NEK2 contributes to radioresistance in esophageal squamous cell carcinoma by inducing protective autophagy via regulating TRIM21.

BACKGROUND: Radiotherapy (RT) has been identified as a vital treatment for esophageal squamous cell carcinoma (ESCC), while the development of radioresistance remains a major obstacle in ESCC management. The aim of this study was to investigate the effect of NIMA-related kinase 2 (NEK2) on radioresistance in ESCC cells and to reveal potential molecular mechanisms. METHODS: Human esophageal epithelial cells (HEEC) and human ESCC cell lines were obtained from the Research Center of the Fourth Hospital of Hebei Medical University (Shijiazhuang, China). Cell Counting Kit-8 (CCK-8) and flow cytometry assays were applied to assess the proliferation ability, cell cycle, apoptosis rates, and ROS production of ESCC cells. The colony-forming assay was used to estimate the effect of NEK2 on radiosensitivity. Autophagy was investigated by western blotting analysis, GFP-mRFP-LC3 fluorescence assay, and transmission electron microscopy (TEM). RESULTS: In the present study, our results showed that NEK2 was associated with radioresistance, cell cycle arrest, apoptosis, ROS production, and survival of ESCC. NEK2 knockdown could significantly inhibit growth while enhancing radiosensitivity and ROS production in ESCC cells. Interestingly, NEK2 knockdown inhibited ESCC cell autophagy and reduced autophagic flux, ultimately reversing NEK2-induced radioresistance. Mechanistically, NEK2 bound to and regulated the stability of tripartite motif-containing protein 21 (TRIM21). The accumulation of NEK2-induced light chain 3 beta 2 (LC3B II) can be reversed by the knockdown of TRIM21. CONCLUSION: These results demonstrated that NEK2 activated autophagy through TRIM21, which may provide a promising therapeutic strategy for elucidating NEK2-mediated radioresistance in ESCC.

Relationship Between Pericarotid Fat Density and Pathology-Based Carotid Plaque Risk Characteristics.

OBJECTIVES: In this study, the authors aimed to evaluate the relationship between pericarotid fat density (PFD) and pathologic carotid plaque risk characteristics. METHODS: The authors retrospectively evaluated 58 patients (mean age: 66.66 ± 7.26 y, 44 males) who were subjected to both carotid endarterectomy and carotid artery computed tomography angiography (CTA) at the authors' institution. The computed tomography values of the adipose tissue around the most severe stenosis carotid artery were measured, and the removed plaques were sent to the Department of Pathology for American Heart Association (AHA) classification. The Wilcoxon signed-rank test was used to detect the difference in PFD values between the operative and nonoperative sides. According to carotid plaque risk characteristics, the associations between PFD and 4 different risk characteristic subgroups were analyzed. The Student t test and χ2 test were used to compare differences between different risk subgroups. Receiver operating characteristic curve analysis was used to evaluate the predictive efficacy of PFD for carotid plaque risk characteristics. RESULTS: The operative side had higher mean Hounsfield units (HU) values compared with the nonoperative side (P < 0.001). The AHA VI and the intraplaque hemorrhage (IPH) subgroups had higher mean HU values compared with the non-AHA VI and the non-IPH subgroups (P < 0.05). Male patients presented with IPH more than female patients (P = 0.047). The results of receiver operating characteristic curve analysis showed that the mean HU value (operative side; area under the curve: 0.729, Sensitivity (SE): 59.26%, Specificity (SP): 80.65%, P = 0.003) had a certain predictive value for diagnosing high-risk VI plaques. Pericarotid fat density ≥ -68.167 HU is expected to serve as a potential cutoff value to identify AHA VI and non-AHA VI subgroups. CONCLUSION: PFD was significantly associated with vulnerable plaques, high-risk AHA VI plaques, and IPH, which could be an indirect clinical marker for vulnerable plaques.

Irradiation-induced exosomal HMGB1 to confer radioresistance via the PI3K/AKT/FOXO3A signaling pathway in ESCC.

BACKGROUND: Radioresistance is a major cause of treatment failure in esophageal squamous cell carcinoma (ESCC) radiotherapy, and the underlying mechanisms of radioresistance are still unclear. Irradiation (IR) stimulates changes in tumor-derived exosome contents, which can be taken up by recipient cells, playing an important role in the proliferation, cell cycle and apoptosis of recipient cells. This study investigated the effect of IR-induced exosomal high mobility group box 1 (HMGB1) on radioresistance in ESCC cells. METHODS: Plasma exosomes were isolated from 21 ESCC patients and 24 healthy volunteers, and the expression of HMGB1 was examined. Then, the therapeutic effect of radiotherapy was analyzed according to the different expression levels of plasma exosomal HMGB1 in ESCC patients. The uptake of exosomes by recipient cells was verified by immunofluorescence staining, and the localization of exosomes and HMGB1 in cells before and after IR was evaluated. The effects of IR-induced exosomes on cell proliferation, invasion, apoptosis, cell cycle distribution and radioresistance after HMGB1 knockdown were verified. Moreover, western blotting was used to measure changes in the expression of cyclin B1, CDK1, Bax, Bcl2, phosphorylated histone H2AX and the PI3K/AKT/FOXO3A pathway in the HMGB1-knockdown exosome group and the negative control group. RESULTS: The expression of HMGB1 in ESCC plasma exosomes was significantly increased compared with that in healthy volunteers, and high expression of HMGB1 in plasma exosomes was associated with radioresistance (P = 0.016). IR-induced the release of exosomal HMGB1 and promoted proliferation and radioresistance in recipient cells, with a sensitization enhancement ratio (SER) of 0.906 and 0.919, respectively. In addition, IR-induced exosomal HMGB1 promotes G2/M phase arrest by regulating the proteins cyclin B1 and CDK1, cooperating with the proteins Bax and Bcl2 to reduce the apoptosis rate through the PI3K/AKT/FOXO3A signaling pathway, and participated in IR-induced DNA damage repair through γH2AX. CONCLUSION: These findings indicate that high expression of plasma exosomal HMGB1 is associated with an adverse radiotherapy response. IR-induced exosomal HMGB1 enhances the radioresistance of ESCC cells.

