In this study, inhibition of autophagy by specific downregulation of Atg5 using a lentivirus expressing a targeted shRNA, interrupted breast cancer cell cycle arrest in response to D-arabinose treatment, observed as increased expression of CDK1 and Cyclin B1, as well as reduced levels of p21 and p27 and enhanced cell proliferation potential. The gene discussed is ATG5; the disease is breast cancer.