Rhamnogalacturonan II is a Toll-like receptor 4 agonist that inhibits tumor growth by activating dendritic cell-mediated CD8+ T cells

We evaluated the effectiveness of rhamnogalacturonan II (RG-II)-stimulated bone marrow-derived dendritic cells (BMDCs) vaccination on the induction of antitumor immunity in a mouse lymphoma model using EG7-lymphoma cells expressing ovalbumin (OVA). BMDCs treated with RG-II had an activated phenotype. RG-II induced interleukin (IL)-12, IL-1β, tumor necrosis factor-α (TNF-α) and interferon-γ (IFN-γ) production during dendritic cell (DC) maturation. BMDCs stimulated with RG-II facilitate the proliferation of CD8 + T cells. Using BMDCs from the mice deficient in Toll-like receptors (TLRs), we revealed that RG-II activity is dependent on TLR4. RG-II showed a preventive effect of immunization with OVA-pulsed BMDCs against EG7 lymphoma. These results suggested that RG-II expedites the DC-based immune response through the TLR4 signaling pathway. Cancer immunotherapy: Ginseng extract yields potent adjuvant Researchers in Korea report that the immune response against cancer is enhanced by a complex sugar found in the walls of plant cells. Led by Yeong-Min Park of the Pusan National University in Yangsan, the researchers purified the sugar, a polysaccharide called rhamnogalacturonan-II (RG-II), from the leaves of the Asian ginseng plant. In cell culture, the researchers added RG-II to a type of immune cell – dendritic cells – derived from the bone marrow of mice. They showed that the sugar triggered the production of specialized T cells capable of destroying cancerous tissue. They then injected RG-II–treated dendritic cells below the skin of mice with lymphoma and discovered that the treatment delayed tumor growth in the animals. The authors propose that RG-II could be a safe and effective adjuvant to enhance the tumor-killing potential of dendritic cell–based vaccines.