Alemtuzumab is a recombinant humanized IgG1 monoclonal antibody directed against CD52, an antigen expressed on the surface of normal and malignant B and T lymphocytes. Alemtuzumab is approved for the treatment of B-cell chronic lymphocytic leukemia (B-CLL), but the exact mechanism by which the antibody depletes malignant lymphocytes in vivo is not clearly defined. To address this issue, the anti-tumor activity of alemtuzumab was studied in disseminated and subcutaneous xenograft tumor models. The density of CD52 target antigen on the surface of tumor cells appeared to correlate with the anti-tumor activity of alemtuzumab. Deglycosylation of alemtuzumab resulted in a loss of cytotoxicity in vitro and was found to abolish anti-tumor activity in vivo. Individual inactivation of effector mechanisms in tumor-bearing mice indicated that the protective activity of alemtuzumab in vivo was primarily dependent on ADCC mediated by neutrophils and to a lesser extent NK cells. Increasing the number of circulating neutrophils by treatment with G-CSF enhanced the anti-tumor activity of the antibody, thus providing further evidence for the involvement of neutrophils as effector cells in the activity of alemtuzumab.
"The therapeutic antibody was withdrawn from the market in 2012 in order to optimize the pending launch of the agent as a treatment for multiple sclerosis. The predominant mechanism of action of alemtuzumab in vivo has not been clearly defined but involvement of ADCC mediated by NK cells and neutrophils has been suggested by studies employing a human CD52 transgenic mouse model and a xenograft model (Hu et al., 2009; Siders et al., 2010). In addition, CDC and direct induction of apoptosis have been identified as other potential mechanisms of action in in vitro studies (Table 1) (Crowe et al., 1992; Mone et al., 2006). "
[Show abstract][Hide abstract] ABSTRACT: In the last decade several therapeutic antibodies have been Federal Drug Administration (FDA) and European Medicines Agency (EMEA) approved. Although their mechanisms of action in vivo is not fully elucidated, antibody-dependent cellular cytotoxicity (ADCC) mediated by natural killer (NK) cells is presumed to be a key effector function. A substantial role of ADCC has been demonstrated in vitro and in mouse tumor models. However, a direct in vivo effect of ADCC in tumor reactivity in humans remains to be shown. Several studies revealed a predictive value of FcγRIIIa-V158F polymorphism in monoclonal antibody treatment, indicating a potential effect of ADCC on outcome for certain indications. Furthermore, the use of therapeutic antibodies after allogeneic hematopoietic stem cell transplantation is an interesting option. Studying the role of the FcγRIIIa-V158F polymorphism and the influence of Killer-cell Immunoglobuline-like Receptor (KIR) receptor ligand incompatibility on ADCC in this approach may contribute to future transplantation strategies. Despite the success of approved second-generation antibodies in the treatment of several malignancies, efforts are made to further augment ADCC in vivo by antibody engineering. Here, we review currently used therapeutic antibodies for which ADCC has been suggested as effector function.
Frontiers in Immunology 03/2013; 4:76. DOI:10.3389/fimmu.2013.00076
"Since SCID-BEIGE mice lack T and B lymphocytes as well as functional natural killer (NK) cells, it is possible that the CCR4+ Mac-1 tumor cells were eliminated by h1567 through neutrophil-dependent ADCC as neutrophils are intact in SCID-BEIGE mice and they express FcγRIIIA receptors which have been shown to mediated ADCC , . Tumor sections were excised 21 days after AAV8 gene transfer and analyzed histologically for expression of Ly6G, a member of the Ly-6 family of glycosyl-phosphatidylinositol (GPI)-anchored proteins expressed on murine neutrophils , . "
[Show abstract][Hide abstract] ABSTRACT: Although several therapeutic options have become available for patients with Cutaneous T-cell Lymphoma (CTCL), no therapy has been curative. Recent studies have demonstrated that CTCL cells overexpress the CC chemokine receptor 4 (CCR4).
In this study, a xenograft model of CTCL was established and a recombinant adeno-associated viral serotype 8 (AAV8) vector expressing a humanized single-chain variable fragment (scFv)-Fc fusion (scFvFc or "minibody") of anti-CCR4 monoclonal antibody (mAb) h1567 was evaluated for curative treatment. Human CCR4(+) tumor-bearing mice treated once with intravenous infusion of AAV8 virions encoding the h1567 (AAV8-h1567) minibody showed anti-tumor activity in vivo and increased survival. The AAV8-h1567 minibody notably increased the number of tumor-infiltrating Ly-6G(+) FcγRIIIa(CD16A)(+) murine neutrophils in the tumor xenografts over that of AAV8-control minibody treated mice. Furthermore, in CCR4(+) tumor-bearing mice co-treated with AAV8-h1567 minibody and infused with human peripheral blood mononuclear cells (PBMCs), marked tumor infiltration of human CD16A(+) CD56(+) NK cells was observed. The h1567 minibody also induced in vitro ADCC activity through both mouse neutrophils and human NK cells.
Overall, our data demonstrate that the in vivo anti-tumor activity of h1567 minibody is mediated, at least in part, through CD16A(+) immune effector cell ADCC mechanisms. These data further demonstrate the utility of the AAV-minibody gene transfer system in the rapid evaluation of candidate anti-tumor mAbs and the potency of h1567 as a potential novel therapy for CTCL.
PLoS ONE 09/2012; 7(9):e44455. DOI:10.1371/journal.pone.0044455 · 3.23 Impact Factor
"Pre-clinical studies evaluating the treatment of advanced rectal carcinoma have demonstrated that granulocytes are the most effective cell population.3 The anti-tumor activity of alemtuzumab, a monoclonal antibody approved for the treatment of B-cell chronic lymphocytic leukemia, has been shown to be mediated by neutrophils, since increasing the number of circulating neutrophils enhanced the anti-tumor activity of the antibody.4 "
[Show abstract][Hide abstract] ABSTRACT: To verify if patients with cervical neoplasia produce mediators that reduce leukocyte function.
Control neutrophils incubated with normal serum or serum from pre-invasive or invasive neoplasia patients were assayed for chemotaxis. Mediators were assayed in serum and in leukocyte supernatants. Experiments were also performed in random patients after surgery.
Neutrophils incubated with patient sera, but not normal sera, failed to migrate towards the chemoattractants. In invasive neoplasia compared to controls, IL-6 and IL-8, and IL-10 and TNF-α were elevated in serum and in neutrophil supernatants, respectively. Nitrite levels were elevated in mononuclear cell supernatants from patients than controls. After surgery, serum cytokine levels were reduced, mainly in pre-invasive patients. Neutrophils treated with serum from pre-invasive patients undergone surgery had restored migration.
Patients with cervical neoplasia produce mediators, predominantly induced by tumor cells, able to impair the inflammatory response at very early stages of disease.
Clinical Medicine Insights: Oncology 05/2012; 6:233-42. DOI:10.4137/CMO.S9518
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