Homogeneous Polyporus polysaccharide exerts anti-bladder cancer effects via autophagy induction

Context: Polyporus polysaccharide (PPS), the leading bioactive ingredient extracted from Polyporus umbellatus (Pers.) Fr. (Polyporaceae), has been demonstrated to exert anti-bladder Cancer and immunomodulatory functions in macrophages.

Objective: To explore the effects of homogeneous Polyporus polysaccharide (HPP) on the proliferation and Autophagy of bladder Cancer cells co-cultured with macrophages.

Materials and methods: MB49 bladder Cancer cells and RAW264.7 macrophages were co-cultured with or without HPP intervention (50, 100, or 200 μg/mL) for 24 h. The cell counting kit-8 (CCK-8) assay and 5-ethynyl-2″-deoxyuridine (EdU) staining evaluated MB49 cell proliferation. Monodansylcadaverine (MDC) staining and transmission electron microscopy (TEM) observed autophagosomes. Western blotting detected the expression levels of autophagy-related proteins and PI3K/Akt/mTOR pathway proteins.

Results: HPP inhibited the proliferation of MB49 cells co-cultured with RAW264.7 cells but not MB49 cells alone. HPP altered the expression of autophagy-related proteins and promoted the formation of autophagosomes in MB49 cells in the co-culture system. Autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ) not only antagonized HPP-induced Autophagy but also attenuated the inhibitory effects of HPP on MB49 cell proliferation in the co-culture system. HPP or RAW264.7 alone was not sufficient to induce Autophagy in MB49 cells. In addition, HPP suppressed the protein expression of the PI3K/Akt/mTOR pathway in MB49 cells in the co-culture system.

Discussion and conclusions: HPP induced bladder Cancer cell Autophagy by regulating macrophages in the co-culture system, resulting in the inhibition of Cancer cell proliferation. The PI3K/Akt/mTOR pathway was involved in HPP-induced Autophagy in the co-culture system.

Bladder cancer; PI3K/Akt/mTOR pathway.