Zoledronic acid inhibits the growth of leukemic MLL-AF9 transformed hematopoietic cells

A leukemic in vitro model produced by transducing Cord Blood derived-hematopoietic CD34⁺ cells with the MLL-AF9 translocation resulting in the oncogenic fusion protein, is used to assess for sensitivity to Zoledronic acid. These cells are practically immortalized and are of myeloid origin. Proliferation, clonogenic and stromal co-culture assays showed that the MLL-AF9 cells were considerably more sensitive to Zoledronic acid than normal hematopoietic CD34⁺ cells or MS-5 stromal cells. The MLL-AF9 cells were notably more inhibited by Zoledronic acid when cultured as colonies in 3 dimensions, requiring cell-cell contacts compared to suspension expansion cultures. This is coherent with the mechanism of action of Zoledronic acid inhibiting farnesyl diphosphate synthase which results in a block in prenylation of GTPases such that their role in the membrane is compromised for cell-cell contacts. Zoledronic acid can be proposed to target the MLL-AF9 leukemic stem cells before they emerge from the hematopoietic niche, which being in proximity to bone osteoclasts where Zoledronic acid is sequestered can be predicted to result in sufficient levels to result in an anti-leukemic action.

Preclinical activity of sacituzumab govitecan (IMMU-132) in uterine and ovarian carcinosarcomas

Background

Uterine and ovarian carcinosarcomas (CS) are rare cancers with poor prognosis. Sacituzumab-govitecan (SG) is a new class of antibody-drug-conjugate (ADC) targeting the human-trophoblast-cell-surface marker (Trop-2) conjugated with the active metabolite of irinotecan (SN-38). We evaluated the efficacy of SG against biologically aggressive CS.

Methods

Trop-2 expression was evaluated in 10 formalin-fixed-paraffined-embedded (FFPE) CS by immunohistochemistry and 9 primary CS cell-lines by flow-cytometry. One Trop-2 low/negative (SARARK14) and two Trop-2 positive (SARARK4, SARARK9) cell-lines were tested in cell-viability assays . The in vivo antitumor activity of SG was tested in xenografts models (ie, SARARK9) with strong Trop-2 expression.

Results

Strong/diffuse staining was seen in 30% (3/10) of FFPE tumors and 33% (3/9) of primary CS cell lines. Trop-2 positive cell-lines (SARARK4, SARARK9) showed higher sensitivity to SG in vitro when compared to Trop-2 low/negative (SARARK14) cell lines. In xenografts, twice-weekly intravenous administration of SG for three weeks showed a significant tumor growth inhibition when compared to control, to ADC control and to the naked AB (p=0.004, p=0.007 and p=0.0007, respectively). SG significantly improved overall survival at 90 days when compared to control groups (p<0.0001).

Conclusion

SG may represent a novel class of active drugs for carcinosarcomas patients overexpressing Trop-2.

The stem cell-associated transcription co-factor, ZNF521, interacts with GLI1 and GLI2 and enhances the activity of the Sonic hedgehog pathway

ZNF521 is a transcription co-factor with recognized regulatory functions in haematopoietic, osteo-adipogenic and neural progenitor cells. Among its diverse activities, ZNF521 has been implicated in the regulation of medulloblastoma (MB) cells, where the Hedgehog (HH) pathway, has a key role in the development of normal cerebellum and of a substantial fraction of MBs. Here a functional cross-talk is shown for ZNF521 with the HH pathway, where it interacts with GLI1 and GLI2, the major HH transcriptional effectors and enhances the activity of HH signalling. In particular, ZNF521 cooperates with GLI1 and GLI2 in the transcriptional activation of GLI (glioma-associated transcription factor)-responsive promoters. This synergism is dependent on the presence of the N-terminal, NuRD-binding motif in ZNF521, and is sensitive to HDAC (histone deacetylase) and GLI inhibitors. Taken together, these results highlight the role of ZNF521, and its interaction with the NuRD complex, in determining the HH response at the level of transcription. This may be of particular relevance in HH-driven diseases, especially regarding the MBs belonging to the SHH (sonic HH) subgroup where a high expression of ZNF521 is correlated with that of HH pathway components.

ZNF521 Represses Osteoblastic Differentiation in Human Adipose-Derived Stem Cells

Human adipose-derived stem cells (hADSCs) are multipotent mesenchymal cells that can differentiate into adipocytes, chondrocytes, and osteocytes. During osteoblastogenesis, the osteoprogenitor cells differentiate into mature osteoblasts and synthesize bone matrix components. Zinc finger protein 521 (ZNF521/Zfp521) is a transcription co-factor implicated in the regulation of hematopoietic, neural, and mesenchymal stem cells, where it has been shown to inhibit adipogenic differentiation. The present study is aimed at determining the effects of ZNF521 on the osteoblastic differentiation of hADSCs to clarify whether it can influence their osteogenic commitment. The enforced expression or silencing of ZNF521 in hADSCs was achieved by lentiviral vector transduction. Cells were cultured in a commercial osteogenic medium for up to 20 days. The ZNF521 enforced expression significantly reduced osteoblast development as assessed by the morphological and molecular criteria, resulting in reduced levels of collagen I, alkaline phosphatase, osterix, osteopontin, and calcium deposits. Conversely, ZNF521 silencing, in response to osteoblastic stimuli, induced a significant increase in early molecular markers of osteogenesis and, at later stages, a remarkable enhancement of matrix mineralization. Together with our previous findings, these results show that ZNF521 inhibits both adipocytic and osteoblastic maturation in hADSCs and suggest that its expression may contribute to maintaining the immature properties of hADSCs.

Turning Stem Cells Bad: Generation of Clinically Relevant Models of Human Acute Myeloid Leukemia through Gene Delivery- or Genome Editing-Based Approaches

Acute myeloid leukemia (AML), the most common acute leukemia in the adult, is believed to arise as a consequence of multiple molecular events that confer on primitive hematopoietic progenitors unlimited self-renewal potential and cause defective differentiation. A number of genetic aberrations, among which a variety of gene fusions, have been implicated in the development of a transformed phenotype through the generation of dysfunctional molecules that disrupt key regulatory mechanisms controlling survival, proliferation, and differentiation in normal stem and progenitor cells. Such genetic aberrations can be recreated experimentally to a large extent, to render normal hematopoietic stem cells "bad", analogous to the leukemic stem cells. Here, we wish to provide a brief outline of the complementary experimental approaches, largely based on gene delivery and more recently on gene editing, employed over the last two decades to gain insights into the molecular mechanisms underlying AML development and progression and on the prospects that their applications offer for the discovery and validation of innovative therapies.

