Targeting polymerase θ impairs tumorigenesis and enhances radiosensitivity in lung adenocarcinoma

Rao, Xinrui; Xing, Biyuan; Wu, Zilong; Bin, Yawen; Chen, Yunshang; Xu, Yingzhuo; Zhou, Dong; Zhou, Xiaoshu; Wu, Chuangyan; Wang, Ye; Chen, Weibin; Wang, Geng; Zhang, Sheng; Dong, Xiaorong; Meng, Rui; Wu, Gang; Zhou, Rui

doi:10.1111/cas.15727

Cited by 4 publications

(3 citation statements)

References 39 publications

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“…We then measured the expression of IGF2BP2 in radioresistant H1299 (H1299-RR) cells and their parental H1299 cells. The H1299-RR cells were constructed in our laboratory as previously reported [ 23 ], and radioresistance was confirmed by clonogenic survival assay, Rad51 foci formation assay, and neutral comet assay. Compared with the parental line, H1299-RR cells exhibited higher colony formation ability after irradiation (IR) (Fig.…”

Section: Resultsmentioning

confidence: 99%

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FBW7/GSK3β mediated degradation of IGF2BP2 inhibits IGF2BP2-SLC7A5 positive feedback loop and radioresistance in lung cancer

Zhou,

Zhang,

Deng

et al. 2024

J Exp Clin Cancer Res

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Background The development of radioresistance seriously hinders the efficacy of radiotherapy in lung cancer. However, the underlying mechanisms by which radioresistance occurs are still incompletely understood. The N6-Methyladenosine (m6A) modification of RNA is involved in cancer progression, but its role in lung cancer radioresistance remains elusive. This study aimed to identify m6A regulators involved in lung cancer radiosensitivity and further explore the underlying mechanisms to identify therapeutic targets to overcome lung cancer radioresistance. Methods Bioinformatic mining was used to identify the m6A regulator IGF2BP2 involved in lung cancer radiosensitivity. Transcriptome sequencing was used to explore the downstream factors. Clonogenic survival assays, neutral comet assays, Rad51 foci formation assays, and Annexin V/propidium iodide assays were used to determine the significance of FBW7/IGF2BP2/SLC7A5 axis in lung cancer radioresistance. Chromatin immunoprecipitation (ChIP)-qPCR analyses, RNA immunoprecipitation (RIP) and methylated RNA immunoprecipitation (MeRIP)-qPCR analyses, RNA pull-down analyses, co-immunoprecipitation analyses, and ubiquitination assays were used to determine the feedback loop between IGF2BP2 and SLC7A5 and the regulatory effect of FBW7/GSK3β on IGF2BP2. Mice models and tissue microarrays were used to verify the effects in vivo. Results We identified IGF2BP2, an m6A “reader”, that is overexpressed in lung cancer and facilitates radioresistance. We showed that inhibition of IGF2BP2 impairs radioresistance in lung cancer both in vitro and in vivo. Furthermore, we found that IGF2BP2 enhances the stability and translation of SLC7A5 mRNA through m6A modification, resulting in enhanced SLC7A5-mediated transport of methionine to produce S-adenosylmethionine. This feeds back upon the IGF2BP2 promoter region by further increasing the trimethyl modification at lysine 4 of histone H3 (H3K4me3) level to upregulate IGF2BP2 expression. We demonstrated that this positive feedback loop between IGF2BP2 and SLC7A5 promotes lung cancer radioresistance through the AKT/mTOR pathway. Moreover, we found that the ubiquitin ligase FBW7 functions with GSK3β kinase to recognize and degrade IGF2BP2. Conclusions Collectively, our study revealed that the m6A “reader” IGF2BP2 promotes lung cancer radioresistance by forming a positive feedback loop with SLC7A5, suggesting that IGF2BP2 may be a potential therapeutic target to control radioresistance in lung cancer.

