CircMAT2B facilitates the progression of head and neck squamous cell carcinoma via sponging miR-491-5p to trigger ASCT2-mediated glutaminolysis

Circular RNAs (circRNAs) are well-known to exert significant roles in regulating the pathological processes, including human carcinogenesis. Currently, less is known about their exact roles in head and neck squamous cell carcinoma (HNSCC). Herein, we aimed to investigate and validate the role of a novel circRNA, circMAT2B, as well as its potential molecular mechanism in HNSCC progression. A cohort of 41 paired of HNSCC tumor tissues and adjacent normal tissues from HNSCC patients were collected. Further, we characterized circMAT2B expression patterns in HNSCC tissues and cell lines, as well as exploring its association with the prognosis of HNSCC patients. Biological functions on cell proliferation, apoptosis, migration, and invasion were assessed using Cell Counting Kit-8, EdU incorporation, TUNEL, wound healing, and transwell assays. Glutaminolysis was evaluated by measuring glutamine, glutamate, and alpha-ketoglutarate (alpha-KG) levels. The regulatory network of circMAT2B/miR-491-5p/ASCT2 axis was verified by RNA immunoprecipitation and luciferase reporter assays. Western blot was conducted to detect the level of ASCT2 and GLS1. Remarkably overexpressed circMAT2B was observed in HNSCC tissues and cell lines, of which high abundance was positively correlated with patients' poor prognosis. Silencing of circMAT2B inhibited cell proliferation, migration, and invasion, as well as glutaminolysis. miR-491-5p, interacted with ASCT2, was identified to be a downstream target of circMAT2B, thereby involving in circMAT2B-mediated biological effects. In summary, we draw a conclusion that circMAT2B could modulate the processes of cell proliferation, migration, invasion, and glutaminolysis of HNSCC cells partly via the miR-491-5p/ASCT2 axis by a molecular mechanism of competing endogenous RNA (ceRNA), implying an underlying circRNA-targeted therapy for HNSCC treatment.