[Mechanism of Growth Inhibition Effect of 3', 4', 5, 7-tetrahydroxyflavone on A549 Cells]

Objective: To study luteolin-induced non-small cell lung cancer cell line A549 apoptosis and the molecular mechanism for inhibiting its cycle arrest (G2 stage).

Method: MTT assay showed that luteolin had obvious inhibitory effect on A549 and indicated the half inhibition ratio (IC50). Cell cycle and apoptosis were detected by Hoechst 33258 nuclear staining assay, Annexin V-FITC/PI double staining and flow cytometry. Western blotting assay revealed changes in cycle and apoptosis-related proteins induced by luteolin. Possible molecular mechanism was suggested by Western blotting and immunocytochemistry.

Result: Luteolin had an obvious growth inhibitory effect on A549 cells, with IC50 of 45.2 micromol x L(-1) at 48 h. Flow cytometry showed A549 cells mainly arrested in G2 stage after being treated by luteolin, with low expressions in cyclin A, p-CDC2 and p-Rb. Hoechst 33258 nuclear staining and Annexin V-FITC/PI double staining showed that the luteolin treatment group showed a significant apoptosis rate than the non-treatment group. Western blotting found luteolin can increase phosphorylation of JNK and decrease that of NF-kappaKB (p65). Immunocytochemistry results revealed luteolin can inhibit TNF-alpha-stimulated p65 from nuclear translocation as a transcription factor and thus promoting cell apoptosis.

Conclusion: Luteolin can obviously induce apoptosis of human non-small cell lung cancer cell A549 possibly by increasing phosphorylation of JNK to activate mitochondria apoptosis pathway, while inhibiting NF-kappaB from nuclear translocation as a transcription factor.