Abstract

Purpose: Ionizing radiation induces cellular damage through both direct and indirect mechanisms, which may include effects from epigenetic changes. The purpose of this study was to determine the effect of ionizing radiation on DNA methylation patterns that may be associated with altered gene expression. Materials and methods: Sixteen human tumor cell lines originating from various cancers were initially tested for radiation sensitivity by irradiating them with γ-radiation in vitro and subsequently, radiation sensitive and resistant cell lines were treated with different doses of a demethylating agent, 5-Aza-2′-Deoxycytidine (5-aza-dC) and a chromatin modifier, Trichostatin-A (TSA). Survival of these cell lines was measured using 3-(4, 5-Dimethylthiazol- 2-yl)-2, 5-diphenyltetrazolium (MTT) and clonogenic assays. The effect of radiation on global DNA methylation was measured using reverse phase high performance liquid chromatography (RP-HPLC). The transcription response of methylated gene promoters, from cyclin-dependent kinase inhibitor 2A (p16 INK4a) and ataxia telangiectasia mutated (ATM) genes, to radiation was measured using a luciferase reporter assay. Results: γ-radiation resistant (SiHa and MDAMB453) and sensitive (SaOS2 and WM115) tumor cell lines were examined for the relationship between radiation sensitivity and DNA methylation. Treatment of cells with 5-aza-dC and TSA prior to irradiation enhanced DNA strand breaks, G2/M phase arrest, apoptosis and cell death. Exposure to γ-radiation led to global demethylation in a time-dependent manner in tumor cells in relation to resistance and sensitivity to radiation with concomitant activation of p16 INK4a and ATM gene promoters. Conclusion: These results provide important information on alterations in DNA methylation as one of the determinants of radiation effects, which may be associated with altered gene expression. Our results may help in delineating the mechanisms of radiation resistance in tumor cells, which can influence diagnosis, prognosis and eventually therapy for human cancers.

Original languageEnglish
Pages (from-to)1086-1096
Number of pages11
JournalInternational Journal of Radiation Biology
Volume87
Issue number11
DOIs
Publication statusPublished - 11-2011

Fingerprint

Tumor Cell Line
Methylation
decitabine
DNA Methylation
Radiation
Radiation Tolerance
trichostatin A
Cyclin-Dependent Kinase Inhibitor p16
Ataxia Telangiectasia
Radiation Effects
Ionizing Radiation
Neoplasms
Genes
Gene Expression
Cell Line
DNA Breaks
G2 Phase
Reverse-Phase Chromatography
Luciferases
Epigenomics

All Science Journal Classification (ASJC) codes

  • Radiological and Ultrasound Technology
  • Radiology Nuclear Medicine and imaging

Cite this

@article{51676986d7cb490ba431827a8388ce94,
title = "γ-radiation induces cellular sensitivity and aberrant methylation in human tumor cell lines",
abstract = "Purpose: Ionizing radiation induces cellular damage through both direct and indirect mechanisms, which may include effects from epigenetic changes. The purpose of this study was to determine the effect of ionizing radiation on DNA methylation patterns that may be associated with altered gene expression. Materials and methods: Sixteen human tumor cell lines originating from various cancers were initially tested for radiation sensitivity by irradiating them with γ-radiation in vitro and subsequently, radiation sensitive and resistant cell lines were treated with different doses of a demethylating agent, 5-Aza-2′-Deoxycytidine (5-aza-dC) and a chromatin modifier, Trichostatin-A (TSA). Survival of these cell lines was measured using 3-(4, 5-Dimethylthiazol- 2-yl)-2, 5-diphenyltetrazolium (MTT) and clonogenic assays. The effect of radiation on global DNA methylation was measured using reverse phase high performance liquid chromatography (RP-HPLC). The transcription response of methylated gene promoters, from cyclin-dependent kinase inhibitor 2A (p16 INK4a) and ataxia telangiectasia mutated (ATM) genes, to radiation was measured using a luciferase reporter assay. Results: γ-radiation resistant (SiHa and MDAMB453) and sensitive (SaOS2 and WM115) tumor cell lines were examined for the relationship between radiation sensitivity and DNA methylation. Treatment of cells with 5-aza-dC and TSA prior to irradiation enhanced DNA strand breaks, G2/M phase arrest, apoptosis and cell death. Exposure to γ-radiation led to global demethylation in a time-dependent manner in tumor cells in relation to resistance and sensitivity to radiation with concomitant activation of p16 INK4a and ATM gene promoters. Conclusion: These results provide important information on alterations in DNA methylation as one of the determinants of radiation effects, which may be associated with altered gene expression. Our results may help in delineating the mechanisms of radiation resistance in tumor cells, which can influence diagnosis, prognosis and eventually therapy for human cancers.",
author = "Ashok Kumar and Rai, {Padmalatha S.} and Raghavendra Upadhya and Vishwanatha and {Shama Prasada}, K. and {Satish Rao}, {B. S.} and Kapettu Satyamoorthy",
year = "2011",
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language = "English",
volume = "87",
pages = "1086--1096",
journal = "International Journal of Radiation Biology",
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γ-radiation induces cellular sensitivity and aberrant methylation in human tumor cell lines. / Kumar, Ashok; Rai, Padmalatha S.; Upadhya, Raghavendra; Vishwanatha, ; Shama Prasada, K.; Satish Rao, B. S.; Satyamoorthy, Kapettu.

