Y particular for CDSuping Zhanga,1, Christina C. N. Wua,1, JessieF. Fecteaua, Bing Cuia, Liguang Chena, Ling Zhanga, Rongrong Wua, Laura Rassentia, Fitzgerald Laoa, Stefan Weigandb, and Thomas J. Kippsa,a Division of Medicine, University of California at San Diego Moores Cancer Center, La Jolla, CA 92093; and bDepartment of Discovery Oncology, Pharma Research, and Early Development, Roche Diagnostics GmbH, 82377 Penzberg, GermanyEdited by Dennis A. Carson, University of California at San Diego, La Jolla, CA, and authorized March four, 2013 (received for critique December 20, 2012)Chronic lymphocytic leukemia (CLL) cells express high levels of CD44, a cellsurface glycoprotein receptor for hyaluronic acid. We discovered that a humanized mAb distinct for CD44 (RG7356) was directly cytotoxic for leukemia B cells, but had little effect on typical B cells. Additionally, RG7356 could induce CLL cells that expressed the zetaassociated protein of 70 kDa (ZAP70) 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 once they were stimulated through ligation on the Bcell receptor with anti. RG7356 induced rapid internalization of CD44 on CLL cells at 37 , resulting in decreased expression of ZAP70, which we discovered was complexed with CD44. Administration of this mAb at a concentration of 1 mg/kg to immunedeficient mice engrafted with human CLL cells resulted in comprehensive clearance of engrafted leukemia cells. These studies indicate that this mAb could have therapeutic activity, especially in individuals with CLL that express ZAP70.196862-45-0 supplier cell survivalmight happen in vivo, in which case CD44 could possibly be a great target for therapy. In this study, we evaluated the expression amount of surface CD44 on CLL cells and examined the activity of a humanized antiCD44 monoclonal antibody (mAb; RG7356; Roche) (15) on leukemia cells in vitro and in vivo. ResultsExpression of CD44 on CLL Cells. CLL cells from 59 patients and| preclinical research | animal model | antibody therapycell chronic lymphocytic leukemia (CLL) is characterized by the clonal expansion of mature, antigenstimulated CD5/ CD23 B cells in blood, secondary lymphoid tissues, and marrow (1). Many of the circulating CLL cells in patients are arrested inside the G0/G1 phase in the cell cycle and express higher levels of antiapoptotic proteins (two). CLL as a result has been characterized as a approach of defective apoptosis, in lieu of elevated proliferation. Nonetheless, regardless of their apparent longevity in vivo, CLL cells undergo spontaneous and druginduced apoptosis in vitro, unless rescued by monocytederived Nurselike cells (NLCs), follicular dendritic cells, or mesenchymal stromal cells (MSCs) (3).Ethyl 4-methyl-1H-pyrrole-2-carboxylate web Therefore, it has been postulated that CLL cells receive survival signals from these accessory cells, which constitute component on the CLL Bcell microenvironment in secondary lymphoid tissues and marrow (six).PMID:33484233 These survival signals can inhibit spontaneous or druginduced apoptosis, particularly for CLL cells that express unmutated Ig heavychain variable genes (IGHVs) and/or the zetaassociated protein of 70 kDa (ZAP70), which normally will not be expressed by typical B cells (7). Individuals with leukemia cells that possess such qualities usually have a relatively brief interval from diagnosis to initial therapy compared with sufferers with CLL cells that express mutated IGHVs or th.