Ataxia Telangiectasia Mutated Expression Research Articles

Silencing of ATM expression by siRNA technique contributes to glioma stem cell radiosensitivity in vitro and in vivo.

Evidence has shown that both high expression of the ataxia-telangiectasia mutated (ATM) gene and glioma stem cells (GSCs) are responsible for radioresistance in glioma. Thus, we hypothesized that brain tumor radiosensitivity may be enhanced via silencing of the ATM gene in GSCs. In the present study we successfully induced GSCs from two cell lines and used CD133 and nestin to identify GSCs. A lentivirus was used to deliver siRNA-ATMPuro (Agroup) to GSCs prior to radiation, while siRNA-HKPuro (Ngroup) and GSCs (Cgroup) were used as negative and blank controls, respectively. RT-qPCR and western blotting were performed to verify the efficiency of the siRNA-ATM technique. The expression of the ATM gene and ATM protein were significantly downregulated post-transfection. Cell Counting Kit-8 (CCK-8) and colony formation assays revealed that the Agroup demonstrated weak cell proliferation and lower survival fractions post-irradiation compared to the C/Ngroups. Flow cytometry was used to examine the percentage of cell apoptosis and G2phase arrest, which were both higher in the Agroup than in the C/Ngroups. We found that the comet tail percentage evaluated by comet assay was higher in the Agroup than in the C/Ngroups. After radiation treatment, three radiosensitive genes [p53, proliferating cell nuclear antigen (PCNA), survivin] exhibited a decreasing tendency as determined by RT-qPCR. Mice underwent subcutaneous implantation, followed by radiation, and the resulting necrosis and hemorrhage were more obvious in the Agroup than in the Ngroups. In conclusion, silencing of ATM via the siRNA technique improved radiosensitivity of GSCs both invitro and invivo.

ATM Expression Predicts Veliparib and Irinotecan Sensitivity in Gastric Cancer by Mediating P53-Independent Regulation of Cell Cycle and Apoptosis

Identification of synthetically lethal cellular targets and synergistic drug combinations is important in cancer chemotherapy as they help to overcome treatment resistance and increase efficacy. The Ataxia Telangiectasia Mutated (ATM) kinase is a nuclear protein that plays a major role in the initiation of DNA repair signaling and cell-cycle check points during DNA damage. Although ATM was shown to be associated with poor prognosis in gastric cancer, its implications as a predictive biomarker for cancer chemotherapy remain unexplored. The present study evaluated ATM-induced synthetic lethality and its role in sensitization of gastric cancer cells to PARP and TOP1 inhibitors, veliparib (ABT-888) and irinotecan (CPT-11), respectively. ATM expression was detected in a panel of gastric cell lines, and the IC50 against each inhibitors was determined. The combinatorial effect of ABT-888 and CPT-11 in gastric cancer cells was also determined both in vitro and in vivo ATM deficiency was found to be associated with enhanced sensitivity to ABT-888 and CPT-11 monotherapy, hence suggesting a mechanism of synthetic lethality. Cells with high ATM expression showed reduced sensitivity to monotherapy; however, they showed a higher therapeutic effect with ABT-888 and CPT-11 combinatorial therapy. Furthermore, ATM expression was shown to play a major role in cellular homeostasis by regulating cell-cycle progression and apoptosis in a P53-independent manner. The present study highlights the clinical utility of ATM expression as a predictive marker for sensitivity of gastric cancer cells to PARP and TOP1 inhibition and provides a deeper mechanistic insight into ATM-dependent regulation of cellular processes. Mol Cancer Ther; 15(12); 3087-96. ©2016 AACR.

Antisense Oligonucleotides Modulating Activation of a Nonsense-Mediated RNA Decay Switch Exon in the ATM Gene.

