MiR-138 indirectly regulates the MDR1 promoter by NF-κB/p65 silencing

Area of Science:

• Molecular Biology
• Gene Regulation
• Cancer Research

Background:

• MicroRNAs (miRNAs) primarily mediate post-transcriptional gene silencing in the cytoplasm.
• Emerging evidence suggests nuclear roles for miRNAs in gene expression regulation.
• Previous studies linked miR-138 to multidrug resistance (MDR) in leukemia via P-glycoprotein (P-gp) downregulation, but the transcriptional mechanism was unclear.

Purpose of the Study:

• To elucidate the transcriptional regulatory mechanisms of miR-138 in MDR1 gene expression.
• To investigate the potential indirect regulation of the MDR1 promoter by miR-138.
• To explore the role of NF-κB/p65 in miR-138-mediated MDR1 regulation and inflammatory responses.

Main Methods:

• Bioinformatic analysis to identify potential miR-138 binding sites in the MDR1 gene promoter.
• In silico analysis of transcription factors involved in MDR1 regulation.
• Luciferase reporter assays, Western blot, and flow cytometry to assess miR-138's effect on NF-κB/p65 and MDR1 expression.
• Experiments using the U937 human macrophage-like cell line to evaluate miR-138's impact on NF-κB target genes (IL-6, TNF-α).

Main Results:

• No direct miR-138 binding sites were found in the MDR1 promoter region.
• In silico analysis identified NF-κB/p65 as a potential target for miR-138.
• miR-138 was shown to inhibit NF-κB/p65, leading to indirect modulation of human MDR1 expression.
• In U937 cells, miR-138 expression reduced NF-κB/p65, IL-6, and TNF-α mRNA levels and secreted cytokines.

Conclusions:

• miR-138 indirectly regulates MDR1 expression in leukemia cells by inhibiting the transcription factor NF-κB/p65.
• This mechanism highlights a novel pathway for controlling multidrug resistance in cancer.
• miR-138 may also target other canonical NF-κB-regulated genes, suggesting broader implications in leukemia and inflammatory processes.