DDR1

Gene Summary

Gene:DDR1; discoidin domain receptor tyrosine kinase 1
Aliases: CAK, DDR, NEP, HGK2, PTK3, RTK6, TRKE, CD167, EDDR1, MCK10, NTRK4, PTK3A
Location:6p21.33
Summary:Receptor tyrosine kinases play a key role in the communication of cells with their microenvironment. These kinases are involved in the regulation of cell growth, differentiation and metabolism. The protein encoded by this gene belongs to a subfamily of tyrosine kinase receptors with homology to Dictyostelium discoideum protein discoidin I in their extracellular domain, and that are activated by various types of collagen. Expression of this protein is restricted to epithelial cells, particularly in the kidney, lung, gastrointestinal tract, and brain. In addition, it has been shown to be significantly overexpressed in several human tumors. Alternatively spliced transcript variants encoding different isoforms have been described for this gene. [provided by RefSeq, Feb 2011]
Databases:VEGA, OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:epithelial discoidin domain-containing receptor 1
Source:NCBIAccessed: 16 March, 2017

Ontology:

What does this gene/protein do?
Show (30)

Cancer Overview

Research Indicators

Publications Per Year (1992-2017)
Graph generated 16 March 2017 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • Tumor Burden
  • Cadherins
  • Apoptosis
  • Neoplasm Proteins
  • Chromosome 6
  • Up-Regulation
  • siRNA
  • Discoidin Domain Receptors
  • Viral Matrix Proteins
  • Biomarkers, Tumor
  • MicroRNAs
  • Receptor Protein-Tyrosine Kinases
  • Non-Small Cell Lung Cancer
  • RTPCR
  • Gene Expression Profiling
  • Messenger RNA
  • Western Blotting
  • Cancer Gene Expression Regulation
  • Discoidin Domain Receptor 1
  • Tyrosine
  • Oligonucleotide Array Sequence Analysis
  • Liver Cancer
  • Immunohistochemistry
  • Syk Kinase
  • Breast Cancer
  • Cell Adhesion
  • Lung Cancer
  • Viral Proteins
  • Transforming Growth Factor beta
  • Ukraine
  • beta Catenin
  • Cell Movement
  • Transfection
  • Protein-Tyrosine Kinases
  • Gene Expression
  • Cell Proliferation
  • Mutation
  • Receptors, Mitogen
  • Phosphorylation
  • Neoplasm Invasiveness
Tag cloud generated 16 March, 2017 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: DDR1 (cancer-related)

Ezzoukhry Z, Henriet E, Piquet L, et al.
TGF-β1 promotes linear invadosome formation in hepatocellular carcinoma cells, through DDR1 up-regulation and collagen I cross-linking.
Eur J Cell Biol. 2016; 95(11):503-512 [PubMed] Related Publications
Transforming growth factor-β1 (TGF-β1) is an important player in chronic liver diseases inducing fibrogenesis and hepatocellular carcinoma (HCC) development. TGF-β1 promotes pleiotropic modifications at the cellular and matrix microenvironment levels. TGF-β1 was described to enhance production of type I collagen and its associated cross-linking enzyme, the lysyl oxidase-like2 (LOXL2). In addition, TGF-β1 and type I collagen are potent inducers of invadosomes. Indeed, type I collagen fibers induce the formation of active linear invadosomes through the discoidin domain receptor 1 (DDR1). The goal of our study was to address the role of TGF-β1 in collagen cross-linking and its impact on the formation of linear invadosomes in liver cancer cells. We first report a significant correlation between expressions of TGF-β1, and type I collagen, LOXL2, DDR1 and MT1-MMP in human HCCs. We demonstrate that TGF-β1 promotes a Smad4-dependent up-regulation of DDR1, together with LOXL2, in cultured HCC cells. Moreover, we show that LOXL2-induced collagen cross-linking enhances linear invadosome formation. Altogether, our data demonstrate that TGF-β1 favors linear invadosome formation through the expressions of both the inducers, such as collagen and LOXL2, and the components such as DDR1 and MT1-MMP of linear invadosomes in cancer cells. Meanwhile, our data uncover a new TGF-β1-dependent regulation of DDR1 expression.

Mizerska-Kowalska M, Bojarska-Junak A, Jakubowicz-Gil J, Kandefer-Szerszeń M
Neutral endopeptidase (NEP) is differentially involved in biological activities and cell signaling of colon cancer cell lines derived from various stages of tumor development.
Tumour Biol. 2016; 37(10):13355-13368 [PubMed] Free Access to Full Article Related Publications
The presented studies were aimed at exploring the role of neutral endopeptidase (NEP) in the function of colon cancer cell lines LS 180 and SW 620, derived from different grades and stages of tumor development. NEP silencing by siRNA resulted in decreased viability and proliferation accompanied by increased apoptosis in both cell lines. Additionally, cell cycle arrest at the G2/M phase was observed, but only in LS 180 cells. Opposite to these results, serum-stimulated migration was increased in both cell lines. Furthermore, NEP silencing influenced the invasive activity of LS 180 and SW 620 cells in an opposite manner: while LS 180 cells showed an enhanced invasiveness, SW 620 cells exerted a reduced activity. An exploration of the activity of signaling molecules responsible for the function of tumor cells-Akt, PTEN, and FAK-after NEP silencing indicated that the endopeptidase is involved in their regulation. The increased phosphorylation level of Akt was accompanied by a decrease in PTEN in the presence of a high concentration of serum. A reduced concentration of serum did not change the phosphorylation status of Akt. Enhanced autophosphorylation of FAK was observed in LS 180 and SW 620 cells cultivated in a medium with a high concentration of serum. Taken together, these results confirm that NEP is implicated in the regulation of the survival, growth, and motile activity of colon cancer. This is also the first report which shows that NEP mediates cancer cell migration and invasiveness, but not growth and survival, through Akt/FAK signaling pathways.