ATM (ataxia-telangiectasia, mutated) is an important cancer susceptibility gene that encodes a key apical kinase in the DNA damage response pathway. ATM mutations in the germ line result in ataxia-telangiectasia (A-T), a rare genetic syndrome associated with hypersensitivity to double-strand DNA breaks and predisposition to lymphoid malignancies. ATM expression is limited by a tightly regulated nonsense-mediated RNA decay (NMD) switch exon (termed NSE) located in intron 28. In this study, we identify antisense oligonucleotides that modulate NSE inclusion in mature transcripts by systematically targeting the entire 3.1-kb-long intron. Their identification was assisted by a segmental deletion analysis of transposed elements, revealing NSE repression upon removal of a distant antisense Alu and NSE activation upon elimination of a long terminal repeat transposon MER51A. Efficient NSE repression was achieved by delivering optimized splice-switching oligonucleotides to embryonic and lymphoblastoid cells using chitosan-based nanoparticles. Together, these results provide a basis for possible sequence-specific radiosensitization of cancer cells, highlight the power of intronic antisense oligonucleotides to modify gene expression, and demonstrate transposon-mediated regulation of NSEs.

Abstract 4937: Atm expression predicts ABT-888 and CPT-11 sensitivity in gastric cancer cells by mediating p53 independent regulation of cell cycle and apoptosis

Abstract Background: Identification of synthetically lethal cellular targets and synergistic drug combinations are important in cancer chemo therapy as they help to overcome treatment resistance and increase efficacy. The Ataxia Telangiectasia Mutated (ATM) kinase is a nuclear protein that plays a major role in the initiation of DNA repair signalling and cell cycle check points during DNA damage. Although ATM was shown to be associated with poor prognosis in gastric cancer, its potential implication as a predictive biomarker for cancer chemotherapy remains unexplored. The present study evaluated ATM induced synthetic lethality and its role in sensitization of gastric cancer cells to PARP and TOP1 inhibitors, ABT-888 and CPT-11 respectively. Methods: ATM expression in a panel of 10 gastric cancer cells were detected by immunohistochemistry and the IC50 against ABT-888 and CPT-11 was determined by MTS cell proliferation assay. The synergistic effect of ABT-888 and CPT-11 in gastric cancer cells was determined by cell cycle and DNA damage assays. ATM expression was knocked down using siRNA and its effect in P53 induced cell cycle regulation and apoptosis was determined by immunoblot analysis. Results and Conclusion: ATM deficiency was found to be associated with enhanced sensitivity to ABT-888 and CPT-11 monotherapy, hence suggesting a mechanism of synthetic lethality. Cells with high ATM expression showed reduced sensitivity to monotherapy, however showed a higher synergistic effect towards ABT-888 and CPT-11 combinational therapy that predisposed cells to enhanced drug sensitivity. Furthermore, ATM expression was shown to play a major role in cellular homeostasis by regulating cell cycle progression and apoptosis in a P53 independent manner. The present study highlights the clinical utility of ATM expression as a predictive marker for sensitivity of gastric cancer cell to PARP and TOP1 inhibition and provides a deeper mechanistic insight into ATM dependent regulation of cellular processes. Citation Format: Vinod Vijayasubhash, Shihui Tan, Fui Leng Yan, Natalia Liem, Wei Peng Yong. Atm expression predicts ABT-888 and CPT-11 sensitivity in gastric cancer cells by mediating p53 independent regulation of cell cycle and apoptosis. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4937.

