miR-122-5p Restrains Pancreatic Cancer Cell Growth and Causes Apoptosis by Negatively Regulating ASCT2

Background/aim: System ASC amino acid transporter-2 (ASCT2) is abnormally highly expressed in tumor cells and closely associated with a poor prognosis, but the regulatory mechanism of abnormally high ASCT2 expression is scarcely investigated. MicroRNAs (miRNAs) that are abnormally expressed regulate gene expression to have either oncogenic or tumor-suppressive effects in pancreatic cancer (PC). MicroRNA-122-5p (miR-122-5p) dysregulation has been seen in various cancer entities, but the biological function of miR-122-5p in PC and its regulation mechanisms remain unknown.

Materials and methods: Western blot and quantitative RT-PCR were used to measure the expression of miR-122-5p, ASCT2, and apoptosis-related proteins. CCK-8 assays were used to elucidate the effect on cell proliferation. Flow cytometry (FCM) assays were utilized to evaluate cell apoptosis. A dual-luciferase reporter assay was utilized to determine if miR-122a-5p directly targeted ASCT2. Glutamine consumption and the α-ketoglutarate (α-KG) and adenosine triphosphate (ATP) contents were determined using respective assays.

Results: MiR-122-5p expression was low whereas ASCT2 expression was high in PC tissues and cells. Overexpressing miR-122-5p restrained pancreatic cancer cell proliferation, accelerated apoptosis, and decreased glutamine consumption, α-ketoglutarate (α-KG) production and ATP generation, whereas suppressing miR-122-5p had the opposite effect. Moreover, the reporter gene test established ASCT2 as a miR-122-5p target. Overexpression of miR-122-5p decreased ASCT2 expression, whereas miR-122-5p repression increased ASCT2 expression. In addition, miR-122-5p also regulated apoptosis-related pathways.

Conclusion: MiR-122-5p may function as a tumor suppressor by inhibiting the proliferation, glutamine metabolism, and inducing apoptosis via altering the expression of ASCT2 in pancreatic cancer cells.