A novel DNA damage repair gene-related prognostic model for evaluating the prognosis and tumor microenvironment infiltration of esophageal squamous cell carcinoma.

BACKGROUND: This study aimed to investigate the potential prognostic value of DNA damage repair genes (DDRGs) in esophageal squamous cell carcinoma (ESCC) and their relationship with immune-related characteristics. METHODS: We analyzed DDRGs of the Gene Expression Omnibus database (GSE53625). Subsequently, the GSE53625 cohort was used to construct a prognostic model based on least absolute shrinkage and selection operator regression, and Cox regression analysis was used to construct a nomogram. The immunological analysis algorithms explored the differences between the potential mechanism, tumor immune activity, and immunosuppressive genes in the high- and low-risk groups. Of the prognosis model-related DDRGs, we selected PPP2R2A for further investigation. Functional experiments were conducted to evaluate the effect on ESCC cells in vitro. RESULTS: A 5-DDRG (ERCC5, POLK, PPP2R2A, TNP1 and ZNF350) prediction signature was established for ESCC, stratifying patients into two risk groups. Multivariate Cox regression analysis showed that the 5-DDRG signature was an independent predictor of overall survival. Immune cells such as CD4 T cells and monocytes displayed lower infiltration levels in the high-risk group. Additionally, the immune, ESTIMATE, and stromal scores in the high-risk group were all considerably higher than those in the low-risk group. Functionally, knockdown of PPP2R2A significantly suppressed cell proliferation, migration and invasion in two ESCC cell lines (ECA109 and TE1). CONCLUSION: The clustered subtypes and prognostic model of DDRGs could effectively predict the prognosis and immune activity of ESCC patients.

NEK2 promotes esophageal squamous cell carcinoma cell proliferation, migration and invasion through the Wnt/ß-catenin signaling pathway.

OBJECTIVES: The NEK2 (never in mitosis gene A-related kinase 2), a serine/threonine kinase involved in chromosome instability and tumorigenesis. Hence, this study aimed to explore the molecular function of NEK2 in esophageal squamous cell carcinoma (ESCC). METHODS: By available transcriptome datasets (GSE53625 cohort, GSE38129 cohort, and GSE21293 cohort), we analyzed the differentially expressed genes in invading and non-invading ESCC. Subsequently, we evaluated the association between NEK2 expression level and clinical outcomes through Kaplan-Meier analysis method. The quantitative real-time polymerase chain reaction (qRT-PCR) and western blotting (WB) analyses were performed to determine the expression levels of NEK2 mRNA and protein, respectively. We knocked down the NEK2 expression in ESCC cells (ECA109 and TE1), and evaluated the NEK2 biology function associated with ESCC cell proliferation, migration, invasion, and colony formation abilities. Finally, the downstream pathway of NEK2 was analyzed through Gene Set Enrichment Analysis (GSEA) and validated the regulatory mechanism of NEK2 on the potential pathway through WB. RESULTS: We found that NEK2 was highly expressed in ESCC cells compared with human esophageal epithelial cells (HEEC) (P < 0.0001), and high NEK2 expression was remarkably associated with poor survival (P = 0.019). Knockdown of NEK2 showed the significant inhibitory effect for tumorigenesis, and suppressed the ESCC cells proliferation, migration, invasion, and formation of colonies abilities. Additionally, GSEA revealed that Wnt/ß-catenin pathway was a downstream pathway of NEK2. WB results further validated the regulatory mechanism of NEK2 for Wnt/ß-catenin signaling. CONCLUSIONS: Our results indicated that NEK2 promotes ESCC cell proliferation, migration and invasion by activating the Wnt/ß-catenin pathway. NEK2 could be a promising target for ESCC.

Gambogic acid affects ESCC progression through regulation of PI3K/AKT/mTOR signal pathway.

Esophageal squamous cell carcinoma (ESCC) is an invasive gastrointestinal malignancy and in urgent need of new effective therapies. Gambogic acid (GA) exhibits anti-cancer effects in many cancer cells, but it remains to be determined whether GA has the same effect on ESCC. Here, we reported that GA treatment caused an inhibition in ESCC cell proliferation, migration and invasion. Meanwhile, GA induced dose-dependent apoptosis of ESCC cells, repressed the expression of Bcl2 and up-regulated the levels of Bax protein, cleaved-PARP1 and cleaved-caspase 3/9. Further investigation showed that GA down-regulated the levels of PI3K, p-AKT and p-mTOR, while promoted PTEN expression in ESCC cells. Taken together, we provided the first demonstration that GA exerts anti-tumor effects on ESCC cells presumably through regulating PTEN-PI3K-AKT-mTORpathway, suggestive of a therapeutic potential for ESCC.