We established BECN1-knockout human triple-negative breast cancer (TNBC) MDA-MB-231 cells using the CRISPR/Cas9 system, and functional analyses revealed that BECN1 deficiency suppressed MDA-MB-231 cell proliferation by inducing arrest of the cell cycle at the G1 phase in vitro7, which suggested that BECN1 regulates the cell cycle. Here, BECN1 is linked to triple-negative breast carcinoma.