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Published on: June 9, 2017
eIF3a-PPP2R5A-mediated ATM/ATR dephosphorylation is essential for irinotecan-induced DNA damage response
Chao Mei1,2, Ze-En Sun1,2, Li-Ming Tan3
1Department of Clinical Pharmacology, Hunan Key Laboratory of Pharmacogenetics, National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, China.
Objectives:
The individual differences and pervasive resistance seriously hinder the optimization of irinotecan-based therapeutic effectiveness. Eukaryotic translation initiation factor 3a (eIF3a) plays a key role in tumour occurrence, prognosis and therapeutic response. This study focused on the role of eIF3a in irinotecan-induced DNA damage response.
Materials And Methods:
The cck8 cell viability and clone survival analyses were used to test the regulatory role of eIF3a on irinotecan sensitivity in HT29 and CACO2 cell lines in vitro. This regulatory role was also verified in vivo by conducting subcutaneous xenograft model. Irinotecan-induced DNA damage, cell cycle arrest and apoptosis were tested by flow cytometry analysis, TUNEL staining, western blot and comet assays. The immunofluorescence, co-IP, luciferase reporter assay, RIP and flow cytometric analyses were carried out to investigate the underline mechanism.
Results:
We demonstrated that eIF3a continuously activates ATM/ATR signal by translationally inhibiting PPP2R5A, a phosphatase that directly dephosphorylates and inactivates ATM/ATR after DNA repair complete. Suppression of PPP2R5A resulted in chronic ATM/ATR phosphorylation and activation, impairing DNA repair and enhancing irinotecan sensitivity.
Conclusions:
Our study suggested eIF3a with a high potential to influence phenotypic functions, which may contribute substantially to the early identification of susceptible individuals and the provision of personalized medication to irinotecan-treated patients.
Insights
Eukaryotic translation initiation factor 3a (eIF3a) enhances irinotecan effectiveness by inhibiting PPP2R5A, which sustains ATM/ATR signaling. This finding aids in identifying patients likely to respond to irinotecan therapy.
Area of Science:
- Oncology
- Molecular Biology
- Cancer Therapeutics
Background:
- Individual differences and resistance limit irinotecan efficacy.
- Eukaryotic translation initiation factor 3a (eIF3a) is implicated in tumor development and treatment response.
- Understanding eIF3a's role in DNA damage response is crucial for optimizing irinotecan therapy.
Purpose of the Study:
- To investigate the role of eIF3a in the DNA damage response induced by irinotecan.
- To elucidate the mechanism by which eIF3a affects irinotecan sensitivity.
Main Methods:
- Cell viability and survival assays (CCK8, clone survival) were performed in HT29 and CACO2 cell lines.
- In vivo studies utilized subcutaneous xenograft models.
- DNA damage, cell cycle arrest, apoptosis, and signaling pathways (ATM/ATR) were analyzed using flow cytometry, TUNEL staining, Western blot, comet assays, immunofluorescence, co-IP, luciferase reporter assays, and RIP analysis.
Main Results:
- eIF3a translationally inhibits PPP2R5A, a phosphatase that deactivates ATM/ATR.
- Inhibition of PPP2R5A leads to sustained ATM/ATR activation, impairing DNA repair.
- Suppression of eIF3a enhanced irinotecan sensitivity by promoting DNA repair.
Conclusions:
- eIF3a plays a significant role in phenotypic functions related to irinotecan treatment.
- Targeting eIF3a may offer a strategy for personalized medicine in irinotecan therapy.
- This research provides insights for early identification of patients susceptible to irinotecan treatment.
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