Elotuzumab, targeting signaling lymphocytic activation molecule family 7 (SLAMF7), has been approved in combination with lenalidomide and dexamethasone (ELd) for relapsed/refractory multiple myeloma (MM) based on the findings of the phase III randomized trial ELOQUENT-2 (NCT01239797). Four-year follow-up analyses of ELOQUENT-2 have demonstrated that progression-free survival was 21% in ELd versus 14% in Ld. Elotuzumab binds a unique epitope on the membrane IgC2 domain of SLAMF7, exhibiting a dual mechanism of action: natural killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC) and enhancement of NK cell activity. The ADCC is mediated through engagement between Fc portion of elotuzumab and FcgRIIIa/CD16 on NK cells. Enhanced NK cell cytotoxicity results from phosphorylation of the immunoreceptor tyrosine-based switch motif (ITSM) that is induced via elotuzumab binding and recruits the SLAM-associated adaptor protein EAT-2. The coupling of EAT-2 to the phospholipase Cg enzymes SH2 domain leads to enhanced Ca2+ influx and MAPK/Erk pathway activation, resulting in granule polarization and enhanced exocytosis in NK cells. Elotuzumab does not stimulate the proliferation of MM cells due to a lack of EAT-2. The inhibitory effects of elotuzumab on MM cell growth are not induced by the lack of CD45, even though SHP-2, SHP-1, SHIP-1, and Csk may be recruited to phosphorylated ITSM of SLAMF7. ELd improves PFS in patients with high-risk cytogenetics, i.e. t(4;14), del(17p), and 1q21 gain/amplification. Since the immune state is paralytic in advanced MM, the efficacy of ELd with minimal toxicity may bring forward for consideration of its use in the early stages of the disease.
We describe a 57-year-old woman who was diagnosed as precursor B-cell acute lymphoblastic leukemia with marked eosinophilia (ALL-eo). She presented with low grade fever and eosinophilia (absolute count 16.5 × 10(9)/l). Most of eosinophils had hypogranular cytoplasm. Immature cells were absent in her peripheral blood. Since her platelet count was low, bone marrow examination was carried out. 57.2 % of nucleated cells were blastic cells positive for CD10, 19, and 20. Chromosomal analysis revealed a karyotype of 46,XX,t(5;14)(q31;q32). Despite induction chemotherapy, her disease progressed and she died of sepsis a month later. ALL-eo is extremely rare and the diagnosis might be delayed unless leukemic cells are seen in peripheral blood. Therefore, bone marrow should be examined as soon as possible in cases with eosinophilia not only for the differential diagnosis of eosinophilic disorders but also not to overlook ALL-eo.
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