We have previously reported that adoptive transfer of tumor-draining lymph node (TDLN) B cells confers tumor regression in a spontaneous pulmonary metastasis mouse model of breast cancer. In this study, we identified IL-10-producing cells within these B cells, and found that IL-10 removal, either by using IL-10−/− TDLN B cells or by systemic neutralization of IL-10, significantly augmented the therapeutic efficacy of adoptively transferred TDLN B cells. Depletion of IL-10 in B-cell adoptive transfers significantly increased cytotoxic lymphocytes (CTLs) and B-cell activity of peripheral blood mononuclear cells (PBMCs) and splenic cells in the recipient. Activated TDLN B cells express Fas ligand, which was further enhanced by co-culture of these TDLN B cells with 4T1 tumor cells. Effector B cells killed tumor cells directly in vitro in an antigen-specific and Fas ligand-dependent manner. Trafficking of TDLN B cells in vivo suggested that they were recruited to the tumor and lung as well as secondary lymphoid organs. These findings further define the biological function of antitumor effector B cells, which may offer alternative cellular therapies to cancer.

Osteosarcoma is one of the most malignant neoplasms in adolescents, and it generally develops multidrug resistance. Escin, a natural mixture of triterpene saponins isolated from Aesculus hippocastanum (horse chestnut), has demonstrated potent anti-tumour potential in vitro and in vivo. In the present study, we found that escin inhibited osteosarcoma proliferation in a dose- and time-dependent manner. Additionally, escin-induced apoptosis was evidenced by the increased expression of caspase-related proteins and the formation of apoptotic bodies. Escin also induced autophagy, with elevated LC3, ATG5, ATG12 and Beclin expression as well as autophagosome formation. Inhibition of escin-induced autophagy promoted apoptosis. Moreover, p38 mitogen-activated protein kinases (MAPKs) and reactive oxygen species (ROS) were activated by escin. A p38 MAPK inhibitor partially attenuated the autophagy and apoptosis triggered by escin, but a ROS scavenger showed a greater inhibitory effect. Finally, the therapeutic efficacy of escin against osteosarcoma was demonstrated in an orthotopic model. Overall, escin counteracted osteosarcoma by inducing autophagy and apoptosis via the activation of the ROS/p38 MAPK signalling pathway; these findings provide evidence for escin as a novel and potent therapeutic for the treatment of osteosarcoma.