Loss of ataxia-telangiectasia-mutated protein expression correlates with poor prognosis but benefits from anthracycline-containing adjuvant chemotherapy in breast cancer

We investigated the correlation of ataxia-telangiectasia-mutated (ATM) protein expression with clinicopathological features and prognosis in patients with breast cancer. ATM expression was determined by immunohistochemistry in 420 surgically resected breast tumors. ATM loss was observed in 126/407 evaluable cases (31.0%), and was significantly associated with larger tumor size, lymph node metastasis, higher tumor grade, and ER- and/or PR-negative status. ATM loss was also associated with significantly lower disease-free survival rates than those in patients with intact ATM (5-year disease-free survival rate 81.2 vs. 90.7%, p=0.015). In multivariate analysis, ATM loss combined with abnormal p53 expression was an independent predictor of shorter disease-free survival [hazard ratio (HR) 3.48; 95% confidence interval (CI), 1.48-8.17, p=0.004]. A tendency towards a poorer prognosis was observed for tumoral ATM loss alone, although statistical significance was not reached (HR 1.74; 95% CI 0.95-3.20; p=0.075). In subgroup analysis, ATM loss was associated with shorter disease-free survival in patients who did not receive adjuvant anthracycline chemotherapy (5-year disease-free survival rate 92.7% in intact ATM group vs. 68.1% in ATM loss group, p=0.002), but this poor prognosis was overcome in patients who did (5-year disease-free survival rate 89.8 vs. 84.4%, p=0.243), suggesting more benefit from anthracycline-based chemotherapy. Tumors with loss of ATM expression have a poor prognosis and their prognoses are dependent on the use of adjuvant anthracycline. ATM loss might be a practical tool for predicting benefits from anthracycline-based adjuvant therapy.

Abstract P4-07-08: The prognostic significance of ataxia-telangiectasia-mutated (ATM) and p53 expression in breast cancer

Abstract The purpose of this study was to investigate the correlation of ataxia-telangiectasia-mutated (ATM) protein and p53 expression with clinicopathological features and prognosis in patients with sporadic breast cancers. The expression of ATM and p53 was determined by immunohistochemistry in 420 surgically resected breast cancers. Loss of ATM was observed in 126 out of 407 evaluable cases (31.0%), and was significantly associated with aggressive features with large tumor size, lymph node metastasis, higher tumor grade, and negativity of ER and/or PR. ATM loss was associated with a significantly shorter disease-free survival (DFS) (p = 0.019). Abnormal p53 expression was found in 39.3% of tumors (157 out of 400), conferring a worse DFS as well (p = 0.002). When investigated together, combined ATM and p53 expression status were associated with a worse DFS (p = 0.002). On multivariate analysis, ATM loss and abnormal p53 expression status was an independent predictor of poorer DFS (intact ATM and normal p53 vs. ATM loss and abnormal p53, HR 3.350; 95% CI 1.496 - 7.502; p = 0.003). Furthermore, in patients treated with adjuvant anthracyclines, either p53 alone or p53 combined with ATM significantly influenced DFS (p = 0.004, p = 0.015, respectively). The present study demonstrates that expression of ATM and p53 is an independent prognostic marker in breast cancers, and might be a practical tool for predicting benefits from anthracycline-based adjuvant therapy. Citation Format: Suh KJ, Ryu HS, Lee K-H, Im S-A, Kim T-Y, Kim H, Yang Y, Moon H-G, Han S-W, Oh D-Y, Han W, Kim T-Y, Park IA, Noh D-Y, Bang Y-J. The prognostic significance of ataxia-telangiectasia-mutated (ATM) and p53 expression in breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-07-08.

Early marker of DNA damage response, atm, as a predictor of clinical outcome following radiotherapy in rectal cancer patients

Early marker of DNA damage response, atm, as a predictor of clinical outcome following radiotherapy in rectal cancer patients

Histopathology of interspincteric resection specimens of low rectal cancer: An institutional experience of a series of 41 patients

Histopathology of interspincteric resection specimens of low rectal cancer: An institutional experience of a series of 41 patients

Infection of a Single Cell Line with Distinct Strains of Human Cytomegalovirus Can Result in Large Variations in Virion Production and Facilitate Efficient Screening of Virus Protein Function.

