Tommaso Zanocco-Marani

The Kinetic Status of Hematopoietic Stem Cell Subpopulations Underlies a Differential Expression of Genes Involved in Self‐Renewal, Commitment, and Engraftment

The gene expression profile of CD34− hematopoietic stem cells (HSCs) and the correlations with their biological properties are still poorly understood. To address this issue, we used the DNA microarray technology to compare the expression profiles of different peripheral blood hemopoietic stem/progenitor cell subsets, lineage‐negative (Lin−) CD34−, Lin−CD34+, and Lin+CD34+ cells. The analysis of gene categories differentially expressed shows that the expression of CD34 is associated with cell cycle entry and metabolic activation, such as DNA, RNA, and protein synthesis. Moreover, the significant upregulation in CD34− cells of pathways inhibiting HSC proliferation induces a strong differential expression of cyclins, cyclin‐dependent kinases (CDKs), CDK inhibitors, and growth‐arrest genes. According to the expression of their receptors and transducers, interleukin (IL)‐10 and IL‐17 showed an inhibitory effect on the clonogenic activity of CD34− cells. Conversely, CD34+ cells were sensitive to the mitogenic stimulus of thrombopoietin. Furthermore, CD34− cells express preferentially genes related to neural, epithelial, and muscle differentiation. The analysis of transcription factor expression shows that the CD34 induction results in the upregulation of genes related to self‐renewal and lineage commitment. The preferential expression in CD34+ cells of genes supporting the HSC mobilization and homing to the bone marrow, such as chemokine receptors and integrins, gives the molecular basis for the higher engraftment capacity of CD34+ cells. Thus, the different kinetic status of CD34− and CD34+ cells, detailed by molecular and functional analysis, significantly influences their biological behavior.

Identification of a molecular signature predictive of sensitivity to differentiation induction in acute myeloid leukemia

Acute myeloid leukemia (AML) blasts are immature committed myeloid cells unable to spontaneously undergo terminal maturation, and characterized by heterogeneous sensitivity to natural differentiation inducers. Here, we show a molecular signature predicting the resistance or sensitivity of six myeloid cell lines to differentiation induced in vitro with retinoic acid or vitamin D. The identified signature was further validated by TaqMan assay for the prediction of response to an in vitro differentiation assay performed on 28 freshly isolated AML blast populations. The TaqMan assay successfully predicts the in vitro resistance or responsiveness of AML blasts to differentiation inducers. Furthermore, performing a meta-analysis of publicly available microarray data sets, we also show the accuracy of our prediction on known phenotypes and suggest that our signature could become useful for the identification of patients eligible for new therapeutic strategies.

ZFP36L1 Negatively Regulates Erythroid Differentiation of CD34+ Hematopoietic Stem Cells by Interfering with the Stat5b Pathway

ZFP36L1 negatively regulates erythroid differentiation of human hematopoietic progenitors by directly binding the 3′ UTR of Stat5b mRNA, thereby triggering its degradation. This study shows that posttranscriptional regulation is involved in the control of hematopoietic differentiation.

ZFP36 expression impairs glioblastoma cell lines viability and invasiveness by targeting multiple signal transduction pathways

RNA binding proteins belonging to the TIS11/TTP gene family regulate the stability of multiple targets. Their inactivation or deregulated expression has recently been related to cancer, and it has been suggested that they are capable of displaying tumor suppressor activities. Here we describe three new targets of ZFP36 (PIM-1, PIM-3 and XIAP) and show by different approaches that its ectopic expression is capable of impairing glioblastoma cell lines viability and invasiveness by interfering with different transduction pathways. Moreover, we provide evidence that compounds capable of inducing the expression of TIS11/TTP genes determine a comparable biological effect on the same cell contexts.

TFE3 transcription factor regulates the expression of MAFB during macrophage differentiation.

Transcription Factor for Immunoglobulin Heavy-Chain Enhancer 3 (Tfe3) is a transactivator of metabolic genes that are regulated through an EBox located in their promoters. It is involved in physiological processes such as osteoclast and macrophage differentiation, as well as in pathological processes such as translocations underlying different cancer diseases. MAFB is a basic region/leucine zipper transcription factor that affects transcription by binding specific DNA regions known as MARE. It plays a pivotal role in regulating lineage-specific hematopoiesis by repressing transcription of erythroid specific genes in myeloid cells and enhancing expression of macrophage and megakaryocytic genes. Here we have shown MAFB to be highly induced in human hematopoietic cells undergoing macrophage differentiation following Tfe3 ectopic expression, and to be down regulated, compared to the controls, in the same cell population following Phorbol Esters (PMA) dependent differentiation coupled to Tfe3 gene silencing. Electrophoretic mobility shift assays identified a Tfe3-binding site (EBox) in the MAFB promoter region that is conserved in different mammalian species. MAFB promoter was transactivated by co-expression of Tfe3 in reporter gene assays while deletion or mutation of the MAFB EBox prevented transactivation by Tfe3. Both of these genes were previously included in the group of transcription factors able to drive macrophage differentiation. The observation that MAFB belongs to the Tfe3 regulon suggests the existence of a pathway where these two gene families act synergistically to determine differentiation.

