Chemosensitization of doxorubicin against lung cancer by nature borneol, involvement of TRPM8-regulated calcium mobilization

Abstract

Background Lung cancer possesses high mortality rate and tolerances to multiple chemotherapeutics. Natural Borneol (NB) is a monoterpenoid compound that found to facilitate the bioavailability of drugs. In this study, we attempted to investigate effects of NB on the chemosensitivity in A549 cells and try to elucidate its therapeutic target. Methods The effects of NB on chemosensitivity in A549 cells was examined by MTT assay. The mechanism studies were evaluated by flow cytometry and western blotting assay. Surface plasmon resonance (SPR) and LC-MS combined analysis (MS-SPRi) was performed to elucidate the candidate target of NB contributes to this synergism. The chemosensitizing capacity of NB in vivo was conducted in nude mice bearing A549 tumors. Results NB pretreatment sensitizes A549 cells to low dosage of DOX, leading to a 15.7% to 41.5% increase in apoptosis, which is corelated with ERK and AKT inactivation but activation of phosphor-p38MAPK, -JNK and p53. Furthermore, this synergism depends on reactive oxygen species (ROS) generation. The MS-SPRi analysis reveals that the transient receptor potential melastatin-8 (TRPM8) is the interaction target of NB in potentiating DOX killing potency. Genetically knock down of TRPM8 significantly suppress the chemosensitizing effects of NB with the involvement of inhibiting ROS generation through restraining calcium mobilization. Moreover, pretreatment of NB synergistically enhanced the anticancer effects of DOX to delay tumor progression in vivo. Conclusions These results suggest that TRPM8 may be a valid therapeutic target in the potential application of NB serves as a chemosensitizer for lung cancer treatment.