The role of RASA2 in predicting radioresistance in lung cancer through regulation of p53.

Abstract

One of the most common causes of lung cancer relapse after clinical treatment is radioresistance. However, the mechanism underlying radioresistance remains unclear. In this study, we investigated the role of Ras p21 protein activator (RASA2) in non-small cell lung cancer (NSCLC). The messenger RNA (mRNA) of RASA2 was tested via reverse-transcription quantitative polymerase chain reaction (RT-qPCR) of cancer tissues from patients with NSCLC. Computed tomography (CT) and bioluminescent imaging (BLI) were used to monitor the tumor growth of patients and orthotopic mice, respectively. Protein-protein interaction was quantified via immunoprecipitation and glutathione S transferase (GST) pulldown assay. Western blotting was used to evaluate the phosphorylation and ubiquitination level of p53. The results indicated a negative correlation between the mRNA expression levels of RASA2 in tumor tissues with patients' response to radiotherapy. Patients with a high expression of RASA2 had a lower objective response rate (ORR) after 1 month of radiotherapy than patients with low expression of RASA2 after 1 month of radiotherapy. In terms of mechanism, we proved that RASA2 can directly bind to p53 to promote the phosphorylation of p53, which inhibits its transcriptional activity and further promotes its degradation through the ubiquitin/proteasome pathway. In this process, the apoptosis of tumor cells is inhibited due to impaired p53 surveillance, which leads to radioresistance. Our results demonstrate that RASA2 negatively regulates p53 in cancer cells and therefore promotes radioresistance, providing a new predictive biomarker and a potential therapeutic target for radioresistance.