Carotenuto F, Albertini MC, Coletti D, et al.
How Diet Intervention via Modulation of DNA Damage Response through MicroRNAs May Have an Effect on Cancer Prevention and Aging, an in Silico Study.
Int J Mol Sci. 2016; 17(5) [PubMed] Free Access to Full Article Related Publications
The DNA damage response (DDR) is a molecular mechanism that cells have evolved to sense DNA damage (DD) to promote DNA repair, or to lead to apoptosis, or cellular senescence if the damage is too extensive. Recent evidence indicates that microRNAs (miRs) play a critical role in the regulation of DDR. Dietary bioactive compounds through miRs may affect activity of numerous genes. Among the most studied bioactive compounds modulating expression of miRs are epi-gallocatechin-3-gallate, curcumin, resveratrol and n3-polyunsaturated fatty acids. To compare the impact of these dietary compounds on DD/DDR network modulation, we performed a literature search and an in silico analysis by the DIANA-mirPathv3 software. The in silico analysis allowed us to identify pathways shared by different miRs involved in DD/DDR vis-à-vis the specific compounds. The results demonstrate that certain miRs (e.g., -146, -21) play a central role in the interplay among DD/DDR and the bioactive compounds. Furthermore, some specific pathways, such as "fatty acids biosynthesis/metabolism", "extracellular matrix-receptor interaction" and "signaling regulating the pluripotency of stem cells", appear to be targeted by most miRs affected by the studied compounds. Since DD/DDR and these pathways are strongly related to aging and carcinogenesis, the present in silico results of our study suggest that monitoring the induction of specific miRs may provide the means to assess the antiaging and chemopreventive properties of particular dietary compounds.

Koussounadis A, Langdon SP, Um I, et al.
Dynamic modulation of phosphoprotein expression in ovarian cancer xenograft models.
BMC Cancer. 2016; 16:205 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: The dynamic changes that occur in protein expression after treatment of a cancer in vivo are poorly described. In this study we measure the effect of chemotherapy over time on the expression of a panel of proteins in ovarian cancer xenograft models. The objective was to identify phosphoprotein and other protein changes indicative of pathway activation that might link with drug response.
METHODS: Two xenograft models, platinum-responsive OV1002 and platinum-unresponsive HOX424, were used. Treatments were carboplatin and carboplatin-paclitaxel. Expression of 49 proteins over 14 days post treatment was measured by quantitative immunofluorescence and analysed by AQUA.
RESULTS: Carboplatin treatment in the platinum-sensitive OV1002 model triggered up-regulation of cell cycle, mTOR and DDR pathways, while at late time points WNT, invasion, EMT and MAPK pathways were modulated. Estrogen receptor-alpha (ESR1) and ERBB pathways were down-regulated early, within 24 h from treatment administration. Combined carboplatin-paclitaxel treatment triggered a more extensive response in the OV1002 model modulating expression of 23 of 49 proteins. Therefore the cell cycle and DDR pathways showed similar or more pronounced changes than with carboplatin alone. In addition to expression of pS6 and pERK increasing, components of the AKT pathway were modulated with pAKT increasing while its regulator PTEN was down-regulated early. WNT signaling, EMT and invasion markers were modulated at later time points. Additional pathways were also observed with the NFκB and JAK/STAT pathways being up-regulated. ESR1 was down-regulated as was HER4, while further protein members of the ERBB pathway were upregulated late. By contrast, in the carboplatin-unresponsive HOX 424 xenograft, carboplatin only modulated expression of MLH1 while carboplatin-paclitaxel treatment modulated ESR1 and pMET.
CONCLUSIONS: Thirteen proteins were modulated by carboplatin and a more robust set of changes by carboplatin-paclitaxel. Early changes included DDR and cell cycle regulatory proteins associating with tumor volume changes, as expected. Changes in ESR1 and ERBB signaling were also observed. Late changes included components of MAPK signaling, EMT and invasion markers and coincided in time with reversal in tumor volume reduction. These results suggest potential therapeutic roles for inhibitors of such pathways that may prolong chemotherapeutic effects.

Gorre M, Mohandas PE, Kagita S, et al.
Significance of ATM Gene Polymorphisms in Chronic Myeloid Leukemia - a Case Control Study from India.
Asian Pac J Cancer Prev. 2016; 17(2):815-21 [PubMed] Related Publications
BACKGROUND: Development of chronic myeloid leukemia (CML) involves formation of double strand breaks (DSBs) which are initially sensed by the ataxia telangiectasia mutated (ATM) signal kinase to induce a DNA damage response (DDR). Mutations or single nucleotide polymorphisms in ATM gene are known to influence the signaling capacity resulting in susceptibility to certain genetic diseases such as cancers.
MATERIALS AND METHODS: In the present study, we have analyzed -5144A>T (rs228589) and C4138T (rs3092856) polymorphisms of theATM gene through polymerase chain reaction- restriction fragment length polymorphism (PCR-RFLP) in 925 subjects (476 CML cases and 449 controls).
RESULTS: The A allele of -5144A>T polymorphism and T allele of C4138T polymorphism which were known to be influencing ATM signaling capacity are significantly associated with enhanced risk for CML independently and also in combination (evident from the haplotype and diplotype analyses). Significant elevation in the frequencies of both the risk alleles among high risk groups under European Treatment and Outcome Study (EUTOS) score suggests the possible role of these polymorphisms in predicting the prognosis of CML patients.
CONCLUSIONS: This study provides the first evidence of association of functional ATM gene polymorphisms with the increased risk of CML development as well as progression.

Frenzel LP, Reinhardt HC, Pallasch CP
Concepts of Chronic Lymphocytic Leukemia Pathogenesis: DNA Damage Response and Tumor Microenvironment.
Oncol Res Treat. 2016; 39(1-2):9-16 [PubMed] Related Publications
Pathogenesis of chronic lymphocytic leukemia (CLL) is characterized by specific genetic aberrations and alterations of cellular signaling pathways. In particular, a disturbed DNA damage response (DDR) and an activated B-cell receptor signaling pathway play a major role in promoting CLL cell survival. External stimuli are similarly essential for CLL cell survival and lead to activation of the PI3K/AKT and MAPK pathways. Activation of nuclear factor-kappa B (NFkB) influences the disturbed anti-apoptotic balance of CLL cells. Losses or disabling mutations in TP53 and ATM are frequent events in chemotherapy-naïve patients and are further enriched in chemotherapy-resistant patients. As these lesions define key regulatory elements of the DDR pathway, they also determine treatment response to genotoxic therapy. Novel therapeutic strategies therefore try to circumvent defective DDR signaling and to suppress the pro-survival stimuli received from the tumor microenvironment. With increasing knowledge on specific genetic alterations of CLL, we may be able to target CLL cells more efficiently even in the situation of mutated DDR pathways or protection by microenvironmental stimuli.

