Autophagy inhibition induced by EM-2 augments apoptosis via ROS-mediated ATM-Chk2-p53-p21 and MAPK pathway in lung and breast carcinoma

Lung cancer (LC) and breast cancer (BC) are two common malignant tumors with the highest incidence rate in men and women worldwide, respectively. As the treatment effect of currently available therapies for LC and BC is unsatisfied, searching for new therapeutic drugs has become an urgent need to be addressed. EM-2, a natural sesquiterpene lactone isolated from Elephantopus mollis H.B.K., has been previously documented to exert anti-tumor effects on many cancers. However, the underlying molecular mechanisms have not been clearly elucidated. Thus, in the present study, we further investigated the anticancer effect of EM-2 on LC and BC with focusing on the involved molecular mechanisms. Our results suggest that EM-2 induces the impaired autophagy, which subsequently promotes ER stress-mediated apoptosis as well as ROS generation. ROS accumulation induced by EM-2 further simultaneously induces G2/M cell cycle arrest through ATM-Chk2-p53-p21 pathway and augments cell apoptosis via MAPK-mediated mitochondrial signaling pathway in LC and BC cells. These results may provide the experimental basis for future clinical application of EM-2 in the treatment for LC and BC. To further uncover the molecular mechanism of EM-2's anti-cancer effect, transcriptome profiling by RNA sequencing (RNA-Seq) was conducted. We separately treated A549 cell lines with DMSO and 6 μM EM-2 for 24 hours. We then extracted total RNA from A549 cells using TRIzol Reagent (Invitrogen Corporation) in accordance with the manufactuere's protocol. RNA libraries for RNA-Seq were constructed using MGIEasy RNA library preparation kit as described in the manufacturer's protocol. RNA-Seq was then performed on BGISEQ-500 by Beijing Genomic Institution.