ZNF423: A New Player in Estrogen Receptor-Positive Breast Cancer

Preventive therapy can target hormone-responsive breast cancer (BC) by treatment with selective estrogen receptor modulators (SERMs) and reduce the incidence of BC. Genome-wide association studies have identified single nucleotide polymorphisms (SNPs) with relevant predictive values, SNPs in the ZNF423 gene were associated with decreased risk of BC during SERM therapy, and SNPs in the Cathepsin O gene with an increased risk. ZNF423, which was not previously associated with BC is a multifunctional transcription factor known to have a role in development, neurogenesis, and adipogenesis and is implicated in other types of cancer. ZNF423 is transcriptionally controlled by the homolog ZNF521, early B cell factor transcription factor, epigenetic silencing of the promoter by CpG island hyper-methylation, and also by ZNF423 itself in an auto-regulatory loop. In BC cells, ZNF423 expression is found to be induced by estrogen, dependent on the binding of the estrogen receptor and calmodulin-like 3 to SNPs in ZNP423 intronic sites in proximity to consensus estrogen response elements. ZNF423 has also been shown to play a mechanistic role by trans-activating the tumor suppressor BRCA1 and thus modulating the DNA damage response. Even though recent extensive trial studies did not classify these SNPs with the highest predictive values, for inclusion in polygenic SNP analysis, the mechanism unveiled in these studies has introduced ZNF423 as a factor important in the control of the estrogen response. Here, we aim at providing an overview of ZNF423 expression and functional role in human malignancies, with a specific focus on its implication in hormone-responsive BC.

Validation of a novel shotgun proteomic workflow for the discovery of protein-protein interactions: focus on ZNF521

The study of protein-protein interactions is increasingly relying on mass spectrometry (MS). The classical approach of separating immunoprecipitated proteins by SDS-PAGE followed by in-gel digestion is long and labor-intensive. Besides, it is difficult to integrate it with most quantitative MS-based workflows, except for stable isotopic labeling of amino acids in cell culture (SILAC). This work describes a fast, flexible and quantitative workflow for the discovery of novel protein-protein interactions. A cleavable cross-linker, dithiobis[succinimidyl propionate] (DSP), is utilized to stabilize protein complexes before immunoprecipitation. Protein complex detachment from the antibody is achieved by limited proteolysis. Finally, protein quantitation is performed via (18)O labeling. The workflow has been optimized concerning (i) DSP concentration and (ii) incubation times for limited proteolysis, using the stem cell-associated transcription cofactor ZNF521 as a model target. The interaction of ZNF521 with the core components of the nuclear remodelling and histone deacetylase (NuRD) complex, already reported in the literature, was confirmed. Additionally, interactions with newly discovered molecular partners of potentially relevant functional role, such as ZNF423, Spt16, Spt5, were discovered and validated by Western blotting.

UMG Lenti: novel lentiviral vectors for efficient transgene- and reporter gene expression in human early hematopoietic progenitors

Lentiviral vectors are widely used to investigate the biological properties of regulatory proteins and/or of leukaemia-associated oncogenes by stably enforcing their expression in hematopoietic stem and progenitor cells. In these studies it is critical to be able to monitor and/or sort the infected cells, typically via fluorescent proteins encoded by the modified viral genome. The most popular strategy to ensure co-expression of transgene and reporter gene is to insert between these cDNAs an IRES element, thus generating bi-cistronic mRNAs whose transcription is driven by a single promoter. However, while the product of the gene located upstream of the IRES is generally abundantly expressed, the translation of the downstream cDNA (typically encoding the reporter protein) is often inconsistent, which hinders the detection and the isolation of transduced cells. To overcome these limitations, we developed novel lentiviral dual-promoter vectors (named UMG-LV5 and –LV6) where transgene expression is driven by the potent UBC promoter and that of the reporter protein, EGFP, by the minimal regulatory element of the WASP gene. These vectors, harboring two distinct transgenes, were tested in a variety of human haematopoietic cell lines as well as in primary human CD34⁺ cells in comparison with the FUIGW vector that contains the expression cassette UBC-transgene-IRES-EGFP. In these experiments both UMG-LV5 and UMG–LV6 yielded moderately lower transgene expression than FUIGW, but dramatically higher levels of EGFP, thereby allowing the easy distinction between transduced and non-transduced cells. An additional construct was produced, in which the cDNA encoding the reporter protein is upstream, and the transgene downstream of the IRES sequence. This vector, named UMG-LV11, proved able to promote abundant expression of both transgene product and EGFP in all cells tested. The UMG-LVs represent therefore useful vectors for gene transfer-based studies in hematopoietic stem and progenitor cells, as well as in non-hematopoietic cells.

Critical role of zinc finger protein 521 in the control of growth, clonogenicity and tumorigenic potential of medulloblastoma cells

The stem cell-associated transcription co-factor ZNF521 has been implicated in the control of hematopoietic, osteo-adipogenic and neural progenitor cells. ZNF521 is highly expressed in cerebellum and in particular in the neonatal external granule layer that contains candidate medulloblastoma cells-of-origin, and in the majority of human medulloblastomas. Here we have explored its involvement in the control of human and murine medulloblastoma cells.

The effect of ZNF521 on growth and tumorigenic potential of human medulloblastoma cell lines as well as primary Ptc1^−/+ mouse medulloblastoma cells was investigated in a variety of in vitro and in vivo assays, by modulating its expression using lentiviral vectors carrying the ZNF521 cDNA, or shRNAs that silence its expression.

Enforced overexpression of ZNF521 in DAOY medulloblastoma cells significantly increased their proliferation, growth as spheroids and ability to generate clones in single-cell cultures and semisolid media, and enhanced their migratory ability in wound-healing assays. Importantly, ZNF521-expressing cells displayed a greatly enhanced tumorigenic potential in nude mice. All these activities required the ZNF521 N-terminal motif that recruits the nucleosome remodeling and histone deacetylase complex, which might therefore represent an appealing therapeutic target. Conversely, silencing of ZNF521 in human UW228 medulloblastoma cells that display high baseline expression decreased their proliferation, clonogenicity, sphere formation and wound-healing ability. Similarly, Zfp521 silencing in mouse Ptc1^−/+ medulloblastoma cells drastically reduced their growth and tumorigenic potential.

