The influence of AKT isoforms on radiation sensitivity and DNA repair in colon cancer cell lines

In response to ionizing radiation, several signaling cascades in the cell are activated to repair the DNA breaks, prevent apoptosis, and keep the cells proliferating. AKT is important for survival and proliferation and may also be an activating factor for DNA-PKcs and MRE11, which are essential proteins in the DNA repair process. AKT (PKB) is hyperactivated in several cancers and is associated with resistance to radiotherapy and chemotherapy. There are three AKT isoforms (AKT1, AKT2, and AKT3) with different expression patterns and functions in several cancer tumors. The role of AKT isoforms has been investigated in relation to radiation response and their effects on DNA repair proteins (DNA-PKcs and MRE11) in colon cancer cell lines. The knockout of AKT1 and/or AKT2 affected the radiation sensitivity, and a deficiency of both isoforms impaired the rejoining of radiation-induced DNA double strand breaks. Importantly, the active/phosphorylated forms of AKT and DNA-PKcs associate and exposure to ionizing radiation causes an increase in this interaction. Moreover, an increased expression of both DNA-PKcs and MRE11 was observed when AKT expression was ablated, yet only DNA-PKcs expression influenced AKT phosphorylation. Taken together, these results demonstrate a role for both AKT1 and AKT2 in radiotherapy response in colon cancer cells involving DNA repair capacity through the nonhomologous end joining pathway, thus suggesting that AKT in combination with DNA-PKcs inhibition may be used for radiotherapy sensitizing strategies in colon cancer.

[1]  B. Hemmings,et al.  Physiological roles of PKB/Akt isoforms in development and disease. , 2007, Biochemical Society transactions.

[2]  M. Birnbaum,et al.  Selective inhibition of Ras, phosphoinositide 3 kinase, and Akt isoforms increases the radiosensitivity of human carcinoma cell lines. , 2005, Cancer research.

[3]  Genetic inactivation of AKT1, AKT2, and PDPK1 in human colorectal cancer cells clarifies their roles in tumor growth regulation (Proceedings of the National Academy of Sciences of the United States of America (2010) 107 (2598-2603) DOI: 10.1073/pnas.0914018107) , 2010 .

[4]  David J. Chen,et al.  Threonine 2609 Phosphorylation of the DNA-Dependent Protein Kinase Is a Critical Prerequisite for Epidermal Growth Factor Receptor–Mediated Radiation Resistance , 2012, Molecular Cancer Research.

[5]  R. Deng,et al.  PKB/Akt promotes DSB repair in cancer cells through upregulating Mre11 expression following ionizing radiation , 2011, Oncogene.

[6]  S. Jackson,et al.  DNA-dependent protein kinase. , 1997, The international journal of biochemistry & cell biology.

[7]  David J. Chen,et al.  DNA-PK phosphorylates histone H2AX during apoptotic DNA fragmentation in mammalian cells. , 2006, DNA repair.

[8]  Anthony W. Parker,et al.  The dynamics of Ku70/80 and DNA-PKcs at DSBs induced by ionizing radiation is dependent on the complexity of damage , 2012, Nucleic acids research.

[9]  H. Grönberg,et al.  A Systematic Overview of Radiation Therapy Effects in Rectal Cancer , 2003, Acta oncologica.

[10]  R. Pearson,et al.  Relative Expression Levels Rather Than Specific Activity Plays the Major Role in Determining In Vivo AKT Isoform Substrate Specificity , 2011, Enzyme research.

[11]  Anne E Carpenter,et al.  CellProfiler: image analysis software for identifying and quantifying cell phenotypes , 2006, Genome Biology.

[12]  D. Durocher,et al.  MRE11 promotes AKT phosphorylation in direct response to DNA double-strand breaks , 2011, Cell cycle.

[13]  David J. Chen,et al.  Function of erbB receptors and DNA-PKcs on phosphorylation of cytoplasmic and nuclear Akt at S473 induced by erbB1 ligand and ionizing radiation. , 2011, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[14]  Xiao-dan Liu,et al.  Inactivation of DNA-dependent protein kinase leads to spindle disruption and mitotic catastrophe with attenuated checkpoint protein 2 Phosphorylation in response to DNA damage. , 2010, Cancer research.

[15]  J. Ferlay,et al.  Global Cancer Statistics, 2002 , 2005, CA: a cancer journal for clinicians.

