Accumulating evidence reported that circRNAs play an important role in many kinds of biological processes, including cell proliferation, metastasis, migration and invasion.18, 34 In our study, we observed that inhibition of CDR1as expression may increase the sensitivity of breast cancer drug‐resistant cells to cisplatin; breast cancer cells presented decreased clone formation rate, and breast cancer cells had increased apoptosis as well as up‐regulated Bax/Bcl2 and cleaved‐Caspase‐3/Caspase‐3. This evidence concerns the gene BCL2 and breast cancer.