title: CTLA-4 is not restricted to the lymphoid cell lineage and can function as a target molecule for apoptosis induction of leukemic cells.
abstract: The expression of cytotoxic T-lymphocyte antigen-4 (CTLA-4) molecule in human normal and neoplastic hematopoietic cells, both on the cell membrane and in the intracellular compartment, was evaluated. Flow cytometric analysis carried out with a panel of anti-CTLA-4 human single-chain fragment of variable domain (scFv) antibodies revealed that CTLA-4 was not expressed on the surface, whereas it was highly expressed within the cytoplasm, in freshly isolated peripheral blood mononuclear cells (PBMCs), T cells, B cells, CD34(+) stem cells, and granulocytes. Various treatments with agents able to specifically activate each cell type induced CTLA-4 expression on the surface of these cells. Similarly, increased CTLA-4 expression was observed in different hematopoietic cell lines although they also expressed surface CTLA-4, at different degrees of intensity, before activation. Surprisingly, CTLA-4 RNA transcripts were detectable in such cell lines only after nested polymerase chain reaction (PCR) specific for CTLA-4 extracellular domain, suggesting a very fast CTLA-4 RNA processing accompanied by prolonged CTLA-4 protein accumulation. We further demonstrated surface expression of CTLA-4 in a variety of acute and chronic myeloid leukemias (AMLs and CMLs) and B- and T-lymphoid leukemias, either adult or pediatric. CTLA-4 was expressed in 25% to 85% of AMLs and CMLs depending on the leukemia subtype and the epitope analyzed, whereas in acute B- and T-leukemias CTLA-4 expression was mainly cytoplasmic. Chronic B leukemias appeared to express CTLA-4, both on the surface and in cytoplasm, whereas few cases tested of chronic T leukemias were negative. Two anti-CTLA-4 immunotoxins (scFvs-saporin) induced in vitro apoptosis of neoplastic cells from a representative AML, suggesting a novel immunotherapeutic approach to AML based on CTLA-4 targeting.
authors.affiliation: Laboratory of Immunogenetics and Laboratory of Molecular Morphogenesis, National Cancer Research Institute, Advanced Biotechnology Center, Genoa, Italy. mariapia.pistillo@istge.it
authors.forename: Maria Pia
authors.initials: MP
authors.lastname: Pistillo
authors.forename: Pier Luigi
authors.initials: PL
authors.lastname: Tazzari
authors.forename: Giulio Lelio
authors.initials: GL
authors.lastname: Palmisano
authors.forename: Ivana
authors.initials: I
authors.lastname: Pierri
authors.forename: Andrea
authors.initials: A
authors.lastname: Bolognesi
authors.forename: Francesca
authors.initials: F
authors.lastname: Ferlito
authors.forename: Paolo
authors.initials: P
authors.lastname: Capanni
authors.forename: Letizia
authors.initials: L
authors.lastname: Polito
authors.forename: Marina
authors.initials: M
authors.lastname: Ratta
authors.forename: Stefano
authors.initials: S
authors.lastname: Pileri
authors.forename: Milena
authors.initials: M
authors.lastname: Piccioli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Basso
authors.forename: Laura
authors.initials: L
authors.lastname: Rissotto
authors.forename: Roberto
authors.initials: R
authors.lastname: Conte
authors.forename: Marco
authors.initials: M
authors.lastname: Gobbi
authors.forename: Fiorenzo
authors.initials: F
authors.lastname: Stirpe
authors.forename: Giovanni Battista
authors.initials: GB
authors.lastname: Ferrara
mesh_terms: D000069594:Abatacept; D015703:Antigens, CD; D000943:Antigens, Differentiation / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017209:Apoptosis / Q000187:drug effects*; D001773:Blood Cells; D060908:CTLA-4 Antigen; D002460:Cell Line; D019070:Cell Lineage; D003593:Cytoplasm / Q000737:chemistry; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells; D006801:Humans; D007118:Immunoassay; D018796:Immunoconjugates; D000922:Immunotoxins / Q000494:pharmacology; D007938:Leukemia / Q000473:pathology* / Q000628:therapy; D007962:Leukocytes / Q000166:cytology / Q000378:metabolism; D008213:Lymphocyte Activation; D012333:RNA, Messenger / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D000943:Antigens, Differentiation; D060908:CTLA-4 Antigen; C556706:CTLA4 protein, human; D018796:Immunoconjugates; D000922:Immunotoxins; D012333:RNA, Messenger; D000069594:Abatacept