However, 256, 288 and 411 tumor-specific circRNAs were found in triple negative (TN), estrogen receptor positive (ER+) and HER2-positive breast cancer subtypes, respectively.74 Another study found the putative tumor suppressor, circFOXO3, to be significantly downregulated in breast tumor samples relative to benign samples47 and this circRNA is likely to have a role in breast cancer progression.75 Finally, a circRNA from ABCB10 was shown to be upregulated in breast cancer and knockdown of this circRNA in vitro suppressed proliferation of breast cancer cells and enhanced apoptosis.76 Here, ESR1 is linked to breast cancer.