Our data strongly support the notion that ZNF521, through the recruitment of the NuRD complex, contributes to the clonogenic growth, migration and tumorigenicity of medulloblastoma cells.

IRF5 is a target of BCR-ABL kinase activity and reduces CML cell proliferation

Interferon regulatory factor 5 (IRF5) modulates the expression of genes controlling cell growth and apoptosis. Previous findings have suggested a lack of IRF5 transcripts in both acute and chronic leukemias. However, to date, IRF5 expression and function have not been investigated in chronic myeloid leukemia (CML). We report that IRF5 is expressed in CML cells, where it interacts with the BCR-ABL kinase that modulates its expression and induces its tyrosine phosphorylation. Tyrosine-phosphorylated IRF5 displayed reduced transcriptional activity that was partially restored by imatinib mesylate (IM). Interestingly, a mutant devoid of a BCR-ABL consensus site (IRF5(Y104F)) still presented significant tyrosine phosphorylation. This finding suggests that the oncoprotein phosphorylates additional tyrosine residues or induces downstream signaling pathways leading to further IRF5 phosphorylation. We also found that ectopic expression of IRF5 decreases the proliferation of CML cell lines by slowing their S-G2 transition, increasing the inhibition of BCR-ABL signaling and enhancing the lethality effect observed after treatment with IM, α-2-interferon and a DNA-damaging agent. Furthermore, IRF5 overexpression successfully reduced the clonogenic ability of CML CD34-positive progenitors before and after exposure to the above-indicated cytotoxic stimuli. Our data identify IRF5 as a downstream target of the BCR-ABL kinase, suggesting that its biological inactivation contributes to leukemic transformation.

Identification of H ferritin-dependent and independent genes in K562 differentiating cells by targeted gene silencing and expression profiling

Ferritin is best known as the key molecule in intracellular iron storage, and is involved in several metabolic processes such as cell proliferation, differentiation and neoplastic transformation. We have recently demonstrated that the shRNA silencing of the ferritin heavy subunit (FHC) in a melanoma cell line is accompanied by a consistent modification of gene expression pattern leading to a reduced potential in terms of proliferation, invasiveness, and adhesion ability of the silenced cells. In this study we sought to define the repertoire of genes whose expression might be affected by FHC during the hemin-induced differentiation of the erythromyeloid cell line K562. To this aim, gene expression profiling was performed in four different sets of cells: i) wild type K562; ii) sh-RNA FHC-silenced K562; iii) hemin-treated wild-type K562; and iv) hemin-treated FHC-silenced K562. Statistical analysis of the gene expression data, performed by two-factor ANOVA, identified three distinct classes of transcripts: a) Class 1, including 657 mRNAs whose expression is modified exclusively during hemin-induced differentiation of K562 cells, independently from the FHC relative amounts; b) Class 2, containing a set of 70 mRNAs which are consistently modified by hemin and FHC-silencing; and c) Class 3, including 128 transcripts modified by FHC-silencing but not by hemin. Our data indicate that FHC may function as a modulator of gene expression during erythroid differentiation and add new findings to the knowledge of the complex gene network modulated during erythroid differentiation.

Abstract 5045: Critical role of zinc finger protein 521 in the control of growth, clonogenicity and tumorigenic potential of medulloblastoma cells

The stem cell-associated transcription co-factor ZNF521 has been implicated in the control of haematopoietic, osteogenic and neural progenitors. Very high expression of this factor is present in cerebellum and particularly in the granule layer of neonatal cerebellum, that contains candidate cells-of-origin of medulloblastoma. Here we have explored the possible involvement of ZNF521 in the development of this tumour.

As an experimental system we used the human medulloblastoma cell line, DAOY, and primary cells from medulloblastomas occurring in Ptc1-/+ mice. To investigate the effect of ZNF521 on the growth and tumourigenic potential of these cells, its expression was modulated using lentiviral vectors carrying the ZNF521 cDNA, or containing shRNAs that silence its expression.

Enforced overexpression of ZNF521 in DAOY cells, that normally produce relatively low amounts of this protein, was associated with a significant increase in their proliferation rate. This was mirrored by an increase in the ability to grow as spheroids and clonogenicity in single-cell cultures and in semisolid media, and accompanied by an enhanced migratory capacity in wound-healing assays. Finally, ZNF521-expressing DAOY cells demonstrated a greatly enhanced tumourigenic potential in nude mice. All these activities required the presence of an N-terminal domain of ZNF521 that recruits the nucleosome remodeling and histone deacetylase (NuRD) complex. Consistently with the effects of ZNF521 overexpression in DAOY, silencing of Zfp521 in Ptc1-/+ medulloblastoma cells resulted in a drastic decrease in their proliferation and tumourigenic potential, lending further support to the notion that zinc finger protein 521 may contribute to the generation and/or maintenance of the cancer-initiating cell compartment in this cancer. Preliminary experiments detected a selective up-regulation of HES5 mRNA in DAOY overexpressing ZNF521, raising the possibility that some of the effects illustrated here may at least in part be mediated by the co-operation of ZNF521 with the Notch pathway.

Citation Format: Raffaella Spina, Gessica Filocamo, Enrico Iaccino, Stefania Scicchitano, Michela Lupia, Emanuela Chiarella, Tiziana Mega, Daniela Pelaggi, Maria Mesuraca, Eli E. Bar, Heather M. Bond, Charles G. Eberhart, Christian Steinkuhler, Gianni Morrone. Critical role of zinc finger protein 521 in the control of growth, clonogenicity and tumorigenic potential of medulloblastoma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5045. doi:10.1158/1538-7445.AM2013-5045

Note: This abstract was not presented at the AACR Annual Meeting 2013 because the presenter was unable to attend.