Previously, we reported that the absence of the ataxia telangiectasia mutated (ATM) kinase, a critical DNA damage response (DDR) signaling component for double-strand breaks, caused no change in HCMV Towne virion production. Later, others reported decreased AD169 viral titers in the absence of ATM. To address this discrepancy, human foreskin fibroblasts (HFF) and three ATM(-) lines (GM02530, GM05823, and GM03395) were infected with both Towne and AD169. Two additional ATM(-) lines (GM02052 and GM03487) were infected with Towne. Remarkably, both previous studies' results were confirmed. However, the increased number of cell lines and infections with both lab-adapted strains confirmed that ATM was not necessary to produce wild-type-level titers in fibroblasts. Instead, interactions between individual virus strains and the cellular microenvironment of the individual ATM(-) line determined efficiency of virion production. Surprisingly, these two commonly used lab-adapted strains produced drastically different titers in one ATM(-) cell line, GM05823. The differences in titer suggested a rapid method for identifying genes involved in differential virion production. In silico comparison of the Towne and AD169 genomes determined a list of 28 probable candidates responsible for the difference. Using serial iterations of an experiment involving virion entry and input genome nuclear trafficking with a panel of related strains, we reduced this list to four (UL129, UL145, UL147, and UL148). As a proof of principle, reintroduction of UL148 largely rescued genome trafficking. Therefore, use of a battery of related strains offers an efficient method to narrow lists of candidate genes affecting various virus life cycle checkpoints. Human cytomegalovirus (HCMV) infection of multiple cell lines lacking ataxia telangiectasia mutated (ATM) protein produced wild-type levels of infectious virus. Interactions between virus strains and the microenvironment of individual ATM(-) lines determined the efficiency of virion production. Infection of one ATM(-) cell line, GM05823, produced large titer differentials dependent on the strain used, Towne or AD169. This discrepancy resolved a disagreement in the literature of a requirement for ATM expression and HCMV reproduction. The titer differentials in GM08523 cells were due, in part, to a decreased capacity of AD169 virions to enter the cell and traffic genomes to the nucleus. In silico comparison of the Towne, AD169, and related variant strains' genomes was coupled with serial iterations of a virus entry experiment, narrowing 28 candidate proteins responsible for the phenotype down to 4. Reintroduction of UL148 significantly rescued genome trafficking. Differential behavior of virus strains can be exploited to elucidate gene function.

Ataxia-telangiectasia mutated (ATM) participates in the regulation of ionizing radiation-induced cell death via MAPK14 in lung cancer H1299 cells.

The role of Ataxia-telangiectasia mutated (ATM) in response to DNA damage has previously been studied, but its underlying mechanisms specific to ionizing radiation (IR) have remained to be elucidated. In this study, function of ATM on radiation-induced cell death in lung cancer H1299 cells was analysed. Human lung cancer cells, H1299, were used, and cell models with ATM(-/-) and MAPK14(-/-) were established by genetic engineering. Radiosensitivity was analysed using colony formation assays. Western blotting and co-immunoprecipitation were implemented to detect protein expression and interaction. MDC staining and GFP-LC3 relocalization were used to detect autophagy. Autophagy as well as phosphorylation of ATM was activated by ionizing radiation. Both the inhibitor of ATM, KU55933 and ATM silencing reduced phosphorylation of ATM and MAPKAPK2 expression. Both ATM(-/-) and MAPK14(-/-) cells displayed hypersensitivity. IR increased autophagy level by more than 129% in DMSO-treated cells, while only by 47% and 27% in KU55933-treated and ATM(-/-) cells respectively. MAPK14 knock-down alone gave rise to the basal autophagy level, but decreased notably after IR. KU55933 and ATM knock-down inhibited IR-induced autophagy by activating mTOR pathways. Both Beclin1-PI3KIII and Beclin1-MAPKAPK2 interactions as were remarkably affected by silencing either ATM or MAPK14. ATM promoted IR-induced autophagy via the MAPK14 pathway, mTOR pathway and Beclin1/PI3KIII complexes. MAPK14 contributed to radiosensitization of H1299 cells.