Cekan P, Hasegawa K, Pan Y, et al.
RCC1-dependent activation of Ran accelerates cell cycle and DNA repair, inhibiting DNA damage-induced cell senescence.
Mol Biol Cell. 2016; 27(8):1346-57 [PubMed] Free Access to Full Article Related Publications
The coordination of cell cycle progression with the repair of DNA damage supports the genomic integrity of dividing cells. The function of many factors involved in DNA damage response (DDR) and the cell cycle depends on their Ran GTPase-regulated nuclear-cytoplasmic transport (NCT). The loading of Ran with GTP, which is mediated by RCC1, the guanine nucleotide exchange factor for Ran, is critical for NCT activity. However, the role of RCC1 or Ran⋅GTP in promoting cell proliferation or DDR is not clear. We show that RCC1 overexpression in normal cells increased cellular Ran⋅GTP levels and accelerated the cell cycle and DNA damage repair. As a result, normal cells overexpressing RCC1 evaded DNA damage-induced cell cycle arrest and senescence, mimicking colorectal carcinoma cells with high endogenous RCC1 levels. The RCC1-induced inhibition of senescence required Ran and exportin 1 and involved the activation of importin β-dependent nuclear import of 53BP1, a large NCT cargo. Our results indicate that changes in the activity of the Ran⋅GTP-regulated NCT modulate the rate of the cell cycle and the efficiency of DNA repair. Through the essential role of RCC1 in regulation of cellular Ran⋅GTP levels and NCT, RCC1 expression enables the proliferation of cells that sustain DNA damage.

Ambrogio C, Gómez-López G, Falcone M, et al.
Combined inhibition of DDR1 and Notch signaling is a therapeutic strategy for KRAS-driven lung adenocarcinoma.
Nat Med. 2016; 22(3):270-7 [PubMed] Related Publications
Patients with advanced Kirsten rat sarcoma viral oncogene homolog (KRAS)-mutant lung adenocarcinoma are currently treated with standard chemotherapy because of a lack of efficacious targeted therapies. We reasoned that the identification of mediators of Kras signaling in early mouse lung hyperplasias might bypass the difficulties that are imposed by intratumor heterogeneity in advanced tumors, and that it might unveil relevant therapeutic targets. Transcriptional profiling of Kras(G12V)-driven mouse hyperplasias revealed intertumor diversity with a subset that exhibited an aggressive transcriptional profile analogous to that of advanced human adenocarcinomas. The top-scoring gene in this profile encodes the tyrosine kinase receptor DDR1. The genetic and pharmacological inhibition of DDR1 blocked tumor initiation and tumor progression, respectively. The concomitant inhibition of both DDR1 and Notch signaling induced the regression of KRAS;TP53-mutant patient-derived lung xenografts (PDX) with a therapeutic efficacy that was at least comparable to that of standard chemotherapy. Our data indicate that the combined inhibition of DDR1 and Notch signaling could be an effective targeted therapy for patients with KRAS-mutant lung adenocarcinoma.

Capell BC, Drake AM, Zhu J, et al.
MLL1 is essential for the senescence-associated secretory phenotype.
Genes Dev. 2016; 30(3):321-36 [PubMed] Free Access to Full Article Related Publications
Oncogene-induced senescence (OIS) and therapy-induced senescence (TIS), while tumor-suppressive, also promote procarcinogenic effects by activating the DNA damage response (DDR), which in turn induces inflammation. This inflammatory response prominently includes an array of cytokines known as the senescence-associated secretory phenotype (SASP). Previous observations link the transcription-associated methyltransferase and oncoprotein MLL1 to the DDR, leading us to investigate the role of MLL1 in SASP expression. Our findings reveal direct MLL1 epigenetic control over proproliferative cell cycle genes: MLL1 inhibition represses expression of proproliferative cell cycle regulators required for DNA replication and DDR activation, thus disabling SASP expression. Strikingly, however, these effects of MLL1 inhibition on SASP gene expression do not impair OIS and, furthermore, abolish the ability of the SASP to enhance cancer cell proliferation. More broadly, MLL1 inhibition also reduces "SASP-like" inflammatory gene expression from cancer cells in vitro and in vivo independently of senescence. Taken together, these data demonstrate that MLL1 inhibition may be a powerful and effective strategy for inducing cancerous growth arrest through the direct epigenetic regulation of proliferation-promoting genes and the avoidance of deleterious OIS- or TIS-related tumor secretomes, which can promote both drug resistance and tumor progression.

Soriano A, París-Coderch L, Jubierre L, et al.
MicroRNA-497 impairs the growth of chemoresistant neuroblastoma cells by targeting cell cycle, survival and vascular permeability genes.
Oncotarget. 2016; 7(8):9271-87 [PubMed] Free Access to Full Article Related Publications
Despite multimodal therapies, a high percentage of high-risk neuroblastoma (NB) become refractory to current treatments, most of which interfere with cell cycle and DNA synthesis or function, activating the DNA damage response (DDR). In cancer, this process is frequently altered by deregulated expression or function of several genes which contribute to multidrug resistance (MDR). MicroRNAs are outstanding candidates for therapy since a single microRNA can modulate the expression of multiple genes of the same or different pathways, thus hindering the development of resistance mechanisms by the tumor. We found several genes implicated in the MDR to be overexpressed in high-risk NB which could be targeted by microRNAs simultaneously. Our functional screening identified several of those microRNAs that reduced proliferation of chemoresistant NB cell lines, the best of which was miR-497. Low expression of miR-497 correlated with poor patient outcome. The overexpression of miR-497 reduced the proliferation of multiple chemoresistant NB cell lines and induced apoptosis in MYCN-amplified cell lines. Moreover, the conditional expression of miR-497 in NB xenografts reduced tumor growth and inhibited vascular permeabilization. MiR-497 targets multiple genes related to the DDR, cell cycle, survival and angiogenesis, which renders this molecule a promising candidate for NB therapy.

