End Processing Factor APLF Promotes NHEJ Efficiency and Contributes to TMZ- and Ionizing Radiation-Resistance in
Wei Dong1, Lanlan Li2, Xuepeng Teng1
1Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academic Sciences, Jinan, Shandong, People's Republic of China.
Purpose:
Glioblastoma (GBM) is the most commonly diagnosed primary brain tumor in adults. Despite a variety of advances in the understanding of GBM cancer biology during recent decades, very few of them were applied into treatment, and the survival rate of GBM patients has not been improved majorly due to the low chemosensitivity to temozolomide (TMZ) or low radiosensitivity. Therefore, it is urgent to elucidate mechanisms of TMZ- and IR-resistance and develop novel therapeutic strategies to improve GBM treatment.
Methods:
TMZ- and IR-resistant cell lines were acquired by continuous exposing parental GBM cells to TMZ or IR for 3 months. Cell viability was determined by using Sulforhodamine B (SRB) assay. Protein and mRNA expression were examined by Western blotting assay and quantitative polymerase chain reaction (qPCR) assay, respectively. Homologous recombination (HR) and nonhomologous end joining (NHEJ) efficiency were measured by HR and NHEJ reporter assay. Cell apoptosis was determined by Caspase3/7 activity. Autophagy was analyzed using CYTO-ID® Autophagy detection kit. Tumor growth was examined by U87 xenograft mice model.
Results:
DNA repair efficiency of non-homologous end joining (NHEJ) pathway is significantly increased in TMZ- and IR-resistant GBM cells. Importantly, APLF, which is one of the DNA end processing factors in NHEJ, is upregulated in TMZ- and IR-resistant GBM cells and patients. APLF deficiency significantly decreases NHEJ efficiency and improves cell sensitivity to TMZ and IR both in vitro and in vivo.
Conclusion:
Our study provides evidence for APLF serving as a promising, novel target in GBM chemo- and radio-therapy.
Insights
APLF upregulation increases resistance to glioblastoma treatments like temozolomide (TMZ) and radiotherapy (IR). Targeting APLF enhances DNA repair inhibition, improving glioblastoma treatment effectiveness.
Area of Science:
- Oncology
- Molecular Biology
- Genetics
Background:
- Glioblastoma (GBM) is a primary brain tumor with poor patient survival rates.
- Low sensitivity to temozolomide (TMZ) and radiotherapy (IR) significantly limits GBM treatment efficacy.
- Understanding resistance mechanisms is crucial for developing improved therapeutic strategies.
Purpose of the Study:
- To investigate the mechanisms underlying TMZ- and IR-resistance in glioblastoma.
- To identify novel therapeutic targets for overcoming GBM treatment resistance.
Main Methods:
- Established TMZ- and IR-resistant GBM cell lines.
- Assessed cell viability, protein and mRNA expression, DNA repair pathway efficiency (NHEJ and HR), apoptosis, and autophagy.
- Utilized Western blotting, qPCR, reporter assays, and a U87 xenograft mouse model.
Main Results:
- TMZ- and IR-resistant GBM cells exhibit increased non-homologous end joining (NHEJ) DNA repair efficiency.
- APLF, a key NHEJ factor, is upregulated in resistant GBM cells and patients.
- APLF deficiency reduced NHEJ efficiency and sensitized GBM cells to TMZ and IR in vitro and in vivo.
Conclusions:
- APLF plays a significant role in GBM resistance to chemo- and radiotherapy.
- APLF represents a promising novel therapeutic target for enhancing GBM treatment outcomes.
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