In: International Journal of Radiation Biology, Vol. 87, No. 11, 11.2011, p. 1086-1096.

Research output: Contribution to journalArticle

TY - JOUR

T1 - γ-radiation induces cellular sensitivity and aberrant methylation in human tumor cell lines

AU - Kumar, Ashok

AU - Rai, Padmalatha S.

AU - Upadhya, Raghavendra

AU - Vishwanatha,

AU - Shama Prasada, K.

AU - Satish Rao, B. S.

AU - Satyamoorthy, Kapettu

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N2 - Purpose: Ionizing radiation induces cellular damage through both direct and indirect mechanisms, which may include effects from epigenetic changes. The purpose of this study was to determine the effect of ionizing radiation on DNA methylation patterns that may be associated with altered gene expression. Materials and methods: Sixteen human tumor cell lines originating from various cancers were initially tested for radiation sensitivity by irradiating them with γ-radiation in vitro and subsequently, radiation sensitive and resistant cell lines were treated with different doses of a demethylating agent, 5-Aza-2′-Deoxycytidine (5-aza-dC) and a chromatin modifier, Trichostatin-A (TSA). Survival of these cell lines was measured using 3-(4, 5-Dimethylthiazol- 2-yl)-2, 5-diphenyltetrazolium (MTT) and clonogenic assays. The effect of radiation on global DNA methylation was measured using reverse phase high performance liquid chromatography (RP-HPLC). The transcription response of methylated gene promoters, from cyclin-dependent kinase inhibitor 2A (p16 INK4a) and ataxia telangiectasia mutated (ATM) genes, to radiation was measured using a luciferase reporter assay. Results: γ-radiation resistant (SiHa and MDAMB453) and sensitive (SaOS2 and WM115) tumor cell lines were examined for the relationship between radiation sensitivity and DNA methylation. Treatment of cells with 5-aza-dC and TSA prior to irradiation enhanced DNA strand breaks, G2/M phase arrest, apoptosis and cell death. Exposure to γ-radiation led to global demethylation in a time-dependent manner in tumor cells in relation to resistance and sensitivity to radiation with concomitant activation of p16 INK4a and ATM gene promoters. Conclusion: These results provide important information on alterations in DNA methylation as one of the determinants of radiation effects, which may be associated with altered gene expression. Our results may help in delineating the mechanisms of radiation resistance in tumor cells, which can influence diagnosis, prognosis and eventually therapy for human cancers.

AB - Purpose: Ionizing radiation induces cellular damage through both direct and indirect mechanisms, which may include effects from epigenetic changes. The purpose of this study was to determine the effect of ionizing radiation on DNA methylation patterns that may be associated with altered gene expression. Materials and methods: Sixteen human tumor cell lines originating from various cancers were initially tested for radiation sensitivity by irradiating them with γ-radiation in vitro and subsequently, radiation sensitive and resistant cell lines were treated with different doses of a demethylating agent, 5-Aza-2′-Deoxycytidine (5-aza-dC) and a chromatin modifier, Trichostatin-A (TSA). Survival of these cell lines was measured using 3-(4, 5-Dimethylthiazol- 2-yl)-2, 5-diphenyltetrazolium (MTT) and clonogenic assays. The effect of radiation on global DNA methylation was measured using reverse phase high performance liquid chromatography (RP-HPLC). The transcription response of methylated gene promoters, from cyclin-dependent kinase inhibitor 2A (p16 INK4a) and ataxia telangiectasia mutated (ATM) genes, to radiation was measured using a luciferase reporter assay. Results: γ-radiation resistant (SiHa and MDAMB453) and sensitive (SaOS2 and WM115) tumor cell lines were examined for the relationship between radiation sensitivity and DNA methylation. Treatment of cells with 5-aza-dC and TSA prior to irradiation enhanced DNA strand breaks, G2/M phase arrest, apoptosis and cell death. Exposure to γ-radiation led to global demethylation in a time-dependent manner in tumor cells in relation to resistance and sensitivity to radiation with concomitant activation of p16 INK4a and ATM gene promoters. Conclusion: These results provide important information on alterations in DNA methylation as one of the determinants of radiation effects, which may be associated with altered gene expression. Our results may help in delineating the mechanisms of radiation resistance in tumor cells, which can influence diagnosis, prognosis and eventually therapy for human cancers.

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