Zinc finger protein 521 antagonizes early B-cell factor 1 and modulates the B-lymphoid differentiation of primary hematopoietic progenitors

Zinc finger protein 521 (EHZF/ZNF521) is a multi-functional transcription co-factor containing 30 zinc fingers and an amino-terminal motif that binds to the nucleosome remodelling and histone deacetylase (NuRD) complex. ZNF521 is believed to be a relevant player in the regulation of the homeostasis of the hematopoietic stem/progenitor cell compartment, however the underlying molecular mechanisms are still largely unknown. Here, we show that this protein plays an important role in the control of B-cell development by inhibiting the activity of early B-cell factor-1 (EBF1), a master factor in B-lineage specification. In particular, our data demonstrate that: (1) ZNF521 binds to EBF1 via its carboxyl-terminal portion and this interaction is required for EBF1 inhibition; (2) NuRD complex recruitment by ZNF521 is not essential for the inhibition of transactivation of EBF1-dependent promoters; (3) ZNF521 represses EBF1 target genes in a human B-lymphoid molecular context; and (4) RNAi-mediated silencing of ZNF521/Zfp521 in primary human and murine hematopoietic progenitors strongly enhances the generation of B-lymphocytes in vitro. Taken together, our data indicate that ZNF521 can antagonize B-cell development and lend support to the notion that it may contribute to conserve the multipotency of primitive lympho-myeloid progenitors by preventing or delaying their EBF1-driven commitment toward the B-cell lineage.

Efficient transcriptional targeting of human hematopoietic stem cells and blood cell lineages by lentiviral vectors containing the regulatory element of the Wiskott-Aldrich syndrome gene

The ability to effectively transduce human hematopoietic stem cells (HSCs) and to ensure adequate but "physiological" levels of transgene expression in different hematopoietic lineages represents some primary features of a gene-transfer vector. The ability to carry, integrate, and efficiently sustain transgene expression in HSCs strongly depends on the vector. We have constructed lentiviral vectors (LV) containing fragments of different lengths of the hematopoietic-specific regulatory element of the Wiskott-Aldrich syndrome (WAS) gene-spanning approximately 1,600 and 170 bp-that direct enhanced green fluorescent protein (EGFP) expression. The performance of vectors carrying the 1,600 and 170 bp fragments of the WAS gene promoter was compared with that of a vector carrying the UbiquitinC promoter in human cord blood CD34(+) cells and their differentiated progeny both in vitro and in vivo in non-obese diabetic mice with severe combined immunodeficiency. All vectors displayed a similar transduction efficiency in CD34(+) cells and promoted long-term EGFP expression in different hematopoietic lineages, with an efficiency comparable to, and in some instances (for example, the 170-bp promoter) superior to, that of the UbiquitinC promoter. Our results clearly demonstrate that LV containing fragments of the WAS gene promoter/enhancer region can promote long-term transgene expression in different hematopoietic lineages in vitro and in vivo and represent suitable and highly efficient vectors for gene transfer in gene-therapy applications for different hematological diseases and for research purposes. In particular, the 170-bp carrying vector, for its reduced size, could significantly improve the transduction/expression of large-size genes.

Early hematopoietic zinc finger protein prevents tumor cell recognition by natural killer cells

Early hematopoietic zinc finger/zinc finger protein 521 (EHZF/ZNF521) is a novel zinc finger protein expressed in hematopoietic stem and progenitor cells and is down-regulated during their differentiation. Its transcript is also abundant in some hematopoietic malignancies. Analysis of the changes in the antigenic profile of cells transfected with EHZF cDNA revealed up-regulation of HLA class I cell surface expression. This phenotypic change was associated with an increased level of HLA class I H chain, in absence of detectable changes in the expression of other Ag-processing machinery components. Enhanced resistance of target cells to NK cell-mediated cytotoxicity was induced by enforced expression of EHZF in the cervical carcinoma cell line HeLa and in the B lymphoblastoid cell line IM9. Preincubation of transfected cells with HLA class I Ag-specific mAb restored target cell susceptibility to NK cell-mediated lysis, indicating a specific role for HLA class I Ag up-regulation in the NK resistance induced by EHZF. A potential clinical significance of these findings is further suggested by the inverse correlation between EHZF and MHC class I expression levels, and autologous NK susceptibility of freshly explanted multiple myeloma cells.

Early Hematopoietic Zinc Finger (EHZF/ZNF521) prevents tumor cell recognition by Natural Killer cells. (41.43)

EHZF/ZNF521 is a novel zinc finger protein expressed in hematopoietic stem and progenitor cells and is downregulated during their differentiation. Its transcript is also abundant in some hematopoietic malignancies. Analysis of the changes in the antigenic profile of cells transfected with EHZF cDNA revealed upregulation of HLA class I cell surface expression. This phenotypic change was associated with increased level of HLA class I heavy chain, in absence of detectable changes in the expression of other antigen processing machinery (APM) components. Enhanced resistance of target cells to NK cell-mediated cytotoxicity was induced by enforced expression of EHZF in the cervical carcinoma cell line HeLa and in the B-lymphoblastoid cell line IM9. Preincubation of transfected cells with HLA class I antigen-specific mAb restored target cell susceptibility to NK cell-mediated lysis, indicating a specific role for HLA class I antigen upregulation in the NK resistance induced by EHZF. A potential clinical significance of these findings is further suggested by the inverse correlation between EHZF and MHC class I expression levels, and autologous NK susceptibility of freshly explanted multiple myeloma cells.

IL-2 signals through Sgk1 and inhibits proliferation and apoptosis in kidney cancer cells

The interleukin-2 is a cytokine that is essential for lymphocytic survival and function. Ectopic expression of the IL-2 receptor in epithelial tissues has been reported previously, although the functional significance of this expression is still being investigated. We provided novel structural and functional information on the expression of the IL-2 receptor in kidney cancer cells and in other normal and neoplastic human epithelial tissues. In A-498 kidney cancer cells, we showed that IL-2 binding to its own receptor triggers a signal transduction pathway leading to the inhibition of proliferation and apoptosis. We found that the inhibition of proliferation is associated with Erk1/2 dephosphorylation, whereas the survival signals appear to be mediated by Sgk1 activation. This investigation focuses on the IL-2 induced regulation of Sgk1 and describes a role of the IL-2 receptor and Sgk1 in the regulation of epithelial tumor cell death and survival.

