Ku-dependent non-homologous end-joining as the major pathway contributes to sublethal damage repair in mammalian cells

Liu, Min; Lee, Solah; Liu, Bailong; Wang, Hongyan; Dong, Lihua; Wang, Ya

doi:10.3109/09553002.2015.1075178

Cited by 11 publications

(7 citation statements)

References 28 publications

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“…Our results in the glioma cell lines proficient (M059K) and defective (M059J) for DNA-PKcs suggest that tumour cells with p53 mutation, regardless of whether or not they have intact NHEJ, are likely to be fraction size insensitive. These observations are consistent with loss of fractionation sensitivity in p53-mutant CHO cell lines defective in NHEJ which rely on HR repair with cells accumulating in S/G2 phase of the cell cycle with fractionated RT 29 , 51 , 52 .…”

Section: Discussionsupporting

confidence: 81%

TP53 modulates radiotherapy fraction size sensitivity in normal and malignant cells

Anbalagan

Ström

Downs

et al. 2021

Sci Rep

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Recent clinical trials in breast and prostate cancer have established that fewer, larger daily doses (fractions) of radiotherapy are safe and effective, but these do not represent personalised dosing on a patient-by-patient basis. Understanding cell and molecular mechanisms determining fraction size sensitivity is essential to fully exploit this therapeutic variable for patient benefit. The hypothesis under test in this study is that fraction size sensitivity is dependent on the presence of wild-type (WT) p53 and intact non-homologous end-joining (NHEJ). Using single or split-doses of radiation in a range of normal and malignant cells, split-dose recovery was determined using colony-survival assays. Both normal and tumour cells with WT p53 demonstrated significant split-dose recovery, whereas Li-Fraumeni fibroblasts and tumour cells with defective G1/S checkpoint had a large S/G2 component and lost the sparing effect of smaller fractions. There was lack of split-dose recovery in NHEJ-deficient cells and DNA-PKcs inhibitor increased sensitivity to split-doses in glioma cells. Furthermore, siRNA knockdown of p53 in fibroblasts reduced split-dose recovery. In summary, cells defective in p53 are less sensitive to radiotherapy fraction size and lack of split-dose recovery in DNA ligase IV and DNA-PKcs mutant cells suggests the dependence of fraction size sensitivity on intact NHEJ.

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Section: Discussionsupporting

confidence: 81%

TP53 modulates radiotherapy fraction size sensitivity in normal and malignant cells

Anbalagan

Ström

Downs

et al. 2021

Sci Rep

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“…Recently our SLDR survival experiments not only confirmed previously published CHO cell results (Somaiah et al 2013), but also verified the results in mouse and human cells (Liu et al 2015). These results clarify that NHEJ is the major pathway for SLDR (Liu et al 2015).…”

Section: Both Sldr and Pldr Depend Mainly On Nhejsupporting

confidence: 90%

“…These results clarify that NHEJ is the major pathway for SLDR (Liu et al 2015). Using the same cell lines (wild type, HRR deficient and NHEJ deficient CHO, mouse and human cells), we performed PLDR survival experiments and obtained similar results to SLDR.…”

Section: Both Sldr and Pldr Depend Mainly On Nhejsupporting

confidence: 63%

“…Different from NHEJ, HRR needs an extended template for a sister chromatin exchange and is more efficient in the S/G2 phases (Jackson et al 2009, Rothkamm et al 2003). A recent study reported that SLDR could not be observed in NHEJ deficient CHO cells (Somaiah et al 2013), suggesting that NHEJ is the major pathway for SLDR, and we used different repair deficient mouse or human cell lines to further demonstrate that SLDR depends mainly on NHEJ (Liu et al 2015). Since it remains unclear which repair pathway, NHEJ or HRR, or both contributes to PLDR (Hall et al 2010), although different groups reported that some DNA repair related factors affect the efficiency of PLDR (Arlett et al 1984, Autsavapromporn et al 2013, Boothman et al 1989, Riballo et al 2004, Veuger et al 2003, Wilson et al 1989), it is also necessary to clarify this issue.…”

