Ivan Horak

Ulcerative colitis-like disease in mice with a disrupted interleukin-2 gene

Mice deficient for interleukin-2 develop normally during the first 3-4 weeks of age. However, later on they become severely compromised, and about 50% of the animals die between 4 and 9 weeks after birth. Of the remaining mice, 100% develop an inflammatory bowel disease with striking clinical and histological similarity to ulcerative colitis in humans. The alterations of the immune system are characterized by a high number of activated T and B cells, elevated immunoglobulin secretion, anti-colon antibodies, and aberrant expression of class II major histocompatibility complex molecules. The data provide evidence for a primary role of the immune system in the etiology of ulcerative colitis and strongly suggest that the disease results from an abnormal immune response to a normal antigenic stimulus.

Immunodeficiency and Chronic Myelogenous Leukemia-like Syndrome in Mice with a Targeted Mutation of the ICSBP Gene

Interferon consensus sequence binding protein (ICSBP) is a transcription factor of the interferon (IFN) regulatory factor (IRF) family. Mice with a null mutation of ICSBP exhibit two prominent phenotypes related to previously described activities of the IRF family. The first is enhanced susceptibility to virus infections associated with impaired production of IFN(gamma). The second is deregulated hematopoiesis in both ICSBP-/- and ICSBP+/- mice that manifests as a syndrome similar to human chronic myelogenous leukemia. The chronic period of the disease progresses to a fatal blast crisis characterized by a clonal expansion of undifferentiated cells. Normal mice injected with cells from mice in blast crisis developed acute leukemia within 6 weeks of transfer. These results suggest a novel role for ICSBP in regulating the proliferation and differentiation of hematopoietic progenitor cells.

Adults and children with small non-cleaved-cell lymphoma have a similar excellent outcome when treated with the same chemotherapy regimen.

PURPOSE We have used identical treatment protocols for adults and children with small non-cleaved-cell lymphoma (SNCL) for many years and report here the results of two successive treatment regimens in these age groups. PATIENTS AND METHODS Seventy-two patients (39 adults and 33 children) were treated with protocol 77-04 between 1977 and 1985. All patients, except those with resected abdominal disease, received 15 cycles of a combination of cyclophosphamide (CTX), doxorubicin (ADR), prednisone (PRED), vincristine (VCR), high-dose methotrexate (MTX), and intrathecal (IT) therapy. Forty-one patients (20 adults and 21 children) were treated with protocol 89-C-41, which has been used since 1989. High-risk patients received four alternating cycles (with a total duration of 12 to 15 weeks) of an intensified version of protocol 77-04 without PRED (CODOX-M), and a new drug combination consisting of ifosfamide, etoposide, high-dose cytarabine (ara-C), and IT MTX (IVAC). Low-risk patients received three cycles of the CODOX-M regimen. High-risk patients were randomized to either receive or not receive granulocyte-macrophage colony-stimulating factor (GM-CSF). RESULTS Event-free survival (EFS) in protocol 77-04 was 56% at 2 years and beyond. EFS in protocol 89-C-41 was 92% at 2 years and beyond. GM-CSF was associated with increased thrombocytopenia. CONCLUSION Adults and children with SNCL have a similar prognosis when treated with the same chemotherapy. EFS in high-risk patients has been markedly improved by including IVAC in protocol 89-C-41, and excellent results can be achieved with only four cycles of therapy. In protocol 89-C-41, GM-CSF was not beneficial.

Sialylation is essential for early development in mice

Sialic acids are widely expressed as terminal carbohydrates on glycoconjugates of eukaryotic cells. Sialylation is crucial for a variety of cellular functions, such as cell adhesion or signal recognition, and regulates the biological stability of glycoproteins. The key enzyme of sialic acid biosynthesis is the bifunctional UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (UDP-GlcNAc 2-epimerase), which catalyzes the first two steps of sialic acid biosynthesis in the cytosol. We report that inactivation of the UDP-GlcNAc 2-epimerase by gene targeting causes early embryonic lethality in mice, thereby emphasizing the fundamental role of this bifunctional enzyme and sialylation during development. The need of UDP-GlcNAc 2-epimerase for a defined sialylation process is exemplified with the polysialylation of the neural cell adhesion molecule in embryonic stem cells.

