title: Identification in CLL of circulating intraclonal subgroups with varying B-cell receptor expression and function.
abstract: Chronic lymphocytic leukemia (CLL) is a tumor of circulating B cells, variably stimulated and anergized following exposure to antigen in lymphoid tissues. Down-modulation of surface IgM (sIgM) occurs, but expression and signal capacity can recover in vitro and apparently in vivo during recirculation. We have now dissected individual circulating clones of CLL cases according to sIgM expression level by differential binding to bead-bound anti-IgM. Four clear subgroups (SG1-4) with increasing sIgM were identified in 37/37 cases. Engagement of sIgM induced phosphorylation of PLCγ2 and ERK1/2 at levels ranging from very low in SG1 to high in SG4. Phosphorylation was suppressed by the BTK inhibitor ibrutinib. Expression of CXCR4 also increased from SG1 to SG4, but markers of previous activation and proliferation were dominant in SG1. Incubation of whole CLL populations in vitro led to striking increases in CXCR4 expression as well as recovery of sIgM. Clonal analysis reveals dynamic SGs following presumed antigen stimulation in tissues. SG4 represents a fully recovered, potentially dangerous population equipped to migrate to tissue and receive a proliferative stimulus. SG1 likely represents a postmitotic unresponsive "resting" population. The effect of ibrutinib on the small SG4 population may be the critical factor in therapeutic success.
authors: Haematology Oncology Group.
authors: Vânia
authors: V
authors: Coelho
authors: Sergey
authors: S
authors: Krysov
authors: Andrew
authors: A
authors: Steele
authors: Marina
authors: M
authors: Sanchez Hidalgo
authors: Peter W
authors: PW
authors: Johnson
authors: Prabhjoat S
authors: PS
authors: Chana
authors: Graham
authors: G
authors: Packham
authors: Freda K
authors: FK
authors: Stevenson
authors: Francesco
authors: F
authors: Forconi
mesh_terms: D055910:Antibodies, Immobilized; D001402:B-Lymphocytes / Q000378:metabolism / Q000473:pathology*; D002999:Clone Cells / Q000378:metabolism / Q000473:pathology; D005434:Flow Cytometry; D006801:Humans; D007075:Immunoglobulin M / Q000378:metabolism*; D016130:Immunophenotyping; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000378:metabolism / Q000473:pathology*; D020935:MAP Kinase Signaling System / Q000502:physiology; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism
chemical_list: D055910:Antibodies, Immobilized; C527276:CXCR4 protein, human; D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell; D019718:Receptors, CXCR4; D011956:Receptors, Cell Surface