Zhao MJ, Song YF, Niu HT, et al.
Adenovirus-mediated downregulation of the ubiquitin ligase RNF8 sensitizes bladder cancer to radiotherapy.
Oncotarget. 2016; 7(8):8956-67 [PubMed] Free Access to Full Article Related Publications
The ubiquitin ligase RNF8 promotes the DNA damage response (DDR). We observed that the expression of RNF8 was increased in bladder cancer cells and that this change in RNF8 expression could be reversed by adenovirus-mediated shRNA treatment. Moreover, we found that RNF8 knockdown sensitized bladder cancer cells to radiotherapy, as demonstrated by reduced cell survival. Additionally, the absence of RNF8 induced a high rate of apoptosis and impaired double-strand break repair signaling after radiotherapy. Furthermore, experiments on nude mice showed that combining shRNF8 treatment with radiotherapy suppressed implanted bladder tumor growth and enhanced apoptotic cell death in vivo. Altogether, our results indicated that RNF8 might be a novel target for bladder cancer treatment.

Evans JR, Zhao SG, Chang SL, et al.
Patient-Level DNA Damage and Repair Pathway Profiles and Prognosis After Prostatectomy for High-Risk Prostate Cancer.
JAMA Oncol. 2016; 2(4):471-80 [PubMed] Related Publications
IMPORTANCE: A substantial number of patients diagnosed with high-risk prostate cancer are at risk for metastatic progression after primary treatment. Better biomarkers are needed to identify patients at the highest risk to guide therapy intensification.
OBJECTIVE: To create a DNA damage and repair (DDR) pathway profiling method for use as a prognostic signature biomarker in high-risk prostate cancer.
DESIGN, SETTING, AND PARTICIPANTS: A cohort of 1090 patients with high-risk prostate cancer who underwent prostatectomy and were treated at 3 different academic institutions were divided into a training cohort (n = 545) and 3 pooled validation cohorts (n = 232, 130, and 183) assembled for case-control or case-cohort studies. Profiling of 9 DDR pathways using 17 gene sets for GSEA (Gene Set Enrichment Analysis) of high-density microarray gene expression data from formalin-fixed paraffin-embedded prostatectomy samples with median 10.3 years follow-up was performed. Prognostic signature development from DDR pathway profiles was studied, and DDR pathway gene mutation in published cohorts was analyzed.
MAIN OUTCOMES AND MEASURES: Biochemical recurrence-free, metastasis-free, and overall survival.
RESULTS: Across the training cohort and pooled validation cohorts, 1090 men were studied; mean (SD) age at diagnosis was 65.3 (6.4) years. We found that there are distinct clusters of DDR pathways within the cohort, and DDR pathway enrichment is only weakly correlated with clinical variables such as age (Spearman ρ [ρ], range, -0.07 to 0.24), Gleason score (ρ, range, 0.03 to 0.20), prostate-specific antigen level (ρ, range, -0.07 to 0.10), while 13 of 17 DDR gene sets are strongly correlated with androgen receptor pathway enrichment (ρ, range, 0.33 to 0.82). In published cohorts, DDR pathway genes are rarely mutated. A DDR pathway profile prognostic signature built in the training cohort was significantly associated with biochemical recurrence-free, metastasis-free, and overall survival in the pooled validation cohorts independent of standard clinicopathological variables. The prognostic performance of the signature for metastasis-free survival appears to be stronger in the younger patients (HR, 1.67; 95% CI, 1.12-2.50) than in the older patients (HR, 0.77; 95% CI, 0.29-2.07) on multivariate Cox analysis.
CONCLUSIONS AND RELEVANCE: DNA damage and repair pathway profiling revealed patient-level variations and the DDR pathways are rarely affected by mutation. A DDR pathway signature showed strong prognostic performance with the long-term outcomes of metastasis-free and overall survival that may be useful for risk stratification of high-risk prostate cancer patients.

Kralovicova J, Knut M, Cross NC, Vorechovsky I
Exon-centric regulation of ATM expression is population-dependent and amenable to antisense modification by pseudoexon targeting.
Sci Rep. 2016; 6:18741 [PubMed] Free Access to Full Article Related Publications
ATM is an important cancer susceptibility gene that encodes a critical apical kinase of the DNA damage response (DDR) pathway. We show that a key nonsense-mediated RNA decay switch exon (NSE) in ATM is repressed by U2AF, PUF60 and hnRNPA1. The NSE activation was haplotype-specific and was most promoted by cytosine at rs609621 in the NSE 3' splice-site (3'ss), which is predominant in high cancer risk populations. NSE levels were deregulated in leukemias and were influenced by the identity of U2AF35 residue 34. We also identify splice-switching oligonucleotides (SSOs) that exploit competition of adjacent pseudoexons to modulate NSE levels. The U2AF-regulated exon usage in the ATM signalling pathway was centred on the MRN/ATM-CHEK2-CDC25-cdc2/cyclin-B axis and preferentially involved transcripts implicated in cancer-associated gene fusions and chromosomal translocations. These results reveal important links between 3'ss control and ATM-dependent responses to double-strand DNA breaks, demonstrate functional plasticity of intronic variants and illustrate versatility of intronic SSOs that target pseudo-3'ss to modify gene expression.

Matà R, Palladino C, Nicolosi ML, et al.
IGF-I induces upregulation of DDR1 collagen receptor in breast cancer cells by suppressing MIR-199a-5p through the PI3K/AKT pathway.
Oncotarget. 2016; 7(7):7683-700 [PubMed] Free Access to Full Article Related Publications
Discoidin Domain Receptor 1 (DDR1) is a collagen receptor tyrosine-kinase that contributes to epithelial-to-mesenchymal transition and enhances cancer progression. Our previous data indicate that, in breast cancer cells, DDR1 interacts with IGF-1R and positively modulates IGF-1R expression and biological responses, suggesting that the DDR1-IGF-IR cross-talk may play an important role in cancer. In this study, we set out to evaluate whether IGF-I stimulation may affect DDR1 expression. Indeed, in breast cancer cells (MCF-7 and MDA-MB-231) IGF-I induced significant increase of DDR1 protein expression, in a time and dose dependent manner. However, we did not observe parallel changes in DDR1 mRNA. DDR1 upregulation required the activation of the PI3K/AKT pathway while the ERK1/2, the p70/mTOR and the PKC pathways were not involved. Moreover, we observed that DDR1 protein upregulation was induced by translational mechanisms involving miR-199a-5p suppression through PI3K/AKT activation. This effect was confirmed by both IGF-II produced by cancer-associated fibroblasts from human breast cancer and by stable transfection of breast cancer cells with a human IGF-II expression construct. Transfection with a constitutively active form of AKT was sufficient to decrease miR-199a-5p and upregulate DDR1. Accordingly, IGF-I-induced DDR1 upregulation was inhibited by transfection with pre-miR-199a-5p, which also impaired AKT activation and cell migration and proliferation in response to IGF-I. These results demonstrate that, in breast cancer cells, a novel pathway involving AKT/miR-199a-5p/DDR1 plays a role in modulating IGFs biological responses. Therefore, this signaling pathway may represent an important target for breast cancers with over-activation of the IGF-IR axis.