Loss of ATM accelerates pancreatic cancer formation and epithelial-mesenchymal transition.

Pancreatic ductal adenocarcinoma (PDAC) is associated with accumulation of particular oncogenic mutations and recent genetic sequencing studies have identified ataxia telangiectasia-mutated (ATM) mutations in PDAC cohorts. Here we report that conditional deletion of ATM in a mouse model of PDAC induces a greater number of proliferative precursor lesions coupled with a pronounced fibrotic reaction. ATM-targeted mice display altered TGFβ-superfamily signalling and enhanced epithelial-to-mesenchymal transition (EMT) coupled with shortened survival. Notably, our mouse model recapitulates many features of more aggressive human PDAC subtypes. Particularly, we report that low expression of ATM predicts EMT, a gene signature specific for Bmp4 signalling and poor prognosis in human PDAC. Our data suggest an intimate link between ATM expression and pancreatic cancer progression in mice and men.

ATM, THMS, and RRM1 protein expression in nasopharyngeal carcinomas treated with curative intent.

In advanced nasopharyngeal carcinoma (NPC), biomarkers may help predict survival. Tumoral expression of ataxia-telangiectasia mutated (ATM), thymidylate synthetase (THMS), and ribonucleotide reductase subunit M1 (RRM1), was correlated with survival in patients with nonmetastatic NPC using quantitative fluorescence immunohistochemistry with automated quantitative digital image analysis. Of the 146 patients included, 58 patients (40%) received concurrent chemoradiation therapy; the remainder was treated with radiation. Overall survival (OS) at 5 years was 71% (95% confidence interval [CI], 62% to 78%); disease-free survival (DFS) was 48% (95% CI, 39% to 57%). OS worsened for increasing values of ATM (hazard ratio [HR], 2.83; 95% CI, 1.01-7.94; p = .049) for values greater than the 75th percentile compared to less than the 25th percentile, but improved for tumors with higher THMS levels (HR, 0.44; 95% CI, 0.20-0.94; p = .033) for values greater than the 25th percentile compared to less than or equal to the 25th percentile. RRM1 was not associated with OS (p = .748). No biomarkers were associated with DFS. In our cohort, relative overexpression of ATM and low THMS levels were associated with worse OS. © 2015 Wiley Periodicals, Inc. Head Neck 38: E384-E391, 2016.

MiR-181a promotes G1/S transition and cell proliferation in pediatric acute myeloid leukemia by targeting ATM.

Abnormal expression of miRNAs is intimately related to a variety of human cancers. The purpose of this study is to confirm the expression of miR-181a and elucidate its physiological function and mechanism in pediatric acute myeloid leukemia (AML). Pediatric AML patients and healthy controls were enrolled, and the expression of miR-181a and ataxia telangiectasia mutated (ATM) in tissues were examined using quantitative PCR. Moreover, cell proliferation and cell cycle were evaluated in several cell lines (HL60, NB4 and K562) by using flow cytometry after transfected with miR-181a mimics and inhibitors, or ATM siRNA and control siRNA. Finally, ATM as the potential target protein of miR-181a was examined. We found that miR-181a was significantly increased in pediatric AML, which showed an inverse association with ATM expression. Overexpressed miR-181a in cell lines significantly enhanced cell proliferation, as well as increased the ratio of S-phase cells by miR-181a mimics transfection in vitro. Luciferase activity of the reporter construct identified ATM as the direct molecular target of miR-181a. ATM siRNA transfection significantly enhanced cell proliferation and increased the ratio of S-phase cells in vitro. The results revealed novel mechanism through which miR-181a regulates G1/S transition and cell proliferation in pediatric AML by regulating the tumor suppressor ATM, providing insights into the molecular mechanism in pediatric AML.

Ataxia-telangiectasia mutated (ATM) silencing promotes neuroblastoma progression through a MYCN independent mechanism.

