hsa-mir-921: Hsa-mir-921 is a microRNA that has been predicted to interact with has_circ_0007843 and is found to be overexpressed specifically in the BRCAX-C group [PMC3833208] [PMC8324362]. Functional studies have shown that hsa-mir-921 significantly decreases the luciferase activity of CHO cells after transfection with the CBR1 3′-UTR construct carrying the major rs9024 G allele, as well as a decreased level of CBR1 protein and CBR1 activity in lymphoblastoid cells that contain the homozygous major rs9024 G allele [PMC3486798]. Hsa-mir-921 selectively binds only to the CBR1 3′-UTR construct carrying the G allele, and its co-transfection with pCBR1-1096A failed to produce a significant decrease in luciferase activity [PMC3486798]. Hsa-mir-921 accelerates decay of CBR1 mRNA compared to miRNA mimic negative control, suggesting its role in regulating CBR1 expression [PMC3486798]. Hsa-mir-921 is co-expressed with CBR1 in human liver and heart tissue, indicating its potential role in regulating CBR1 expression in these tissues [PMC3486798]. The inhibitory effects of hsa-mir-921 on CBR1 mRNA expression are interfered by the 3′-UTR SNP rs9024 [PMC9606405].