Characterization of a New Humanized Anti-CD20 Monoclonal Antibody, IMMU-106, and Its Use in Combination with the Humanized Anti-CD22 Antibody, Epratuzumab, for the Therapy of Non-Hodgkin’s Lymphoma

Purpose: A new humanized anti-CD20 monoclonal antibody (MAb), IMMU-106, was evaluated to elucidate its action as an antilymphoma therapeutic, as a single agent, and in combination with the anti-CD22 MAb, epratuzumab. Experimental Design: Antiproliferative effects, apoptotic effects, and the ability of IMMU-106 to mediate complement-mediated cytotoxicity and antibody-dependent cellular cytotoxicity on a panel of non-Hodgkin’s lymphoma (NHL) cell lines were compared with the chimeric anti-CD20 MAb, rituximab, and evaluated in light of the various levels of antigen expression by the cell lines. In vivo therapy studies were performed in SCID mice bearing disseminated Raji lymphoma. Results: The mechanisms of cytotoxicity of IMMU-106 were found to be similar to rituximab, and include direct apoptosis, antibody-dependent cellular cytotoxicity, and complement-mediated cytotoxicity. IMMU-106 was also found to be very similar to rituximab in terms of antigen-binding specificity, binding avidity, and dissociation constant. Treatment of Raji-bearing SCID mice with IMMU-106 yielded median survival increases of up to 4.2-fold compared with control mice. Survival in mice treated with IMMU-106 plus epratuzumab was compared with IMMU-106 treatment alone. Although the combined treatment did not improve median survival, an increased proportion of long-term survivors was observed. An enhanced antiproliferative effect was also observed in vitro in SU-DHL-6 cells when IMMU-106 was combined with epratuzumab. These findings are consistent with the up-regulation of CD22 expression observed after pretreatment of NHL cells in vitro with CD20 MAb (IMMU-106). Conclusions: It is expected that in humans IMMU-106 should be at least as effective as rituximab and, due to its human framework construction, it may exhibit different pharmacokinetic, toxicity, and therapy profiles. In addition, it may be possible to enhance efficacy by combination therapy comprised of anti-CD20 and other B-cell lineage targeting MAbs, such as epratuzumab. The current results emphasize that in vitro as well as in vivo studies with many of the NHL cell lines were generally predictive of the known activity of anti-CD20 MAbs in NHL patients, as well as the enhanced efficacy of epratuzumab combined with rituximab observed in early clinical trials.

Combination antibody therapy with epratuzumab and rituximab in relapsed or refractory non-Hodgkin's lymphoma

PURPOSE To explore the safety and therapeutic activity of combination anti-B-cell monoclonal antibody therapy in non-Hodgkins lymphoma (NHL). PATIENTS AND METHODS Twenty-three patients with recurrent B-cell lymphoma received anti-CD22 epratuzumab 360 mg/m(2) and anti-CD20 rituximab 375 mg/m(2) monoclonal antibodies weekly for four doses each. Sixteen patients had indolent histologies (15 with follicular lymphoma) and seven had aggressive NHL (all diffuse large B-cell lymphoma [DLBCL]). Indolent patients had received a median of one (range, one to six) prior treatment, with 31% refractory to their last therapy and 81% with high-risk Follicular Lymphoma International Prognostic Index scores. Patients with DLBCL had a median of three (range, one to eight) prior regimens (14% resistant to last treatment) and 71% had high intermediate-risk or high-risk International Prognostic Index scores. All patients were rituximab naïve. RESULTS Treatment was well tolerated, with toxicities principally infusion-related and predominantly grade 1 or 2. Ten (67%) patients with follicular NHL achieved an objective response (OR), including nine of 15 (60%) with complete responses (CRs and unconfirmed CRs). Four of six assessable patients (67%) with DLBCL achieved an OR, including three (50%) CRs. Median time to progression for all indolent NHL patients was 17.8 months. CONCLUSION The full-dose combination of epratuzumab with rituximab was well tolerated and had significant clinical activity in NHL, suggesting that this combination should be tested in comparison with single-agent treatment.

ISG15, an Interferon-Stimulated Ubiquitin-Like Protein, Is Not Essential for STAT1 Signaling and Responses against Vesicular Stomatitis and Lymphocytic Choriomeningitis Virus

ABSTRACT ISG15 is an interferon-induced ubiquitin-like modifier which can be conjugated to distinct, but largely unknown, proteins. ISG15 has been implicated in a variety of biological activities, which encompass antiviral defense, immune responses, and pregnancy. Mice lacking UBP43 (USP18), the ISG15-deconjugating enzyme, develop a severe phenotype with brain injuries and lethal hypersensitivity to poly(I:C). It has been reported that an augmented conjugation of ISG15 in the absence of UBP43 induces prolonged STAT1 phosphorylation and that the ISG15 conjugation plays an important role in the regulation of JAK/STAT and interferon signaling (O. A. Malakhova, M. Yan, M. P. Malakhov, Y. Yuan, K. J. Ritchie, K. I. Kim, L. F. Peterson, K. Shuai, and D. E. Zhang, Genes Dev. 17:455-460, 2003). Here, we report that ISG15−/− mice are viable and fertile and display no obvious abnormalities. Lack of ISG15 did not affect the development and composition of the main cellular compartments of the immune system. The interferon-induced antiviral state and immune responses directed against vesicular stomatitis virus and lymphocytic choriomeningitis virus were not significantly altered in the absence of ISG15. Furthermore, interferon- or endotoxin-induced STAT1 tyrosine-phosphorylation, as well as expression of typical STAT1 target genes, remained unaffected by the lack of ISG15. Thus, ISG15 is dispensable for STAT1 and interferon signaling.