Neuroblastoma, a childhood cancer with highly heterogeneous biology and clinical behavior, is characterized by genomic aberrations including amplification of MYCN. Hemizygous deletion of chromosome 11q is a well-established, independent marker of poor prognosis. While 11q22-q23 is the most frequently deleted region, the neuroblastoma tumor suppressor in this region remains to be identified. Chromosome bands 11q22-q23 contain ATM, a cell cycle checkpoint kinase and tumor suppressor playing a pivotal role in the DNA damage response. Here, we report that haploinsufficiency of ATM in neuroblastoma correlates with lower ATM expression, event-free survival, and overall survival. ATM loss occurs in high stage neuroblastoma without MYCN amplification. In SK-N-SH, CLB-Ga and GI-ME-N human neuroblastoma cells, stable ATM silencing promotes neuroblastoma progression in soft agar assays, and in subcutaneous xenografts in nude mice. This effect is dependent on the extent of ATM silencing and does not appear to involve MYCN. Our findings identify ATM as a potential haploinsufficient neuroblastoma tumor suppressor, whose inactivation mirrors the increased aggressiveness associated with 11q deletion in neuroblastoma.

Low ATM protein expression in malignant tumor as well as cancer-associated stroma are independent prognostic factors in a retrospective study of early-stage hormone-negative breast cancer.

IntroductionThe serine/threonine protein kinase ataxia telangiectasia mutated (ATM) is critical in maintaining genomic integrity. Upon DNA double-strand breaks, ATM phosphorylates key downstream proteins including p53 and BRCA1/2, thereby orchestrating complex signaling pathways involved in cell cycle arrest, DNA repair, senescence and apoptosis. Although sporadic mutation of ATM occurs rarely in breast cancer, the status of its protein expression and its clinical significance in breast cancer remain not well established. Our study was designed to investigate the influence of ATM protein in both tumor and cancer-associated stroma on clinical outcome in hormone-positive (HPBC) and hormone-negative (HNBC) early-stage breast cancer (EBC).MethodsTissue microarrays (TMAs), containing formalin-fixed, paraffin-embedded resected tumors from two cohorts of patients (HPBC cohort: n = 130; HNBC cohort: n = 168) diagnosed at the Tom Baker Cancer Centre, Calgary, Canada, were analyzed for ATM protein expression using fluorescence immunohistochemistry (IHC) and automated quantitative analysis (AQUA). ATM expression levels were measured within the tumor as a whole (tATM) as indicated by pan-cytokeratin expression, tumor nuclear compartment (nATM) as indicated by both DAPI and pan-cytokeratin-positive results, and cancer-associated stroma (csATM) as indicated by vimentin-positive and pan-cytokeratin-negative results. ATM expression levels within these compartments were correlated with clinical outcome.ResultsWhile tATM and nATM were significantly lower in tumors compared to normal breast epithelial tissues, csATM was significantly higher than the corresponding normal tissue compartment. In addition, the median expression level of both tATM and nATM were two- to threefold lower (P <0.001) in HNBC than in HPBC. In both HNBC and HPBC cohorts, patients with low tATM, nATM and csATM tumors had significantly poorer survival outcomes than those with a high tATM, nATM and csATM, but this effect was more pronounced in HNBC. A multivariate analysis demonstrates that these biomarkers predict survival independent of tumor size and lymph node status, but only in the HNBC cohort (P <0.001).ConclusionsLow ATM protein expression in both malignant tumor and stromal compartments likely contributes to the aggressive nature of breast cancer and is an independent prognostic factor associated with worse survival in HNBC patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13058-015-0575-2) contains supplementary material, which is available to authorized users.

ATM has a major role in the double-strand break repair pathway dysregulation in sporadic breast carcinomas and is an independent prognostic marker at both mRNA and protein levels.

