Loss of the retinoblastoma tumor suppressor: differential action on transcriptional programs related to cell cycle control and immune function.

Functional inactivation of the retinoblastoma tumor suppressor gene product (RB) is a common event in human cancers. Classically, RB functions to constrain cellular proliferation, and loss of RB is proposed to facilitate the hyperplastic proliferation associated with tumorigenesis. To understand the repertoire of regulatory processes governed by RB, two models of RB loss were utilized to perform microarray analysis. In murine embryonic fibroblasts harboring germline loss of RB, there was a striking deregulation of gene expression, wherein distinct biological pathways were altered. Specifically, genes involved in cell cycle control and classically associated with E2F-dependent gene regulation were upregulated via RB loss. In contrast, a program of gene expression associated with immune function and response to pathogens was significantly downregulated with the loss of RB. To determine the specific influence of RB loss during a defined period and without the possibility of developmental compensation as occurs in embryonic fibroblasts, a second system was employed wherein Rb was acutely knocked out in adult fibroblasts. This model confirmed the distinct regulation of cell cycle and immune modulatory genes through RB loss. Analyses of cis-elements supported the hypothesis that the majority of those genes upregulated with RB loss are regulated via the E2F family of transcription factors. In contrast, those genes whose expression was reduced with the loss of RB harbored different promoter elements. Consistent with these analyses, we found that disruption of E2F-binding function of RB was associated with the upregulation of gene expression. In contrast, cells harboring an RB mutant protein (RB-750F) that retains E2F-binding activity, but is specifically deficient in the association with LXCXE-containing proteins, failed to upregulate these same target genes. However, downregulation of genes involved in immune function was readily observed with disruption of the LXCXE-binding function of RB. Thus, these studies demonstrate that RB plays a significant role in both the positive and negative regulations of transcriptional programs and indicate that loss of RB has distinct biological effects related to both cell cycle control and immune function.

Determination of non-bilayer phospholipid arrangements and their antibodies in placentae and sera of patients with hypertensive disorders of pregnancy.

Studies suggest that preeclampsia (PE) originates in the placenta and is associated with deficient trophoblast invasion of spiral arteries. The direct cause remains unknown, but preeclampsia is often associated with circulating factors that can induce generalized endothelial dysfunction. Antiphospholipid antibodies (APA) in circulation are also associated with vascular diseases. Although the quantification of APA is not currently used as a prognostic of the risk of PE, studies suggest that thrombophilias play a role in PE pathogenesis. In fact, the pathology of placentae from PE and Antiphospholipid syndrome patients is similar; atherosis, thrombosis and infarction, and endothelium activation represent the pathological mechanisms. We identified a new antibody which recognizes non-bilayer phospholipid arrangements (NPA) in membrane models and in cell membranes in vivo, and which triggered an autoimmune-like disease in mice. We evaluated the presence of NPA in the placentae and in sera, and whether NPA induced NPA antibodies in patients with hypertensive disorders of pregnancy (HDP). Results showed increased levels of NPA in the syncytiotrophoblast, extravillous cytotrophoblast, syncytial knots and the amnion epithelial cell membranes of the placenta, as well as increases in NPA and NPA antibodies in sera from HDP patients, when compared with controls. This suggests that NPA derived from placenta could be one of multiple factors associated with pregnancy pathologies.

Serum levels of prolactin, growth hormone, and cortisol in burn patients: correlations with severity of burn, serum cytokine levels, and fatality.

In this study, we measured serum prolactin (PRL), cortisol, growth hormone, interleukin (IL)-1beta, IL-6, IL-8, IL-10, IL-12, and tumor necrosis factor-alpha in patients admitted with small-to-moderate burn injuries. Serum samples were obtained at the time of admission from 49 adult male burn patients with ages ranging from 18 to 91 years and TBSA ranging from 0.001 to 60%. The levels of serum PRL, IL-8, IL-6, and IL-1beta correlated positively with the TBSA, whereas only serum IL-8 levels correlated positively with fatality. Each of these factors were increased at least 2-fold at the higher burn severity. Not surprisingly, there was a large degree of variability in the hormone and cytokine levels in this patient population, which presumably reflects individual levels of stress, as well as other physiological variables. We also studied relationships between serum hormone levels and serum cytokine levels in this context. Linear regression analysis revealed a significant positive correlation between the serum PRL level and the levels of IL-10, IL-6, and IL-8. These results indicate that PRL responds to burn injury at early time points and that a subset of cytokines are involved in the early response to burn injury.