Synergistic Anticancer Activity of Combined Use of Caffeic Acid with Paclitaxel Enhances Apoptosis of Non-Small-Cell Lung Cancer H1299 Cells in Vivo and in Vitro

Background/Aims: Caffeic acid (CA) is known to possess multiple biological activities including anti-cancer activities. However, the molecular mechanisms underlying these activities in non-small-cell lung cancer (NSCLC) cells are not fully understood. We attempted to clarify whether CA could enhance paclitaxel (PTX)-induced cytotoxicity in H1299 cells. Methods: First, we tested the cytotoxic effects in both H1299 cells and normal human Bease-2b cells by cell proliferation experiments. Next, we use Annexin V/propidium iodide apoptosis analysis and flow cytometric analysis to investigate apoptosis and cell cycle arrest under the treatments mentioned above. To further pinpoint changes in apoptosis, we tested the caspase-associated apoptotic pathway, which involves the activities of caspase-3 and caspase-9. Moreover, apoptosis-related proteins and MAPK pathway proteins were examined by western blot. An H1299 xenograft nude mice model was used to further evaluate the tumor-suppressing effects of CA and PTX in vivo. Results: Combination treatment with low-dose CA and PTX decreased the proliferation of NSCLC H1299 cells but not normal Beas-2b cells. Flow cytometry showed that H1299 cells were arrested in the sub-G1 phase and apoptosis was significantly increased in H1299 cells after CA treatment. Caspase-3 and caspase-9 activities were both increased after CA treatment. Furthermore, CA increased the PTX-induced activation of Bax, Bid, and downstream cleaved PARP, and phosphorylation of extracellular signal regulated kinase1/2 and c-Jun NH2-terminal protein kinase1/2. An in vivo tumor-suppression assay demonstrated that CA and PTX combined treatment exerted a more effective suppressive effect on tumor growth in H1299 xenografts without causing significant adverse effects. Conclusions: Our results indicated that CA inhibited NSCLC H1299 cell growth by inducing apoptosis and CA and PTX combined produced a synergistic anti-cancer effect in H1299 cells