Abstract. Oleuropein could inhibit growth and/or induce apoptosis in several cancer cell lines. In this study, we investigate how oleuropein strongly induces apoptotic cell death in HeLa human cervical carcinoma cells. Oleuropein induced HeLa cells apoptosis as demonstrated by induction of a sub-G 1 peak in flow cytometry and apoptosis-related morphological changes observed by fluorescence microscopy after being stained by Hoechst 33324. The results also showed that 150 -200 mM oleuropein-treated HeLa cells were arrested at the G 2 /M phase. Western blot analysis revealed that the phosphorylated ATF-2, c-Jun NH 2 -terminal kinase (JNK) protein, p53, p21, Bax, and cytochrome c protein in the cytoplasm significantly increased in a dose-dependent manner after treatment of oleuropein for 24 h. Additionally, increasing levels of Bax in response to JNK/SPAK signaling, which formed mitochondrial membrane channels, accounted for releasing of cytochrome c and activation of caspase-9 and -3. SP600125 (20 mM), a JNK 1/2 inhibitor, markedly suppressed the formation of apoptotic bodies and JNK activation induced by oleuropein at 200 mM. Thus, oleuropein-induced apoptosis was activated by the JNK/SPAK signal pathway. The result shows that oleuropein holds promise as a potential chemotherapeutic agent for the treatment of HeLa cells.

Lung cancer is the main health threat in the world. Recently, oleuropein has been reported to have potent antioxidant and anticancer activities. However, the antitumor effects of oleuropein on H1299 cells are not well understood. Therefore, the purpose of this paper is tantamount to explore the effects of oleuropein on H1299 cells and its underlying mechanism that may be involved. Oleuropein treatment in H1299 cells resulted in cell cycle distribution at G2/M arrest and apoptosis in a dose‐dependent manner. Mitochondria‐mediated apoptosis was verified by the increase in Bax/Bcl‐2 ratio, release of cytochrome c, and activation of caspase‐3 on oleuropein‐induced H1299 cells. In addition, our data also demonstrated that the p38 mitogen‐activated protein kinase (MAPK) signaling pathway has a critical role in oleuropein‐induced apoptosis. Moreover, we used transcriptome analysis to identify differentially expressed genes (DEGs) in H1299 cells by oleuropein and SB203580 treatment. Many DEGs were annotated to metabolic pathways, cell cycle, pathways in cancer, MAPK signaling pathway by Kyoto Encyclopedia of Genes and Genomes and Gene ontology enrichment methods. Network and expression analysis found that DEGs, including RPS6A5, GADD45A, and MKP, play a key role in the p38 MAPK signaling pathway. In H1299 cells, oleuropein resulted in the expression of numerous genes related to cell signaling, metabolism pathway and directly associated with apoptosis. These results illustrated that oleuropein‐induced apoptosis via mitochondrial apoptotic cascade was activated by the p38 MAPK signaling pathway in H1299 cells. Thus, oleuropein as a natural compound and therapeutic drug has potential application value in the treatment of lung cancer.