Olaparib and ionizing radiation trigger a cooperative DNA-damage repair response that is impaired by depletion of the VRK1 chromatin kinase

Abstract

Background The VRK1 chromatin kinase regulates the organization of locally altered chromatin induced by DNA damage. The combination of ionizing radiation with inhibitors of DNA damage responses increases the accumulation of DNA damage in cancer cells, which facilitates their antitumor effect, a process regulated by VRK1. Methods Tumor cell lines with different genetic backgrounds were treated with olaparib to determine their effect on the activation of DNA repair pathways induced by ionizing radiation. The effect of combining olaparib with depletion of the chromatin kinase VRK1 was studied in the context of double-strand breaks repair pathway after treatment with ionizing radiation. The initiation and progression of DDR were studied by specific histone acetylation, as a marker of local chromatin relaxation, and formation of γH2AX and 53BP1 foci. Results In this work, we have studied the effect that VRK1 by itself or in collaboration with olaparib, an inhibitor of PARP, has on the DNA oxidative damage induced by irradiation in order to identify its potential as a new drug target. The combination of olaparib and ionizing radiation increases DNA damage permitting a significant reduction of their respective doses to achieve a similar amount of DNA damage detected by γH2AX and 53BP1 foci. Different treatment combinations of olaparib and ionizing radiation permitted to reach the maximum level of DNA damage at lower doses of both treatments. Furthermore, we have studied the effect that depletion of the VRK1 chromatin kinase, a regulator of DDR, has on this response. VRK1 knockdown impaired all steps in the DDR induced by these treatments, which were detected by a reduction of sequential markers such as H4K16 ac, γH2AX, NBS1 and 53BP1. Moreover, this effect of VRK1 is independent of TP53 or ATM , two genes frequently mutated in cancer. Conclusion The protective DNA damage response induced by ionizing radiation is impaired by the combination of olaparib with depletion of VRK1, and can be used to reduce doses of radiation and their associated toxicity. Proteins implicated in DNA damage responses are suitable targets for development of new therapeutic strategies and their combination can be an alternative form of synthetic lethality. Electronic supplementary material The online version of this article (10.1186/s13046-019-1204-1) contains supplementary material, which is available to authorized users.

<p>Aptamer-Conjugated Gold Nanoparticles Targeting Epidermal Growth Factor Receptor Variant III for the Treatment of Glioblastoma</p>

“…Interestingly, treatment with U2-AuNP can decrease the expression level of 53BP1 (binding protein 1) and the phosphorylation level of ATM and Chk2, which are critical in the response to DNA damage. [38][39][40] In recent years, exposure to gold nanoparticles has been reported to cause transient DNA damage due to the generation of alkali-labile sites and oxidative stress with a decrease in glutathione. 41,42 However, the phosphorylation level of H2A.X showed no change after treatment with U2-AuNP 24 hr.…”

VRK1 (Y213H) homozygous mutant impairs Cajal bodies in a hereditary case of distal motor neuropathy

“…To determine the functional effect of the VRK1(Y213H) mutant, we performed in vitro kinase assays using several of the known VRK1 substrates. These included histones H3 and H2AX associated with chromatin remodeling, 13 coilin required for Cajal body formation, 7 p53, 42 and 53BP1 39 involved in different aspects of DNA damage responses 43 . The mutant VRK1(Y213H) was compared with the wild‐type VRK1.…”

VRK1 Phosphorylates Tip60/KAT5 and Is Required for H4K16 Acetylation in Response to DNA Damage

“…The kinase activity of VRK1 is induced by different types of DNA damage able to cause single or double strand breaks or alkylating lesions [ 19 ]. In response to DNA damage, VRK1 directly phosphorylates histones H3 [ 21 , 32 , 33 , 34 ], H2AX [ 14 , 35 ], NBS1 [ 20 ], and 53BP1 [ 19 , 36 ]. VRK1 also phosphorylates hnRNPA1 in telomerase activation [ 37 ].…”

“…The initial response to DNA damage implicates a local chromatin relaxation that is associated to histone H4 acetylation in K16 [ 41 , 42 , 43 ]. Therefore, H4K16 hypo-acetylation is associated with defective DNA repair [ 36 , 44 ]. The importance of H4K16ac in order to trigger a proper DNA-damage response in a locally altered chromatin indicates that this modification is tightly regulated.…”

“…VRK1 depletion impairs both NBS1 [ 20 ] and 53BP1 [ 19 ] specific phosphorylation and activation in response to DNA damage. Moreover, Tip60 is necessary for the acetylation and activation by autophosphorylation of ATM in response to DNA damage [ 48 ], whereas VRK1 is also essential for ATM activation [ 19 , 20 , 36 ]. Overexpression of Tip60 is associated to a poorer prognosis [ 49 ] and to cisplatin resistance in tumor cells [ 50 ].…”