ABSTRACT
Chronic lymphocytic leukemia (CLL) can be immunosuppressive in humans and mice, and CLL cells share multiple phenotypic markers with regulatory B cells that are competent to produce interleukin (IL)-10 (B10 cells). To identify functional links between CLL cells and regulatory B10 cells, the phenotypes and abilities of leukemia cells from 93 patients with overt CLL to express IL-10 were assessed. CD5(+) CLL cells purified from 90% of the patients were IL-10-competent and secreted IL-10 following appropriate ex vivo stimulation. Serum IL-10 levels were also significantly elevated in CLL patients. IL-10-competent cell frequencies were higher among CLLs with IgV(H) mutations, and correlated positively with TCL1 expression. In the TCL1-transgenic (TCL1-Tg) mouse model of CLL, IL-10-competent B cells with the cell surface phenotype of B10 cells expanded significantly with age, preceding the development of overt, CLL-like leukemia. Malignant CLL cells in TCL1-Tg mice also shared immunoregulatory functions with mouse and human B10 cells. Serum IL-10 levels varied in TCL1-Tg mice, but in vivo low-dose lipopolysaccharide treatment induced IL-10 expression in CLL cells and high levels of serum IL-10. Thus, malignant IL-10-competent CLL cells exhibit regulatory functions comparable to normal B10 cells that may contribute to the immunosuppression observed in patients and TCL1-Tg mice.
Subject(s)
B-Lymphocytes, Regulatory/immunology , B-Lymphocytes/immunology , Interleukin-10/immunology , Leukemia, Lymphocytic, Chronic, B-Cell/immunology , Proto-Oncogene Proteins/metabolism , Proto-Oncogene Proteins/physiology , Animals , B-Lymphocytes/metabolism , B-Lymphocytes/pathology , B-Lymphocytes, Regulatory/metabolism , B-Lymphocytes, Regulatory/pathology , Cells, Cultured , Fluorescent Antibody Technique , Humans , Immunosuppression Therapy , Interleukin-10/metabolism , Leukemia, Lymphocytic, Chronic, B-Cell/metabolism , Leukemia, Lymphocytic, Chronic, B-Cell/pathology , Lipopolysaccharides/pharmacology , Mice , Mice, TransgenicSubject(s)
Anaphase , Cell Cycle Proteins , Fungal Proteins/metabolism , Mitosis , Saccharomyces cerevisiae Proteins , Saccharomyces cerevisiae/cytology , Spindle Apparatus/metabolism , Cell Nucleus/metabolism , Dynactin Complex , Dyneins/genetics , Dyneins/metabolism , Fungal Proteins/genetics , Microtubule-Associated Proteins/genetics , Microtubule-Associated Proteins/metabolism , Mutation/genetics , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolismABSTRACT
GLC7 encodes an essential serine/threonine protein type I phosphatase in Saccharomyces cerevisiae. Three other phosphatases (Ppz1p, Ppz2p, and Sal6p) share >59% identity in their catalytic region with Glc7p. ppz1 ppz2 null mutants have no apparent growth defect on rich media. However, null alleles of PPZ1 and PPZ2, in combination with mutant alleles of GLC7, confer a range of growth defects varying from slow growth to lethality. These results indicate that Glc7p, Ppz1p, and Ppz2p may have overlapping functions. To determine if this overlap extends to interaction with targeting subunits, Glc7p-binding proteins were tested for interaction in the two-hybrid system with the functional catalytic domain of Ppz1p. Ppz1p interacts strongly with a number of Glc7p regulatory subunits, including Glc8p, a protein that shares homology with mammalian PP1 inhibitor I2. Genetic data suggest that Glc8p positively affects both Glc7p and Ppz1p functions. Together our data suggest that Ppz1p and Ppz2p may have overlapping functions with Glc7p and that all three phosphatases may act through common regulatory proteins.