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Objectives: MiR-199a-5p has been shown to be downregulated in multiple malignancies and function as a tumor suppressor. We have previously demonstrated that miR-199a-5p is markedly downregulated in esophageal cancer cell lines compared to esophageal epithelial cells. In several miR-target sequence analysis programs, miR-199a-5p is predicted to bind JUN-B mRNA with high affinity. JUN-B is an important component of the AP1 transcription factor. The objective of this study was to determine expression of JUN-B in esophageal cancer cells as well as to investigate the interaction between miR-199a-5p and JUNB in these cells and to characterize the functional implications of this interaction. Methods: Studies were performed in human esophageal epithelial (hESO) cells and in TE7, SK-GT-4 and OE21 human esophageal cancer cells. Expression of miR-199a-5p and JUNB mRNA in these cell lines was measured by real-time PCR. JUNB protein expression levels were examined by Western blot. Function of miR-199a-5p was tested through its overexpression and silencing. Cellular proliferation was measured using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Results: Levels of miR-199a-5p in TE7, SK-GT-4, and OE21 esophageal cancer cells are markedly reduced compared to hESO cells. JUN-B mRNA and protein expression are correspondingly elevated in these cells compared to hESO cells. JUN-B mRNA and protein expression levels were decreased following miR-199a-5p overexpression in TE7, SK-GT-4 and OE21 cells. In reciprocal experiments, silencing miR-199a-5p in hESO cells resulted in increased JUN-B protein and mRNA levels. Forced expression of miR-199a-5p in TE7, SK-GT-4 and OE21 cells led to a marked decrease in cellular proliferation. Conclusions: MiR-199a-5p expression is significantly reduced in TE7, SK-GT-4, and OE21 esophageal cancer cells relative to hESO cells. Forced expression of miR-199a-5p results in significantly decreased JUN-B mRNA and protein expression in these cells, leading to decreased cellular proliferation. These results add our understanding of the roles by which miR-199a-5p functions as a tumor suppressor in esophageal cancer cells. Further studies will investigate the association of miR-199a-5p with JUN-B mRNA using biotinylated RNA pull-down and luciferase reporter assays, in addition to determining the effect of Jun-B downregulation on AP1 promoter activity. Citation Format: Pornima Phatak, Mohan E. Tulapurkar, James M. Donahue. MicroRNA (miR)199a-5p targets JUN-B to decrease cell proliferation in esophageal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1486. |