Wieringa HW, van der Zee AG, de Vries EG, van Vugt MA
Breaking the DNA damage response to improve cervical cancer treatment.
Cancer Treat Rev. 2016; 42:30-40 [PubMed] Related Publications
Every year, cervical cancer affects ∼500,000 women worldwide, and ∼275,000 patients die of this disease. The addition of platin-based chemotherapy to primary radiotherapy has increased 5-year survival of advanced-stage cervical cancer patients, which is, however, still only 66%. One of the factors thought to contribute to treatment failure is the ability of tumor cells to repair chemoradiotherapy-induced DNA damage. Therefore, sensitization of tumor cells for chemoradiotherapy via inhibition of the DNA damage response (DDR) as a novel strategy to improve therapy effect, is currently studied pre-clinically as well as in the clinic. Almost invariably, cervical carcinogenesis involves infection with the human papillomavirus (HPV), which inactivates part of the DNA damage response. This HPV-mediated partial inactivation of the DDR presents therapeutic targeting of the residual DDR as an interesting approach to achieve chemoradio-sensitization for cervical cancer. How the DDR can be most efficiently targeted, however, remains unclear. The fact that cisplatin and radiotherapy activate multiple signaling axes within the DDR further complicates a rational choice of therapeutic targets within the DDR. In this review, we provide an overview of the current preclinical and clinical knowledge about targeting the DDR in cervical cancer.

Lin X, Ojo D, Wei F, et al.
A Novel Aspect of Tumorigenesis-BMI1 Functions in Regulating DNA Damage Response.
Biomolecules. 2015; 5(4):3396-415 [PubMed] Free Access to Full Article Related Publications
BMI1 plays critical roles in maintaining the self-renewal of hematopoietic, neural, intestinal stem cells, and cancer stem cells (CSCs) for a variety of cancer types. BMI1 promotes cell proliferative life span and epithelial to mesenchymal transition (EMT). Upregulation of BMI1 occurs in multiple cancer types and is associated with poor prognosis. Mechanistically, BMI1 is a subunit of the Polycomb repressive complex 1 (PRC1), and binds the catalytic RING2/RING1b subunit to form a functional E3 ubiquitin ligase. Through mono-ubiquitination of histone H2A at lysine 119 (H2A-K119Ub), BMI1 represses multiple gene loci; among these, the INK4A/ARF locus has been most thoroughly investigated. The locus encodes the p16INK4A and p14/p19ARF tumor suppressors that function in the pRb and p53 pathways, respectively. Its repression contributes to BMI1-derived tumorigenesis. BMI1 also possesses other oncogenic functions, specifically its regulative role in DNA damage response (DDR). In this process, BMI1 ubiquitinates histone H2A and γH2AX, thereby facilitating the repair of double-stranded DNA breaks (DSBs) through stimulating homologous recombination and non-homologous end joining. Additionally, BMI1 compromises DSB-induced checkpoint activation independent of its-associated E3 ubiquitin ligase activity. We review the emerging role of BMI1 in DDR regulation and discuss its impact on BMI1-derived tumorigenesis.

Cataldo A, Cheung DG, Balsari A, et al.
miR-302b enhances breast cancer cell sensitivity to cisplatin by regulating E2F1 and the cellular DNA damage response.
Oncotarget. 2016; 7(1):786-97 [PubMed] Free Access to Full Article Related Publications
The identification of the molecular mechanisms involved in the establishment of the resistant phenotype represents a critical need for the development of new strategies to prevent or overcome cancer resistance to anti-neoplastic treatments.Breast cancer is the leading cause of cancer-related deaths in women, and resistance to chemotherapy negatively affects patient outcomes. Here, we investigated the potential role of miR-302b in the modulation of breast cancer cell resistance to cisplatin.miR-302b overexpression enhances sensitivity to cisplatin in breast cancer cell lines, reducing cell viability and proliferation in response to the treatment. We also identified E2F1, a master regulator of the G1/S transition, as a direct target gene of miR-302b. E2F1 transcriptionally activates ATM, the main cellular sensor of DNA damage. Through the negative regulation of E2F1, miR-302b indirectly affects ATM expression, abrogating cell-cycle progression upon cisplatin treatment. Moreover miR-302b, impairs the ability of breast cancer cells to repair damaged DNA, enhancing apoptosis activation following cisplatin treatment.These findings indicate that miR-302b plays a relevant role in breast cancer cell response to cisplatin through the modulation of the E2F1/ATM axis, representing a valid candidate as therapeutic tool to overcome chemotherapy resistance.

Esposito MT, Zhao L, Fung TK, et al.
Synthetic lethal targeting of oncogenic transcription factors in acute leukemia by PARP inhibitors.
Nat Med. 2015; 21(12):1481-90 [PubMed] Related Publications
Acute myeloid leukemia (AML) is mostly driven by oncogenic transcription factors, which have been classically viewed as intractable targets using small-molecule inhibitor approaches. Here we demonstrate that AML driven by repressive transcription factors, including AML1-ETO (encoded by the fusion oncogene RUNX1-RUNX1T1) and PML-RARα fusion oncoproteins (encoded by PML-RARA) are extremely sensitive to poly (ADP-ribose) polymerase (PARP) inhibition, in part owing to their suppressed expression of key homologous recombination (HR)-associated genes and their compromised DNA-damage response (DDR). In contrast, leukemia driven by mixed-lineage leukemia (MLL, encoded by KMT2A) fusions with dominant transactivation ability is proficient in DDR and insensitive to PARP inhibition. Intriguingly, genetic or pharmacological inhibition of an MLL downstream target, HOXA9, which activates expression of various HR-associated genes, impairs DDR and sensitizes MLL leukemia to PARP inhibitors (PARPis). Conversely, HOXA9 overexpression confers PARPi resistance to AML1-ETO and PML-RARα transformed cells. Together, these studies describe a potential utility of PARPi-induced synthetic lethality for leukemia treatment and reveal a novel molecular mechanism governing PARPi sensitivity in AML.

