Isoquercitrin promotes ferroptosis and oxidative stress in nasopharyngeal carcinoma via the AMPK/NF-κB pathway.

Isoquercitrin has been discovered with various biological properties, including anticancer, anti-inflammation, antioxidation, and neuroprotection. The aim of this study is to explore the efficacy of isoquercitrin in nasopharyngeal carcinoma (NPC) and to disclose its potential regulating mechanisms. CNE1 and HNE1 cells were treated with various concentrations of isoquercitrin. Ferrostatin-1 (Fer-1, a ferroptosis inhibitor) and alpha-lipoic acid (ALA, an activator of the AMP-activated protein kinase [AMPK] pathway) treatments were conducted to verify the effects of isoquercitrin, respectively. Cell viability, proliferation, reactive oxygen species (ROS) generation, and lipid peroxidation were determined, respectively. GPX4 expression and ferroptosis- and pathway-related protein expression were measured. A xenograft tumor model was constructed by subcutaneously inoculating CNE1 cells into the middle groin of each mouse. We found that the IC50 values of CNE1 and HNE1 cells were 392.45 and 411.38 µM, respectively. CNE1 and HNE1 viability and proliferation were both markedly reduced with the increasing concentration of isoquercitrin. ROS generation and lipid peroxidation were both enhanced with declined ferroptosis-related markers under isoquercitrin treatment. The nuclear factor kappa B (NF-κB) pathway, the AMPK pathway, and the interleukin (IL)-1ß expression were all markedly suppressed by isoquercitrin. Moreover, isoquercitrin restrained the tumor growth and enhanced lipid peroxidation and ferroptosis in vivo. Interestingly, both Fer-1 and ALA treatments distinctly offset isoquercitrin-induced effects in vitro and in vivo. These findings indicated that isoquercitrin might enhance oxidative stress and ferroptosis in NPC via AMPK/NF-κB p65 inhibition.

METTL3-mediated m6A modification promotes processing and maturation of pri-miRNA-19a to facilitate nasopharyngeal carcinoma cell proliferation and invasion.

The interplay between N6-methyladenosine (m6A) modification and microRNAs (miRs) participates in cancer progression. This study is conducted to explore the role of miR-19a-3p in nasopharyngeal carcinoma (NPC) cell proliferation and invasion. Reverse transcription quantitative polymerase chain reaction and Western blot showed that miR-19a-3p was upregulated in NPC tissues and cells and related to poor prognosis, methyltransferase-like 3 (METTL3) was highly expressed, whereas BMP and activin membrane-bound inhibitor (BAMBI) was weakly expressed in NPC tissues and cells. miR-19a-3p downregulation inhibited cell proliferation and invasion, whereas miR-19a-3p overexpression played the opposite role. m6A quantification and m6A RNA immunoprecipitation assays showed that METTL3-mediated m6A modification promoted the processing and maturation of pri-miR-19a via DiGeorge syndrome critical region gene 8 (DGCR8). Dual-luciferase assay showed that BAMBI was a target of miR-19a-3p. The rescue experiments showed that BAMBI downregulation reversed the role of miR-19a-3p inhibition in NPC cells. A xenograft tumor model showed that METTL3 downregulation inhibited tumor growth via the miR-19a-3p/BAMBI in vivo. Overall, our findings elicited that METTL3-mediated m6A modification facilitated the processing and maturation of pri-miR-19a via DGCR8 to upregulate miR-19a-3p, and miR-19a-3p inhibited BAMBI expression to promote NPC cell proliferation and invasion, thus driving NPC progression.

Upregulated METTL3 in nasopharyngeal carcinoma enhances the motility of cancer cells.

The roles of RNA m6A modification in carcinogenesis have attracted much interest recently. However, the dysregulation of RNA m6A regulators (writers, readers, and erasers) in nasopharyngeal carcinoma (NPC) has never been reported. In this study, we showed that METTL3, one of the writers, was upregulated in NPC. Functional studies revealed that METTL3 promoted the migration and invasion of NPC cells. However, METTL3 knockdown reversed this effect and inhibited the migration, invasion and metastasis of NPC cells. METTL3 activated the luciferase activity of TOPflash (a reporter for beta-catenin/TCF signaling), and downregulation of METTL3 inhibited the expression of beta-catenin/TCF target genes vimentin and N-cadherin, which are two regulators of epithelial-mesenchymal transition. Moreover, dominant negative beta-catenin blocked the migration and invasion of NPC cells. Further mechanistic studies showed that METTL3 silencing decreased the m6A methylation and total mRNA levels of Tankyrase, a negative regulator of axin. Moreover, Tankyrase overexpression abrogated the repressive effects of METTL3 silencing on the migration of NPC cells. Collectively, our study demonstrates the oncogenic roles of METTL3 in NPC, and suggests that METTL3 might be a therapeutic target for NPC.

