Abstract
Non-small cell lung cancer (NSCLC) is relatively insensitive to chemotherapy. NP [vinorelbine (NVB) + cisplatin] is the standard chemotherapy regimen in clinical treatment; however, its side-effects are intolerable for most patients. In some reports, the TNF-related apoptosis-inducing ligand (TRAIL) can enhance the sensitivity of chemotherapy drugs by inducing apoptosis without toxicity to normal cells. In the present study, we evaluated the antitumor effects of the two drugs (TRAIL and NVB alone or in combination) by inducing apoptosis in vitro and in vivo. Using the human NSCLC cell line (A549) and a BALB/c nude mice model, we observed the cell viability (MTT assay), cell apoptosis [Hoechst staining, Annexin V/propidium iodide (PI) staining assay, immunohistochemical staining, RT-PCR and western blotting] and cell proliferation (soft agar colony formation and cell cycle assay). The results showed that TRAIL and NVB alone inhibited tumor growth both in vivo and in vitro. However, the combination of the two drugs produced a more potent antitumor effect (P<0.05) and caused more severe apoptosis in tumor tissue (P<0.05). The key molecular protein level of the mitochondrial apoptotic pathway (Bax and caspase-3) was further upregulated by the combination of the two drugs (P<0.01) and either drug alone (P<0.05). The mRNA level of Bcl-2 and Bax in the combination group was downregulated and upregulated respectively, when compared with the control group (P<0.01). The combination group of A549 cells also showed lower viability compared with the one drug alone group (P<0.05). Moreover, the Hoechst staining assay and Annexin V/PI staining assay showed that the combination of the two drugs induced a more potent apoptosis than either drug alone (P<0.05, early apoptosis P<0.01, respectively). In addition, the cell colony numbers were deduced after treatment with TRAIL or NVB alone (P<0.05) and the two drug combination (P<0.01). Cell cycle analysis showed that TRAIL and NVB alone markedly increased the percentage of cells in G1 phase (P<0.05) and the combination of the two drugs decreased the percentage of cells in G2 and S phase (P<0.05). Thus, the combination of TRAIL and NVB can inhibit lung cancer cell growth by affecting the level of key signaling protein expression of the apoptosis pathway.