Recent studies have demonstrated that synthetic CpG-ODNs induce regression of highly immunogenic tumors by engaging both the innate and the adaptive immune systems. CpG-ODNs are currently being tested in clinical trials for the treatment of non-Hodgkin B-cell lymphoma, which expresses TLR9 [15]. However, only limited information is currently available about the sensitivity to CpG-ODNs of primary malignant B-cells of different non-Hodgkin lymphoma entities.

Understanding their direct effect on malignant B-cells is important as we consider how this potent class of agents might be used in the immunotherapy of lymphoma. Here, we found that A20.IIA malignant murine cells, related to diffuse large B cells, express TLR9 and are sensitive to CpG-B ODN stimulation in vitro. As reported previously, CpG-ODNs induce a dose-dependent SP600125 in vitro antiproliferative effect [16] and increase apoptotic cell death [17]. This apoptosis has been described as caspase-dependent and is accompanied by up-regulation

of CD95/Fas and its ligand [9]. Another group demonstrated that TLR9 signaling by CpG-B ODNs leads to NF-kB-dependent click here production of autocrine IL-10, which then activates JAK/STAT pathway-dependent tyrosine phosphorylation of STAT1 proteins and thereby engenders an apoptotic pathway in human chronic lymphocytic leukemia B-cells [10]. Comparing primary B-cell lymphomas from patient samples, other authors have showed that cell responsiveness to CpG-ODNs varies, with different GSK126 mw degrees of activation and apoptosis induction [9]. Several studies have reported that CpG-ODNs induce activation of normal B-cells and block apoptosis [7]. Although the molecular mechanisms of these

effects remain unclear, it has been Cobimetinib mouse suggested that reactive oxygen species (ROS) and NFkB activation may play a role [18]. An important question is whether the in vitro responses to CpG motifs that have been observed could produce an in vivo antitumor effect on DLBCL lymphoma mouse models. We used 3 mouse models to begin to answer this question: a primary systemic lymphoma model (subcutaneous lymphoma) and 2 primary central nervous system lymphoma subtypes (cerebral and ocular lymphoma mouse models). The brain and eyes, considered to be immune sanctuaries, are relatively isolated from the systemic immune system by anatomic and physiologic barriers that maintain a local immune tolerance to protect neuronal cells from inflammation [19]. The use of these different models allowed us to compare the responsiveness to CpG-ODNs of the same tumor cells located in different immune microenvironments. Thus, we demonstrated that local administration of CpG-ODNs into subcutaneous lymphoma decreased the tumor burden. This effect is probably attributable to immune cell activation of NK cells and DCs, which activates innate and adaptive immunity. In addition, the CpG-ODNs inhibited proliferation and induced apoptosis of TLR9-positive tumor cell lines in vitro.