Casimiro MC, Di Sante G, Ju X, et al.
Cyclin D1 Promotes Androgen-Dependent DNA Damage Repair in Prostate Cancer Cells.
Cancer Res. 2016; 76(2):329-38 [PubMed] Free Access to Full Article Related Publications
Therapy resistance and poor outcome in prostate cancer is associated with increased expression of cyclin D1. Androgens promote DNA double-strand break repair to reduce DNA damage, and cyclin D1 was also shown to enhance DNA damage repair (DDR). In this study, we investigated the significance of cyclin D1 in androgen-induced DDR using established prostate cancer cells and prostate tissues from cyclin D1 knockout mice. We demonstrate that endogenous cyclin D1 further diminished the dihydrotestosterone (DHT)-dependent reduction of γH2AX foci in vitro. We also show that cyclin D1 was required for the androgen-dependent DNA damage response both in vitro and in vivo. Furthermore, cyclin D1 was required for androgen-enhanced DDR and radioresistance of prostate cancer cells. Moreover, microarray analysis of primary prostate epithelial cells from cyclin D1-deficient and wild-type mice demonstrated that most of the DHT-dependent gene expression changes are also cyclin D1 dependent. Collectively, our findings suggest that the hormone-mediated recruitment of cyclin D1 to sites of DDR may facilitate the resistance of prostate cancer cells to DNA damage therapies and highlight the need to explore other therapeutic approaches in prostate cancer to prevent or overcome drug resistance.

Middleton FK, Patterson MJ, Elstob CJ, et al.
Common cancer-associated imbalances in the DNA damage response confer sensitivity to single agent ATR inhibition.
Oncotarget. 2015; 6(32):32396-409 [PubMed] Free Access to Full Article Related Publications
ATR is an attractive target in cancer therapy because it signals replication stress and DNA lesions for repair and to S/G2 checkpoints. Cancer-specific defects in the DNA damage response (DDR) may render cancer cells vulnerable to ATR inhibition alone. We determined the cytotoxicity of the ATR inhibitor VE-821 in isogenically matched cells with DDR imbalance. Cell cycle arrest, DNA damage accumulation and repair were determined following VE-821 exposure.Defects in homologous recombination repair (HRR: ATM, BRCA2 and XRCC3) and base excision repair (BER: XRCC1) conferred sensitivity to VE-821. Surprisingly, the loss of different components of the trimeric non-homologous end-joining (NHEJ) protein DNA-PK had opposing effects. Loss of the DNA-binding component, Ku80, caused hypersensitivity to VE-821, but loss of its partner catalytic subunit, DNA-PKcs, did not. Unexpectedly, VE-821 was particularly cytotoxic to human and hamster cells expressing high levels of DNA-PKcs. High DNA-PKcs was associated with replicative stress and activation of the DDR. VE-821 suppressed HRR, determined by RAD51 focus formation, to a greater extent in cells with high DNA-PKcs.Defects in HRR and BER and high DNA-PKcs expression, that are common in cancer, confer sensitivity to ATR inhibitor monotherapy and may be developed as predictive biomarkers for personalised medicine.

Alsubhi N, Middleton F, Abdel-Fatah TM, et al.
Chk1 phosphorylated at serine345 is a predictor of early local recurrence and radio-resistance in breast cancer.
Mol Oncol. 2016; 10(2):213-23 [PubMed] Related Publications
Radiation-induced DNA damage activates the DNA damage response (DDR). DDR up-regulation may predict radio-resistance and increase the risk of early local recurrence despite radiotherapy in early stage breast cancers. In 1755 early stage breast cancers, DDR signalling [ATM, ATR, total Ckh1, Chk1 phosphorylated at serine(345) (pChk1), Chk2, p53], base excision repair [PARP1, POLβ, XRCC1, FEN1, SMUG1], non-homologous end joining (Ku70/Ku80, DNA-PKcs) and homologous recombination [RAD51, BRCA1, γH2AX, BLM, WRN, RECQL5, PTEN] protein expression was correlated to time to early local recurrence. Pre-clinically, radio-sensitization by inhibition of Chk1 activation by ATR inhibitor (VE-821) and inhibition of Chk1 (V158411) were investigated in MDA-MB-231 (p53 mutant) and MCF-7 (p53 wild-type) breast cancer cells. In the whole cohort, 208/1755 patients (11.9%) developed local recurrence of which 126 (61%) developed local recurrence within 5 years of initiation of primary therapy. Of the 20 markers tested, only pChk1 and p53 significantly associated with early local recurrence (p value = 0.015 and 0.010, respectively). When analysed together, high cytoplasmic pChk1-nuclear pChk1 (p = 0.039), high cytoplasmic pChk1-p53 (p = 0.004) and high nuclear pChk1-p53 (p = 0.029) co-expression remain significantly linked to early local recurrence. In multivariate analysis, cytoplasmic pChk1 level independently predicted early local recurrence (p = 0.025). In patients who received adjuvant local radiotherapy (n = 949), p53 (p = 0.014) and high cytoplasmic pChk1-p53 (p = 0.017) remain associated with early local recurrence. Pre-clinically, radio-sensitisation by VE-821 or V158411 was observed in both MCF-7 and MDA-MB-231 cells and was more pronounced in MCF-7 cells. We conclude that pChk1 is a predictive biomarker of radiotherapy resistance and early local recurrence.