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Section: Resultsmentioning

confidence: 99%

“…Human lung adenocarcinoma cells including NCI-H1299 (H1299) and A549 were purchased from Procell (Wuhan, China). Radioresistant H1299-RR cells were constructed in our laboratory as previously reported [ 23 ]. All cell lines were authenticated by short tandem repeat (STR) profiling and tested for mycoplasma contamination.…”

Section: Methodsmentioning

confidence: 99%

FBW7/GSK3β mediated degradation of IGF2BP2 inhibits IGF2BP2-SLC7A5 positive feedback loop and radioresistance in lung cancer

Zhou,

Zhang,

Deng

et al. 2024

J Exp Clin Cancer Res

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“…For example, deletion of Polθ is synthetic lethal with various DNA repair genes, including BRCA1/2 mutations [ 68 , 71 , 243 ] and can synergise with PARP inhibitors in HR-defective cancers [ 71 ]. Furthermore, Polθ inhibitors have also been shown to re-sensitise chemoresistant and radioresistant lung cancer cells, as well as sensitising cancer cells that have acquired PARPi resistance [ 244 , 245 , 246 ]. Since Polθ is overexpressed in many cancer types and is correlated with a poor patient prognosis—and that drug targeting might be cancer-specific given that normal tissues are HR-proficient [ 68 ]—small molecule compounds have progressed at a rapid pace.…”

Section: Challenges and Opportunities For The Futurementioning

confidence: 99%

DNA Repair and Therapeutic Strategies in Cancer Stem Cells

Gillespie

Ward

Davies

2023

Cancers

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First-line cancer treatments successfully eradicate the differentiated tumour mass but are comparatively ineffective against cancer stem cells (CSCs), a self-renewing subpopulation thought to be responsible for tumour initiation, metastasis, heterogeneity, and recurrence. CSCs are thus presented as the principal target for elimination during cancer treatment. However, CSCs are challenging to drug target because of numerous intrinsic and extrinsic mechanisms of drug resistance. One such mechanism that remains relatively understudied is the DNA damage response (DDR). CSCs are presumed to possess properties that enable enhanced DNA repair efficiency relative to their highly proliferative bulk progeny, facilitating improved repair of double-strand breaks induced by radiotherapy and most chemotherapeutics. This can occur through multiple mechanisms, including increased expression and splicing fidelity of DNA repair genes, robust activation of cell cycle checkpoints, and elevated homologous recombination-mediated DNA repair. Herein, we summarise the current knowledge concerning improved genome integrity in non-transformed stem cells and CSCs, discuss therapeutic opportunities within the DDR for re-sensitising CSCs to genotoxic stressors, and consider the challenges posed regarding unbiased identification of novel DDR-directed strategies in CSCs. A better understanding of the DDR mediating chemo/radioresistance mechanisms in CSCs could lead to novel therapeutic approaches, thereby enhancing treatment efficacy in cancer patients.

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Novobiocin blocks nucleic acid binding to Polθ and inhibits stimulation of its ATPase activity

Syed,

Filandr,

Patterson-Fortin

et al. 2023

Nucleic Acids Research

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Polymerase theta (Polθ) acts in DNA replication and repair, and its inhibition is synthetic lethal in BRCA1 and BRCA2-deficient tumor cells. Novobiocin (NVB) is a first-in-class inhibitor of the Polθ ATPase activity, and it is currently being tested in clinical trials as an anti-cancer drug. Here, we investigated the molecular mechanism of NVB-mediated Polθ inhibition. Using hydrogen deuterium exchange-mass spectrometry (HX-MS), biophysical, biochemical, computational and cellular assays, we found NVB is a non-competitive inhibitor of ATP hydrolysis. NVB sugar group deletion resulted in decreased potency and reduced HX-MS interactions, supporting a specific NVB binding orientation. Collective results revealed that NVB binds to an allosteric site to block DNA binding, both in vitro and in cells. Comparisons of The Cancer Genome Atlas (TCGA) tumors and matched controls implied that POLQ upregulation in tumors stems from its role in replication stress responses to increased cell proliferation: this can now be tested in fifteen tumor types by NVB blocking ssDNA-stimulation of ATPase activity, required for Polθ function at replication forks and DNA damage sites. Structural and functional insights provided in this study suggest a path for developing NVB derivatives with improved potency for Polθ inhibition by targeting ssDNA binding with entropically constrained small molecules.

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Targeting polymerase θ impairs tumorigenesis and enhances radiosensitivity in lung adenocarcinoma

Cited by 4 publications

References 39 publications

FBW7/GSK3β mediated degradation of IGF2BP2 inhibits IGF2BP2-SLC7A5 positive feedback loop and radioresistance in lung cancer

FBW7/GSK3β mediated degradation of IGF2BP2 inhibits IGF2BP2-SLC7A5 positive feedback loop and radioresistance in lung cancer

DNA Repair and Therapeutic Strategies in Cancer Stem Cells

Novobiocin blocks nucleic acid binding to Polθ and inhibits stimulation of its ATPase activity

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