Role of Calcium Signaling in GA101-Induced Cell Death in Malignant Human B Cells.

Simon Latour,Ariel Savina,Anne-Marie Vacher,Pierre Soubeyran,Valérie Le Morvan,Pierre Vacher,Laurence Bresson-Bepoldin,Marion Zanese,Fontanet Bijou,Francoise Durrieu,Nelly Menard

doi:10.3390/cancers11030291

Abstract

GA101/obinutuzumab is a novel type II anti-CD20 monoclonal antibody (mAb), which is more effective than rituximab (RTX) in preclinical and clinical studies when used in combination with chemotherapy. Ca2+ signaling was shown to play a role in RTX-induced cell death. This report concerns the effect of GA101 on Ca2+ signaling and its involvement in the direct cell death induced by GA101. We reveal that GA101 triggered an intracellular Ca2+ increase by mobilizing intracellular Ca2+ stores and activating Orai1-dependent Ca2+ influx in non-Hodgkin lymphoma cell lines and primary B-Cell Chronic Lymphocytic Leukemia (B-CLL) cells. According to the cell type, Ca2+ was mobilized from two distinct intracellular compartments. In Raji, BL2, and B-CLL cells, GA101 induced a Ca2+ release from lysosomes, leading to the subsequent lysosomal membrane permeabilization and cell death. Inhibition of this calcium signaling reduced GA101-induced cell death in these cells. In SU-DHL-4 cells, GA101 mobilized Ca2+ from the endoplasmic reticulum (ER). Inhibition of ER replenishment, by blocking Orai1-dependent Ca2+ influx, led to an ER stress and unfolded protein response (UPR) which sensitized these cells to GA101-induced cell death. These results revealed the central role of Ca2+ signaling in GA101’s action mechanism, which may contribute to designing new rational drug combinations improving its clinical efficacy.

Highlights

The anti-CD20 monoclonal antibody, rituximab (RTX), combined with chemotherapy, became the standard regimen for treating non-Hodgkin lymphomas (NHL), such as diffuse largeB-cell lymphoma (DLBCL), follicular lymphoma (FL), and chronic lymphocytic leukemia (CLL) [1–3]
Our results revealed that tunicamycin did not induce cell death in B-Cell Chronic Lymphocytic Leukemia (B-CLL) or sensitize cells to GA101 (Figure 5G), suggesting that CLL may be resistant to 2+ influx and lysosomal membrane permeabilization (LMP) in GA101-induced cell death in primary B-Cell Chronic
Release and subsequent LMP were responsible for the cell death induced by GA101 in BL2 and Raji but not in SU-DHL-4 cells; (3) in SU-DHL-4 cells, cell death was repressed by Orai1-dependent Ca2+

Summary

Introduction

The anti-CD20 monoclonal antibody (mAb), rituximab (RTX), combined with chemotherapy, became the standard regimen for treating non-Hodgkin lymphomas (NHL), such as diffuse largeB-cell lymphoma (DLBCL), follicular lymphoma (FL), and chronic lymphocytic leukemia (CLL) [1–3]. The anti-CD20 monoclonal antibody (mAb), rituximab (RTX), combined with chemotherapy, became the standard regimen for treating non-Hodgkin lymphomas (NHL), such as diffuse large. B-cell lymphoma (DLBCL), follicular lymphoma (FL), and chronic lymphocytic leukemia (CLL) [1–. A significant number of patients with DLBCL and most patients with FL or CLL are resistant or relapse [4]. Given that CD20 is highly and expressed on the surface of B cells, it constitutes an ideal therapeutic target in NHL. The development of a new anti-CD20 mAb was the subject of intensive research over the past few years. Anti-CD20 mAbs are generally divided into two distinct classes. Type I mAbs, such as rituximab, induce antibody-dependent cell-mediated cytotoxicity (ADCC), complement dependent

Methods

Results

Conclusion