ABSTRACT
Nasopharyngeal carcinoma (NPC) is a common cancer found in the nasopharynx, which plagues countless NPC patients. MicroRNA-372 (miR-372) has been reported to be involved in various tumors. Here, we explored the important role of miR-372 in radiosensitivity, invasion, and metastasis of NPC. Microarray analysis was conducted to search the NPC-related differentially expressed genes (DEGs) and predict the miRs regulating PBK, which suggested that miR-372 could influence the development of NPC via PBK and the p53 signaling pathway. Importantly, miR-372 was observed to target PBK, thus down-regulating its expression. Then, NPC 5-8F and C666-1 cells were selected, and treated with ionization radiation and alteration of miR-372 and PBK expression to explore the functional role of miR-372 in NPC. The expression of miR-372, PBK, Bcl-2, p53, and Bax as well as the extent of Akt phosphorylation were measured. In addition, cell colony formation, cell cycle, proliferation, apoptosis, migration, and invasion were detected. At last, tumor growth and the effect of miR-372 on radiosensitivity of NPC were evaluated. Besides, over-expressed miR-372 down-regulated Bcl-2 and PBK expression and the extent of Akt phosphorylation while up-regulated the expression of p53 and Bax. Additionally, miR-372 over-expression and radiotherapy inhibited cell clone formation, proliferation, tumor growth, migration, invasion, and cell cycle entry, but promoted cell apoptosis. However, the restoration of PBK in NPC cells expressing miR-372 reversed the anti-tumor effect of miR-372 and activation of the p53 signaling pathway. In conclusion, the study shows that up-regulated miR-372 promotes radiosensitivity by activating the p53 signaling pathway via inhibition of PBK.
Subject(s)
MicroRNAs , Mitogen-Activated Protein Kinase Kinases/metabolism , Nasopharyngeal Carcinoma , Nasopharyngeal Neoplasms , Radiation Tolerance/genetics , Tumor Suppressor Protein p53/metabolism , Animals , Cell Line, Tumor , Cell Movement , Humans , Mice, Inbred BALB C , Mice, Nude , Mitogen-Activated Protein Kinase Kinases/genetics , Nasopharyngeal Carcinoma/genetics , Nasopharyngeal Carcinoma/metabolism , Nasopharyngeal Carcinoma/radiotherapy , Nasopharyngeal Neoplasms/genetics , Nasopharyngeal Neoplasms/metabolism , Nasopharyngeal Neoplasms/radiotherapy , Signal Transduction , Tumor Suppressor Protein p53/genetics , X-RaysABSTRACT
Nasopharyngeal carcinoma (NPC) often develops drug resistance following radiotherapy. The molecular basis of radiotherapy-related multidrug resistance (MDR) remains unclear. In the present study, we investigated the effect of fractionated irradiation on the expression of the MDR-1 gene and the MDR-associated protein P-glycoprotein (P-gp) in CNE1 human NPC cells. CNE1 cells were treated with fractionated X-rays. Drug resistance was determined by MTT assay. The expression levels of MDR-1 and P-gp were analyzed by RT-PCR and western blot analysis, respectively. Differential expression was analyzed by gene chips. The results revealed that low levels of mRNA expression of MDR1 were present in non-irradiated CNE1 cells. Compared with the control, the expression of MDR1 mRNA was gradually increased following fractionated irradiation. On day 21, the expression of MDR1 mRNA was increased 1.59- and 2.19-fold, compared with the control, by treatment with 10 and 20 Gy, respectively. We observed decreased MDR1 expression following treatment with 10 and 20 Gy irradiation on days 28 and 35, compared with day 21. On days 21, 28 and 35, expression was increased 1.37-, 1.40- and 1.15-fold by treatment with 20 Gy compared with 10 Gy. Expression of MDR1 was significantly upregulated by treatment with 50 Gy irradiation compared with the control on days 78 and 106. P-gp expression was consistent with that of MDR1 mRNA expression. The sensitivity of CNE1 cells to cisplatin was reduced following irradiation compared with the control. A total of 26 genes were significantly upregulated and 8 genes were significantly downregulated compared with the control. Results of the present study have shown that MDR1 and P-gp are upregulated in CNE1 cells following irradiation. Multiple genes were involved in the mechanism of radiation-induced drug resistance.