Background:Ataxia telangiectasia mutated (ATM) is a kinase that has a central role in the maintenance of genomic integrity by activating cell cycle checkpoints and promoting repair of DNA double-strand breaks (DSB). In breast cancer, a low level of ATM was correlated with poor outcome; however, the molecular mechanism of this downregulation is still unclear.Methods:We used qRT–PCR assay to quantify mRNA levels of ATM gene in 454 breast tumours from patients with known clinical/pathological status and outcome; reverse phase protein arrays (RPPA) were used to assess the levels of ATM and 14 proteins in 233 breast tumours.Results:ATM mRNA was associated with poor metastasis-free survival (MFS) (P=0.00012) on univariate analysis. ATM mRNA and protein levels were positively correlated (P=0.00040). A low level of ATM protein was correlated with poorer MFS (P=0.000025). ATM expression at mRNA or protein levels are independent prognostic factors on multivariate analysis (P=0.00046 and P=0.00037, respectively). The ATM protein level was positively correlated with the levels of six proteins of the DSB repair pathway: H2AX (P<0.0000001), XRCC5 (P<0.0000001), NBN (P<0.0000001), Mre11 (P=0.0000029), Rad50 (P=0.0064), and TP53BP1 (P=0.026), but not with proteins involved in other pathways that are altered in cancer. Low expression of ATM protein was significantly associated with high miR-203 expression (P=0.011).Conclusion:We confirmed that ATM expression is an independent prognostic marker at both RNA and protein levels. We showed that alteration of ATM is involved in dysregulation of the DSB repair pathway. Finally, miR-203 may be responsible for downregulation of ATM in breast cancers.

Ataxia-telangiectasia-mutated protein kinase levels stratify patients with pancreatic adenocarcinoma into prognostic subgroups with loss being a strong indicator of poor survival.

Recently, aberrations in the gene encoding for ataxia-telangiectasia-mutated (ATM) protein kinase have been reported for pancreatic ductal adenocarcinomas (PDAC). These findings argue that ATM deficiency may play a role during carcinogenesis. Therefore, in this study, we investigated the clinical relevance of ATM expression and ATM activation in PDAC. Both ATM expression and nuclear phosphoSer1981-ATM levels were assessed by immunohistochemistry in a cohort of 133 PDAC and correlated with clinicopathological parameters. We found stratification in prognostic subgroups. Complete loss of Ser1981-ATM was indicative of the worst prognosis (median survival, 10.8 vs 14.3 months [low expression] vs 31.1 months [high expression], P < 0.001). Similarly, analysis of ATM expression demonstrated absent expression levels of ATM to be associated with dismal prognosis (median survival, 9.6 months), whereas expression of ATM in general was associated with increased survival (17.7 months, P = 0.001). Our analysis shows that both ATM expression and activated ATM are prognostic markers in PDAC with respect to standard clinicopathological parameters. These results suggest that ATM should be further explored as prognostic as well as predictive factor with respect to conventional chemotherapies and for putative synthetic lethal approaches.

The ATM inhibitor KU55933 sensitizes radioresistant bladder cancer cells with DAB2IP gene defect

