In breast cancer, a few studies have shown that circRNAs encode peptides, including circ-EIF6, which encodes EIF6-224aa [16]; circ-HER2, which encodes HER2-103 [50]; and circSEMA4B, which encodes SEMA4B-211aa [51], which reportedly participate in the progression and drug resistance of tumors. This evidence concerns the gene ERBB2 and breast cancer.