Early hematopoietic zinc finger protein-zinc finger protein 521: a candidate regulator of diverse immature cells

The early hematopoietic zinc finger protein/zinc finger protein 521 (EHZF/ZNF521) is a recently identified, 1131 amino-acid-long nuclear factor that contains 30 zinc fingers distributed in clusters throughout its sequence. A 13-AA motif, that binds to components of the nuclear remodelling and histone deacetylation (NuRD) complex and is conserved in several trascriptional co-repressors, is located at the amino-terminal end of the molecule. EHZF/ZNF521 expression is high in the most immature cells of the haematopoietic system and declines with differentiation. Its transcript is also abundant in brain, particularly in the cerebellum. Its murine counterpart, Evi3/Zfp521, is enriched in haematopoietic and neural stem cells, in cerebellar granule neuron precursors and in the developing striatum. Enforced expression of EHZF/ZNF521 in haematopoietic progenitors results in their expansion and in inhibition of differentiation. EHZF/ZNF521 is a member of the BMP signalling pathway and an inhibitor of the transcription factor OLF1/EBF1, implicated in the differentiation of neural progenitors and in the specification of the B-cell lineage. EHZF expression is observed in most acute myelogenous leukaemias and is particularly high in those with rearrangements of the MLL gene, where EHZF may contribute to the leukaemic phenotype. EHZF/ZNF521 is also abundant in medulloblastomas and other brain tumours. Taken together, the data available suggest a possible role for this factor in development, stem cell regulation and oncogenesis.

Early hematopoietic zinc finger protein (EHZF), the human homolog to mouse Evi3, is highly expressed in primitive human hematopoietic cells

Comparison of the gene expression repertoire in human hematopoietic progenitors and mature leukocytes led to identification of a transcript expressed in CD34+cells and undetectable in differentiated cells. Sequencing of the cDNA (termed EHZF: early hematopoietic zinc finger) revealed 30 zinc fingers with 96% homology to mouse Evi3, a recently identified gene associated with the retroviral integration site in AKXD-27 B-cell lymphomas. EHZF and Evi3 share high homology with the transcription cofactor OAZ, implicated in the control of olfactory epithelium and B-lymphocyte differentiation and in the bone morphogenic protein (BMP) signal transduction. Here we show that (1) EHZF expression is abundant in human CD34+ progenitors and declines rapidly during cytokine-driven differentiation; (2) significant mRNA levels are found in most acute myelogenous leukemias; (3) in response to BMPs EHZF complexes SMADs 1 and 4, binds to, and enhances the transcriptional activity of, a BMP2/4 responsive element; (4) EHZF inhibits the transcriptional activity of early B-cell factor (EBF), a transcription factor essential for specification of the B-cell lineage. Taken together, our data suggest that EHZF is likely to play a relevant role in the control of human hematopoiesis and might be implicated in the development of hematopoietic malignancies.

Regulation of cell survival in CD95-induced T cell apoptosis: role of NF-kappa B/Rel transcription factors

The activity of NF-kappa B/Rel transcription factors can inhibit the apoptosis induced by TNF, UV or cancer therapy drugs in a number of cell types, including human T lymphocytes. Furthermore, the NF-kappa B/Rel inducer, phorbol-12-myristate-13-acetate (PMA), has been reported to suppress the CD95-induced apoptosis of human T lymphocytes. To verify whether the survival-enhancing effect of PMA required NF-kappa B/Rel activity, we generated two Jurkat cell sublines (AL.7 and AL.8) transfected with a pCMV4-I kappa B alpha construct, and two (AL.3 and AL.5) with the void pCMV4 vector. Compared to wild type, AL.3 and AL.5 cells, the AL.7 and AL.8 sublines displayed markedly lower amounts of NF-kappa B/Rel nuclear complexes and a reduced expression of a kappa B-controlled CAT reporter gene after 1 and 4 h of incubation with PMA, respectively. All the five cell types displayed negligible levels of apoptosis when cultured with medium or PMA alone; when stimulated with the mAb CH-11, the AL.7 and AL.8 sublines displayed apoptotic responses only slightly (<0.5 fold) higher than control cells. On the other hand, the salvage activity of PMA was partially impaired in the AL.7 and AL.8 sublines. PMA inhibited apoptosis by >85% in wild type, AL.3 and AL.5 cells and by <60% in the AL.7 and AL.8 sublines; the apoptosis percentages in the mAb CH-11 + PMA cultures of the I kappa B alpha-transfected cells were >4-fold higher than in control cells. We conclude that the inhibition of the CD95-induced apoptosis by PMA relies on both NF-kappa B/Rel-dependent and -independent mechanisms. The partial contribution of these nuclear factors to the suppression of apoptosis indicates that the NF-kappa B/Rel activity can influence the extent of the CD95-induced T cell death.

Differential expression of UN1, early thymocyte-associated sialoglycoprotein, in breast normal tissue, benign disease and carcinomas

BACKGROUND

The UNI antigen (Ag) is a 120 kDa sialoglycoprotein which has been primarily found in human undifferentiated CD3dim thymocytes and leukemic T-cell lines, but subsequently also detected in solid tumors. We studied the expression of this Ag in a panel of normal and pathological breast tissues.

MATERIALS AND METHODS

Analysis of UN1 Ag expression on tissue specimens was performed by immunohistochemistry and Western blotting.

RESULTS

No Ag expression was found in 14 sections of normal tissue and 10 sections of benign nonproliferative lesions. Progressively increasing levels of UN1 Ag expression were found in fibroadenomas (24 positive out of 27 cases), proliferative lesions (9 cases), in situ (17 cases) and invasive carcinomas (56 cases). Finally, the highest expression was observed in 10 metastatic lesions.

CONCLUSION

These data suggest that UN1 Ag is a promising marker of potential value for immunophenotyping studies and therapeutic applications in breast diseases.