[16]  F. Liu,et al.  PDK2: the missing piece in the receptor tyrosine kinase signaling pathway puzzle. , 2005, American journal of physiology. Endocrinology and metabolism.

[17]  K. Khanna,et al.  DNA double-strand breaks: signaling, repair and the cancer connection , 2001, Nature Genetics.

[18]  Hoyun Lee,et al.  The Akt isoforms are present at distinct subcellular locations. , 2010, American journal of physiology. Cell physiology.

[19]  B. Stenerlöw,et al.  Repair of Radiation-Induced Heat-Labile Sites is Independent of DNA-PKcs, XRCC1 and PARP , 2008, Radiation research.

[20]  Chen Wang,et al.  Detection and repair of ionizing radiation-induced DNA double strand breaks: new developments in nonhomologous end joining. , 2013, International journal of radiation oncology, biology, physics.

[21]  B. Hemmings,et al.  PKBalpha/Akt1 acts downstream of DNA-PK in the DNA double-strand break response and promotes survival. , 2008, Molecular cell.

[22]  T. McGraw,et al.  The Akt kinases: Isoform specificity in metabolism and cancer , 2009, Cell cycle.

[23]  Shaomeng Wang,et al.  Targeting of AKT1 enhances radiation toxicity of human tumor cells by inhibiting DNA-PKcs-dependent DNA double-strand break repair , 2008, Molecular Cancer Therapeutics.

[24]  P. Dennis,et al.  Akt1 deletion prevents lung tumorigenesis by mutant K-ras , 2011, Oncogene.

[25]  T. Kunkel,et al.  The role of hMLH1, hMSH3, and hMSH6 defects in cisplatin and oxaliplatin resistance: correlation with replicative bypass of platinum-DNA adducts. , 1998, Cancer research.

[26]  B. Stenerlöw,et al.  The effect of a dimeric Affibody molecule (ZEGFR:1907)2 targeting EGFR in combination with radiation in colon cancer cell lines. , 2011, International journal of oncology.

[27]  Stephen McLaughlin,et al.  PIK3CA and PTEN Gene and Exon Mutation-Specific Clinicopathologic and Molecular Associations in Colorectal Cancer , 2013, Clinical Cancer Research.

[28]  H. Bryant.  DNA double-strand break damage and repair assessed by pulsed-field gel electrophoresis. , 2012, Methods in molecular biology.

[29]  L. Mazzucchelli,et al.  Multi-Determinants Analysis of Molecular Alterations for Predicting Clinical Benefit to EGFR-Targeted Monoclonal Antibodies in Colorectal Cancer , 2009, PloS one.

[30]  P. Kirschmeier,et al.  AKT1, AKT2 and AKT3-dependent cell survival is cell line-specific and knockdown of all three isoforms selectively induces apoptosis in 20 human tumor cell lines , 2007, Cancer biology & therapy.

[31]  U. Landegren,et al.  Direct observation of individual endogenous protein complexes in situ by proximity ligation , 2006, Nature Methods.

[32]  Jeffrey S. Morris,et al.  Phase II study of capecitabine (Xeloda) and concomitant boost radiotherapy in patients with locally advanced rectal cancer. , 2006, International journal of radiation oncology, biology, physics.

[33]  K. Kinzler,et al.  Genetic inactivation of AKT1, AKT2, and PDPK1 in human colorectal cancer cells clarifies their roles in tumor growth regulation , 2010, Proceedings of the National Academy of Sciences.

[34]  A. Jemal,et al.  Global Cancer Statistics , 2011 .

[35]  David J. Chen,et al.  Akt Promotes Post-Irradiation Survival of Human Tumor Cells through Initiation, Progression, and Termination of DNA-PKcs–Dependent DNA Double-Strand Break Repair , 2012, Molecular Cancer Research.

[36]  A. Jemal,et al.  Global cancer statistics , 2011, CA: a cancer journal for clinicians.

[37]  Lewis C. Cantley,et al.  AKT/PKB Signaling: Navigating Downstream , 2007, Cell.

[38]  K. Dittmann,et al.  Radiation-induced EGFR-signaling and control of DNA-damage repair , 2007, International journal of radiation biology.

[39]  A. Carnero.  The PKB/AKT pathway in cancer. , 2010, Current pharmaceutical design.