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Maria Pia Pistillo

Publications and source records attributed to Maria Pia Pistillo.

6 recordsLinked to original sources
PubMed2005

CTLA-4 is constitutively expressed on tumor cells and can trigger apoptosis upon ligand interaction.

CTLA-4 (CD152) is a cell surface receptor that behaves as a negative regulator of the proliferation and the effector function of T cells. We have previously shown that CTLA-4 is also expressed on neoplastic lymphoid and myeloid cells, and it can be targeted to induce apoptosis. In our study, we have extended our analysis and have discovered that surface expression of CTLA-4 is detectable by flow cytometry on 30 of 34 (88%) cell lines derived from a variety of human malignant solid tumors including carcinoma, melanoma, neuroblastoma, rhabdomyosarcoma and osteosarcoma (but not in primary osteoblast-like cultures). However, by reverse transcriptase-PCR, CTLA-4 expression was detected in all cell lines. We have also found, by immunohistochemistry, cytoplasmic and surface expression of CTLA-4 in the tumor cells of all 6 osteosarcoma specimens examined and in the tumour cells of all 5 cases (but only weakly or no positivity at all in neighbouring nontumor cells) of ductal breast carcinomas. Treatment of cells from CTLA-4-expressing tumor lines with recombinant forms of the CTLA-4-ligands CD80 and CD86 induced apoptosis associated with sequential activation of caspase-8 and caspase-3. The level of apoptosis was reduced by soluble CTLA-4 and by anti-CTLA-4 scFvs antibodies. The novel finding that CTLA-4 molecule is expressed and functional on human tumor cells opens up the possibility of antitumor therapeutic intervention based on targeting this molecule.

Antigens, CD↗
PubMed2005

HLA-E surface expression is independent of the availability of HLA class I signal sequence-derived peptides in human tumor cell lines.

Human leukocyte antigen (HLA)-E is a nonclassic HLA class I molecule whose expression at the cell surface of tumor cells might allow them to escape T- and natural killer (NK)-cell immune surveillance. In this study, we analyzed HLA-E expression in a panel of human HLA-typed tumor cell lines of different histotypes by flow cytometry with anti-HLA-E monoclonal antibodies and by reverse transcriptase-polymerase chain reaction. Although specific HLA-E transcripts were detected in all cell lines, except in HELA, surface expression was detected at different intensities on seven (23%) of 30 cell lines with higher frequency and intensity among osteosarcoma cell lines. HLA-E-positive tumor cell lines mainly expressed the HLA-A*02 class I allele. Some tumor cell lines demonstrating HLA class I A* or Cw* alleles, which we expected to allow HLA-E surface expression on the basis of reported data on lymphoid cells, instead were HLA-E negative. All tumor cell lines were either tapasin and TAP-1 positive by flow cytometry, except two osteosarcoma cell lines, a finding that suggests an intact assembly machinery for peptide loading. We conclude that the concomitant presence of the appropriate HLA class I alleles with leader sequence-derived peptides and HLA-E heavy chain may not be sufficient to allow HLA-E surface expression in tumor cell lines as opposed to lymphoid cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2002

CTLA-4 is not restricted to the lymphoid cell lineage and can function as a target molecule for apoptosis induction of leukemic cells.

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.

Abatacept↗
PubMed2002

Detection of a novel specificity (CTLA-4) in ATG/TMG globulins and sera from ATG-treated leukemic patients.

BACKGROUND: T-cell costimulation has been shown to provide positive signals for T-cell activation and generation of effector activity. In this study, we analyzed the presence of antibodies (Abs) against the T-lymphocyte costimulatory molecules CD28, CTLA-4, CD80, and CD86 in anti-T-lymphocyte (ATG) and antithymocyte (TMG) globulin preparations to address their mechanism of action. We focused our attention on the role of CTLA-4-specific Abs in the immunosuppressive effect of ATG/TMG, because anti-CTLA-4 agonistic Abs may suppress T-cell proliferation and nonagonistic Abs may lead to T-cell depletion through an Ab-dependent cell cytotoxicity mechanism. METHODS: ATG/TMG and patients' sera were tested for binding to recombinant human costimulatory molecules by ELISA techniques. CTLA-4 specificity was also analyzed by cytoplasmic immunofluorescence staining of a CTLA-4 transfectant by competitive inhibition immunofluorescence and by cell proliferation assay in allogeneic mixed lymphocyte reaction (MLR). RESULTS: Either ATG or TMG predominantly contained anti-CTLA-4 Abs, with higher reactivity in ATG followed by anti-CD86 and -CD28 Abs, whereas anti-CD80 Abs were found only in ATG. Anti-CTLA-4 Abs present in ATG/TMG recognized the native form of CTLA-4 molecule, and their removal reduced the effect of ATG in an allogeneic MLR. Kinetic studies indicated that such Abs were present in the sera of 12 ATG-treated leukemic patients up to 21 days after ATG administration. CONCLUSIONS: These data suggest that the novel anti-CTLA-4 Abs found in ATG may greatly contribute to its immunosuppressive effect, thus accounting for the absence of rejection and exceptionally low incidence of graft-versus-host disease in the group of patients analyzed.

Abatacept↗
PubMed2002

Analysis of HLA-G expression in breast cancer tissues.

Among the different mechanisms by which cancer can elude the immune system, alterations in the expression of human leukocyte antigen (HLA) class I molecules on tumor cells may play a crucial role by impairing the HLA molecules interaction with T and natural killer (NK) cells specific receptors. More recently, aberrant expression of HLA-G has been described in different tumor tissues in addition to HLA class I downregulation. The HLA-G molecule is a nonclassical HLA class I antigen selectively expressed by trophoblast and thymic epithelial cells. Several studies reported that the HLA-G function might represent an additional mechanism of tumor immune escape, mainly inhibiting NK and cytotoxic T-cell activity. Here we report the analysis of HLA-G expression both at RNA level by reverse transcriptase-polymerase chain reaction and at protein level by Western blot and immunohistochemistry in 25 breast cancer patient tissues. The aim of this study was to elucidate the HLA-G gene expression pattern in breast tumor tissues and correlate it with HLA class I alterations. Our results demonstrated that HLA-G molecules expression was never found even in a group of patients revealing HLA class I total loss, and that HLA-G is not expressed in breast cancer tissue with a low-tumor grade (G1-G2) and minimal stromal contamination.

Blotting, Western↗