Fetal ontogeny and tumor expression of the early thymic antigen UN1

UN1 antigen (Ag), a 100-120 kDa sialoglycoprotein, was initially identified on immature thymocytes (CD3(dim)), a small subpopulation of CD4(+) peripheral blood T-lymphocytes, on leukemic T-cell lines and in fetal thymus. Biochemical analysis of the Ag has identified molecular features that are characteristic of cell-membrane-associated mucin-like glycoproteins. To investigate the biological role and the potential usefulness of the Ag, we have more extensively studied the pattern of UN1 Ag expression in a panel of fetal tissues, at different gestational ages, and on adult normal and tumor specimens. In the fetal samples examined by immunohistochemistry, including intestine, liver, lung and adrenal gland, we found that UN1 Ag is widely expressed during early stages of fetal development and down-regulated during ontogenesis. Very poor or not detectable expression of UN1 Ag was found at late gestational age. Immunohistochemical, Western blot and flow cytometric analysis of a panel of normal adult tissues and benign lesions failed to find Ag expression, whereas UN1 Ag was highly detectable in a variety of cancer specimens from breast, lung, gastrointestinal, gynaecological malignancies and melanomas. Based on these data UN1 Ag, for the wide expression on fetal tissues, the down-regulation during ontogeny and the re-expression in cancer cells, may be considered a novel oncofetal Ag of interest for biological investigation and clinical applications.

A 5' regulatory sequence containing two Ets motifs controls the expression of the Wiskott-Aldrich syndrome protein (WASP) gene in human hematopoietic cells

The recently-identified Wiskott-Aldrich syndrome protein gene (WASP) is responsible for the Wiskott-Aldrich X-linked immunodeficiency as well as for isolated X-linked thrombocytopenia (XLT). To characterize the regulatory sequences of the WASP gene, we have isolated, sequenced and functionally analyzed a 1.6-Kb DNA fragment upstream of the WASP coding sequence. Transfection experiments showed that this fragment is capable of directing efficient expression of the reporter chloramphenicol acetyltransferase (CAT) gene in all human hematopoietic cell lines tested. Progressive 5' deletions showed that the minimal sequence required for hematopoietic-specific expression consists of 137 bp upstream of the transcription start site. This contains potential binding sites for several hematopoietic transcription factors and, in particular, two Ets-1 consensus that proved able to specifically bind to proteins present in nuclear extracts of Jurkat cells. Overexpression of Ets-1 in HeLa resulted in transactivation of the CAT reporter gene under the control of WASP regulatory sequences. Disruption of the Ets-binding sequences by side-directed mutagenesis abolished CAT expression in Jurkat cells, indicating that transcription factors of the Ets family play a key role in the control of WASP transcription.

CD36 is rapidly and transiently upregulated on phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes. Analysis by a new monoclonal antibody (UN7)

The monoclonal antibody (mAb) UN7, clustered as an anti-CD36 mAb, has been used to test the cell surface expression of CD36 on peripheral blood lymphocytes (PBL) following mitogenic stimulation. CD36, scarcely expressed on resting cell membranes, was rapidly upregulated on PBL after phytohemagglutinin (PHA) stimulation. The antigen was detected on the cell surface after 15 min of stimulation, increased rapidly by 60 min and peaked between 3 and 12 h, declining thereafter. The inhibition of protein synthesis by cycloheximide did not modify the PHA-induced expression of CD36. Neither the anti-CD3 OKT3 mAb nor the anti-CD2 BIL 2.29 and 9.1 mAbs induced any significant upregulation of the molecule. The addition of anti-CD28 15E8 mAb or IL-2 or IFN-gamma to PHA or anti-CD3 or anti-CD2 mAbs did not influence the pattern of CD36 expression. The phorbol-2-myristate-13-acetate (PMA), alone or in combination with ionomycin, was unable to activate the expression of CD36, while it inhibited the PHA-induced upregulation. The PHA-induced upregulation of CD36 was partially inhibited by the addition of LY294002 or wortmannin, while not affected by that of calphostin C. Thus, CD36 was found to be early and transiently upregulated by PHA stimulation on PBL. The rapid modulation of the molecule was not related to new protein synthesis, but was probably due to the insertion into the plasma membrane of a presynthetized protein pool.

Purification and characterization of a human sialoglycoprotein antigen expressed in immature thymocytes and fetal tissues

The monoclonal antibody UN1 was previously produced in our laboratory on the basis of selective reactivity with human thymocytes and has been classified as unclustered by the 5th and 6th International Workshop and Conference on Human Leukocyte Differentiation Antigens. The antigen recognized by mAb UN1 was found to be expressed on the cell surface of immature human thymocytes, a subpopulation of peripheral T lymphocytes and on several fetal tissues including thymus. The UN1 antigen is purified from children's thymus by ion-exchange and affinity chromatography. Two-dimensional electrophoresis shows that the purified antigen displays microheterogeneity appearing as multiple spots over a pI range 4.4-5.0 at 100-120 kDa. Treatment with neuraminidase results in a retarded migration in SDS-PAGE, an increase in isoelectric point and a reduction in carbohydrate content, indicating a substantial content of sialic acid. Glycosidase digestion and lectin-binding analysis indicate that the carbohydrate residues are essentially O-linked. A preliminary analysis has detected the UN1 antigen in human breast carcinoma tissues but not in normal breast. The biochemical features and the pattern of expression of the UN1 antigen indicate that this molecule may have the characteristics typical of the family of cell-membrane-associated mucin-like glycoproteins; a number of these molecules are thought to have a role in cell-cell interaction, tumor progression and metastasis.

Identification by differential display of transcripts regulated during hematopoietic differentiation

The polymerase chain reaction-based differential display method (DDRT-PCR) was used to identify mRNAs differentially expressed during the maturation of human CD34+ progenitor cells stimulated to differentiate in vitro towards granulomonocytic or erythroid lineages with a mixture of hemopoietins (kit ligand + interleukin 3 + GM-CSF in the absence or presence of erythropoietin, respectively). Three cDNA transcripts (B32, B41, and B56) display differential expression during cytokine-induced maturation of CD34+ cells. These clones have no homology with already-described sequences. Primer extension cofirmed the presence of the corresponding mRNA. The levels of mRNA corresponding to B32 are enhanced in the later phases of the granulomonocytic as well as in the erythroid differentiation of CD34+ cells. The mRNA identified by B41 was induced by a late stage in only granulomonocytic differentiation of CD34+ cells. The mRNA corresponding to B56 was instead present in nonstimulated CD34+ cells, declined in the early stages of differentiation, and reappeared at later stages in cells treated with both combinations of cytokines. Expression of these genes was detected in a number of acute myelogenous leukemias, as well as in some leukemic cell lines. B32 and B41 were downregulated in KG-1 cells induced to differentiate towards the monocytic lineage, whereas the levels of B56 were unchanged. In K562 cells, clones B41 and B56 were downregulated only in the late phases of PMA-induced megakaryocytic differentiation and during erythroid differentiation. B32 was rapidly downregulated when K562 cells were induced to differentiate towards either megakaryocytic or erythroid phenotypes. These transcripts represent novel hematopoietic cDNAs that should prove of value for the study of human blood cells and their disorders.

