OBJECTIVE: Lung cancer is one of the main causes of cancer-related mortality globally, and it poses considerable therapeutic challenges. Polo-like kinase 1 (PLK1) exhibits upregulation in lung cancer, and PLK1 silencing promotes autophagy in lung cancer cells, which inhibits tumor progression. The phosphatase and tensin homolog deleted on chromosome ten (PTEN) acts as a tumor suppressor gene. This study aimed to investigate whether PTEN regulates autophagy and inhibits lung cancer-cell proliferation by suppressing PLK1. MATERIAL AND METHODS: In this study, we evaluated cell proliferation by silencing or overexpressing PLK1 and PTEN in A549 cells through 5-ethynyl-2'-deoxyuridine labeling and cloning experiments. The autophagy levels were detected through transmission electron microscopy, real-time quantitative polymerase chain reaction, and Western blot. Finally, the results of RESULTS: The upregulation of PTEN suppressed PLK1 expression in lung cancer cells and reduced their proliferation rate. In addition, the overexpression of PTEN has been associated with the growth of lung cancer tumors. In parallel, the levels of autophagy of lung cancer cells rose in response to PTEN upregulation CONCLUSION: This study revealed that PTEN promotes the autophagy of lung cancer cells and inhibits cell proliferation and tumor growth by suppressing PLK1 expression. This finding provides a new strategy for lung cancer treatment by utilizing the autophagy-regulating effect of PTEN to inhibit lung cancer growth by targeting PLK1.