In recent decades, the rapid development of radiotherapy has dramatically increased the cure rate of malignant tumors. Heavy-ion radiotherapy, which is characterized by the “Bragg Peak” because of its excellent physical properties, induces extensive unrepairable DNA damage in tumor tissues, while normal tissues in the path of ion beams suffer less damage. However, there are few prognostic molecular biomarkers that can be used to assess the efficacy of heavy ion radiotherapy. In this study, we focus on non-small cell lung cancer (NSCLC) radiotherapy and use RNA sequencing and bioinformatic analysis to investigate the gene expression profiles of A549 cells exposed to X-ray or carbon ion irradiation to screen the key genes involved in the stronger tumor-killing effect induced by carbon ions. The potential ceRNA network was predicted and verified by polymerase chain amplification, western blotting analysis, colony formation assay, and apoptosis assay. The results of the experiments indicated that lncRNA EBLN3P plays a critical role in inhibiting carbon ion-induced cell proliferation and inducing apoptosis of NSCLC cells. These functions were achieved by the EBLN3P/miR-144-3p/TNPO1 (transportin-1) ceRNA network. In summary, the lncRNA EBLN3P functions as a ceRNA to mediate lung cancer inhibition induced by carbon ion irradiation by sponging miR-144-3p to regulate TNPO1 expression, indicating that EBLN3P may be a promising target for increasing the treatment efficacy of conventional radiotherapy for NSCLC.

Background Radiotherapy plays an important role in numerous tumor clinical treatments and over 65% of cancer patients need to accept radiotherapy all over the world. However, tumor angiogenesis and metastasis induced by conventional photon radiotherapy adversely impact the survival of patients, and limit the clinical radiotherapy efficiency. Heavy-ion radiotherapy has attracted wide attention in recent years because of its excellent physical property and outstanding tumor control rate, however, the underlying gene expression regulation mechanism response to heavy-ion irradiation remains elusive. Methods RNA-sequencing (RNA-seq) and public database analysis were employed to identify the differential molecular changes in lung adenocarcinoma cells exposed to both X-ray and carbon ion (C-ion) irradiation. The expression of the identified LINC00167 was verified by real-time quantitative PCR in different lung cancer cell lines and pulmonary bronchial epithelial cell lines. The content of serum vascular endothelial growth factor (VEGF) and transforming growth factor beta 1 (TGF-β1) of 8 lung cancer patients who received X-ray or carbon ion radiotherapy were detected by ELISA experiment. Loss-of-function and gain-of-function experiments were performed to explore the biological roles of LINC00167 and miR-663a in lung cancer cell angiogenesis and metastasis. Comprehensive biochemical and biological techniques were utilized to explore the functions of LINC00167 in tumor angiogenesis and metastasis induced by different radiation types. Results In this study, we confirmed that LINC00167 was highly expressed and induced by X-ray irradiation in lung cancer cells. Moreover, increased LINC00167 expression was positively correlated with tumor angiogenesis and metastasis caused by conventional photon radiotherapy. LINC00167 worked as a sponge of miR-663a to positively regulate the expression of TGF-β1 and the downstream VEGF signaling and then promoted the tumor angiogenesis and metastasis of lung cancer cells. LINC00167 could strengthen the pro-angiogenesis and metastasis ability of lung cancer cells. Photon radiation-induced LINC00167 promoted angiogenesis both in vitro and in vivo. Conclusion Our data suggest that LINC00167/miR-663a/TGF-β1 axis is involved in the differential angiogenic response of lung adenocarcinoma cells exposed to X-ray or C-ion irradiation, providing the molecular mechanisms underlying the suppressed angiogenic response induced by carbon ion radiotherapy.