Expression of growth hormone receptor by peripheral blood lymphocytes in children: evaluation in clinical conditions of impaired growth

OBJECTIVE

It is widely accepted that the haematopoietic system is a target of growth hormone action and that GH may act as a lymphokine. The expression of GH receptors (GHR) on human peripheral blood lymphocytes (PBL) has been reported previously in adult donors by dual fluorochrome flow cytometry. The aim of this study was to apply the cytofluorimetric method to the analysis of GHR expression on PBL in various human conditions characterized by different patterns of growth due to age or physiopathological conditions.

SUBJECTS AND DESIGN

PBL from 38 normal (control) subjects (7 newborns, 18 prepubertal children, 13 adults) were studied in order to provide age-related physiological data. Twenty-two short children (18 with idiopathic short stature, 4 with Ullrich-Turner syndrome) were studied to determine the expression of GHR in conditions of impaired longitudinal growth which may or may not require GH treatment.

METHODS

Analysis was performed using a fluorescein isothiocyanate (FITC)-conjugated antibody specific for the GHR (mAb263) and phycoerythrin (PE)-anti CD2 (T and natural killer cells) or PE-anti CD2 (B cells) in dual fluorochrome flow cytometric assays. Results were expressed as mean fluorescent intensity (MFI).

RESULTS

Adult CD2+ coils exhibited a significantly higher GHR expression (MFI 347 +/- 40) than that expressed in children and newborns (MFI 285 +/- 36 and 299 +/- 41, respectively, P < 0.001). A significantly increased expression of GHR on CD2+ cells was also found in short children (MFI 330 +/- 42 vs 285 42- 36, respectively; P < 0.002), whereas Ullrich-Turner syndrome patients did not show any difference from their age and gender matched controls (254 +/- 52 and 288 +/- 40, respectively). A negative relationship was found between GHR expression on CD2+ cells and height-SDS (r - 0.54, P < 0.0001) or BMI (r - 0.4, P < 0.015) in controls and short children, independent of their GH secretory status. Expression of GHR and CD20+ cells was higher than that expressed on CD2+ cells in all subjects. No appreciable differences were found in the MFI levels of GHR expression on CD20+ cells either among the different age group controls or between short children or Ullrich-Turner syndrome patients. A significant downregulation of expression was shown in CD20+ (P < 0.008) but not CD2+ cells after 6 months of GH treatment in 6 short children who had a poor response to GH provocative tests.

CONCLUSIONS

GH receptor expression on immune cells in non-syndromic short children appears to be inversely related to the linear growth expression and BMI of the subjects, contrary to findings with hepatic derived serum GHBP. This finding may reflect alternate exon usage in lymphoid cells, and indicates that GH has a distinctive role in the immune system.

Differential regulation of the expression of interleukin-2 receptor gamma-chain during the in vitro differentiation of human myeloid cells

The common gamma-chain (gamma c) is a shared component of cell-surface receptors for the interleukins- 2, -4 and -7, and possibly others. We studied its expression in cells and cell lines of myeloid origin and found ubiquitous presence of gamma c mRNA in all cells examined. Differential regulation of gamma c expression was observed in myeloid cell lines induced to differentiate in vitro. In K-562 erythromyeloid cells, a sharp rise in the levels of gamma c mRNA and protein accompanied megakaryocytic, but not erythroid, differentiation. Surface binding of interleukin-2, as well as the transcripts for cognate receptor chains, were scarcely detectable in K-562 cells, whereas a significant increase in the binding of granulocyte-macrophage colony-stimulating factor specifically occurred during their megakaryocytic maturation. Our data indicate that expression of gamma c is a common feature of human myeloid cells, and suggest that its expression may be a requirement for human myelopoiesis.

Differential expression of surface membrane growth hormone receptor on human peripheral blood lymphocytes detected by dual fluorochrome flow cytometry

Although several reports indicate proliferative and functional effects of human GH (hGH) on peripheral blood lymphocytes (PBL), no information is available about hGH receptor (GHR) expression in PBL subsets. Here, the surface membrane GHR levels were investigated in different human PBL subpopulations using a fluorescein isothiocyanate (FITC)-conjugated monoclonal antibody specific for the GHR (mAb263) in dual fluorochrome flow cytometric assays. Strong GHR expression was found in B-cells (CD20+), whereas CD2+ lymphocytes, including T-cells as well as natural killer cells, exhibited considerably lower levels of receptor expression. Similarly, using FITC-labeled recombinant hGH, receptor expression on CD20+ cells was significantly higher than that on CD2+ cells. Abundant expression of GHR in B-lymphocytes was confirmed by reverse transcriptase-polymerase chain reaction analysis of GHR messenger ribonucleic acid from isolated B-cells. Accordingly, the B-cell merits greater consideration as a GH target cell. The use of FITC-labeled mAb263 and hGH is of potential use for the study of GHR levels in patients exhibiting different types of growth disorders. Because of its high specificity for GHR, FITC-labeled mAb263 is also of considerable value for specifically demonstrating the presence of GHR, because hGH may interact with and act through PRL receptor, as shown previously in human neutrophils.

A novel monoclonal antibody recognizing human thymocytes and B-cell chronic lymphocytic leukemia cells

This paper describes a new murine monoclonal antibody, UN5, raised against human thymocytes. This antibody recognizes a molecule of approximately 45 kDa on thymocytes. Flow cytometric analysis reveals a high intensity of labeling with the majority of thymocytes, whereas only CD20+ cells from peripheral whole-blood samples are weakly stained. Peripheral T cells, granulocytes, platelets and red blood cells do not express this antigen, while monocytes are only weakly labeled by UN5. Furthermore, the UN5 antibody discriminates between different types of B-cell malignancies, reacting with a subgroup of B-cell chronic lymphocytic leukemias and hairy cell leukemias, but not with the other kinds of hematopoietic malignancies tested. Antibody UN5 should prove a useful tool for the study of T-cell precursors and for analysis of both normal and neoplastic B cells.

