Hodgkin lymphoma (HL) is characterized by the presence of a small number of tumor cells in a rich background of inflammatory cells, but the contribution of the abundant nontumor cells to HL pathogenesis is poorly understood. We showed that migratory CD4 + cells induced by HL cells were hyporesponsive to T-cell receptor stimulation and suppressed the activation/proliferation of the effector CD4 + T cells in an autologous setting. We further showed that HL cells in the affected lymph nodes were surrounded by a large number of lymphocytes expressing both CC chemokine receptor 4 (CCR4) and FOXP3. These findings indicate that the migratory cells induced by HL cells function as regulatory T (Treg) cells so that these cells create a favorable environment for the tumor cells to escape from host immune system. In addition, we showed that a chimeric anti-CCR4 monoclonal antibody (mAb) could deplete CCR4 + T cells and inhibit the migration of CD4 + CD25 + T cells in vitro. Recognition of the importance of CCR4 + Treg cells in the pathogenesis of HL will allow rational design of more effective treatments, such as use of an anti-CCR4 mAb, to overcome the suppressive effect of CCR4 + Treg cells on the host immune response to tumor cells. (Cancer Res 2006; 66(11): 5716-22)

Purpose: Adult T-cell leukemia/lymphoma (ATLL) has a very poor prognosis. We have developed the humanized defucosylated anti-CC chemokine receptor 4 (CCR4) monoclonal antibody KW-0761 as a next generation immunotherapeutic agent. The first aim of the present study was to evaluate whether the antitumor activity of KW-0761 would likely be sufficient for therapeutic clinical application against ATLL. The second aim was to fully elucidate the mechanism of antibody-dependent cellular cytotoxicity (ADCC) mediated by this defucosylated monoclonal antibody.Experimental Design: The antitumor activity of KW-0761 against ATLL cell lines was evaluated in vitro using human cells and in mice in vivo. Primary ATLL cells from 23 patients were evaluated for susceptibility to autologous ADCC with KW-0761 by two independent methods.Results: KW-0761 showed potent antitumor activity against ATLL cell lines both in vitro and in the ATLL mouse model in vivo. In addition, KW-0761 showed potent antitumor activity mediated by highly enhanced ADCC against primary ATLL cells both in vitro and ex vivo in an autologous setting. The degree of KW-0761 ADCC against primary ATLL cells in an autologous setting was mainly determined by the amount of effector natural killer cells present, but not the amount of the target molecule CCR4 on the ATLL cell surface.Conclusion: KW-0761 should be sufficiently active for therapeutic clinical application for ATLL. In addition, combination treatment strategies that augment natural killer cell activity should be promising for amplifying the effect of KW-0761. In the near future, the actual efficacy of KW-0761 will be established in pivotal clinical trials. Clin Cancer Res; 16(5); 1520-31. ©2010 AACR.

In this study, we investigated the catalytic properties of N,N-dimethylformamide (DMF)-stabilized gold nanoclusters (AuNCs) in the reduction of 4-nitrophenol (PNP) to 4-aminophenol by NaBH(4), a well known model reaction to be catalyzed by metal surfaces. The DMF-stabilized AuNCs were prepared in DMF by a surfactant-free method. The DMF-stabilized AuNCs showed high catalytic activity even when used in small quantities (∼10(-7) g). The pseudo-first-order rate constant (k(app)) and activation energy were estimated to be 3 × 10(-3) s(-1) and 31 kJ mol(-1), respectively, with 1.0 μM of the gold catalyst at 298 K. The catalytic activity of the DMF-stabilized AuNCs was strongly influenced by the layer of adsorbed DMF on the Au NCs. This layer of adsorbed DMF prohibited the reactants from penetrating to the surface of the AuNCs via the diffusion at the beginning of the reaction, resulting in an induction time (t(0)) before PNP reduction began. Restructuring of the DMF layer (essentially a form of activation) was the key to achieving high catalytic activity. In addition, atomically monodisperse Au(25)(SG)(18)NCs (SG: glutathione) showed higher catalytic activity in the PNP reduction (k(app) = 8 × 10(-3) s(-1)) even with a low catalyst concentration (1.0 μM), and there was no induction time (t(0)) in spite of the strongly binding ligand glutathione. This suggested that the catalytically active surface sites of the Au(25)(SG)(18)NCs were not sterically hindered, possibly because of the unique core-shell-like structure of the NCs. Retaining these open sites on AuNCs may be the key to making the NCs effective catalysts.

Purpose There are no suitable small animal models to evaluate human antibody-dependent cellular cytotoxicity (ADCC) in vivo, due to species incompatibilities. Thus, the Wrst aim of this study was to establish a human tumor-bearing mouse model in which human immune cells can engraft and mediate ADCC, but where the endogenous mouse immune cells cannot mediate ADCC. The second aim was to evaluate ADCC mediated in these humanized mice by the defucosylated anti-CC chemokine receptor 4 (CCR4) monoclonal antibody (mAb) which we have developed and which is now in phase I clinical trials. Experimental design NOD/Shi-scid, IL-2R null (NOG) mice were the recipients of human immune cells, and CCR4-expressing Hodgkin lymphoma (HL) and cutaneous T-cell lymphoma (CTCL) cell lines were used as target tumors. Results Humanized mice have been established using NOG mice. The chimeric defucosylated anti-CCR4 mAb KM2760 showed potent antitumor activity mediated by robust ADCC in these humanized mice bearing the HL or CTCL cell lines. KM2760 signiWcantly increased the number of tumor-inWltrating CD56-positive NK cells which mediate ADCC, and reduced the number of tumor-inWltrating FOXP3-positive regulatory T (Treg) cells in HL-bearing humanized mice. Conclusions Anti-CCR4 mAb could be an ideal treatment modality for many diVerent cancers, not only to directly kill CCR4-expressing tumor cells, but also to overcome the suppressive eVect of Treg cells on the host immune response to tumor cells. In addition, using our humanized mice, we can perform the appropriate preclinical evaluation of many types of antibody based immunotherapy.

Adult T-cell leukemia/lymphoma (ATLL) patients are highly immunocompromised, but the underlying mechanism responsible for this state remains obscure. Recent studies demonstrated that FOXP3, which is a master control gene of naturally occurring regulatory T (Treg) cells, is expressed in the tumor cells from a subset of patients with ATLL. Since most ATLL cells express both CD4 and CD25, these tumors might originate from CD4