Introduction: The incidence and mortality rates of lung cancer rank top in the different types of cancers in China. Licochalcone A (LA) is a flavonoid extracted from the roots of licorice with antitumor effects in various cancers in vitro  and in vivo . However, the role of LA in non-small cell lung cancer (NSCLC) remains largely unclear.
Methods: The cell viability was measured by MTT assay, Edu staining and colony formation assay. Apoptosis was investigated using Annexin V/PI double-stained assays with flow cytometry. Real-time quantitative RT-PCR was carried out to investigate the expression of mRNA of related proteins. Western blotting was used to investigate the expression of related proteins.
Results: The results show that LA inhibits the proliferation of NSCLC cells in a dose-dependent manner and induces apoptotic cell death. Moreover, LA significantly suppresses the expression of c-IAP1, c-IAP2, XIAP, Survivin, c-FLIP_L and RIP1 without influencing the level of mRNA. Cycloheximide chase assay demonstrates that LA greatly decreases the stability of Survivin, XIAP and RIP1. Mechanistic studies indicate that LA induces cytoprotective autophagy since block of autophagy with CQ greatly enhances LA-induced anticancer activities. Furthermore, LA rapidly induces ERK and p38 activation in a time-dependent manner in both A549 and H460 cells, but suppresses the activities of c-Jun N-terminal kinase (JNK); suppression of ERK not p38 with inhibitor attenuates LA-induced autophagy, while it remarkably enhances LA-induced cytotoxicity in lung cancer cells and further promotes the degradation of apoptosis-related proteins.
Discussion: The results of this study provide novel insights on the role of apoptosis-related proteins and the MAPKs pathway in the anticancer activities of LA.
Keywords: non-small cell lung cancer, NSCLC, licochalcone A, LA, inhibitors of apoptosis proteins, IAPs, RIP1, ERK, autophagy