Structural characteristics of a fructan-type polysaccharide from Asparagus cochinchinensis rhizome and its anti-osteosarcoma activity mediated via macrophage polarization.

Repolarization of tumor-associated macrophages (TAM) from the M2 to the M1 phenotype has emerged as a promising approach in cancer immunotherapy. In this study, a neutral fructan-type polysaccharide, ACRP (Asparagus cochinchinensis rhizome polysaccharide), was extracted from the rhizome of A. cochinchinensis. The molecular weights were calculated by HPGPC as Mn = 2617 Da, Mw = 3426 Da, and Mw/Mn = 1.31. Structural characterization indicated that ACRP consists of a backbone composed of β-(2 → 1)-linked Fruf and α-(1 → 6)-linked Glcp residues, terminating with T-Glcp and 2-Fruf units. In vitro assays showed that ACRP significantly activated macrophages by enhancing phagocytic potential and promoting the production of reactive oxygen species (ROS), nitric oxide (NO), TNF-α, and IL-12p70. Moreover, ACRP effectively reprogrammed M2-polarized macrophages toward the M1 phenotype, resulting in enhanced apoptosis and reduced clonogenic potential of LM8 and K7M2 osteosarcoma cells, thus indicating potent antitumor efficacy. Mechanistic studies revealed that this phenotypic transformation was mediated by activating the TLR4/MyD88/NF-κB pathway. In vivo studies using an LM8 tumor-bearing mouse model showed that ACRP modulated macrophage polarization and elevated CD3+CD4+ and CD3+CD8+ T lymphocytes, which significantly suppressed osteosarcoma progression. These findings indicate that ACRP has potent immunomodulatory and anti-tumor effects by activating innate immune responses and may represent a promising therapeutic candidate for osteosarcoma immunotherapy.