BRCA1 and neoplasm: In addition, more studies are needed, for example, studies of the concrete mechanism by which miR-664b-5p expression was increased after the chemotherapy treatment combined with PARP inhibition and studies to determine the correlation between miR-664b-5p and the clinical features, such as progression free survival (PFS), etc. In conclusion, we found for the first time, to the best of our knowledge, that miR-664b-5p functions as a tumour suppressor and has an important role in chemotherapy sensitivity by targeting CCNE2 in BRCA1-mutated TNBC.