Ciro R. Rinaldi

Point Mutations in Two EVI1 Zn Fingers Abolish EVI1-GATA1 Interaction and Allow Erythroid Differentiation of Murine Bone Marrow Cells

ABSTRACT EVI1 is an aggressive nuclear oncoprotein deregulated by recurring chromosomal abnormalities in myelodysplastic syndrome (MDS). The expression of the corresponding gene is a very poor prognostic marker for MDS patients and is associated with severe defects of the erythroid lineage. We have recently shown that the constitutive expression of EVI1 in murine bone marrow results in a fatal disease with features characteristic of MDS, including anemia, dyserythropoiesis, and dysmegakaryopoiesis. These lineages are regulated by the DNA-binding transcription factor GATA1. EVI1 has two zinc finger domains containing seven motifs at the N terminus and three motifs at the C terminus. Supported by results of assays utilizing synthetic DNA promoters, it was earlier proposed that erythroid-lineage repression by EVI1 is based on the ability of this protein to compete with GATA1 for DNA-binding sites, resulting in repression of gene activation by GATA1. Here, however, we show that EVI1 is unable to bind to classic GATA1 sites. To understand the mechanism utilized by EVI1 to repress erythropoiesis, we used a combination of biochemical assays, mutation analyses, and in vitro bone marrow differentiation. The results indicate that EVI1 interacts directly with the GATA1 protein rather than the DNA sequence. We further show that this protein-protein interaction blocks efficient recognition or binding to DNA by GATA1. Point mutations that disrupt the geometry of two zinc fingers of EVI1 abolish the protein-protein interaction, leading to normal erythroid differentiation of normal murine bone marrow in vitro.

EVI1 Impairs Myelopoiesis by Deregulation of PU.1 Function

EVI1 is an oncogene inappropriately expressed in the bone marrow (BM) of approximately 10% of myelodysplastic syndrome (MDS) patients. This disease is characterized by severe anemia and multilineage myeloid dysplasia that are thought to be a major cause of mortality in MDS patients. We earlier reported on a mouse model that constitutive expression of EVI1 in the BM led to fatal anemia and myeloid dysplasia, as observed in MDS patients, and we subsequently showed that EVI1 interaction with GATA1 blocks proper erythropoiesis. Whereas this interaction could provide the basis for the erythroid defects in EVI1-positive MDS, it does not explain the alteration of myeloid differentiation. Here, we have examined the expression of several genes activated during terminal myelopoiesis in BM cells and identified a group of them that are altered by EVI1. A common feature of these genes is their regulation by the transcription factor PU.1. We report here that EVI1 interacts with PU.1 and represses the PU.1-dependent activation of a myeloid promoter. EVI1 does not seem to inhibit PU.1 binding to DNA, but rather to block its association with the coactivator c-Jun. After mapping the PU.1-EVI1 interaction sites, we show that an EVI1 point mutant, unable to bind PU.1, restores the activation of PU.1-regulated genes and allows a normal differentiation of BM progenitors in vitro.

Repression of RUNX1 Activity by EVI1: A New Role of EVI1 in Leukemogenesis

Recurring chromosomal translocations observed in human leukemia often result in the expression of fusion proteins that are DNA-binding transcription factors. These altered proteins acquire new dimerization properties that result in the assembly of inappropriate multimeric transcription complexes that deregulate hematopoietic programs and induce leukemogenesis. Recently, we reported that the fusion protein AML1/MDS1/EVI1 (AME), a product of a t(3;21)(q26;q22) associated with chronic myelogenous leukemia and acute myelogenous leukemia, displays a complex pattern of self-interaction. Here, we show that the 8th zinc finger motif of MDS1/EVI1 is an oligomerization domain involved not only in interaction of AME with itself but also in interactions with the parental proteins, RUNX1 and MDS1/EVI1, from which AME is generated. Because the 8th zinc finger motif is also present in the oncoprotein EVI1, we have evaluated the effects of the interaction between RUNX1 and EVI1 in vitro and in vivo. We found that in vitro, this interaction alters the ability of RUNX1 to bind to DNA and to regulate a reporter gene, whereas in vivo, the expression of the isolated 8th zinc finger motif of EVI1 is sufficient to block the granulocyte colony-stimulating factor-induced differentiation of 32Dcl3 cells, leading to cell death. As EVI1 is not detected in normal bone marrow cells, these data suggest that its inappropriate expression could contribute to hematopoietic transformation in part by a new mechanism that involves EVI1 association with key hematopoietic regulators, leading to their functional impairment.

