Luteolin Induces Apoptosis by Up-regulating miR-34a in Human Gastric Cancer Cells

Luteolin (39, 49, 5, 7-tetrahydroxyflavone) is a natural flavonoid that exists in several types of vegetables, fruits, and medicinal herbs that inhibits tumorigenesis in different types of cancer. In this study, we demonstrate luteolin-mediated regulation of cell apoptosis in a gastric cancer cell line through inhibition of the apoptosis regulatory protein Bcl-2. MTT and flow cytometric analysis indicate that luteolin inhibits cell proliferation and induces apoptosis in gastric cancer cells. Quantitative real-time polymerase chain reaction (qRT-PCR) revealed that miR-34a expression is downregulated in the majority of human primary gastric cancer tissues (8/12, 66.7%), compared with adjacent, pair-matched non-tumor tissues. Target analysis indicated that micro RNA (miR)-34a directly regulates Bcl-2, and miR-34a overexpression decreased Bcl-2 protein level in gastric cancer cells. We also found that luteolin upregulates miR-34a expression and downregulates Bcl-2 expression. Furthermore, anti-miR-34a oligonucleotides (AMO) partly reverse luteolin-induced Bcl-2 downregulation in gastric cancer cells. Based on these results, we can draw the conclusion that luteolin partly decreases Bcl-2 expression through upregulating miR-34a expression. This study shows for the first time that the miR-34a pathway plays an important role in luteolin-induced apoptosis in gastric cancer cells.