Spontaneous γH2AX foci in human solid tumor-derived cell lines in relation to p21<sup>WAF1</sup> and WIP1 expression

Razmik Mirzayans, Bonnie Andrais, April Scott, Ying W. Wang, Robert H Weiss, David Murray

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Phosphorylation of H2AX on Ser139 (γH2AX) after exposure to ionizing radiation produces nuclear foci that are detectable by immunofluorescence microscopy. These so-called γH2AX foci have been adopted as quantitative markers for DNA double-strand breaks. High numbers of spontaneous γH2AX foci have also been reported for some human solid tumor-derived cell lines, but the molecular mechanism(s) for this response remains elusive. Here we show that cancer cells (e.g., HCT116; MCF7) that constitutively express detectable levels of p21<sup>WAF1</sup> (p21) exhibit low numbers of γH2AX foci (<3/nucleus), whereas p21 knockout cells (HCT116p21−/−) and constitutively low p21-expressing cells (e.g., MDA-MB-231) exhibit high numbers of foci (e.g., >50/nucleus), and that these foci are not associated with apoptosis. The majority (>95%) of cells within HCT116p21−/− and MDA-MB-231 cultures contain high levels of phosphorylated p53, which is localized in the nucleus. We further show an inverse relationship between γH2AX foci and nuclear accumulation of WIP1, an oncogenic phosphatase. Our studies suggest that: (i) p21 deficiency might provide a selective pressure for the emergence of apoptosis-resistant progeny exhibiting genomic instability, manifested as spontaneous γH2AX foci coupled with phosphorylation and nuclear accumulation of p53; and (ii) p21 might contribute to positive regulation of WIP1, resulting in dephosphorylation of γH2AX.

Original languageEnglish (US)
Pages (from-to)11609-11628
Number of pages20
JournalInternational Journal of Molecular Sciences
Volume16
Issue number5
DOIs
StatePublished - May 20 2015

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Tumor Cell Line
cultured cells
Tumors
tumors
Cells
Phosphorylation
Apoptosis
HCT116 Cells
Double-Stranded DNA Breaks
Genomic Instability
Ionizing Radiation
Fluorescence Microscopy
Phosphoric Monoester Hydrolases
phosphorylation
apoptosis
Cell death
Neoplasms
multiple docking adapters
progeny
phosphatases

Keywords

  • Apoptosis
  • P21<sup>WAF1</sup>
  • P53
  • WIP1
  • γH2AX foci

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Spectroscopy
  • Inorganic Chemistry
  • Catalysis
  • Molecular Biology
  • Computer Science Applications

Cite this

Spontaneous γH2AX foci in human solid tumor-derived cell lines in relation to p21<sup>WAF1</sup> and WIP1 expression. / Mirzayans, Razmik; Andrais, Bonnie; Scott, April; Wang, Ying W.; Weiss, Robert H; Murray, David.

In: International Journal of Molecular Sciences, Vol. 16, No. 5, 20.05.2015, p. 11609-11628.

Research output: Contribution to journalArticle

Mirzayans, Razmik ; Andrais, Bonnie ; Scott, April ; Wang, Ying W. ; Weiss, Robert H ; Murray, David. / Spontaneous γH2AX foci in human solid tumor-derived cell lines in relation to p21<sup>WAF1</sup> and WIP1 expression. In: International Journal of Molecular Sciences. 2015 ; Vol. 16, No. 5. pp. 11609-11628.
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