Analysis of CD20-dependent cellular cytotoxicity by G-CSF-stimulated neutrophils

Abstract

Rituximab, a chimeric CD20 monoclonal antibody (mAb), is widely used in the treatment of patients with low-grade nonHodgkin's lymphoma. Possible anti-tumour mechanisms involve complement-mediated lysis and/or antibody-dependent cellular cytotoxicity (ADCC). Because G-CSF greatly enhances the cytotoxicity of neutrophils (PMN) in ADCC, the clinical efficacy of rituximab might be enhanced by the addition of G-CSF. Therefore, we investigated the neutrophil-mediated CD20-dependent cellular cytotoxicity in B cell lines. In contrast to previous studies by others, we found that G-CSF-primed PMN are capable of functioning as effector cells in CD20-dependent cellular cytotoxicity. However, HLA class II mAbs were far more effective. The differences between HLA class II-and CD20-mediated PMN-ADCC were not due to: (1) the use of chimeric (hIgG1) mAbs vs mIgG2a mAbs; (2) HLA class II-induced apoptosis as an 'ADCC-sensitising' mechanism; (3) CD20-induced inhibition of ADCC; (4) inferior membrane mobility of CD20. Analysis of Fc␥receptor (Fc␥R) involvement showed that although CD20-induced ADCC was mediated mainly via Fc␥RI, for optimal lysis Fc␥RI and Fc␥RII were both required. In contrast, in HLA class II-dependent ADCC both Fc␥RI and II were capable of independently inducing maximum lysis. The mechanism underlying these differences in Fc␥R-binding and activation remains to be elucidated. Leukemia (2002) 16, 693-699.

Treatment of relapsed B-cell non-Hodgkin's lymphoma with a combination of chimeric anti-CD20 monoclonal antibodies (rituximab) and G-CSF: final report on safety and efficacy

“…Although in our study the influence of G-CSF on the expression of FcgRIIIa NK was not investigated, we did find a decrease in the expression of FcgRIIIb on neutrophils from all patients. Since we previously demonstrated that ADCC of G-CSF-stimulated neutrophils on B cells was mediated mainly by FcgRI, 28 we do not think that the decrease in FcgRIIIb expression on the neutrophils influenced the response to the combination of rituximab and G-CSF in this study.…”

“…20 We found however, that chimeric CD20 mAbs were capable of inducing ADCC in B cells with G-CSF-primed neutrophils as effector cells, whereas unstimulated neutrophils could not induce CD20-dependent ADCC. 28 Thus, as intended, G-CSF administration resulted in FcgRI-positive, cytotoxic neutrophils. Last systemic chemotherapy regimen.…”

Rituximab therapy in malignant lymphoma

“…Currently, only phase II studies or preliminary data are available preventing any definitive conclusions (Davis et al, 2000b;Kimby, 2002). Phase I trials combining rituximab with other cytokines such as IL-2, IL-12, granulocyte-colony stimulating factor and granulocyte macrophage colonystimulating factor have shown promising preliminary results that need to be confirmed in phases II trials (van der Kolk et al, 2002;Eisenbeis et al, 2004).…”

Pegfilgrastim Enhances the Antitumor Effect of Therapeutic Monoclonal Antibodies

“…FcgRIIIb is the most abundant Fcg receptor on neutrophils, but evidence suggests that it is not involved in efficient tumor cell cytotoxicity (15). Antibody-dependent killing of tumor cells by neutrophils in the absence of G-CSF is described to be nonexistent or weak (16,17) and is likely mediated through FcgRIIa (18). Therefore, specific targeting of FcgRI has been proposed, as this may overcome potential inhibitory signals through FcgRIIb when IgG mAbs are employed (19).…”