Holothurian triterpene glycoside cucumarioside A2-2 induces macrophages activation and polarization in cancer immunotherapy

BACKGROUND

Despite intensive developments of adoptive T cell and NK cell therapies, the efficacy against solid tumors remains elusive. Our study demonstrates that macrophage-based cell therapy could be a potent therapeutic option against solid tumors.

METHODS

To this end, we determine the effect of a natural triterpene glycoside, cucumarioside A2-2 (CA2-2), on the polarization of mouse macrophages into the M1 phenotype, and explore the antitumor activity of the polarized macrophage. The polarization of CA2-2-pretreated macrophages was analyzed by flow cytometry and confocal imaging. The anti-cancer activity of CA2-2 macrophages was evaluated against 4T1 breast cancer cells and EAC cells in vitro and syngeneic mouse model in vivo.

RESULTS

Incubation of murine macrophages with CA2-2 led to polarization into the M1 phenotype, and the CA2-2-pretreated macrophages could selectively target and kill various types of cancer in vitro. Notably, loading near-infrared (NIR) fluorochrome-labeled nanoparticles, MnMEIO-mPEG-CyTE777, into macrophages substantiated that M1 macrophages can target and penetrate tumor tissues in vivo efficiently.

CONCLUSION

In this study, CA2-2-polarized M1 macrophages significantly attenuated tumor growth and prolonged mice survival in the syngeneic mouse models. Therefore, ex vivo CA2-2 activation of mouse macrophages can serve as a useful model for subsequent antitumor cellular immunotherapy developments.

Glycosides from edible sea cucumbers stimulate macrophages via purinergic receptors

Since ancient times, edible sea cucumbers have been considered a jewel of the seabed and used in Asian folk medicine for stimulation of resistance against different diseases. However, the power of this sea food has not been established on a molecular level. A particular group of triterpene glycosides was found to be characteristic metabolites of the animals, responsible for this biological action. Using one of them, cucumarioside A₂-2 (CA₂-2) from the edible Cucumaria japonica species as an example as well as inhibitory analysis, patch-clamp on single macrophages, small interfering RNA technique, immunoblotting, SPR analysis, computer modeling and other methods, we demonstrate low doses of CA₂-2 specifically to interact with P2X receptors (predominantly P2X4) on membranes of mature macrophages, enhancing the reversible ATP-dependent Ca²⁺ intake and recovering Ca²⁺ transport at inactivation of these receptors. As result, interaction of glycosides of this type with P2X receptors leads to activation of cellular immunity.