Preferential nuclear accumulation of JAK2V617F in CD34+ but not in granulocytic, megakaryocytic, or erythroid cells of patients with Philadelphia-negative myeloproliferative neoplasia

Recently, Dawson et al identified a previously unrecognized nuclear role of JAK2 in the phosphorylation of histone H3 in hematopoietic cell lines. We searched nuclear JAK2 in total bone marrow (BM) cells and in 4 sorted BM cell populations (CD34(+), CD15(+), CD41(+), and CD71(+)) of 10 myeloproliferative neoplasia (MPN) patients with JAK2V617F mutation and 5 patients with wild-type JAK2 MPN. Confocal immunofluorescent images and Western blot analyses of nuclear and cytoplasmic fractions found nuclear JAK2 in CD34(+) cells of 10 of 10 JAK2-mutated patients but not in patients with wild-type JAK2. JAK2 was predominantly in the cytoplasmic fraction of differentiated granulocytic, megakaryocytic, or erythroid cells obtained from all patients. JAK2V617F up-regulates LMO2 in K562 and in JAK2V617F-positive CD34(+) cells. The selective JAK2 inhibitor AG490 normalizes the LMO2 levels in V617F-positive K562 and restores the cyto-plasmic localization of JAK2.

RUNX1-RUNX1 homodimerization modulates RUNX1 activity and function.

RUNX1 (AML1, CBFα2, PEBP2αB) is a transcription factor essential for the establishment of the hematopoietic stem cell. It is generally thought that RUNX1 exists as a monomer that regulates hematopoietic differentiation by interacting with tissue-specific factors and its DNA consensus through its N terminus. RUNX1 is frequently altered in human leukemia by gene fusions or point mutations. In general, these alterations do not affect the N terminus of the protein, and it is unclear how they consistently lead to hematopoietic transformation and leukemia. Here we report that RUNX1 homodimerizes through a mechanism involving C terminus-C terminus interaction. This RUNX1-RUNX1 interaction regulates the activity of the protein in reporter gene assays and modulates its ability to induce hematopoietic differentiation of hematopoietic cell lines. The promoters of genes regulated by RUNX1 often contain multiple RUNX1 binding sites. This arrangement suggests that RUNX1 could homodimerize to bring and hold together distant chromatin sites and factors and that if the dimerization region is removed by gene fusions or is altered by point mutations, as observed in leukemia, the ability of RUNX1 to regulate differentiation could be impaired.

Consistent Up-regulation of Stat3 Independently of Jak2 Mutations in a New Murine Model of Essential Thrombocythemia

Janus-activated kinase 2 (JAK2) mutations are common in myeloproliferative disorders; however, although they are detected in virtually all polycythemia vera patients, they are found in approximately 50% of essential thrombocythemia (ET) patients, suggesting that converging pathways/abnormalities underlie the onset of ET. Recently, the chromosomal translocation 3;21, leading to the fusion gene AML1/MDS1/EVI1 (AME), was observed in an ET patient. After we forced the expression of AME in the bone marrow (BM) of C57BL/6J mice, all the reconstituted mice died of a disease with symptoms similar to ET with a latency of 8 to 16 months. Peripheral blood smears consistently showed an elevated number of dysplastic platelets with anisocytosis, degranulation, and giant size. Although the AME-positive mice did not harbor Jak2 mutations, the BM of most of them had significantly higher levels of activated Stat3 than the controls. With combined biochemical and biological assays we found that AME binds to the Stat3 promoter leading to its up-regulation. Signal transducers and activators of transcription 3 (STAT3) analysis of a small group of ET patients shows that in about half of the patients, there is STAT3 hyperactivation independently of JAK2 mutations, suggesting that the hyperactivation of STAT3 by JAK2 mutations or promoter activation may be a critical step in development of ET.

