Nano-pectic polysaccharide from vinegar-baked Radix Bupleuri enhances methotrexate efficacy against hepatocellular carcinoma via BCRP and MRP2 downregulation.

Unsatisfactory curative effects and low accumulation of chemotherapeutics at the target site are major limitations for hepatocellular carcinoma (HCC) treatment. Herein, a new polysaccharide with chemotherapy-sensitising activity was isolated from vinegar-baked Radix Bupleuri (VBRB), which was named VRP3-4. It is a pectic polysaccharide with a molecular weight (Mw) of 14.38 kDa, composed of galacturonic acid (GalA), arabinose (Ara), rhamnose (Rha), and galactose (Gal) in a molar ratio of 76.89:11.51:7.18: 4.42. The backbone of VRP3-4 is made up of 1, 4-linked-α-GalpA, a small fraction of 1, 3, 4-linked-α-GalpA and Rhap. Additionally, 1, 5-linked-α-Araf is connected to O-3 of GalpA as a side chain, and it self-assembles into a nanoparticle in solution. VRP3-4 significantly enhanced the anti-proliferative effect of methotrexate (MTX) on HCC cells by 59.37 % and increased its intracellular uptake by 1.90 times. In vivo experiments indicated that VRP3-4 markedly enhanced the tumour inhibition of MTX. Mechanism analysis revealed that the synergistic effect was achieved by downregulating the expression of breast cancer resistance protein (BCRP) and multidrug resistance-associated protein 2 (MRP2). Pull-down assay further indicated that VRP3-4 directly targeted BCRP and MRP2. These findings identify a polysaccharide of VBRB as the potential HCC-targeting material to sensitise chemotherapeutics in HCC treatment.