Therapy-induced senescence (TIS) in glioblastoma (GBM) residual disease and escape from TIS account for resistance and recurrence, but the mechanism of TIS manifestation remains obscure. Here, we demonstrate that replication stress (RS) is critical for the induction of TIS in residual cells by employing an in vitro GBM therapy-resistance cellular model. Interestingly, we found a ‘biphasic’ mode of DNA damage after radiation treatment and reveal that the second phase of DNA damage arises majorly in the S phase of residual cells due to RS. Mechanistically, we show that persistent phosphorylated ATR is a safeguard for radiation resilience, whereas the other canonical RS molecules remain unaltered during the second phase of DNA damage. Importantly, RS preceded the induction of senescence, and ATR inhibition resulted in TIS reduction, leading to apoptosis. Moreover, ATR inhibition sensitized PARP-1 inhibitor-induced enhanced TIS-mediated resistance, leading to cell death. Our study demonstrates the crucial role of RS in TIS induction and maintenance in GBM residual cells, and targeting ATR alone or in combination with a PARP-1 inhibitor will be an effective strategy to eliminate TIS for better treatment outcomes.

Keywords:
Replication stress, ATR, Therapy-induced senescence, Biphasic DNA damage response, Glioblastoma, Therapy resistance

Author contributions

Conceptualization: A.G., S.D.; Methodology: A.G., B.S., S.D.; Validation: A.G., B.S.; Formal analysis: A.G., B.S.; Investigation: A.G., B.S.; Resources: S.D.; Writing - original draft: A.G., B.S., S.D.; Writing - review & editing: A.G., B.S., S.D.; Visualization: A.G., B.S.; Supervision: S.D.; Project administration: S.D.; Funding acquisition: S.D.

Funding

A.G. acknowledges Department of Science and Technology, Ministry of Science and Technology, India (DST)-Science and Engineering Research Board (SERB), New Delhi, India, for partially providing the National Post-Doctoral Fellowship (PDF/ 2016/00158) and the Advanced Centre for Treatment, Research and Education in Cancer (ACTREC), Navi Mumbai, for financial support as an Institutional Post-Doctoral Fellowship. S.D. acknowledges financial support from the Department of Atomic Energy, Government of India [1/3(7)/2020/TMC/R&D-II/8823 and 1/3(6)/2020/TMC/R&D-II/3805].

Data availability

All relevant data can be found within the article and its supplementary information.

First Person

This article has an associated First Person interview with the first author of the paper.

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