Antitumor Activity of Portulaca Oleracea L. Polysaccharide on HeLa Cells Through Inducing TLR4/NF-κB Signaling

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We have previously shown that Portulaca oleracea L. polysaccharide (POL-P3b) possesses the ability to inhibit cervical cancer cell growth in vitro and in vivo. In this study, we explored how toll-like receptor 4 (TLR4) signaling correlated with the antitumor mechanism of POL-P3b. Western blotting was utilized to detect the expression of TLR4 and the downstream signaling pathway. The level of inflammatory mediator was quantified using enzyme-linked immunosorbent assay (ELISA) kits. The effects of POL-P3b on the proliferation and apoptosis in HeLa cells were determined by WST-8 assay and Hoechst 33342/propidium iodide (PI) assay. Our results demonstrated that lipopolysaccharide (LPS) binding to TLR4 on tumor cells could enhance HeLa cell proliferation and increase the expression of TLR4 and the downstream molecules. Treating HeLa cells with POL-P3b could decrease the proliferation of HeLa cells, and upregulate Bax level and downregulate Bcl-2 level in a concentration-dependent manner. In addition, POL-P3b inhibited the protein expression levels of TLR4, MyD88, TRAF6, Activator Protein-1 (AP-1) and nuclear factor-κB (NF-κB) subunit P65 in HeLa cells. Furthermore, POL-P3b also reduced the production of cytokine/chemokine. Taken together, the present work suggested the antitumor mechanism of POL-P3b by downregulating TLR4 downstream signaling pathway and inducing cell apoptosis. Our results may provide direct evidence to suggest that POL-P3b should be considered as a potent nutrient supplement for oncotherapy.

Funding

We are grateful for funding from the Natural Science Foundation (project no. QC2010102) of Heilongjiang Province, China.

Declaration of interest

The authors declare that they have no conflict of interest.