Polysaccharides Derived from Saposhnikovia divaricata May Suppress Breast Cancer Through Activating Macrophages

Saposhnikovia divaricata (SD) has been used in traditional Chinese medicine to treat pain, inflammation, and arthritis. Recently, it has been reported that SD extract may inhibit tumor growth, but the mechanism involved is elusive. The aim of this study was to investigate the anti-tumor activity of polysaccharides derived from SD in breast cancer and the underlying mechanisms.

Polysaccharides isolated from SD were analyzed using Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS). Their effects on cell growth of U937, MCF-7, and MDA-MB-231, and tumor growth in a mouse MDA-MB 231 xenograft model were examined. Their role in U937 activation, MCF-7, and MDA-MB 231 cytokine release profiles were also tested.

In vitro studies showed that SD polysaccharides (SDPs) promoted U937 cell growth dose-dependently, with no obvious effect on growth of breast cancer cell lines MCF-7 and MDA-MB-231. SDP also showed an antagonistic effect against the growth inhibition of U937 by the culture supernatants of MCF-7 and MDA-MB-231, and reversed the polarization status of U937. Treatment of SCID mice bearing MDA-MB-231-derived xenograft tumors with SDP significantly reduced tumor growth. At all tested concentrations, no obvious toxic side-effects were recorded.

We tentatively concluded that SDPs potently promote the growth of U937 and activate it to inhibit the tumor growth of SCID mice bearing MDA-MB-231-derived xenograft tumors indirectly, with no obvious growth inhibition effects on MCF-7 and MDA-MB-231 in vitro. Our finding indicated that SDP could be a potential anticancer agent for breast cancer.