Srihari S, Singla J, Wong L, Ragan MA
Inferring synthetic lethal interactions from mutual exclusivity of genetic events in cancer.
Biol Direct. 2015; 10:57 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Synthetic lethality (SL) refers to the genetic interaction between two or more genes where only their co-alteration (e.g. by mutations, amplifications or deletions) results in cell death. In recent years, SL has emerged as an attractive therapeutic strategy against cancer: by targeting the SL partners of altered genes in cancer cells, these cells can be selectively killed while sparing the normal cells. Consequently, a number of studies have attempted prediction of SL interactions in human, a majority by extrapolating SL interactions inferred through large-scale screens in model organisms. However, these predicted SL interactions either do not hold in human cells or do not include genes that are (frequently) altered in human cancers, and are therefore not attractive in the context of cancer therapy.
RESULTS: Here, we develop a computational approach to infer SL interactions directly from frequently altered genes in human cancers. It is based on the observation that pairs of genes that are altered in a (significantly) mutually exclusive manner in cancers are likely to constitute lethal combinations. Using genomic copy-number and gene-expression data from four cancers, breast, prostate, ovarian and uterine (total 3980 samples) from The Cancer Genome Atlas, we identify 718 genes that are frequently amplified or upregulated, and are likely to be synthetic lethal with six key DNA-damage response (DDR) genes in these cancers. By comparing with published data on gene essentiality (~16000 genes) from ten DDR-deficient cancer cell lines, we show that our identified genes are enriched among the top quartile of essential genes in these cell lines, implying that our inferred genes are highly likely to be (synthetic) lethal upon knockdown in these cell lines. Among the inferred targets are tousled-like kinase 2 (TLK2) and the deubiquitinating enzyme ubiquitin-specific-processing protease 7 (USP7) whose overexpression correlates with poor survival in cancers.
CONCLUSION: Mutual exclusivity between frequently occurring genetic events identifies synthetic lethal combinations in cancers. These identified genes are essential in cell lines, and are potential candidates for targeted cancer therapy. Availability: http://bioinformatics.org.au/tools-data/underMutExSL

Day FR, Ruth KS, Thompson DJ, et al.
Large-scale genomic analyses link reproductive aging to hypothalamic signaling, breast cancer susceptibility and BRCA1-mediated DNA repair.
Nat Genet. 2015; 47(11):1294-303 [PubMed] Free Access to Full Article Related Publications
Menopause timing has a substantial impact on infertility and risk of disease, including breast cancer, but the underlying mechanisms are poorly understood. We report a dual strategy in ∼70,000 women to identify common and low-frequency protein-coding variation associated with age at natural menopause (ANM). We identified 44 regions with common variants, including two regions harboring additional rare missense alleles of large effect. We found enrichment of signals in or near genes involved in delayed puberty, highlighting the first molecular links between the onset and end of reproductive lifespan. Pathway analyses identified major association with DNA damage response (DDR) genes, including the first common coding variant in BRCA1 associated with any complex trait. Mendelian randomization analyses supported a causal effect of later ANM on breast cancer risk (∼6% increase in risk per year; P = 3 × 10(-14)), likely mediated by prolonged sex hormone exposure rather than DDR mechanisms.

Willers H, Gheorghiu L, Liu Q, et al.
DNA Damage Response Assessments in Human Tumor Samples Provide Functional Biomarkers of Radiosensitivity.
Semin Radiat Oncol. 2015; 25(4):237-50 [PubMed] Free Access to Full Article Related Publications
Predictive biomarkers are urgently needed for individualization of radiation therapy and treatment with radiosensitizing anticancer agents. Genomic profiling of human cancers provides us with unprecedented insight into the mutational landscape of genes directly or indirectly involved in the response to radiation-induced DNA damage. However, to what extent this wealth of structural information about the cancer genome produces biomarkers of sensitivity to radiation remains to be seen. Investigators are increasingly studying the subnuclear accumulation (ie, foci) of proteins in the DNA damage response (DDR), such as gamma-H2AX, 53BP1, or RAD51, as a surrogate of treatment sensitivity. Recent findings from preclinical studies have demonstrated the predictive potential of DDR foci by correlating foci with clinically relevant end points such as tumor control probability. Therefore, preclinical investigations of DDR foci responses are increasingly moving into cells and tissues from patients, which is the major focus of this review. The advantage of using DDR foci as functional biomarkers is that they can detect alterations in DNA repair due to various mechanisms. Moreover, they provide a global measurement of DDR network function without needing to know the identities of all the components, many of which remain unknown. Foci assays are thus expected to yield functional insight that may complement or supersede genomic information, thereby giving radiation oncologists unique opportunities to individualize cancer treatments in the near future.

Lezina L, Aksenova V, Fedorova O, et al.
KMT Set7/9 affects genotoxic stress response via the Mdm2 axis.
Oncotarget. 2015; 6(28):25843-55 [PubMed] Free Access to Full Article Related Publications
Genotoxic stress inflicted by anti-cancer drugs causes DNA breaks and genome instability. DNA double strand breaks induced by irradiation or pharmacological inhibition of Topoisomerase II activate ATM (ataxia-telangiectasia-mutated) kinase signalling pathway that in turn triggers cell cycle arrest and DNA repair. ATM-dependent gamma-phosphorylation of histone H2Ax and other histone modifications, including ubiquitnylation, promote exchange of histones and recruitment of DNA damage response (DDR) and repair proteins. Signal transduction pathways, besides DDR itself, also control expression of genes whose products cause cell cycle arrest and/or apoptosis thus ultimately affecting the sensitivity of cells to genotoxic stress. In this study, using a number of experimental approaches we provide evidence that lysine-specific methyltransferase (KMT) Set7/9 affects DDR and DNA repair, at least in part, by regulating the expression of an E3 ubiquitin ligase, Mdm2. Furthermore, we show that Set7/9 physically interacts with Mdm2. Several cancer cell lines with inverse expression of Set7/9 and Mdm2 displayed diminished survival in response to genotoxic stress. These findings are signified by our bioinformatics studies suggesting that the unleashed expression of Mdm2 in cancer patients with diminished expression of Set7/9 is associated with poor survival outcome.

De Cecco L, Capaia M, Zupo S, et al.
Interleukin 21 Controls mRNA and MicroRNA Expression in CD40-Activated Chronic Lymphocytic Leukemia Cells.
PLoS One. 2015; 10(8):e0134706 [PubMed] Free Access to Full Article Related Publications
Several factors support CLL cell survival in the microenvironment. Under different experimental conditions, IL21 can either induce apoptosis or promote CLL cell survival. To investigate mechanisms involved in the effects of IL21, we studied the ability of IL21 to modulate gene and miRNA expressions in CD40-activated CLL cells. IL21 was a major regulator of chemokine production in CLL cells and it modulated the expression of genes involved in cell movement, metabolism, survival and apoptosis. In particular, IL21 down-regulated the expression of the chemokine genes CCL4, CCL3, CCL3L1, CCL17, and CCL2, while it up-regulated the Th1-related CXCL9 and CXCL10. In addition, IL21 down-regulated the expression of genes encoding signaling molecules, such as CD40, DDR1 and PIK3CD. IL21 modulated a similar set of genes in CLL and normal B-cells (e.g. chemokine genes), whereas other genes, including MYC, TNF, E2F1, EGR2 and GAS-6, were regulated only in CLL cells. An integrated analysis of the miRNome and gene expression indicated that several miRNAs were under IL21 control and these could, in turn, influence the expression of potential target genes. We focused on hsa-miR-663b predicted to down-regulate several relevant genes. Transfection of hsa-miR-663b or its specific antagonist showed that this miRNA regulated CCL17, DDR1, PIK3CD and CD40 gene expression. Our data indicated that IL21 modulates the expression of genes mediating the crosstalk between CLL cells and their microenvironment and miRNAs may take part in this process.

