Evaluating combinatorial effects of galbanic acid and arsenic trioxide
on ATL cells
Abstract
Abstract Background and Purpose: Galbanic acid (GBA), a sesquiterpene
coumarin compound isolated from Ferula species, has noticeable
anti-cancer effects. In current research, we investigated effects of GBA
in combination with arsenic trioxide (ATO) on MT-2 cells, an Adult T
cell leukemia (ATL) cell line. ATL is a malignancy caused by human T
cell leukemia virus type 1 (HTLV-1). Experimental Approach: The MT-2
cells were treated with each agent alone at various concentrations.
After determination of IC50 values, MT-2 cells were treated with 20 µM
GBA combined with 4 µM ATO. The viability of MT-2 cells was evaluated by
alamar blue assay and cell cycle distribution was assessed by PI
staining. Furthermore, the activity of P-glycoprotein (P-gp) in the
presence of GBA was studied by mitoxantrone efflux assay. To understand
the molecular mechanisms of GBA+ATO treatment in MT-2 cells, the mRNA
expression of RelA, p53, CDK4, c-MYC, c-FLIPL, and c-FLIPS was measured
by real-time PCR. Key Results: GBA+ATO synergistically inhibited
proliferation of MT-2 cells and induced apoptotic cell death. GBA and
ATO also synergized to induce cell cycle arrest with an apparent sub-G1
cells accumulation. Rate of mitoxantrone accumulation in MT-2 cells was
enhanced in the presence of GBA, indicating GBA has inhibitory effects
on the functionality of the P-gp efflux pump. The real-time PCR analysis
revealed that GBA+ATO combination downregulated the expression of p53,
CDK4, c-FLIPL, and c-FLIPS. Statistical analysis revealed a significant
relation between p53 expression and c-FLIPS. Conclusion and
Implications: The GBA+ATO combination could be considered as a new
therapeutic approach for ATL patients.