the expression of many apoptosis‐involved genes. In MM‐231 cells, RA arrested the cells in the G0/G1 phase. In contrast, the data suggest that RA causes S‐phase arrest in MM‐468 cells and leads to a 2‐fold greater apoptotic effect than in MM‐231 cells. In MM‐231 cells, RA significantly upregulated the mRNA expression of three genes; harakiri (HRK), tumor necrosis factor receptor superfamily 25 (TNFRSF25), and BCL2 interacting protein 3 (BNIP3). In contrast, in MM‐468 cell line, the compound induced a significant transcription activation in five genes, including (TNF), baculoviral IAP repeat‐containing 3 (BIRC3), receptor‐interacting serine/threonine‐protein kinase 2 (RIPK2), BNIP3, and growth arrest and DNA damage‐inducible 45 alpha (GADD45A). Furthermore, RA repressed the expression of TNF receptor superfamily 11B (TNFRSF11B) in MM‐231 cells in comparison to the ligand TNF superfamily member 10 (TNFSF10) in MM‐468 cells. In conclusion, the data suggest that the polyphenol RA may have therapeutic potential for TNBC. However, RA should be further evaluated for in‐vivo studies and in non‐cancer cells.Support or Funding InformationU54 RCMI

Expression and prognostic significance of the P53‐related DNA damage repair proteins checkpoint kinase 1 (CHK1) and growth arrest and DNA‐damage‐inducible 45 alpha (GADD45A) in human oral squamous cell carcinoma

DNA damage repair is a key factor in the maintenance of cell genome stability, plays an important role in the regulation of tumour evolution, and can affect the prognosis of cancer patients. This study aimed to detect the protein expression of the DNA damage repair protein P53 and its upstream and downstream regulators, CHK1, GADD45A, and MDM2, in oral squamous cell carcinoma (OSCC), in order to analyse the association between the expression of these proteins and overall survival, and to assess their prognostic implications for OSCC patients. The expression of the above proteins was detected by immunohistochemistry in 80 human OSCC tissue samples and in non-cancerous tissue samples. Compared to that in the non-cancerous tissue, the expression of CHK1, GADD45A, and MDM2 in OSCC tissue was significantly increased. The protein expression of the tumour suppressor gene P53 was also increased. Patients with high CHK1 and MDM2 expression levels had a reduced survival time and a poor prognosis, whereas patients with high GADD45A expression levels had a good prognosis. Our results indicate that high CHK1 expression is an independent risk factor for poor OSCC prognosis, and that CHK1 may be a potential target for OSCC clinical treatment.

GADD45a Mediated Cell Cycle Inhibition Is Regulated By P53 In Bladder Cancer.

BackgroundBladder cancer (BC) is one of the most prevalent malignancies of the genitourinary system, yet the underlying mechanism of BC progression still remains unclear. Growth arrest and DNA damage-inducible 45 alpha (GADD45a) is a repressive gene implicated in cell cycle regulation, as well as in human cancers development. However, its role in BC remains to be determined.MethodsFirst, quantitative real-time polymerase chain reaction (PCR) and Western blot assays were used to detect GADD45a expression in BC tissues and adjacent non-tumor tissues, as well as in bladder cancer cell lines, respectively. Then, cell counting kit-8 (CCK-8) assays, colony formation assays, and flow cytometry assays were used to measure the ability of cell growth, proliferation and cell cycle distribution. Lentiviral infection technology was used to increase gene expression, while siRNA interfering technology was used to knockdown gene expression. Finally, nude mice were used to construct tumor-burdened models in vivo by injecting tumor cells subcutaneously.ResultsPCR results showed that the level of GADD45a mRNA and protein levels were lower in BC tissues than in adjacent normal tissues. After increasing GADD45a expression, both the ability of growth and proliferation of BC cells were seriously impaired. Additionally, the upregulation of GADD45a expression resulted in BC cell cycle in G2/M and S phases in a p53-regulated pathway.ConclusionGADD45a-mediated cell cycle inhibition is regulated by p53 in bladder cancer cells.