A RNA antagonist of hypoxia-inducible factor-1α, EZN-2968, inhibits tumor cell growth

Hypoxia-inducible factor-1 (HIF-1) is a transcription factor that plays a critical role in angiogenesis, survival, metastasis, drug resistance, and glucose metabolism. Elevated expression of the α-subunit of HIF-1 (HIF-1α), which occurs in response to hypoxia or activation of growth factor pathways, is associated with poor prognosis in many types of cancer. Therefore, down-regulation of HIF-1α protein by RNA antagonists may control cancer growth. EZN-2968 is a RNA antagonist composed of third-generation oligonucleotide, locked nucleic acid, technology that specifically binds and inhibits the expression of HIF-1α mRNA. In vitro, in human prostate (15PC3, PC3, and DU145) and glioblastoma (U373) cells, EZN-2968 induced a potent, selective, and durable antagonism of HIF-1 mRNA and protein expression (IC50, 1-5 nmol/L) under normoxic and hypoxic conditions associated with inhibition of tumor cell growth. Additionally, down-regulation of HIF-1α protein by EZN-2968 led to reduction of its transcriptional targets and of human umbilical vein endothelial cell tube formation. In vivo, administration of EZN-2968 to normal mice led to specific, dose-dependent, and highly potent down-regulation of endogenous HIF-1α and vascular endothelial growth factor in the liver. The effect can last for days after administration of single dose of EZN-2968 and is associated with long residence time of locked nucleic acid in certain tissues. In efficacy studies, tumor reduction was found in nude mice implanted with DU145 cells treated with EZN-2968. Ongoing phase I studies of EZN-2968 in patients with advanced malignancies will determine optimal dose and schedule for the phase II program. [Mol Cancer Ther 2008;7(11):3598–608]

AML1-ETO Inhibits Maturation of Multiple Lymphohematopoietic Lineages and Induces Myeloblast Transformation in Synergy with ICSBP Deficiency

The translocation (8;21), generating the AML1-ETO fusion protein, is one of the most frequent chromosomal abnormalities associated with acute myelogenous leukemia (AML). To elucidate its role in oncogenesis, bone marrow (BM) cells were infected with a retroviral vector carrying AML1-ETO and transplanted into mice. In contrast to previous transgenic mouse models, we show that AML1-ETO directly stimulates granulopoiesis, suppresses erythropoiesis, and impairs the maturation of myeloid, B, and T lymphoid cells in vivo. To determine the significance of earlier findings that expression of the tumor suppressor ICSBP is often downregulated in AML myeloblasts, AML1-ETO was introduced into BM cells derived from mice lacking the interferon regulatory factor ICSBP. Our findings demonstrate that AML1-ETO synergizes with an ICSBP deficiency to induce myeloblastic transformation in the BM, reminiscent of AML.

Interleukin‐2 Deficient Mice: A New Model to Study Autoimmunity and Self‐Tolerance

Previous work revealed IL-2 as a key cytokine regulating the growth, differentiation and function of lymphocytes (for review see Smith 1988. Paul 1989). It is a glycoprotein of about 15 kD (Gillis et al. 1978) which mediates cell communications via a complex receptor system composed of three subunits. apy (for review see Taniguchi & Minami 1993. Kishimoto et al. 1994). Only the a-chain is specific for IL-2. the p-subunit is used also by IL-15 (Giri et al. 1994. Burton et al. 1994) and the y-subunit is used by IL-2, IL-4. IL-7. lL-9 and IL-15 (Noguchi et al. 1993, Russell et al. 1993. Kondo et al. 1993). Since IL-2 is considered as an indispensable factor for cytotoxic responses, it is used as an immunotherapeutic agent for the treatment of patients with disseminated cancers and with infectious diseases (Rosenberg 1988, Kaplan et al. 1991, Fauci 1993). However, the exact role of IL-2 in vivo is far from being understood. Its elucidation was hampered by a lack of suitable experimental systems that would allow to evaluate the pleiotropic activities of this interleukin in the context of the whole immune system. The technology of targeted mutagenesis in mouse germline developed in the laboratories of Capecchi and Smithies (Thomas & Capecchi 1989,