Gene expression profile of Vitamin D3 treated HL60 cells shows an incomplete molecular phenotypic conversion to monocytes.

By high density oligonucleotide microarrays we have studied the expression profile of proliferating and VD treated HL60 cells and the molecular phenotype of VD monocytes and that of CD14+ peripheral monocytes has been compared. The results indicate that important changes in functional categories of the differentially expressed genes underlie the differentiation transition from myeloblasts to monocytes. This differential gene expression pattern leads to an increased expression of mRNAs involved in surface and external activities since many of the VD induced genes belong to ligand binding, receptors, cell surface antigens, defense/immunity and adhesion molecules functional categories. The results also indicate that the molecular phenotypes of monocytes and VD induced cells diverge for a small but significant set of defense related genes. Particularly, class II MHC genes are not expressed in these cells. Furthermore, the high levels of expression of these genes induced by serum treatment of monocytes are decreased by VD.

Requirement of the coiled-coil domains of p92 c-Fes for nuclear localization in myeloid cells upon induction of differentiation

The nonreceptor tyrosine kinase Fes is implicated in myeloid cells differentiation. It has been observed that its localization can be cytoplasmic, perinuclear, or nuclear. To further characterize this point, we studied Fes subcellular localization in myeloid cell lines (HL60 and K562) and in COS1 cells. Fes was observed in both the nucleus and the cytoplasm of HL60, K562 cells overexpressing Fes and only in the cytoplasm of COS1 cells, suggesting that nuclear localization is cell context dependent. Moreover, in myeloid cells, the treatment with differentiation-inducing agents such as retinoic acid, phorbol esters and vitamin D, is followed by an increase of the oligomeric form of Fes in the nucleus. In fact, oligomerization seems to be necessary for translocation to occur, since Fes mutants missing the coiled-coil domains are not able to form oligomers and fail to localize in the nucleus. The active form of Fes is tyrosine phosphorylated; however, phosphorylation is not required for Fes to localize in the nucleus, since tyrosine kinase inhibitors do not block the translocation process.

Development of an IL-6 antagonist peptide that induces apoptosis in 7TD1 cells

Interleukin-6 (IL-6) is a pleiotropic cytokine involved in the regulation of proliferation and differentiation of hematopoietic cells and in the pathogenesis of many diseases, including multiple myeloma. This study pursues a way to interfere with IL-6 pathway in an attempt to modulate its biological activity. Here we describe the rational design and biological evaluation of peptides able to antagonize the murine IL-6 activity by interfering with IL-6 Receptor alpha in 7TD1 cells, a IL-6-dependent B-cell line. Of the peptide tested, only Guess 4a is capable of interfering with IL-6 transducing pathway, therefore inducing growth arrest and apoptosis of 7TD1 cells.

Loss of ZFP36 expression in colorectal cancer correlates to wnt/ β-catenin activity and enhances epithelial-to-mesenchymal transition through upregulation of ZEB1, SOX9 and MACC1

The mRNA-destabilizing protein ZFP36 has been previously described as a tumor suppressor whose expression is lost during colorectal cancer development. In order to evaluate its role in this disease, we restored ZFP36 expression in different cell contexts, showing that the presence of this protein impairs the epithelial-to-mesenchymal transition (EMT) and induces a higher susceptibility to anoikis. Consistently, we found that ZFP36 inhibits the expression of three key transcription factors involved in EMT: ZEB1, MACC1 and SOX9. Finally, we observed for the first time that its expression negatively correlates with the activity of Wnt/β-catenin pathway, which is constitutively activated in colorectal cancer. This evidence provides a clue on the mechanism leading to the loss of ZFP36 in CRC.

Italian family with two independent mutations: 3358T/A in BRCA1 and 8756delA in BRCA2 genes

Hereditary breast/ovarian cancer is a well-characterized clinical entity, largely attributed to the inheritance of BRCA1 or BRCA2 mutations. Among general population, the mutations frequency of these genes is very low; therefore, the identification of two independent mutations in the same family is a rare event. This study reports the presence of two mutations, one in the BRCA1 and the second in the BRCA2 gene in an Italian Caucasian kindred. This family is composed of more than 250 individuals, spanning through five generations, among which endogamy was a common phenomenon. Considering the tumor spectrum, this family is characterized by a high incidence of different types of cancer. In our study, we considered only three out of seven family units for BRCA1 and BRCA2 analysis. In one of the family units, we found independent mutations of both BRCA genes. The BRCA1 mutation on exon 11 (3358T→A) was identified originally in the index case and subsequently in 18 members of this family, whereas the same mutation was not detected in a related family member with male breast cancer. The male breast cancer patient led to the identification, through mutational analysis, of a new BRCA2 mutation (8756delA). This BRCA2 mutation was also found in the male breast cancer patients daughter. The discovery of the BRCA2 mutation allowed us to alert the patients daughter who, otherwise, could be falsely reassured since she had a negative BRCA1 test.