Caren Furlonger

Targeted disruption of IRF-1 or IRF-2 results in abnormal type I IFN gene induction and aberrant lymphocyte development

Interferon regulatory factor 1 (IRF-1), a transcriptional activator, and its antagonistic repressor, IRF-2, were originally identified as regulators of the type I interferon (IFN) system. We have generated mice deficient in either IRF-1 or IRF-2 by gene targeting in embryonic stem cells. IRF-1-deficient fibroblasts lacked the normally observed type I IFN induction by poly(I):poly(C), while they induced type I IFN to similar levels as the wild type following Newcastle disease virus (NDV) infection. In contrast, IRF-2-deficient fibroblasts showed up-regulated type I IFN induction by NDV infection. A profound reduction of TCR alpha beta+CD4-CD8+ T cells in IRF-1-deficient mice, with a thymocyte developmental defect, reveals a critical role for IRF-1 in T cell development. IRF-2-deficient mice exhibited bone marrow suppression of hematopoiesis and B lymphopoiesis and mortality following lymphocytic choriomeningitis virus infection.

Cytokine Signaling and Hematopoietic Homeostasis Are Disrupted in Lnk-deficient Mice

The adaptor protein Lnk, and the closely related proteins APS and SH2B, form a subfamily of SH2 domain-containing proteins implicated in growth factor, cytokine, and immunoreceptor signaling. To elucidate the physiological function of Lnk, we derived Lnk-deficient mice. Lnk −/− mice are viable, but display marked changes in the hematopoietic compartment, including splenomegaly and abnormal lymphoid and myeloid homeostasis. The in vitro proliferative capacity and absolute numbers of hematopoietic progenitors from Lnk − / − mice are greatly increased, in part due to hypersensitivity to several cytokines. Moreover, an increased synergy between stem cell factor and either interleukin (IL)-3 or IL-7 was observed in Lnk − / − cells. Furthermore, Lnk inactivation causes abnormal modulation of IL-3 and stem cell factor–mediated signaling pathways. Consistent with these results, we also show that Lnk is highly expressed in multipotent cells and committed precursors in the erythroid, megakaryocyte, and myeloid lineages. These data implicate Lnk as playing an important role in hematopoiesis and in the regulation of growth factor and cytokine receptor–mediated signaling.

Caspase-3 regulates cell cycle in B cells: a consequence of substrate specificity.

Caspases are important for apoptosis but are also involved in mammalian cell survival and cell division. Here we report that caspase-3 is a negative regulator of B cell cycling. Mice deficient in caspase-3 (Casp3−/− mice) have increased numbers of splenic B cells that show normal apoptosis but enhanced proliferation in vivo and hyperproliferation after mitogenic stimulation in vitro. Cdkn1a encodes p21 (also called Waf1 or Cip1), a cyclin-dependent kinase (CDK) inhibitor. Although expression of p21 was increased, CDK activities and proliferating cell nuclear antigen (PCNA) were increased in Casp3−/− B cells. Using Casp3−/−Cdkn1a−/− mice, we show that the hyperproliferation of Casp3−/− B cells is abolished when Cdkn1a is also deleted. Our genetic and biochemical data demonstrate that caspase-3 is essential in the regulation of B cell homeostasis.

Structure-activity relationships of orotidine-5'-monophosphate decarboxylase inhibitors as anticancer agents.

A series of 6-substituted and 5-fluoro-6-substituted uridine derivatives were synthesized and evaluated for their potential as anticancer agents. The designed molecules were synthesized from either fully protected uridine or the corresponding 5-fluorouridine derivatives. The mononucleotide derivatives were used for enzyme inhibition investigations against ODCase. Anticancer activities of all the synthesized derivatives were evaluated using the nucleoside forms of the inhibitors. 5-Fluoro-UMP was a very weak inhibitor of ODCase. 6-Azido-5-fluoro and 5-fluoro-6-iodo derivatives are covalent inhibitors of ODCase, and the active site Lys145 residue covalently binds to the ligand after the elimination of the 6-substitution. Among the synthesized nucleoside derivatives, 6-azido-5-fluoro, 6-amino-5-fluoro, and 6-carbaldehyde-5-fluoro derivatives showed potent anticancer activities in cell-based assays against various leukemia cell lines. On the basis of the overall profile, 6-azido-5-fluoro and 6-amino-5-fluoro uridine derivatives exhibited potential for further investigations.