Figure 4. let-7f-5p/TARBP2 comprises a feedback loop induced by hypoxia. (A) TARBP2 expression was decreased in OS cell lines in a hypoxic environment and TARBP2 was downregulated in OS cell lines. qRT-PCR and western blotting were used to quantitate the endogenous levels of TARBP2 in hFOB cells and HOS, U2OS, and Saos OS cells. (B) qRT-PCR and western blotting were used to evaluate the expression of TARBP2 following transfection with the TARBP2 overexpression plasmid or siRNA in Saos cells. (C) Upregulation of TARBP2 in Saos cells showed a significant decrease in let-7f-5p expression when compared with its negative counterpart, while downregulation of TARBP2 in Saos cells showed increased let-7f-5p expression when compared with control cells. (D) The regulation of TARBP2 on let-7f-5p expression is more pronounced in hypoxia condition. (E) Hypoxia inhibited let-7f-5p expression is caused by reactive oxygen species (ROS) accumulation.