Upregulation of a novel lncRNA LINC01980 promotes tumor growth of esophageal squamous cell carcinoma

An increasing number of long noncoding RNAs (lncRNAs) have been discovered, and dysregulation of lncRNAs plays critical roles in tumorigenesis and tumor progression. In this study, we identified a novel lncRNA LINC01980, located in both the cytoplasm and nucleus, which was significantly upregulated in esophageal squamous cell carcinoma (ESCC) tissues through microarray profiling. Further analysis revealed that LINC01980 overexpression was positively correlated with deeper invasion of cancer, positive lymph node metastasis, and advanced TNM stage. Additionally, high LINC01980 expression in ESCC tissues was associated with poor prognosis. In vitro and in vivo experiments demonstrated that LINC01980 promoted ESCC growth. EdU incorporation assay implied that LINC01980 accelerated ESCC proliferation. Flow cytometry analysis showed that knockdown of LINC01980 induced cell cycle arrest and increased apoptosis. Microarray analysis indicated that LINC01980 upregulated the expression of growth arrest and DNA damage inducible 45 alpha (GADD45A). Further experiments demonstrated that GADD45A promoted ESCC cell growth, indicating that GADD45A may be a downstream target of LINC01980. In conclusion, this study identified LINC01980 as a novel potential oncogene in ESCC, which can be a promising biomarker for prognosis and therapeutic targeting in ESCC.

Antineoplastic activity of isoliquiritigenin, a chalcone compound, in androgen-independent human prostate cancer cells linked to G2/M cell cycle arrest and cell apoptosis

Isoliquiritigenin is a natural chalcone derived from Glycyrrhiza, which has been reported to have anti-tumor activity in recent years. Here, we investigate the anticancer efficacy and associated mechanisms of isoliquiritigenin in human prostate cancer PC-3 and 22RV1 cells. Isoliquiritigenin (25–50μM) inhibited cell proliferation, induced cell apoptosis, and caused G2/M cell cycle arrest in vitro. This agent also repressed the growth of PC-3 xenograft tumors in vivo with the results of hematoxylin/eosin staining and immunohistochemistry staining showing differences between isoliquiritigenin-treated groups and control group. Next, we used microarray transcriptional profiling to identify isoliquiritigenin-regulated genes on PC-3 prostate cancer cells. Multiple genes involved in cell cycle, DNA damage, and apoptosis signaling pathways were changed remarkably with the treatment of isoliquiritigenin. Molecular studies revealed that G2/M arrest was associated with a decrease in cyclin B1, cyclin-dependent kinase 1 (CDK1), and phosphorylated CDK1 (Thr14, Tyr15, and Thr161), whereas the expression of 14-3-3σ and growth arrest and DNA damage-inducible 45 alpha (GADD45A) was increased. The complexes of cyclin B1–CDK1 were also examined to show a decrease in the binding of CDK1 with cyclin B1. In addition, treatment with relatively high concentrations of isoliquiritigenin induced apoptosis, mainly associated with enhancing apoptosis regulator (Bax/Bcl-2) ratio. Collectively, these findings indicate that isoliquiritigenin modulates cyclin B1–CDK1 for G2/M arrest, together with an alteration of cell cycle regulators and apoptotic factors in human prostate cancer cells. However, we observed pleiotropic effects for isoliquiritigenin in microarray results, suggesting that other biological mechanisms also contribute to its efficacy, which could be of interest for future investigations.

Terminal differentiation induction as DNA damage response in hematopoietic stem cells by GADD45A.

