Galbanic Acid Improves Accumulation and Toxicity of Arsenic Trioxide in MT-2 Cells.

Abstract

Galbanic acid (GBA) is a sesquiterpene coumarin with valuable pharmacological effects. Adult T-cell lymphoma (ATL) is an aggressive lymphoid malignancy with a low survival rate. Although arsenic trioxide (ATO) is a standard therapeutic agent for ATL treatment, the efficacy of chemotherapy is limited due to the chemoresistance of cells. The present study was carried out to investigate whether GBA in combination with ATO would improve cytotoxicity against ATL cells. GBA was isolated from the roots of Ferula szowitsiana by column chromatography on silica gel. MT-2 cells were treated with 20 μM GBA + 4 μM ATO, and viability was evaluated by alamarBlue assay. The cell cycle was analyzed by PI staining, while the activity of P-glycoprotein (P-gp) was evaluated by mitoxantrone efflux assay. To understand the molecular mechanisms of GBA effects, the expression of NF-κB (RelA), P53, CDK4, c-MYC, c-FLIPL, and c-FLIPS was evaluated using real-time PCR. Combinatorial use of GBA + ATO significantly reduced the viability of MT-2 cells and induced cell cycle arrest in the sub-G1 phase. GBA improved mitoxantrone accumulation in cells, indicating that this agent has inhibitory effects on the functionality of the P-gp efflux pump. Moreover, real-time PCR analysis revealed that GBA + ATO negatively regulated the expression of P53, CDK4, c-FLIPL, and c-FLIPS. Due to the interesting effects of GBA on the accumulation and toxicity of ATO, combinatorial use of these agents could be considered a new therapeutic approach for ATL treatment.