URP70-1, a novel polysaccharide from the roots of Uncaria rhynchophylla induced apoptosis by regulating GRP78/CHOP-ERK-Bax/Bcl-2 pathway.

Polysaccharides derived from medicinal plants have drawn significant attention for their potential anti-tumor properties and favorable safety profiles. In this research, a novel polysaccharide with anti-tumor activity, named URP70-1, was isolated from the roots of Uncaria rhynchophylla. Structural characterization determined URP70-1 to be a novel 8.2 kDa polysaccharide composed of L-arabinose (52.8%), D-galactose (35.4%), and D-xylose (11.8%). Methylation and NMR spectroscopic analyses further elucidated its primary structure, comprising a backbone of →3,5)-L-Araf-(1→, →4)-D-Galp-(1→, and →2,5)-L-Araf-(1 → residues, with side chains containing →3)-L-Araf-(1→, →5)-L-Araf-(1→, →6)-D-Galp-(1→, L-Araf-(1→, D-Xylp-(1→, and D-Galp-(1 → residues. In vivo evaluation using a zebrafish xenograft model demonstrated that URP70-1 significantly inhibited tumor proliferation in a dose-dependent manner, with no observed toxicity. In vitro studies on CT26 colon carcinoma cells confirmed that URP70-1 suppressed cell viability and migration, elevated intracellular ROS levels, and reduced mitochondrial membrane potential, ultimately promoting apoptosis. Mechanistic investigations revealed that URP70-1 entered cells and induced endoplasmic reticulum stress via the GRP78-EIF2S1-CHOP pathway, while concurrently activating the ROS/ERK/p38 signaling axis. This led to mitochondrial dysfunction, an increased Bax/Bcl-2 ratio, cytochrome C release, and activation of the caspase cascade. Collectively, these findings highlight URP70-1 as a structurally novel polysaccharide with potent anti-tumor activity mediated through endoplasmic reticulum stress and mitochondrial apoptosis pathways, providing a foundation for its further development as a potential therapeutic agent against colon cancer.