Hematopoietic stem cells (HSCs) sustain lifelong blood cell regeneration by balancing their ability for self-renewal with their ability to differentiate into all blood cell types. To prevent organ exhaustion and malignant transformation, long-lived HSCs, in particular, must be protected from exogenous and endogenous stress, which cause severe DNA damage. When DNA is damaged, distinct DNA repair mechanisms and cell fate controls occur in adult HSCs compared with committed cells. Growth arrest and DNA damage-inducible 45 alpha (GADD45A) is known to coordinate a variety of cellular stress responses, indicating the molecule is an important stress mediator. So far, the function of GADD45A in hematopoietic stem and progenitor cells is controversial and appears highly dependent on the cell type and stress stimulus. Recent studies have analyzed its role in cell fate decision control of prospectively isolated HSCs and have revealed unexpected functions of GADD45A, as discussed here. The upregulation of GADD45A by DNA damage-causing conditions results in enhanced HSC differentiation, probably to efficiently eliminate aberrant HSCs from the system. These findings, in concert with a few studies on other stem cell systems, have led us to propose DNA damage-induced differentiation as a novel DNA damage response mechanism in stem cells that circumvents the fatal consequences of cumulative DNA damage in the stem cell compartment.

DNA-damage response gene GADD45A induces differentiation in hematopoietic stem cells without inhibiting cell cycle or survival.

Hematopoietic stem cells (HSCs) maintain blood cell production life‐long by their unique abilities of self‐renewal and differentiation into all blood cell lineages. Growth arrest and DNA‐damage‐inducible 45 alpha (GADD45A) is induced by genotoxic stress in HSCs. GADD45A has been implicated in cell cycle control, cell death and senescence, as well as in DNA‐damage repair. In general, GADD45A provides cellular stability by either arresting the cell cycle progression until DNA damage is repaired or, in cases of fatal damage, by inducing apoptosis. However, the function of GADD45A in hematopoiesis remains controversial. We revealed the changes in murine HSC fate control orchestrated by the expression of GADD45A at single cell resolution. In contrast to other cellular systems, GADD45A expression did not cause a cell cycle arrest or an alteration in the decision between cell survival and apoptosis in HSCs. Strikingly, GADD45A strongly induced and accelerated the differentiation program in HSCs. Continuous tracking of individual HSCs and their progeny via time‐lapse microscopy elucidated that once GADD45A was expressed, HSCs differentiate into committed progenitors within 29 hours. GADD45A‐expressing HSCs failed to long‐term reconstitute the blood of recipients by inducing multilineage differentiation in vivo. Importantly, γ‐irradiation of HSCs induced their differentiation by upregulating endogenous GADD45A. The differentiation induction by GADD45A was transmitted by activating p38 Mitogen‐activated protein kinase (MAPK) signaling and allowed the generation of megakaryocytic‐erythroid, myeloid, and lymphoid lineages. These data indicate that genotoxic stress‐induced GADD45A expression in HSCs prevents their fatal transformation by directing them into differentiation and thereby clearing them from the system. Stem Cells 2016;34:699–710