Purpose: Our preliminary results showed that differentially expressed in ovarian cancer-2/disabled homolog 2 (DOC-2/DAB2) interactive protein (DAB2IP), a putative tumor suppressor gene, is down-regulated in bladder cancer (BCa) with aggressive phenotypes. In this study, we investigated how DAB2IP knockdown influenced BCa cell response to ionizing radiation (IR) and discussed possible ways to enhance cell radiosensitivity.Methods and materials: The small interfering RNA (siRNA) system was implemented to inhibit endogenous DAB2IP expression in two human BCa cell lines, T24 and 5637. Cell sensitivity to IR alone or combined treatment was measured by a colony formation assay (CFA). Western blot was used to determine the phosphorylation levels of ataxia-telangiectasia mutated (ATM), catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) and related DNA damage repair (DDR) proteins. Immunofluorescence as well as a flow cytometry assay were employed to detect DNA double-strand break (DSB) repair and cell cycle distribution, respectively.Results: DAB2IP-knockdown of BCa cells (i.e., siDAB2IP) exhibit increased clonogenic survival in response to IR compared with control cells (i.e., siCON) expressing an endogenous level of DAB2IP. The mechanism in siDAB2IP cells could be explained by elevated ATM expression and activation, increased S phase cell distribution as well as faster DSB repair kinetics. 2-morpholin-4-yl-6-thianthren-1-yl-pyran-4-one (KU55933) significantly sensitized siDAB2IP cells to IR due to inhibition of the phosphorylation of ATM and its downstream targets following IR and slower DSB repair kinetics.Conclusions: Loss of DAB2IP expression in BCa cells signifies their radioresistance. KU55933, which suppresses ATM phosphorylation upon irradiation, could be applied in the radiotherapy of BCa patients with a DAB2IP gene defect.

ATM may be a protective factor in endometrial carcinogenesis with the progesterone pathway.

The purpose of the study was to explore the role and mechanism of ataxia-telangiectasia mutated (ATM) protein in endometrial carcinogenesis. A reverse-phase protein array (RPPA) was used to analyze the expression of ATM signal pathway proteins in Ishikawa and progesterone-insensitive Ishikawa. ATM expression was detected in endometrium specimens by immunohistochemistry, including 8 cases with proliferative endometrium, 6 cases with secretory endometrium, 10 cases with simple hyperplasia (SH), 13 cases of complex hyperplasia (CH), 11 cases of endometrial atypical hyperplasia (EAH), and 83 cases with type I endometrial cancer. The relationship between ATM expression and other clinicopathological indicators was also examined in type I endometrial cancer patients. The mechanisms of ATM were explored in vitro with the endometrial cell lines Ishikawa and RL95-2. A cell counting kit-8 (CCK-8) test and Western blot analysis were performed to test proliferation and protein expression. Statistical analysis was performed with SPSS19.0. The significance level was set at 0.05. ATM was increased with medroxyprogesterone acetate (MPA) stimulation in Ishikawa in RPPA. ATM expression gradually decreased in endometrial hyperplasic lesions compared with the normal proliferative and secretory endometrium and was the lowest in type I endometrial cancer. ATM expression was negatively correlated with pathological grades in type I endometrial cancer. In vitro, ATM silencing retarded proliferation inhibition in Ishikawa and RL95-2 treated with MPA. ATM silencing could down-regulate the MPA-stimulated signal proteins, including Chk2, P53, and caspase-3 in vitro. MPA might exert its role through activating the ATM-associated pathway, ATM-Chk2-P53-caspase-3 (active), preserving normal endometrium and protecting it from malignancies. ATM might be a promising indicator for endometrial hyperplasia and cancer.

Inhibitory Effect of α-Pinene on SGC-7901 Cell Proliferation and the Mechanism of ATM Kinase Signaling Pathway

Objective: To research the inhibitory effect on SGC-7901 cells of α-pinene, and the related mechanism of α-pinene. Methods: Used the MTT method to detect inhibition rate and western blotting to detect the influence on expression of ATM, Phos-S1981ATM, H2AX, γH2AX, CHK2 and p-CHK2, p53 and phos-p53 cell cycle related protein in SGC-7901 cells. Results: The research found α-pinene could inhibit the proliferation of SGC-7901 cells observably in vitro, and the inhibition rate assumes the dependence on concentration; and western blotting results showed that, α-pinene could activate phospho-ATM, increase the amount of γH2AX (p 0.05). Conclusions: α-pinene could inhibit the proliferation of SGC-7901 cells, and by inducing ATM (Ataxia Telangiectasia-Mutated) kinase signal pathway in DNA damage response, activating cell cycle checkpoint, making the cell cycle arrest then exerts its anti-tumor effects.