(2003) report the antitumor activities of CpG ODN.6 In FCCP particular, intra-tumoral (i.t.) injection of CpG ODN offers been shown to be superior to systemic administration through the induction of i.t. and with CpG ODN only in SCID mice ( em P /em ? ?0.05 and em P /em ? ?0.01, respectively). These results suggested the combination therapy with anti-BST2 mAb and CpG ODN has a significant antitumor activity and induces tumor infiltration of NK cells and macrophages. Combination therapy with CpG ODN and anti-BST2 mAb or additional antitumor mAb depending on ADCC may symbolize a new treatment option for malignancy. strong class=”kwd-title” Keywords: Antitumor antibody, bone marrow stromal antigen 2, CpG oligodeoxynucleotides, macrophage, natural killer FCCP cell Molecularly targeted monoclonal antibodies (mAb) for malignancy have demonstrated highly specific inhibition of target molecules, while avoiding severe adverse events compared with cytotoxic providers.1 Antitumor mAbs, which depend on antibody-dependent cellular cytotoxicity (ADCC) and/or antibody-dependent cellular phagocytosis (ADCP) via immune effector cells such as tumor infiltrating natural killer (NK) cells and macrophages, have been considered to perform an important part.2 In addition, it has been reported that decreased infiltration of NK cells is associated with a worse prognosis.3 Moreover, cancer-induced immunosuppression of NK cells has been reported in individuals with various types of cancers, leading to decreased ADCC.4 Therefore, enhancing tumor infiltration of NK cells and macrophages and reducing immmunosuppression are important to induce efficient ADCC and ADCP in individuals with malignancy. CpG oligodeoxynucleotides (ODN) are potent immunostimulants identified by Toll-like receptor 9 on dendritic cells and B cells.5 Ishii em et?al /em . (2003) statement the antitumor activities of CpG ODN.6 In particular, intra-tumoral (i.t.) injection of CpG ODN offers been shown to be FCCP superior to systemic administration through the induction of i.t. infiltration of NK cells.6 Previously, our group reported that bone marrow stromal antigen 2 (BST2) is a therapeutic target for FCCP endometrial malignancy and demonstrated a potent activity of anti-BST mAb against BST2-positive endometrial malignancy cells through ADCC.7 BST2 was originally identified as a cell surface membrane and expression levels of BST2 are increased in myeloma,8 making it a potential target for antibody-based therapies against malignancy. Because CpG ODN induce i.t. infiltration of NK cells and macrophages, combination therapy with CpG ODN with molecularly targeted mAb depending on ADCC and/or ADCP may demonstrate superior synergistic antitumor activity. The aim of the present study was to evaluate the synergistic antitumor activity of anti-BST2 mAb and CpG ODN and to elucidate the underlying mechanisms using a xenograft model of BST2-positive endometrial malignancy cells. Materials and Methods Cell lines and tradition HEC-88nu cells were from the Japanese Collection of Study Bioresources (JCRB, Osaka, Japan) and managed in DMEM (Wako Pure Chemical Industries, Osaka, Japan) supplemented with 20% FBS and 1% penicillinCstreptomycin (Nacalai Tesque, Kyoto, Japan) at 37C under a humidified atmosphere with 5% CO2. All experiments are explained in Supplementary Data S1. Results Anti-bone marrow stromal antigen 2 monoclonal antibody and CpG oligodeoxynucleotides show significant dose-dependent antitumor activity To determine the optimum concentrations of anti-BST2 mAb and CpG ODN for combination therapy, we evaluated the individual dose-dependent antitumor activity of anti-BST2 mAb and CpG ODN. For the anti-BST2 mAb group, SCID mice xenografted with tumor cells were treated with i.p. injection of 400?L of PBS or anti-BST2 mAb (12.5, 50 and 200?g in 400?L of PBS/mouse). As demonstrated in Figure?Number1(a),1(a), anti-BST2 mAb exhibited a significant dose-dependent reduction in tumor weight ( em P?=? /em 0.0135) and a dose-dependent tendency toward reduced tumor volume ( em P?=? /em 0.0552). In the CpG ODN group, xenografted SCID mice were treated with i.t. injection of PBS or CpG ODN (10, 20 and 40?g in 10?L of PBS/mouse). As demonstrated in Number?Figure1(b),1(b), CpG ODN exhibited a significant dose-dependent reduction in tumor volume and tumor weight ( em P?=? /em 0.0319 and em P?=? /em 0.0196, respectively). These results demonstrate that both anti-BST2 mAb and CpG ODN have a dose-dependent antitumor activities. Open in a separate window Number 1 Anti-bone marrow stromal antigen 2 (BST2) monoclonal antibodies (mAb) and CpG oligodeoxynucleotides (ODN) monotherapy have dose-dependent antitumor activity in SCID Rabbit Polyclonal to TLK1 mice: (a) xenografted SCID mice treated with.