Dendritic cell differentiation and tumor cell apoptosis induced by components of a poly-phenylpropanoid polysaccharide complex.

BACKGROUND As part of the indigenous folk medicine in Japan, aqueous extracts of pine cones have been used for over a century to treat cancer and other illnesses and references to their use can be found in ancient Greek literature. However, the mechanisms by which such extracts work are largely unknown. MATERIALS AND METHODS Murine bone marrow (BM)-derived dendritic cells (DCs) and human monocyte U937 cells were treated in vitro with an extract prepared from pine cones (termed poly-phenylpropanoid polysaccharide complex, PPC). RESULTS The components of the PPC were separated into different molecular weight fractions with distinct biological activities. One fraction, consisting of relatively high molecular weight material, was found to induce the differentiation of murine BM cells into immature DC, as well as the maturation of immature DCs into mature DCs. A second fraction, consisting of low molecular weight material, was found to inhibit the in vitro growth of the U937 cells and two other human cancer cell lines. The inhibition of tumor cell growth was found to be associated with the generation of reactive oxygen species (ROS) and the induction of a mitochondria-dependent apoptotic pathway. CONCLUSION The effects on dendritic cells and the inhibition of tumor growth, if they occur to a significant level in vivo, could help explain the apparent usefulness of PPC in the treatment of cancer.