Cholesterol efflux from macrophages mediated by high-density lipoprotein subfractions, which differ principally in apolipoprotein A-I and apolipoprotein A-II ratios

High-density lipoprotein (HDL) was fractionated by preparative isoelectric focussing into six distinct subpopulations. The major difference between the subfractions was in the molar ratio of apolipoprotein A-I to apolipoprotein A-II, ranging from 2.1 to 0.5. The least acidic particles had little apolipoprotein A-II, were larger and contained the most lipid. The efflux capacity of the HDL subfractions was tested with mouse peritoneal macrophages and a mouse macrophage cell line (P388D1), either fed with acetylated low-density lipoprotein or free cholesterol. All the HDL subfractions were equally able to efflux cholesterol. The efflux was concentration dependant and linear for the first 6 h. The HDL subfractions bound with high affinity (Kd = 6.7-7.9 micrograms/ml) at 4 degrees C to the cell surface of P388D1 cells (211,000-359,000 sites/cell). Ligand blotting showed that all the HDL subfractions bound to membrane polypeptides at 60, 100, and 210 kDa. These HDL binding proteins may represent HDL receptors. In summary HDL particles, which differed principally in ratio of apolipoprotein A-I to apolipoprotein A-II behaved in a similar manner for both cholesterol efflux and cell surface binding.

Identification and characterization of a T cell growth inhibitory factor produced by K562 erythromyeloid cells

Cells of the human erythroleukemia cell line K562 constitutively secrete a factor that inhibits human T lymphocyte proliferation induced via CD3/Ti. The factor, termed K-TIF (K562-derived T cell inhibitory factor) is produced in either the presence or absence of fetal calf serum in cultures of K562 cells and can be precipitated by 70% NH4SO4. Gel filtration chromatography on Superose 12 resin by FPLC showed that the inhibitory factor has a molecular weight of approximately 30-35 kDa. A protein of this size, metabolically labeled with [35S]methionine, specifically bound human peripheral blood mononuclear cells. Chromatofocusing with Mono P by FPLC (pH gradient 7.2-5) indicates that the inhibitory factor has an isoelectric point of 6.0-6.4.

Characterization and purification of proteins which bind high-density lipoprotein. A putative cell-surface receptor

High-density lipoprotein (HDL) is shown by ligand blotting to bind membrane-associated polypeptides with sizes of 60, 100 and 210 kDa. Binding was concentration-dependent and competed by excess unlabelled HDL. All the major apolipoproteins of HDL, apoA-I, apoA-II and apoA-IV, bound independently. The 100 kDa and 210 kDa HDL-binding activities were purified from membranes of Hep3B tumour cells by ion-exchange chromatography and gel filtration. The binding activities at 100 kDa and 210 kDa co-purified. After treatment with disulphide-reducing reagent, the 210 kDa band was no longer present and an increase was observed in the amount and binding ability of the 100 kDa polypeptide. The 100 kDa binding protein labelled at the cell surface with 125I could be immunoprecipitated after cross-linking to cell-surface-bound HDL. It is proposed that this HDL-binding activity, a putative cell-surface receptor for HDL, exists totally or in part as a high-molecular-mass complex composed of 100 kDa subunits.

A recombinant apoA-1-protein A hybrid reproduces the binding parameters of HDL to its receptor

We have constructed a plasmid, pLM8, containing the coding sequence of the mature human apoA-1 fused to the coding sequence of the IgG-binding domains of protein A (PA) from Staphylococcus aureus. The hybrid gene is transcribed in Escherichia coli under the control of a heat-sensitive repressor, leading to the synthesis of large amounts of hybrid protein (apoA-1--PA). The hybrid protein was purified by denaturation with urea and alkali, renaturation and affinity chromatography on an IgG Sepharose column. ApoA-1--PA is soluble and has an Mr of 316 kd, as determined by gel filtration. This is five times the monomer size of 62 kd, predicted from the sequence and found by SDS-PAGE analysis. Cell surface binding activity of the hybrid protein was tested using two different cell types (J774 macrophages and Fao hepatocytes) and compared to human high density lipoprotein (HDL). High-affinity binding was found for both ligands in both cell lines (Kd = 3.4 X 10(-8)M in Fao cells, 4.9 X 10(-8) M in J774 cells for apoA-1--PA and 3.0 X 10(-8) M in Fao cells, 2.8 X 10(-8) M in J774 cells for HDL), with approximately 2 X 10(5) high-affinity binding sites per cell. ApoA-1--PA and HDL effectively competed with each other for binding to the cell surface. Additionally, they both bound to a 110-kd polypeptide on a ligand blot, identifying an HDL receptor. The binding parameters of HDL were very similar to those of apoA-1--PA.(ABSTRACT TRUNCATED AT 250 WORDS)

Interactions of soya-bean agglutinin with purified glycoconjugates and soya-bean seed components

A radioaffinity assay for lectin binding to receptors was developed and characterized by using the interactions between soya-bean agglutinin and four glycoconjugates, namely thyroglobulin, galactomannan, fetuin and asialofetuin. On application of the assay to soya-bean extracts a wide range of seed components were found to have the capacity to interact with soya-bean agglutinin. These included both trichloroacetic acid-soluble and trichloroacetic acid-insoluble glycoconjugates and two classes of particulate matter distinguished by their differential solubility in Triton X-100.

Characterization of soybean endopeptidase activity using exogenous and endogenous substrates

Endopeptidase activity in mature soybean seeds (Glycine max), has been measured using an exogenous substrate, [(125)I]iodoinsulin B chain. On the basis of pH optimum and the use of specific proteinase inhibitors, two distinct endopeptidase activities can be identified in both the embryonic axis and the cotyledons. One activity is characteristic of a neutral/alkaline metalloendopeptidase(s) and the other of an acidic carboxylendopeptidase(s). Neither activity is membrane-bound. The metalloendopeptidase(s), most probably working with neutral expopeptidases also present in the tissues, is capable of degrading certain subunits of the storage proteins. The beta subunit of conglycinin and additional seed polypeptides remain resistant to degradation. The carboxylpeptidase activity displayed a different specificity towards endogenous substrates; in particular, an acid-soluble polypeptide of apparent molecular weight 30,000 appeared to be the principal substrate for limited proteolytic degradation by the proteinase(s). Soybean agglutinin remained resistant to degradation by either class of endopeptidases.