BRCA1 and Hereditary breast cancer: Studies have shown that in BRCA1/2 PV hereditary breast cancer, certain miRNAs such as miR-148 and miR-335 were downregulated, while certain ones were upregulated, such as miR-21 and miR-206, although the correlation between the varying quantities of non-coding RNAs and differences in tumourigenesis was found to be weak [77].