In vivo administration of interferon gamma does not cause marrow aplasia in mice with a targeted disruption of FANCC

Fanconi anemia proteins and their interacting partners: a molecular puzzle

In recent years, Fanconi anemia (FA) has been the subject of intense investigations, primarily in the DNA repair research field. Many discoveries have led to the notion of a canonical pathway, termed the FA pathway, where all FA proteins function sequentially in different protein complexes to repair DNA cross-link damages. Although a detailed architecture of this DNA cross-link repair pathway is emerging, the question of how a defective DNA cross-link repair process translates into the disease phenotype is unresolved. Other areas of research including oxidative metabolism, cell cycle progression, apoptosis, and transcriptional regulation have been studied in the context of FA, and some of these areas were investigated before the fervent enthusiasm in the DNA repair field. These other molecular mechanisms may also play an important role in the pathogenesis of this disease. In addition, several FA-interacting proteins have been identified with roles in these “other” nonrepair molecular functions. Thus, the goal of this paper is to revisit old ideas and to discuss protein-protein interactions related to other FA-related molecular functions to try to give the reader a wider perspective of the FA molecular puzzle.

Negative feedback regulation of T helper type 1 (Th1)/Th2 cytokine balance via dendritic cell and natural killer T cell interactions

The ability of extracellular stimuli to modulate dendritic cell (DC) activation of natural killer T (NKT) cells was not well understood. We investigated the effects of the T helper type 1 (Th1)/Th2-cytokine environment on DC induction of NKT cell-mediated cytokine production in mice. Pretreatment of myeloid DCs with Th1 or Th2 cytokines, interleukin (IL)-4 or interferon (IFN)-gamma, led to the enhanced production of reciprocal cytokines by NKT cells (eg, IL-4 pretreatment led to the enhanced production of Th1 cytokines) in vitro and in vivo. Thus, the recognition of Th1 or Th2 cytokines by DCs acts as a negative feedback loop to maintain Th1/Th2-cytokine balance via NKT cell functions. Using these data, we manipulated cytokine levels and innate cytolytic activity in vivo to increase an antitumor response. This is the first description of a novel regulation system governing Th1/Th2 cytokine balance involving DCs and NKT cells.

Continuous in vivo infusion of interferon-gamma (IFN-gamma) preferentially reduces myeloid progenitor numbers and enhances engraftment of syngeneic wild-type cells in Fancc-/- mice

Fanconi anemia (FA) is characterized by bone marrow (BM) failure and cancer susceptibility. Identification of the cDNAs of many FA complementation types allows the potential of using gene transfer technology to introduce functional cDNAs as transgenes into autologous stem cells and provide a cure for the BM failure in FA patients. Previous studies in FA murine models and in a phase 1 clinical trial suggest that myelopreparation is required for significant engraftment of exogenous, genetically corrected stem cells. Since myeloid progenitors from Fancc-/- mice and human Fanconi anemia group C protein (FANCC) patients have increased apoptosis in response to interferon gamma (IFN-gamma) in vitro, we hypothesized that IFN-gamma may be useful as a nongenotoxic, myelopreparative conditioning agent. To test this hypothesis, IFN-gamma was administered as a continuous infusion to Fancc-/- and wild-type (WT) mice for 1 week. Primitive and mature myeloid lineages were preferentially reduced in IFN-gamma-treated Fancc-/- mice. Further, IFN-gamma conditioning of Fancc-/- recipients was sufficient as a myelopreparative regimen to allow consistent engraftment of isogenic WT repopulating stem cells. Collectively, these data demonstrate that Fancc-/- hematopoietic cell populations have increased hypersensitivity to IFN-gamma in vivo and that IFN-gamma conditioning may be useful as a nongenotoxic strategy for myelopreparation in this disorder.