Section: Introductionmentioning

confidence: 96%

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DNA repair pathway choice at various conditions immediately post irradiation

Liu

Wang

Lee

et al. 2016

International Journal of Radiation Biology

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Purpose Clarify which DNA double strand break repair pathway, non-homologous end-joining (NHEJ), homologous recombination repair (HRR) or both, plays a key role in potentially lethal damage repair (PLDR). Methods and materials Combining published data and our new potentially lethal damage repair (PLDR) data, we explain whether similar to sublethal damage repair (SLDR), PLDR also mainly depends on NHEJ versus HRR. The PLDR data were used the same cell lines: wild type, HRR or NHEJ deficient fibroblast cells, as those SLDR data published by our laboratory previously. The PLDR condition that we used was as commonly described by many other groups: the cells were collected immediately or overnight post ionizing radiation for colony formation after cultured to a plateau phase with a low concentration of serum medium. Results Enough data from other groups and our lab showed that wild type or HRR deficient cells had efficient PLDR, but NHEJ deficient cell lines did not. Conclusion NHEJ contributes more to PLDR than HRR in mammalian (including human) cells, which is similar to SLDR. Since both SLDR and PLDR are relevant to clinical tumor status while undergoing radiotherapy, such clarification may benefit radiotherapy in the near future.

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“…In general, NHEJ is thought to contribute to ~ 80% of DSB repair in G1 phase and ~70% in G2 phase and to repair DSBs with a half-life of 1–2 h [ 3 ], which is shorter than the time for exposure in all of the above three conditions. The involvement of Ku in sublethal damage repair was demonstrated by split-dose experiments, in which the interval between two doses is 2–4 h [ 21 ]. In the study by Kreder et al ., the time required for irradiation would be shorter than the doubling time [ 20 ].…”

Section: Discussionmentioning

confidence: 99%

Diminished or inversed dose-rate effect on clonogenic ability in Ku-deficient rodent cells

Tsuchiya

Shimada

Tsukada

et al. 2020

Journal of Radiation Research

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The biological effects of ionizing radiation, especially those of sparsely ionizing radiations like X-ray and γ-ray, are generally reduced as the dose rate is reduced. This phenomenon is known as ‘the dose-rate effect’. The dose-rate effect is considered to be due to the repair of DNA damage during irradiation but the precise mechanisms for the dose-rate effect remain to be clarified. Ku70, Ku86 and DNA-dependent protein kinase catalytic subunit (DNA-PKcs) are thought to comprise the sensor for DNA double-strand break (DSB) repair through non-homologous end joining (NHEJ). In this study, we measured the clonogenic ability of Ku70-, Ku86- or DNA-PKcs-deficient rodent cells, in parallel with respective control cells, in response to high dose-rate (HDR) and low dose-rate (LDR) γ-ray radiation (~0.9 and ~1 mGy/min, respectively). Control cells and murine embryonic fibroblasts (MEF) from a severe combined immunodeficiency (scid) mouse, which is DNA-PKcs-deficient, showed higher cell survival after LDR irradiation than after HDR irradiation at the same dose. On the other hand, MEF from Ku70−/− mice exhibited lower clonogenic cell survival after LDR irradiation than after HDR irradiation. XR-V15B and xrs-5 cells, which are Ku86-deficient, exhibited mostly identical clonogenic cell survival after LDR and HDR irradiation. Thus, the dose-rate effect in terms of clonogenic cell survival is diminished or even inversed in Ku-deficient rodent cells. These observations indicate the involvement of Ku in the dose-rate effect.

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Ku-dependent non-homologous end-joining as the major pathway contributes to sublethal damage repair in mammalian cells

Cited by 11 publications

References 28 publications

TP53 modulates radiotherapy fraction size sensitivity in normal and malignant cells

TP53 modulates radiotherapy fraction size sensitivity in normal and malignant cells

DNA repair pathway choice at various conditions immediately post irradiation

Diminished or inversed dose-rate effect on clonogenic ability in Ku-deficient rodent cells

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