Combined Treatment of Caffeic Acid Phenethyl Ester With Docetaxel Inhibits Survival of Non-small-cell Lung Cancer Cells via Suppression of c-MYC

Background/Aim: Non-small-cell lung cancer (NSCLC) comprises approximately 85% of lung cancer. Treatment with docetaxel prolongs the survival of patients with NSCLC. However, the development of resistance to docetaxel has compromised its efficacy. Caffeic acid phenethyl ester (CAPE) has been reported to suppress survival and radiotherapy resistance in lung cancer cells. We determined in this study if combination treatment of docetaxel with CAPE suppresses the proliferation and the survival of NSCLC cells more effectively. Materials and Methods: Proliferation, viability, flow cytometric and comet assays were used to examine the difference in anticancer effects of combined treatment as compared to docetaxel treatment alone. Western blot and gene overexpression were used to unravel the underlying molecular mechanism. Results: Treatment with docetaxel or CAPE alone dose-dependently suppressed the proliferation and survival of H1299 and A549 cells. Combined treatment of docetaxel with CAPE caused greater inhibition of survival of H1299 and A549 cells. Docetaxel alone and the combined treatment both dose-dependently increased apoptosis of H1299 cells; however, combined treatment induced much more apoptosis than docetaxel alone. Combined treatment suppressed the protein expression of phospho-protein kinase B (AKT, Ser 473), S-phase protein 2 (SKP2), MYC proto-oncogene bHLH transcription factor (c-MYC), epidermal growth factor receptor (EGFR), phospho-EGFR (Tyr 1045, and Tyr 992) but increased levels of cleaved caspase 3 and cytochrome c proteins in H1299 and A549 cells. The inhibition of expression of SKP2, c-MYC, phospho-EGFR (Tyr 992) proteins by combined treatment was significantly greater than that with treatment using either CAPE or docetaxel alone. Overexpression of c-MYC in rescued proliferation of H1299 cells under combination treatment. Conclusion: Our study revealed that the combination of CAPE with docetaxel is more effective at reducing the proliferation and survival of NSCLC cells, and this is via inhibition of c-MYC. Combined therapy of docetaxel and CAPE may benefit patients with NSCLC.