ATM is activated in blood monocytes after tumor radiation

Almost one million of cancer patients receive radiotherapy in USA every year. Therefore, it is very important to estimate their therapeutic responses to radiation and potential injury of normal tissues which can be manifested later in life [1]. Measure of potential radiation damage is also critically important in the event of a nuclear accident or terrorism efforts. Conventional approaches which allow to measure radiation damage and based on the evaluation of radiation-induced changes in blood chemistry and cell count and cytogenetic assessment of chromosomal aberrations [2] do not satisfy to contemporary demands of radiation medicine. Therefore, developing of new approaches evaluating radiation damage is acutely important in our days. Earlier we found that radiation induced expression of specific set of genes that encoded secreted bioactive proteins and were p53-dependent [3]. Moreover, we detected radiation-induced changes in activities of a number of transcription factors (TF) in mouse liver using transfection in vivo of TF plasmids developed by Attagene Inc. (Gudkov, Komarova, Makarov, personal observations). Acute response proteins and inflammatory cytokines, such as C-reactive protein, IL-6 [4] were detected in blood of animals after radiation. It was found that several proteins change their expression or undergo post-translational modifications after radiation and can be considered as putative markers of radiation exposure including CDKN1A (cyclin-dependent kinase inhibitor 1A), GADD45A (growth arrest and DNA-damage-inducible 45 alpha), BLM (Bloom syndrome protein), Tp53 (tumor protein p53), H2AX (Histone 2AX) and ATM (ataxia telangiectasia mutated) [5]. ATM, The Ser/Thr protein kinase, is known for its role as a main mobilizer of the cellular response to a radiation-induced severe DNA lesions, double-strand breaks (DSBs). In undamaged cells, quiescent ATM exists as homodimers, which dissociate into active monomers upon activation [6]. It was shown that autophosphorylation at Ser 1981, post transcriptional modification of ATM, is a hallmark of activated human ATM. It is still unclear what is the initial trigger of ATM activation. It was suggested that a chromatin conformational change that follows DSB formation rather than direct contact of ATM with broken DNA might activate ATM. Another studies suggested that direct interaction of ATM with broken DNA is required for its activation [6]. In the recent paper, Bakkenist et al [7] have found that ATM kinase activity is induced in monocytes of peripheral blood of cancer patients after first high dose fraction of Stereotactic body radiation therapy (SBRT), which was delivered to specific tumor targets including non-small cell lung cancer, pancreatic adenocarcinoma, renal cell carcinoma and gastroesophageal adenocarcinoma. This is the first demonstration of ATM serine-1981 phosphorylation and activation of ATM in patients following radiation. The authors detected activation of histone H2AX but in less degree in monocytes of the same patients. A similar picture they observed in vitro titrating dose-dependent induction of ATM and H2AX in cancer cell lines. It would be expected that ATM might be activated as a result of chemotherapeutic treatment in blood monocytes as well (the authors did not test this) because it was shown that ATM might be activated not only by DSBs but by another genotoxic stresses (for example single strand brakes) and nongenotoxic stresses including hypoxia, hyperthermia, oxidative stress [6]. Moreover, it was shown that oxidative stress induced by phorbol myristate acetate was associated with intense phosphorylation of histone H2AX and with ATM activation in human peripheral blood leukocytes [8]. The data presented here show that ATM activation may be an excellent biomarker for exposure to radiation (and other agents) in human patients and may be used in predicting of their therapeutic response. Also, it is clear that even targeted local radiation therapy induces systemic DNA damage response seen in particular as activation of ATM. Systemic inhibition of ATM as the important member of DNA repair complex might increase the efficacy of targeted radiotherapy that is confirmed by recently developed ATM inhibitors (KU-55933, CGK733, and CP466722) that increased radiosensitization of tumor cells [9].

Gene expression following ionising radiation: Identification of biomarkers for dose estimation and prediction of individual response

Purpose: To establish a panel of highly radiation responsive genes suitable for biological dosimetry and to explore inter-individual variation in response to ionising radiation exposure.Materials and methods: Analysis of gene expression in response to radiation was carried out using three independent techniques (Microarray, Multiplex Quantitative Real-Time Polymerase Chain Reaction (MQRT- PCR) and nCounter® Analysis System) in human dividing lymphocytes in culture and peripheral blood leukocytes exposed ex vivo from the same donors.Results: Variations in transcriptional response to exposure to ionising radiation analysed by microarray allowed the identification of genes which can be measured accurately using MQRT PCR and another technique allowing direct count of mRNA copies. We have identified genes which are consistently up-regulated following exposure to 2 or 4 Gy of X-rays at different time points, for all individuals in blood and cultured lymphocytes. Down-regulated genes including cyclins, centromeric and mitotic checkpoint genes, particularly those associated with chromosome instability and cancer could be detected in dividing lymphocytes only.Conclusions: The data provide evidence that there are a number of genes which seem suitable for biological dosimetry using peripheral blood, including sestrin 1 (SESN1), growth arrest and DNA damage inducible 45 alpha (GADD45A), cyclin-dependent kinase inhibitor 1A (CDKN1A), cyclin G1 (CCNG1), ferredoxin reductase (FDXR), p53 up-regulated mediator of apoptosis (BBC3) and Mdm2 p53 binding protein homolog (MDM2). These biomarkers could potentially be used for triage after large-scale radiological incidents and for monitoring radiation exposure during radiotherapy.