Chlorogenic Acid Enhances Beta-Lapachone-Induced Cell Death by Suppressing Autophagy in NQO1-Positive Cancer Cells.

Resistance to apoptosis-inducing drugs frequently occurs in cancer cells, limiting their usefulness in ongoing cancer treatment. Despite ongoing efforts to overcome drug resistance, a definitive solution remains elusive. However, autophagy inhibition has been shown to enhance the effectiveness of some anticancer drugs and is a possible strategy for overcoming drug resistance. In this study, we demonstrate that chlorogenic acid (CGA), a natural antioxidant, significantly enhances beta-lapachone (β-Lap)-induced cell death in cancer cells. The augmented apoptosis induced by CGA is associated with activation of protein kinase A (PKA) in β-Lap-treated cells, independent of the antioxidant properties of CGA. As a result, PKA activation in cancer cells co-treated with β-Lap and CGA effectively inhibits autophagy. Notably, PKA activation leads to phosphorylation of microtubule-associated protein 1 A/1B-light chain 3 (LC3) at the serine 12 residue, causing autophagy suppression irrespective of mTORC activity. Importantly, the cell death induced by β-Lap and CGA in NQO1-overexpressing breast or lung cancers is closely linked to autophagy inhibition. These findings suggest that combining β-Lap and CGA might be a novel strategy for cancer therapy, particularly for overcoming drug resistance caused by autophagy induction in cancer cells.