Nasopharyngeal carcinoma (NPC) is one of the most frequent head and neck malignant tumors and is majorly treated by radiotherapy. However, radiation resistance remains a serious obstacle to the successful treatment of NPC. The aim of this study was to discover the underlying mechanism of radioresistance and to elucidate novel genes that may play important roles in the regulation of NPC radiosensitivity. By using RNA-seq analysis of NPC cell line CNE2 and its radioresistant cell line CNE2R, lncRNA CASC19 was screened out as a candidate radioresistance marker. Both in vitro and in vivo data demonstrated that a high expression level of CASC19 was positively correlated with the radioresistance of NPC, and the radiosensitivity of NPC cells was considerably enhanced by knockdown of CASC19. The incidence of autophagy was enhanced in CNE2R in comparison with CNE2 and another NPC cell line HONE1, and silencing autophagy with LC3 siRNA (siLC3) sensitized NPC cells to irradiation. Furthermore, CASC19 siRNA (siCASC19) suppressed cellular autophagy by inhibiting the AMPK/mTOR pathway and promoted apoptosis through the PARP1 pathway. Our results revealed for the first time that lncRNA CASC19 contributed to the radioresistance of NPC by regulating autophagy. In significance, CASC19 might be a potential molecular biomarker and a new therapeutic target in NPC.

Glioblastoma (GBM) is the most common and malignant primary brain tumor in adults. Radiotherapy has long been an important treatment method of GBM. However, the intrinsic radioresistance of GBM cells is a key reason of poor therapeutic efficiency. Recently, many studies have shown that using the histone deacetylase (HDAC) inhibitor suberoylanilide hydroxamic acid (SAHA) in radiotherapy may improve the prognosis of GBM patients, but the underlying molecular mechanisms remain unclear. In this study, Gene Expression Omnibus (GEO) datasets GSE153982 and GSE131956 were analyzed to evaluate radiation-induced changes of gene expression in GBM without or with SAHA treatment, respectively. Additionally, the survival-associated genes of GBM patients were screened using the Chinese Glioma Genome Atlas (CGGA) database. Taking the intersection of these three datasets, 11 survival-associated genes were discovered to be activated by irradiation and regulated by SAHA. The expressions of these genes were further verified in human GBM cell lines U251, T98G, and U251 homologous radioresistant cells (U251R) by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). It was found that MMP14 mRNA was considerably highly expressed in the radioresistant cell lines and was reduced by SAHA treatment. Transfection of MMP14 siRNA (siMMP14) suppressed cell survivals of these GBM cells after irradiation. Taken together, our results reveal for the first time that the MMP14 gene contributed to SAHA-induced radiosensitization of GBM.