Cancer stem cell-like characteristics and telomerase activity of the nasopharyngeal carcinoma radioresistant cell line CNE-2R.

The radioresistance of nasopharyngeal carcinoma (NPC) may be related to cancer stem cells (CSCs), and the characteristics of CSCs may be maintained by telomerase activity. In this study, we explored the CSC-like characteristics and telomerase activity of the NPC radioresistant cell line CNE-2R. This work provides a foundation for future studies on stem cell-targeted therapies by targeting the radioresistance of NPC. The expression of stem cell-related genes/proteins and the hTERT gene/protein in CNE-2R and its parent radiosensitive cell line CNE-2 were detected using qPCR/Western Blot. Label-retaining cells (LRCs) were detected through immunocytochemistry, and telomerase activity was detected using a PCR-ELISA kit. CD133 expression was detected with flow cytometry. CNE-2R-CD133+ and CNE-2R-CD133- cells were separated with magnetic-activated cell sorting. The proliferation and tumorigenesis capacities of CNE-2R-CD133+, CNE-2R-CD133-, and CNE-2R cells were compared with a CCK-8 assay, sphere formation assay, and an in vivo experiment. Our results showed that the expression of stem cell-related genes and the hTERT gene in CNE-2R cells was higher than those in CNE-2 cells. Similarly, the expression of stem cell-related proteins and the hTERT protein in CNE-2R cells was markedly higher than those in CNE-2 cells. The proportion of LRCs in CNE-2R and CNE-2 cells was (3.10 ± 0.63%) vs (0.40 ± 0.35%; P < 0.001), respectively. Telomerase activity in CNE-2R cells was remarkably higher than that in CNE-2 cells. Flow cytometry suggested that the CD133 positive rates in CNE-2R and CNE-2 cells were (2.49 ± 0.56%) vs (0.76 ± 0.25%; P = 0.008), respectively. Meanwhile, the proliferation capacity, tumorigenesis capacity, and telomerase activity of CNE-2R-CD133+ cells were notably higher than those of CNE-2R-CD133- and CNE-2R cells. Collectively, CNE-2R displayed CSC-like characteristics; our results also showed that CNE-2R cells, especially the sorted CSCs, had high telomerase activity levels.

Cofilin-2 Acts as a Marker for Predicting Radiotherapy Response and Is a Potential Therapeutic Target in Nasopharyngeal Carcinoma.

BACKGROUND The purpose of this study was to determine whether cofilin-2 could serve as a protein marker for predicting radiotherapy response and as a potential therapeutic target in nasopharyngeal carcinoma (NPC). MATERIAL AND METHODS Cofilin-2 protein levels in serum and tissue samples from patients with NPC were assessed by sandwich ELISA and IHC. In vitro, cofilin-2 levels in CNE-2R cells were significantly higher than those of CNE-2 cells. Meanwhile, CNE-2R cells were silenced for cofilin-2 to obtain a stable cofilin-2-RNAi-LV3 cell line. Then, cell proliferation, radiosensitivity, invasion and migration abilities, cell cycle, and apoptosis were evaluated by Cell Counting Kit 8 assay (CCK-8), flow cytometry (FCM), clone formation assay, and in vitro. RESULTS The secreted levels of the cofilin-2 protein in radioresistant NPC patients were significantly higher than those of radiosensitive cases. After cofilin-2 knockdown in nasopharyngeal carcinoma CNE-2R cells, proliferation was decreased, while apoptosis and radiosensitivity were enhanced; cell cycle distribution was altered, and the transplanted tumors in nude mice grew significantly less. CONCLUSIONS Overall, our findings suggest that cofilin-2 acts as a marker for predicting radiotherapy response and is a potential therapeutic target in nasopharyngeal carcinoma.

Reduced QSOX1 enhances radioresistance in nasopharyngeal carcinoma.

Radioresistance is a major cause leads to treatment failure in nasopharyngeal carcinoma (NPC). In our previous study, we identified that QSOX1 is a differentially expressed protein in NPC cell lines with variable radiosensitivities. The present study aimed to investigate the biological behavior of QSOX1 in nasopharyngeal carcinoma (NPC) and its effect on radiosensitivity. The levels of QSOX1 detected by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC) in radioresistant NPC patient sera and tissue samples were markedly lower than those in radiosensitive samples. Small hairpin RNAs (shRNAs) were employed to knock down endogenous QSOX1 expression in CNE-2 cells, and then, radiosensitivity, apoptosis, migration and invasion were assessed using colony formation, Cell Counting Kit-8 (CCK-8), flow cytometry, and transwell assays, respectively. Tumor growth and radioresistance were also evaluated using a xenograft model in nude mice. The shRNA-mediated knockdown of QSOX1 significantly increased cell survival under irradiation (IR) and weakened radiosensitivity, which was likely due to a reduction in the cell apoptosis rate after IR. Moreover, QSOX1 silencing led to the suppression of cellular migration and invasion. Similar results were obtained with the xenograft mouse model. Thus, targeting QSOX1 will provide a new avenue for increasing the sensitivity of NPC to radiotherapy.