BRAF Test and Cytological Diagnosis with a Single Fine Needle Cytology Sample

Objective: Recently, fine needle cytology (FNC) of the thyroid has been combined with biomolecular analysis. In particular, there has been detailed study of the V600E-BRAF mutation. The aim of our study is to demonstrate that with a single thyroid sample it is possible to obtain enough cellular material for both cytological diagnosis and a V600E-BRAF molecular test. Study Design: FNC was carried out under ultrasound guidance aided by an echographist and cytopathologist. We acquired one biopsy for each nodule with a 23-gauge needle without suction. The preparations were smeared by the pathologist onto one glass slide, air dried and stained with Diff-Quick. Cell adequacy was evaluated for each patient. The needle was washed by aspirating 2 ml of physiologic solution which was collected into a tube. The material was collected for molecular testing. Results: The following cytological diagnoses were made: not neoplastic, Tir2 (n = 227); indeterminate, Tir3 (n = 15); suspicious, Tir4 (n = 4), and malignancy, Tir5 (n = 12). The V600E-BRAF mutation was found in 0 of 227 Tir2 specimens, 2 of 15 (13.3%) Tir3 specimens, 2 of 4 (50%) Tir4 specimens and 9 of 12 (75%) Tir5 specimens. Conclusions: Our data showed that, in a routine clinical setting, FNC specimens can be handled properly to provide both morphological and molecular information. In fact, our tests show that with a single specimen it is possible to set up a slide for the cytological diagnosis and to obtain enough residual cellular material for DNA extraction (>70 ng) and for the identification of the V600E-BRAF mutation.

GATA1 is overexpressed in patients with essential thrombocythemia and polycythemia vera but not in patients with primary myelofibrosis or chronic myelogenous leukemia.

A letter to the editor is presented related to the case where GATA1 is overexpressed in patients with essential thrombocythemia and polycythemia vera, but not in patients with primary myelofibrosis or chronic myelogenous leukemia.

Treatment with Ipilimumab: A Case Report of Complete Response in a Metastatic Malignant Melanoma Patient

Introduction: Over the past year, 3 agents have been approved for the treatment of melanoma by the Food and Drug Administration. These include pegylated interferon α-2b for stage III melanoma, vemurafenib for unresectable or metastatic melanoma with BRAF V600E mutation, and ipilimumab for unresectable or metastatic melanoma. Case Presentation: We present here the case of a 65-year-old Caucasian male diagnosed with advanced melanoma in April 2011 and treated with ipilimumab (Yervoy®), a monoclonal antibody targeting cytotoxic T-lymphocyte-associated antigen 4 (CTLA-4), as second-line treatment after progression with dacarbazine, for (wild-type BRAF) metastatic melanoma. The patient was referred to us for several painful lumps on his right arm. A biopsy of one of them revealed melanoma. CT and PET scans did not show any other lesions or a primary site. The patient was started on first-line chemotherapy with dacarbazine 850 mg/m2 on day 1, every 3 weeks. After 3 cycles, the patient showed disease progression with an increase in size of the skin metastasis. Second-line treatment was started with ipilimumab 3 mg/kg on day 1, every 3 weeks. At the end of the treatment, after 4 cycles, we documented a complete clinical response with total resolution of the skin metastasis. At the time of writing this paper, our patient had finished his treatment more than 9 months earlier and is still in complete remission. Conclusion: This is a paradigmatic case where, despite extensive metastatic disease, treatment with ipilimumab has confirmed its efficacy. It is still an open question why only a minority of patients have such a remarkable response, and further trials are warranted to address this important question.

A Case of Abdominal Sarcoidosis in a Patient with Acute Myeloid Leukemia

The allogeneic bone marrow transplantation usually preceded by induction chemotherapy, in fit patients, represents the gold standard in the acute myeloid leukaemia. In the last years, many trials have been set up with the view of improving the number of remissions during the induction by adding new drugs. Several early or late side effects have been described in the literature. We herein present a patient with acute myeloid leukaemia patient who, after chemotherapy, developed ascites that turned out to be abdominal sarcoidosis.