Circular RNAs (circRNAs) are involved in the regulation of gene expression in different physiological and pathological processes. These macromolecules can act as microRNA (miRNA) sponges and play an important role as gene regulators throughout the circRNA‐miRNA pathway. In this study, we established a radioresistance model with the nasopharyngeal carcinoma cell line CNE‐2, and then analyzed the differences in the circRNAs between radioresistant and normal nasopharyngeal carcinoma cell lines using a high‐throughput microarray. Tested circRNAs included 1042 upregulated and 1558 downregulated circRNAs. Relevant signaling pathways associated with the circRNAs and their target miRNAs were analyzed using bioinformatics analysis to determine the radioresistance of the differentially expressed circRNAs. Curcumin was used to treat irradiated cell lines, and changes in the circRNA before and after curcumin treatment were analyzed to investigate the radiosensitization effects of curcumin. The results showed that curcumin could regulate the circRNA‐miRNA‐messenger RNA network and inhibit the epidermal growth factor receptor (EGFR), signal transducers and activators of transcription 3 (STAT3), and growth factor receptor‐bound protein 2 (GRB2) to achieve radiosensitization. Thus, circRNA acted as a miRNA sponge and regulated the expression of miRNA, thereby affecting EGFR, STAT3, and GRB2 expression and radiosensitization.

Circular RNAs (circRNAs) are involved in cancer development via inhibition of miRNAs, which are associated with differentiation, proliferation, migration, and carcinogenicity. Curcumin has antioxidant and anti-cancer properties, and it has also been used as a radiosensitizer. In this study, we explored the potential relationships among curcumin, circRNAs, and nasopharyngeal carcinoma (NPC). We compared the differences in circRNA levels in NPC cell lines after radiotherapy and after treatment with curcumin, using a high-throughput microarray. Further, a circRNA-miRNA-mRNA interaction network between radiation resistance NPC cell lines and tumor stem cells was constructed by applying bioinformatics. Finally, it was demonstrated by reverse transcription-quantitative polymerase chain reaction assay and wound healing assay that curcumin could enhance radiosensitization of NPC cell lines via mediating regulation of tumor stem-like cells by the "hsa_circRNA_102115"-"hsa-miR-335-3p"-"MAPK1" interaction network.

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Shengmai Yin (SMY) is a Chinese herbal decoction that effectively alleviates the side effects of radiotherapy in various cancers and helps achieve radiotherapy's clinical efficacy. In this study, we explored the interaction mechanism among SMY, DNA methylation, and nasopharyngeal carcinoma (NPC). We identified differences in DNA methylation levels in NPC CNE-2 cells and its radioresistant cells (CNE-2R) using the methylated DNA immunoprecipitation array and found that CNE-2R cells showed genome-wide changes in methylation status towards a state of hypomethylation. SMY may restore its original DNA methylation status, and thus, enhance radiosensitivity. Furthermore, we confirmed that the differential gene Tenascin-C (TNC) was overexpressed in CNE-2R cells and that SMY downregulated TNC expression. This downregulation of TNC inhibited NPC cell radiation resistance, migration, and invasion. Furthermore, we found that TNC was hypomethylated in CNE-2R cells and partially restored to a hypermethylated state after SMY intervention. DNA methyltransferases 3a may be the key protein in DNA methylation of TNC.