Scutellaria radix promotes apoptosis in non-small cell lung cancer cells via induction of AMPK-dependent autophagy

Scutellaria Radix (SR) is an herb traditionally used in Asian countries to treat inflammatory diseases. Recent studies report that SR exhibits anticancer activities in various types of tumors. In this study, we investigated the apoptotic and autophagic effect of SR in non-small cell lung cancer (NSCLC), the leading cause of cancer-associated death. Treatment of SR in two NSCLC cell lines, H358 and H2087 cells resulted in suppressed cell viability. Western blot assays showed increased expressions of Bcl-2-associated X protein (Bax), cleaved-caspase 3 and cleaved-Poly ADP ribose polymerase (PARP), key factors of apoptosis. Co-treatment of SR with a caspase inhibitor Z-VAD led to nullification of the antiproliferative effect, suggesting the role of apoptosis in the action mechanism of SR. Further experiments revealed autophagy was involved in the effect of SR. SR-treated NSCLC cells expressed increased ratio of microtubule-associated protein 1A/1B-light chain 3 (LC3)-II/LC3-I. When chloroquine was co-treated with SR, this ratio was further increased, indicating SR treatment induced autophagy in NSCLC cells. Interestingly, loss of autophagy by 3-Methyladenine (3-MA) co-treatment suppressed SR-induced apoptosis. We then evaluated the relevance of AMP-activated protein kinase (AMPK) in the autophagic/apoptotic process in NSCLC by SR treatment. Immunoblot assays showed increased phosphorylation of AMPKα and P70-S6 kinase in SR-treated H358 and H2087 cells. Under AMPK-inhibited conditions by compound C, SR treatment failed to induce both autophagy and apoptosis. Taken together, this study identifies the positive effect of SR in H358 and H2087 cells by inducing apoptosis via AMPK-dependent autophagy. Thus, our results suggest the potential use of SR as a novel therapeutic strategy for NSCLC patients.