For absolute miRNA quantification, the Ct value obtained from a dilution series (ranging from 100 nM down to 10 fM) of chemically synthesized RNA oligonucleotides corresponding to the mature miRNA sequence of let-7b-5p (UGAGGUAGUAGGUUGUGUGGUU) and miRNA-122-5p (UGGAGUGUGACAAUGGUGUUUG) were used to generate standard curves (both were purchased from Sigma).