The effects of Astragalus polysaccharides, tragacanthin, and bassorin on methotrexate-resistant acute lymphoblastic leukemia

Background and purpose

One strategy to overcome methotrexate (MTX) resistance in acute lymphoblastic leukemia is suppressing MDR1 expression. It has been proved Astragalus polysaccharides (APS) exert their anticancer effect by reversing drug resistance. Due to the structural similarity of tragacanthin and bassorin with APS, we aimed to investigate the effects of the aforementioned polysaccharides on the expression of the MDR1 gene in the MTX-treated CCRF-CEM cells.

Experimental approach

Cytotoxicity of APS, bassorin, and tragacanthin on CCRF-CEM, CCRF-CEM/MTX (cells treated with MTX at IC50), and CCRF-CEM/R cells (CCRF-CEM cells resistant to MTX) was evaluated by MTT assay. The effect of all three compounds on MDR1 expression was evaluated using RT-PCR.

Findings/Results

All the concentrations of tragacanthin, bassorin, and APS (except at 0.8-100 μg/mL in CCRF-CEM) decreased the viability of all the cells compared to the negative control group; and against the positive control (MTX-treated cells), only bassorin at 20-100 μg/mL in CCRF-CEM/R and tragacanthin at 50 and 100 μg/mL in CCRF-CEM/MTX and at 2-100 μg/mL in CCRF-CEM/R decreased cell viability. Tragacanthin diminished MDR1 expression in CCRF-CEM/MTX and CCRF-CEM/R cells, which MTX had already induced.

Conclusion and implication

According to the results of this study, tragacanthin was a potent cytotoxic agent against CCRF-CEM cells and enhanced the chemosensitivity of CCRF-CEM/MTX and CCRF-CEM/R cells to MTX by down-regulation of MDR1 gene expression. Therefore, it could be a promising compound against cancer. Other possible mechanisms of action of tragacanthin should be evaluated and further in vitro and in vivo investigations are required.

Effect of bassorin (derived from gum tragacanth) and halloysite nanotubes on physicochemical properties and the osteoconductivity of methylcellulose-based injectable hydrogels

Injectable hydrogels have been known as promising materials for the regeneration of irregular shape tissue defects. In this study, novel thermosensitive methylcellulose (MC) hydrogels containing bassorin (Ba) and halloysite nanotubes (HNTs) have been developed for application in bone tissue engineering. Bassorin isolated from gum tragacanth (GT) with the concentration of 0.25-1.5 w/v% was blended with MC. The best MC/Ba gel (containing 0.5% bassorin) was chosen based on the results of injectability and rheological tests. HNTs (1-7%) were added to this formulation and tested for the physicochemical, mechanical, rheological, degradation, swelling, and biological properties. In vitro biological evaluations including cell proliferation (by MTT assay), cell attachment (by SEM), osteogenic activity (by Alizarin Red staining and alkaline phosphatase assay), and osteogenic gene expression (by quantitative real-time polymerase chain reaction) were done using MG-63 cells. Results showed that bassorin led to the increased gel-forming ability (at a lower temperature) and mechanical properties of MC hydrogel. The presence of HNTs and bassorin affected the degradation rate and swelling degree of MC-based hydrogel. Results showed significant enhancement in cell proliferation, differentiation, and mineralization, as well as higher bone-specific gene expression of the cell on bassorin and HNTs incorporated MC compared to pure MC hydrogel.