Targeting chronic lymphocytic leukemia cells with a humanized monoclonal antibody specific for CD44

Abstract

Chronic lymphocytic leukemia (CLL) cells express high levels of CD44, a cell-surface glycoprotein receptor for hyaluronic acid. We found that a humanized mAb specific for CD44 (RG7356) was directly cytotoxic for leukemia B cells, but had little effect on normal B cells. Moreover, RG7356 could induce CLL cells that expressed the zeta-associated protein of 70 kDa (ZAP-70) to undergo caspasedependent apoptosis, independent of complement or cytotoxic effector cells. The cytotoxic effect of this mAb was not mitigated when the CLL cells were cocultured with mesenchymal stromal cells (MSCs) or hyaluronic acid or when they were stimulated via ligation of the B-cell receptor with anti-μ. RG7356 induced rapid internalization of CD44 on CLL cells at 37°C, resulting in reduced expression of ZAP-70, which we found was complexed with CD44. Administration of this mAb at a concentration of 1 mg/kg to immune-deficient mice engrafted with human CLL cells resulted in complete clearance of engrafted leukemia cells. These studies indicate that this mAb might have therapeutic activity, particularly in patients with CLL that express ZAP-70.cell survival | preclinical studies | animal model | antibody therapy B -cell chronic lymphocytic leukemia (CLL) is characterized by the clonal expansion of mature, antigen-stimulated CD5+/ CD23+ B cells in blood, secondary lymphoid tissues, and marrow (1). Most of the circulating CLL cells in patients are arrested in the G0/G1 phase of the cell cycle and express high levels of antiapoptotic proteins (2). CLL therefore has been characterized as a process of defective apoptosis, rather than increased proliferation. However, despite their apparent longevity in vivo, CLL cells undergo spontaneous and drug-induced apoptosis in vitro, unless rescued by monocyte-derived Nurse-like cells (NLCs), follicular dendritic cells, or mesenchymal stromal cells (MSCs) (3-6). Thus, it has been postulated that CLL cells receive survival signals from these accessory cells, which constitute part of the CLL B-cell microenvironment in secondary lymphoid tissues and marrow (6). These survival signals can inhibit spontaneous or drug-induced apoptosis, particularly for CLL cells that express unmutated Ig heavy-chain variable genes (IGHVs) and/or the zeta-associated protein of 70 kDa (ZAP-70), which typically is not expressed by normal B cells (7). Patients with leukemia cells that possess such characteristics typically have a relatively short interval from diagnosis to initial therapy compared with patients with CLL cells that express mutated IGHVs or that lack expression of .One of the survival signals received by leukemia cells may be mediated via CD44, a surface glycoprotein receptor for the nonsulfated glycosaminoglycan hyaluronic acid (HA), which typically is found in the microenvironment of lymphoid tissues (13). CLL cells express high levels of CD44, particularly those that express unmutated IGHVs and/or . Upon binding HA in the extracellular matrix, CD44 activates the phosphoinositol 3-kinase (PI3K)/AKT and MAPK/ERK ...

Transcriptional divergence and conservation of human and mouse erythropoiesis

“…For example, CD44 is a critical factor in chronic lymphocytic leukemia disease progression, and the use of antibodies specifically targeting CD44 leads to complete clearance of engrafted leukemic cells in xenograft mouse models (43,44). However, examining the CD44 expression profile from erythroid gene expression datasets indicates that, unlike in mice where Cd44 expression decreases upon maturation, human red cells highly express CD44, an observation that we substantiated using flow cytometric analysis of mature red blood cells (Fig.…”

“…2B). Therefore, caution needs to be applied to translate such models between species: CD44 antibodies might be readily absorbed by mature human red blood cells in the circulation, decreasing the effectiveness of such treatments, which could not be identified in preclinical xenograft models (43,44).…”

Surface markers of liver cancer stem cells and innovative targeted-therapy strategies for HCC (Review)

“…IM7 is a murine monoclonal antibody specifically targeting CD44, which has a confirmed inhibitory effect on tumor growth. Zhang et al (87) reported that RG7356, a humanized antibody against CD44, could induce apoptosis of chronic lymphocytic leukemia cells.…”

The role of adhesion molecules in acute myeloid leukemia and (hemato)oncology: A systematic review

“…CD44 has been identified as a key regulator of AML LSC with no documented effect on engrafted normal hematopoietic cells derived from cord blood or human bone marrow 135 . Very recently, a humanized monoclonal antibody specific for CD44 that targets and directly kills chronic lymphocytic leukemia cells, was identified 136 . The cytotoxic effect of anti-CD44 treatment was not mitigated by interaction with mesenchymal stromal cells or hyaluronic acid.…”