Adaptation of the Transcriptome and miRNAome in Response to Hepatocellular Hypoxia

Inadequate supply of oxygen causing hypoxic cellular stress drives metabolic reprograming across diverse physiological conditions, including cancer. The activation of hypoxia-inducible factors (HIFs) to facilitate adaptation to low oxygen environments is well-characterized; however, post-transcriptional regulation by microRNAs (miRNAs) is poorly understood. Here, we investigated the mRNA and miRNA response in hypoxia-mediating reduced growth and cellular metabolism. Next-generation sequencing revealed the impact of hypoxia in cultured human hepatocellular carcinoma cells and identified over 400 mRNAs and 140 miRNAs that were differentially expressed. Hypoxia upregulated mRNA transcripts associated with glycolysis, DNA replication and the PI3K (phosphoinositide 3-kinase)-Akt pathway, which promote anaerobic metabolism for energy production, decreased cell proliferation and genomic instability, respectively. Upregulated miRNAs included miR-197-3p and miR-766-3p, targeting genes involved in lipid biosynthesis and metabolism. Downregulated miRNAs included miR-33a-5p and miR-15a-5p, targeting genes involved in glycolysis and lactate metabolism. Notably, miR-6834 emerged as a potential regulator of mechanistic target of rapamycin (mTOR) signaling and insulin-like growth factor binding protein-1 (IGFBP-1) signaling; miR-6834 overexpression altered 4E-BP1 phosphorylation levels and IGFBP-1 secretion. These findings provide critical insights into miRNA-mRNA regulation of metabolic adaptation and highlight miRNAs as potential targets for interventions with relevance to tumor biology and other hypoxia-associated conditions.