Overexpression of β-Catenin Decreases the Radiosensitivity of Human Nasopharyngeal Carcinoma CNE-2 Cells

Abstract

Background/Aims: Nasopharyngeal carcinoma (NPC) is rare worldwide but remains highly prevalent in endemic regions, notably in southern China. Radiotherapy remains the treatment of choice for NPC, but radioresistance has been identified as a major cause of therapeutic failure. The Wnt/β-catenin signaling has been found to be involved in NPC radioresistance; however, the effect of β-catenin overexpression on radioresistance remains unknown in NPC until now. This study aimed to examine the impact of β-catenin overexpression on the radiosensitivity of human NPC CNE-2 cells. Methods: Immunohistochemistry was performed to detect the β-catenin expression in normal nasopharyngeal specimens and NPC specimens. The human NPC CNE-2 cell line overexpressing β-catenin was modeled by transfection with the pcDNA3.1/Hygro(+)/β-catenin recombinant vector (transfection group), while cells transfected with the pcDNA3.1/Hygro(+) vector served as negative controls and non-transfected cells served as blank controls. The expression of key molecules of the Wnt/β-catenin signaling pathway was determined using Western blotting and qPCR assays, and the changes of radiation sensitivity were measured with a colony-formation assay. Cell viability was measured by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5 -diphenyltetrazolium bromide) assay. In addition, the cell cycle and apoptosis was detected using flow cytometry and the TCF/LEF transcriptional activity was measured with a Dual Luciferase Reporter Assay System. Results: Immunohistochemical staining showed high β-catenin expression in radioresistant NPC specimens, and low expression in radiosensitive NPC specimens and normal nasopharyngeal specimens. Western blotting and qPCR assays detected higher β-catenin expression in the transfection group than in the negative and blank controls (P < 0.01). Down-regulation of GSK-3β expression (P < 0.05) and up-regulation of Cyclin D1 expression (P < 0.01) was detected in β-catenin overexpressing NPC cells exposed to X-ray radiation relative to negative and blank controls. Colony-formation assay revealed higher D₀, D_q and SF in the transfection group than in the negative and blank control groups post-radiation, and the SER in the transfection group was 0.75-fold and 0.68-fold greater than that in the blank and negative control groups, respectively. MTT assay revealed that the viability of CNE-2 cells was significantly higher in the transfection group (96% ± 8.72%) than in the negative control group (74.67 ± 7.05%) and the blank control group (75.33% ± 7.02%) 24 h post-exposure to 6 Gy X-ray radiation (P < 0.05). X-ray radiation led to a lower proportion of CNE-2 cells at the G2/M phase and a lower apoptotic rate in the transfection group than in the negative and blank control groups (P < 0.05). In addition, the TCF/LEF transcriptional activity was higher in the transfection group than in the negative and blank control groups (P < 0.01), and 6 Gy X-ray radiation elevated the TCF/LEF transcriptional activity relative to 0 Gy radiation ...

SALL4 induces radioresistance in nasopharyngeal carcinoma via the ATM/Chk2/p53 pathway

“…The SF curve was calculated according to the multi‐target single‐hit model SF = 1 − (1−e −D/D0 ) N , and the radiobiological parameters SF 2 (SF of 2 Gy), D 0 (mean lethal dose or final slope), D q (quasi‐threshold dose), and N (extrapolation number) were determined using this model. Additionally, the radiation sensitivity enhancement ratio (SER) was calculated using the formula: SER = D 0 of the control group/D 0 of the transfection group . Three parallel samples were set at each radiation dosage.…”

<p>CDK4/6 Inhibitor Palbociclib Amplifies the Radiosensitivity to Nasopharyngeal Carcinoma Cells via Mediating Apoptosis and Suppressing DNA Damage Repair</p>

“…NPC occurs dominantly in the eastern and southeastern parts of Asia, and northern and eastern Africa 1. Although the 5-year control rate of local NPC by radiotherapy can reach 80% to 90%, a proportion of individuals still develop into distant metastasis and local recurrence, which is mainly attributed to radiation resistance 2. Hence, it is crucial to find novel drugs or therapeutic modalities to enhance radiosensitivity and improve prognosis of NPC.…”

A positive feedback loop between Wnt/β‐catenin signaling and hTERT regulates the cancer stem cell‐like traits in radioresistant nasopharyngeal carcinoma cells

“…40 The β-catenin is a key factor of the Wnt signaling pathway, which is positively correlated with the radiosensitivity of multiple cancers, including NPC. [40][41][42][43] There may be regulatory interactions between the Wnt/β-catenin signaling and hTERT, [29][30][31][32] but whether it will affect cancer radiosensitivity, as well as the potential mechanism, has not been reported. This study preliminarily discovered that there was a positive feedback loop between Wnt/β-catenin signaling and hTERT in the radioresistant NPC cell line CNE-2R, which could regulate the telomerase activity and CSC-like traits of CNE-2R cells, finally affecting their radiosensitivity.…”