The therapeutic inhibition of topoisomerase inhibitor and crizotinib combination in EGFR wild and mutant lung cancer cells.

Combination therapy can enhance therapeutic effect by activation of multiple downstream pathways. The present study was aimed to investigate a novel strategy to successfully inhibit the EGFR pathway in EGFR wild and mutated types lung cancer by combination method. Topotecan (TPT) and crizotinib (CRI) were used to evaluate the effect on EGFR-wild, primary and secondary mutant non-small cell lung cancer (NSCLC) cell lines (H1299, HCC827 and H1975 cells). The combination group significantly inhibited the lung cancer growth with combination index (CI) < 1, and they synergistically induced the cell apoptosis by disrupting the balance of Bax and Bcl-xL, loss of mitochondrial membrane potential (MMP), and accumulation of reactive oxygen species (ROS). In addition, EGFR downstream signaling pathways including AKT, ERK, JNK, and p38 MAPK were regulated when treated with the combination regimen. Meanwhile, a nano-liposomes co-loaded CRI and TPT was prepared and exhibited strong cytotoxicity to the lung cancer cells especially H1299 and H1975 cells. The animal study confirmed the synergy between TPT and CRI from the results that they remarkable repressed the tumor growth with the inhibition rate of 81.32 %. The nano-liposomes of TPT and CRI achieved an optimal curative effect (71.52 % of inhibition rate) at 2 mg/kg. Moreover, the synergistic mechanism of the combination was consistent with the in vitro cell experiment by regulating EGFR signaling pathways. Collectively, we proposed a preclinical rationale and potential formulation for the use of a combination therapy consisting of the topoisomerase inhibitor TPT and the ALK-TKI CRI for treatment of lung cancers.