RIPK4 promoted the tumorigenicity of nasopharyngeal carcinoma cells.

RIPK4 (receptor interacting serine/threonine kinase 4) has been reported to be aberrantly expressed in several cancer types. However, its expression pattern and functions in nasopharyngeal carcinoma (NPC) have never been reported. In this study, we have shown that the expression of RIPK4 was up-regulated in NPC tissues. RIPK4 promoted the growth and anchorage-independent growth of NPC cells, and down-regulation of RIPK4 inhibited the growth of NPC cells both in the plate-based culture and on the soft agar. Moreover, RIPK4 promoted the expression of VEGF in the NPC cells and induced the tube formation of HUVEC, and Axitinib (the inhibitor for VEGF receptor) inhibited the tumorigenesis driven by RIPK4. In the molecular mechanism study, RIPK4 was found to enhance the interaction between IKKα and IKKß, and activated NF-kB signaling. Taken together, our study demonstrated the oncogenic roles of RIPK4 in NPC and suggested that RIPK4 might be a therapeutic target.

FOXC2 positively regulates YAP signaling and promotes the glycolysis of nasopharyngeal carcinoma.

YAP signaling has been reported to be dysregulated in numerous cancer types. However, its roles in nasopharyngeal carcinoma (NPC) are poorly understood. Although several studies have shown that FOXC2 promotes the progression of NPC, the underlying molecular mechanism remains largely unknown. Here, we have shown that FOXC2 interacted with YAP and TEAD, and activated YAP signaling. Furthermore, FOXC2-YAP signaling positively regulated the expression of Hexokinase 2 (HK2) and promoted the glycolysis. Moreover, the inhibitor of HK2, 3-BrPA effectively inhibited the tumorigenesis of NPC cells in vitro and in vivo. Collectively, our study demonstrated that FOXC2 promoted the glycolysis in progression of NPC by activating YAP signaling, and suggested that FOXC2 might be promising therapeutic target.

Pyruvate dehydrogenase B promoted the growth and migration of the nasopharyngeal carcinoma cells.

Metabolism alteration is one of the hallmarks of cancer cells. Although several studies have demonstrated that glycolysis played important roles in the progression of nasopharyngeal carcinoma (NPC), the functions of specific metabolism-associated genes remain largely unknown. In this study, it was found that Pyruvate dehydrogenase B (PDHB), which catalyzed the conversion of pyruvate to Acetyl-CoA, was downregulated in NPC cells. Forced expression of PDHB in NPC cells inhibited cell growth and migration, while knocking down the expression of PDHB promoted the growth, migration, and tumorigenesis of NPC cells. Mechanism study showed that PDHB inhibited ERK signaling and cell growth driven by RasV12. Collectively, our study demonstrated the suppressive roles of PDHB in the progression of NPC, and restoring the function of PDHB might be a promising strategy for NPC therapy.

Endoscopy-assisted transoral resection of parapharyngeal space tumors: a retrospective analysis.

The technique of endoscopy-assisted transoral approach (EATA) has improved greatly, which should provide a better alternative for parapharyngeal space (PPS) tumors. Here, we compared curative effects between the resection of parapharyngeal space (PPS) tumors by EATA and external approaches (EAs), including the transcervical, transparotid, and transmandibular approaches. Based on the tumors' position and the relationship with adjacent structures, we selected 20 patients with parapharyngeal space tumor hospitalized in the Second People's Hospital in Shenzhen from January 2008 to December 2013, which were divided into the observation group and the control group with patients' informed consents. In the observation group, the tumors were removed solely by transoral approach under the guidance of endoscopes (EATA), while in the control group, the tumors were resected completely using an external approach (EA). We compared the total removal rate, the operation time, blood loss, postoperative pain, hospitalized time, complication rate, scar, and recurrence between the two groups. All the tumors were completely removed and patients were followed up for 6 months-5 years with no recurrence in either group. There was no significant difference regarding total removal rate, operation time, complication rate, and recurrence rate between the two groups (P > 0.05). However, significant differences were observed in blood loss, hospitalized time, and postoperative pain between the two groups (P < 0.05). PPS tumors could be completely removed by both EATA and EA. However, EATA has advantages of shortened hospitalized time, alleviated blood loss and postoperative pain level, and preservation of facial cosmetic.