Hirsuteine Inhibits the Proliferation of Human Non-Small Cell Lung Cancer (NSCLC) Cells by Inducing Apoptosis and Cell Cycle Arrest

Background: Hirsuteine is an alkaloid compound that can inhibit the proliferative activity of several cancer cell types in vitro, yet no prior reports have explored its ability to inhibit non-small cell lung cancer (NSCLC) growth. As such, herein, we sought to explore the antiproliferative activity of hirsuteine when used to treat human NSCLC A549 and NC I-H1299 cells across a range of tested concentrations (0–25 μM) and to explore the mechanisms underlying its therapeutic efficacy. Methods: The effects of hirsuteine on cell viability was examined via CCK-8 and colony formation assays, while apoptosis was assessed through Hoechst 33,258 staining and flow cytometry. Cell cycle progression was additionally evaluated via propidium iodide staining, while Western blotting and real-time quantitative polymerase chain reaction (qPCR) method were conducted to assess the levels of proteins and genes associated with apoptosis and cell cycle progression, respectively. Results: Hirsuteine markedly suppressed the proliferation of A549 and NCI-H1299 cells in a dose and time-dependent fashion and induced clear changes in cell morphology, resulting in G0-G1 phase cell cycle arrest that was related to the downregulation of Cyclin E and CDK2. Hirsuteine additionally induced robust apoptosis of A549 and NCI-H1299 cells and Bcl-2 downregulation together with the upregulation of Bax, Apaf1, cytoplasmic cytochrome C, cleaved caspase-3 and cleaved caspase-9, together driving this apoptotic cell death. Conclusion: Hirsuteine can effectively suppress the growth of human NSCLC A549 and NCI-H1299 cells and induce apoptotic death in a dose-dependent fashion in vitro , emphasizing the promising of this alkaloid compound as a potent anticancer treatment that warrants study as a treatment for human NSCLC patients.