Autophagy constitutes a barrier to prevent malignant transformation.15 Several lines of evidence demonstrate that BECN1 is a haploinsufficient tumor suppressor.10, 11 Monoallelic deletion of BECN1 gene is frequently observed in a high proportion of sporadic breast and ovarian carcinomas.47 Low expression of BECN1 is also found in colorectal, gastric and intracranial tumors.48 A recent study reported that BECN1 expression is reduced in triple-negative breast cancers compared with other subtypes, lower expression of BECN1 is also associated with poor prognosis.49 In line with this report, we demonstrate that miR-20a directly targets BECN1, SQSTM1 and ATG16L1. Upregulation of miR-20a strongly associates with downregulation of BECN1, SQSTM1 and ATG16L1 in human breast cancers, especially in triple-negative subtypes. Therefore, in addition to the monoallelic loss of BECN1 in breast cancer, miR-20a-mediated downregulation of autophagy pathway might be another mechanism that promotes malignant transformation.