The Chk1 inhibitor SAR-020106 sensitizes human glioblastoma cells to irradiation, to temozolomide, and to decitabine treatment

Abstract

BackgroundGlioblastoma is the most common and aggressive brain tumour in adults with a median overall survival of only 14 months after standard therapy with radiation therapy (IR) and temozolomide (TMZ). In a novel multimodal treatment approach we combined the checkpoint kinase 1 (Chk1) inhibitor SAR-020106 (SAR), disrupting homologue recombination, with standard DNA damage inducers (IR, TMZ) and the epigenetic/cytotoxic drug decitabine (5-aza-2′-deoxycitidine, 5-aza-dC). Different in vitro glioblastoma models are monitored to evaluate if the impaired DNA damage repair may chemo/radiosensitize the tumour cells.MethodsHuman p53-mutated (p53-mut) and -wildtype (p53-wt) glioblastoma cell lines (p53-mut: LN405, T98G; p53-wt: A172, DBTRG) and primary glioblastoma cells (p53-mut: P0297; p53-wt: P0306) were treated with SAR combined with TMZ, 5-aza-dC, and/or IR and analysed for induction of apoptosis (AnnexinV and sub-G1 assay), cell cycle distribution (nuclear PI staining), DNA damage (alkaline comet or gH2A.X assay), proliferation inhibition (BrdU assay), reproductive survival (clonogenic assay), and potential tumour stem cells (nestinpos/GFAPneg fluorescence staining). Potential treatment-induced neurotoxicity was evaluated on nestin-positive neural progenitor cells in a murine entorhinal-hippocampal slice culture model.ResultsSAR showed radiosensitizing effects on the induction of apoptosis and on the reduction of long-term survival in p53-mut and p53-wt glioblastoma cell lines and primary cells. In p53-mut cells, this effect was accompanied by an abrogation of the IR-induced G2/M arrest and an enhancement of IR-induced DNA damage by SAR treatment. Also TMZ and 5-aza-dC acted radioadditively albeit to a lesser extent. The multimodal treatment achieved the most effective reduction of clonogenicity in all tested cell lines and did not affect the ratio of nestinpos/GFAPneg cells. No neurotoxic effects were detected when the number of nestin-positive neural progenitor cells remained unchanged after multimodal treatment.ConclusionThe Chk1 inhibitor SAR-020106 is a potent sensitizer for DNA damage-induced cell death in glioblastoma therapy strongly reducing clonogenicity of tumour cells. Selectively enhanced p53-mut cell death may provide stronger responses in tumours defective of non-homologous end joining (NHEJ). Our results suggest that a multimodal therapy involving DNA damage inducers and DNA repair inhibitors might be an effective anti-tumour strategy with a low risk of neurotoxicity.

The m6A RNA Demethylase ALKBH5 Promotes Radioresistance and Invasion Capability of Glioma Stem Cells

“…CHK1 has also been shown to be upregulated in GBMSCs and preferentially activated following IR. Inhibition of CHK1 increased IR-induced DNA damages and radiosensitivity of GBMSCs [ 4 , 52 ].…”

Harnessing the targeting potential of differential radiobiological effects of photon versus particle radiation for cancer treatment

“…Both kinases relay signals to downstream kinases such as Chk1/2, to trigger its activation, resulting in the inactivation of CDK/cyclin complexes, and consequently cell‐cycle arrest (Cassimere, Mauvais, & Denicourt, 2016; Parplys et al, 2012). Although ATM mainly activates Chk2, and Chk1 is activated by ATR, there is considerable crosstalk between these two pathways, as they share many substrates (Patties et al, 2019; Qiu, Oleinick, & Zhang, 2018). Notably, ATM initiates cellular signalling cascade in response to DSBs, whereas ATR is activated by interrupted replication forks and extensive lesions in SSBs.…”

“…However, radio‐sensitising effects and UCN‐01 cytotoxicity were lower than other Chk1 inhibitors, such as MK‐8776 (Suzuki, Yamamori, Bo, Sakai, & Inanami, 2017). Moreover, the potent Chk1 inhibitor SAR‐020106, sensitises human glioblastoma cells to X‐rays, via inhibition of the p53‐independent G2 checkpoint (Patties et al, 2019). CCT244747, an orally bioavailable Chk1 inhibitor also enhances the radio‐sensitivity of bladder, head, and neck cancer cell lines, by abrogating IR‐induced G2 block, and prematurely entering mitosis (Patel et al, 2017).…”

Impact of Chaperone-Mediated Autophagy in Brain Aging: Neurodegenerative Diseases and Glioblastoma

“…Genotoxic insults together with oxidative stress and starvation are the main stimulus which activates CMA (Park et al, 2015 ). In this regard, CHK1 participates in genome quality control, and it has been associated with physiological neuronal differentiation (Oshikawa et al, 2017 ) and resistance of glioblastoma cells to chemo/radiotherapy (Patties et al, 2019 ). Interestingly, CHK1 has been described as a CMA substrate, as it presents various KFERQ-like motifs in different domains (Kirchner et al, 2019 ).…”