Role of apoptosis in low-dose hyper-radiosensitivity

S. A. Krueger, M. C. Joiner, M. Weinfeld, E. Piasentin, B. Marples

Research output: Contribution to journalArticlepeer-review

74 Scopus citations


Little is known about the mode of cell killing associated with low-dose hyper-radiosensitivity, the radiation response that describes the enhanced sensitivity of cells to small doses of ionizing radiation. Using a technique that measures the activation of caspase 3, we have established a relationship between apoptosis detected 24 h after low-dose radiation exposure and low-dose hyper-radiosensitivity in four mammalian cell lines (T98G, U373, MR4 and 3.7 cells) and two normal human lymphoblastoid cell lines. The existence of low-dose hyper-radiosensitivity in clonogenic survival experiments was found to be associated with an elevated level of apoptosis after low-dose exposures, corroborating earlier observations (Enns et al., Mol. Cancer Res. 2, 557-566, 2004). We also show that enriching populations of MR4 and V79 cells with G 1-phase cells, to minimize the numbers of G2-phase cells, abolished the enhanced low-dose apoptosis. These cell-cycle enrichment experiments strengthen the reported association between low-dose hyper-sensitivity and the radioresponse of G2-phase cells. These data are consistent with our current hypothesis to explain low-dose hyper-radiosensitivity, namely that the enhanced sensitivity of cells to low doses of ionizing radiation reflects the failure of ATM-dependent repair processes to fully arrest the progression of damaged G2-phase cells harboring unrepaired DNA breaks entering mitosis.

Original languageEnglish (US)
Pages (from-to)260-267
Number of pages8
JournalRadiation research
Issue number3
StatePublished - Mar 2007
Externally publishedYes

ASJC Scopus subject areas

  • Biophysics
  • Radiation
  • Radiology Nuclear Medicine and imaging


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