Huo Y, Yang M, Liu W, et al.
High expression of DDR1 is associated with the poor prognosis in Chinese patients with pancreatic ductal adenocarcinoma.
J Exp Clin Cancer Res. 2015; 34:88 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Discoidin domain receptors 1 (DDR1), a subtype of DDRs, has been reported as a critical modulator of cellular morphogenesis, differentiation, migration and invasion.
METHODS AND RESULTS: In this study, we investigated the expression of DDR1 and its clinical association in Chinese patients with pancreatic ductal adenocarcinoma (PDAC). Across a cohort of 30 patients, we examined DDR1 expression in paired PDAC and corresponding adjacent non-tumor tissues by real-time quantitative PCR (RT-qPCR), or western blotting. DDR1 expression is significantly higher in PDAC, as compared to normal adjacent tissue, confirming results from the Oncomine databases. We validated DDR1 expression by immunohistochemistry across a non-overlapping cohort of 205 PDAC specimens. Kaplan-Meier survival curves indicate that increased expression of DDR1 is associated with a poor prognosis in PDAC patients (P = 0.013). Multivariate Cox regression analysis identified DDR1 expression, age, N classification and liver metastasis as independent prognostic factors in PDAC.
CONCLUSIONS: This study demonstrated that DDR1 can well serve as a novel prognostic biomarker in PDAC.

Li S, Zhang Z, Xue J, et al.
Effect of Hypoxia on DDR1 Expression in Pituitary Adenomas.
Med Sci Monit. 2015; 21:2433-8 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Pituitary adenoma is a common intracranial tumor in neurosurgery. Some pituitary adenomas have the characteristics of invasive growth make them unable to be removed completely by surgery leading to easy relapse. Discoidin domain receptor l (DDR1) is a new kind of tyrosine kinase receptor on the cell surface. DDR1 can be activated by tumor microenvironment signal in tumorigenesis, increasing MMP-2/9 expression and promoting the invasive ability of tumor cells. Anoxia can promote tumor growth and metastasis. This study investigated the impact of anoxic environment DDR1 expression in pituitary adenoma.
MATERIAL AND METHODS: A primary hypoxia pituitary adenoma cell model was established and treated with DDR1 inhibitor nilotinib. Real-time PCR and Western blot were used to detect DDR1 mRNA and protein expression. ELISA was used to detect MMP-2/9 changes. MTT method was used to detect pituitary adenoma cell proliferation. We used a transwell chamber to determine pituitary adenoma cell invasion ability.
RESULTS: DDR1 mRNA and protein were significantly overexpressed under hypoxia (P<0.05). MMP-2 and MMP-9 expression was obviously increased in supernatant (P<0.05). Pituitary adenoma cell proliferation and invasive ability improved markedly under hypoxia (P<0.05). Nilotinib could reduce DDR1 expression, decrease MMP-2 and MMP-9 expression, and inhibit pituitary adenoma cells proliferation and invasion.
CONCLUSIONS: Hypoxia can increase DDR1 expression in pituitary adenoma cells, leading to improved MMP-2 and MMP-9 secretion, and promoting pituitary adenoma cell proliferation and invasion.

te Raa GD, Moerland PD, Leeksma AC, et al.
Assessment of p53 and ATM functionality in chronic lymphocytic leukemia by multiplex ligation-dependent probe amplification.
Cell Death Dis. 2015; 6:e1852 [PubMed] Free Access to Full Article Related Publications
The ATM-p53 DNA-damage response (DDR) pathway has a crucial role in chemoresistance in CLL, as indicated by the adverse prognostic impact of genetic aberrations of TP53 and ATM. Identifying and distinguishing TP53 and ATM functional defects has become relevant as epigenetic and posttranscriptional dysregulation of the ATM/p53 axis is increasingly being recognized as the underlying cause of chemoresistance. Also, specific treatments sensitizing TP53- or ATM-deficient CLL cells are emerging. We therefore developed a new ATM-p53 functional assay with the aim to (i) identify and (ii) distinguish abnormalities of TP53 versus ATM and (iii) enable the identification of additional defects in the ATM-p53 pathway. Reversed transcriptase multiplex ligation-dependent probe amplification (RT-MLPA) was used to measure ATM and/or p53-dependent genes at the RNA level following DNA damage using irradiation. Here, we showed that this assay is able to identify and distinguish three subgroups of CLL tumors (i.e., TP53-defective, ATM-defective and WT) and is also able to detect additional samples with a defective DDR, without molecular aberrations in TP53 and/or ATM. These findings make the ATM-p53 RT-MLPA functional assay a promising prognostic tool for predicting treatment responses in CLL.

Gan W, Liu P, Wei W
Akt promotes tumorigenesis in part through modulating genomic instability via phosphorylating XLF.
Nucleus. 2015; 6(4):261-5 [PubMed] Free Access to Full Article Related Publications
To maintain genome stability, mammalian cells have developed a delicate, yet efficient, system to sense and repair damaged DNA, including two evolutionarily conserved DNA damage repair (DDR) pathways: homologous recombination (HR) and non-homologous-end-joining (NHEJ). Deregulation in these repair pathways may lead to genomic instability and subsequent human diseases, including cancer. On the other hand, hyper-activation of the oncogenic Akt signaling pathway has been observed in almost all solid tumors. Emerging evidence has begun to reveal a possible role of active Akt in regulating DDR, possibly through suppression of HR. However, whether and how Akt regulates NHEJ remains largely undefined. To this end, we recently reported that Akt impairs NHEJ by phosphorylating XLF at T181, to trigger its dissociation from the functional DNA ligase IV (LIG4)/XRCC4 complex. Here, we provide an additional perspective discussing how Akt is activated upon DNA damage to regulate DNA repair pathways as well as the cellular apoptotic responses.

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