Systematic evaluation of the anti-tumor effect of Phellinus linteus polysaccharide in thyroid carcinoma in vitro

Background Thyroid carcinoma (TC) is the most common malignant tumor of the endocrine system. Phellinus linteus polysaccharide (PLP) physiologically acts as a suitable anti-tumor molecule. In this study, for the first time, we systematically investigated the anti-tumor activity of PLP in TC, aiming to promote the application of PLP in TC treatment. Methods and results TPC-1 and SW579 cells were treated with or without PLP. After treatment, MTT and EdU proliferation assays were performed to detect cell growth. Cell cycle was analyzed using flow cytometry. JC-1 staining was used to track change of mitochondrial membrane potential (MMP). Apoptotic cells were stained with annexin V-fluorescein isothiocyanate/propidium iodide and subsequently analyzed using flow cytometry. mCherry-GFP-LC3 was overexpressed in TC cells by lentiviral technology and the autophagosome was observed using confocal laser scanning microscope. Transwell migration and Matrigel invasion assays were performed to elucidate cell metastasis. Finally, underlying molecular mechanisms were investigated using RT-qPCR and western blotting. PLP inhibited cell growth in TC cells, which was attributable to the PLP-induced arrest at G(0)/G(1) phase of cell cycle. PLP decreased the MMP, induced cell apoptosis, and promoted mitochondrial autophagy and endoplasmic reticulum autophagy. Furthermore, PLP may promote cell apoptosis via nuclear factor kappa-B pathway. In addition, PLP also inhibited cell migration and invasion through modulating the expression of epithelial-mesenchymal transition molecules such as E-cadherin, N-cadherin, and Vimentin Conclusions PLP exhibits notable anti-tumor activity in TC cells and may be used in TC treatment.