Enhanced expression of thymidine kinase in human cells following ionizing radiation

David A. Boothman, Thomas W. Davis, Walter M. Sahijdak

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Purpose: We investigated the induction of thymidine kinase transcription and enzymatic activity, and the activation of transcription factors binding to the thymidine kinase promoter, in human normal compared to tumor cells in culture before and after ionizing radiation. Methods and Materials: Northern blot, dot-blot, and thymidine kinase enzyme assays were used to observe thymidine kinase transcript and enzymatic changes before and after radiation. Temporal expression of thymidine kinase transcripts following an optimal induction dose of radiation was also studied. Gel mobility shift assays were performed using a 95-base pair fragment of the thymidine kinase promoter (containing the CCAAT box) to analyze transcription factor binding. Results: Thymidine kinase transcript and enzymatic levels were higher in human tumor compared to normal cells. In contrast, levels of x-ray-activated thymidine kinase transcription factors were not significantly different in human neoplastic compared to normal cells. Conclusion: Elevated x-ray-induced thymidine kinase transcripts, enzymatic levels, and transcription factors are consistent with the loss of stringent cell growth regulation associated with neoplastic cells. The induction of thymidine kinase following ionizing radiation may be exploited in chemotherapeutic strategies which use halogenated pyrimidines and/or in various gene therapy strategies.

Original languageEnglish (US)
Pages (from-to)391-398
Number of pages8
JournalInternational journal of radiation oncology, biology, physics
Issue number2
StatePublished - Sep 30 1994


  • DNA binding proteins
  • Enzymatic assay
  • Ionizing radiation
  • Nuclear extracts
  • Transcription factors

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research


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