Brian K. Dieckgraefe

Treatment of active Crohn's disease with recombinant human granulocyte-macrophage colony-stimulating factor

Treatment for Crohns disease is aimed at immunosuppression. Yet inherited disorders associated with defective innate immunity often lead to development of a Crohns-like disease. We performed an open-label dose-escalation trial (4-8 microg/kg per day) to investigate the safety and possible benefit of granulocyte-macrophage colony-stimulating factor (GM-CSF) in the treatment of 15 patients with moderate to severe Crohns disease. No patients had worsening of their disease. Adverse events were negligible and included minor injection site reactions and bone pain. Patients had a significant decrease in mean Crohns disease activity index (CDAI) score during treatment (p<0.0001). After 8 weeks of treatment, mean CDAI had fallen by 190 points. Overall, 12 patients had a decrease in CDAI of more than 100 points, and eight achieved clinical remission. Retreatment was effective, and treatment was associated with increased quality-of-life measures. GM-CSF may offer an alternative to traditional immunosuppression in treatment of Crohns disease.

Knockdown of RNA binding protein musashi-1 leads to tumor regression in vivo.

BACKGROUND & AIMS In the gut, tumorigenesis is thought to arise from the stem cell population located near the base of intestinal and colonic crypts. The RNA binding protein musashi-1 (Msi-1) is a putative intestinal and progenitor/stem cell marker. Msi-1 expression is increased during rat brain development and in APC(min/+) mice tumors. This study examined a potential role of Msi-1 in tumorigenesis. METHODS Msi-1 small interfering RNA (siRNA) was administered as a liposomal preparation to HCT116 colon adenocarcinoma xenografts in athymic nude mice and tumor volume was measured. Cell proliferation was assessed by hexosaminidase and 3-(4,5-dimethylthiazol 2-yl)-2,5-diphenyltetrazolium bromide MTT assays. siRNA-transfected cells were subjected to 12 Gy gamma-irradiation. Apoptosis was assessed by immunoreactive activated caspase-3 and mitosis was assessed by phosphorylated histone H3 staining. The tumor xenografts were stained similarly for phosphorylated histone H3, activated caspase-3, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling, Notch-1, and p21(WAF1). Furthermore, siRNA-transfected cells were subjected to cell-cycle analysis and Western blot analyses for Notch-1 and p21(WAF1). RESULTS Knockdown of Msi-1 resulted in tumor growth arrest in xenografts, reduced cancer cell proliferation, and increased apoptosis alone and in combination with radiation injury. siRNA-mediated reduction of Msi-1 lead to mitotic catastrophe in tumor cells. Moreover, there was inhibition of Notch-1 and up-regulation of p21(WAF1) after knockdown of Msi-1. CONCLUSIONS Our results show the involvement of Msi-1 in cancer cell proliferation, inhibition of apoptosis, and mitotic catastrophe, suggesting an important potential mechanism for its role in tumorigenesis.

Isolation and characterization of a cDNA encoding a novel member of the human regenerating protein family: Reg IV

Human Reg and Reg-related genes constitute a multi-gene family belonging to the calcium (C-type) dependent lectin superfamily. Regenerating gene family members are expressed in the proximal gastrointestinal (GI) tract and ectopically at other sites in the setting of tissue injury. By high-throughput sequence analysis of a large inflammatory bowel disease library, two cDNAs have been isolated which encode a novel member of this multigene family. Based on primary sequence homology, tissue expression profiles, and shared exon-intron junction genomic organization, we assign this gene to the regenerating gene family. Specific protein structural differences suggest that the current three regenerating gene subtypes should be expanded to four. We demonstrate that Reg IV has a highly restricted tissue expression pattern, with prominent expression in the gastrointestinal tract. Reg IV mRNA expression is significantly up-regulated by mucosal injury from active Crohns disease or ulcerative colitis.

Diphenyl difluoroketone: a curcumin derivative with potent in vivo anticancer activity.

Diphenyl difluoroketone (EF24), a molecule having structural similarity to curcumin, was reported to inhibit proliferation of a variety of cancer cells in vitro. However, the efficacy and in vivo mechanism of action of EF24 in gastrointestinal cancer cells have not been investigated. Here, we assessed the in vivo therapeutic effects of EF24 on colon cancer cells. Using hexosaminidase assay, we determined that EF24 inhibits proliferation of HCT-116 and HT-29 colon and AGS gastric adenocarcinoma cells but not of mouse embryo fibroblasts. Furthermore, the cancer cells showed increased levels of activated caspase-3 and increased Bax to Bcl-2 and Bax to Bcl-xL ratios, suggesting that the cells were undergoing apoptosis. At the same time, cell cycle analysis showed that there was an increased number of cells in the G(2)-M phase. To determine the effects of EF24 in vivo, HCT-116 colon cancer xenografts were established in nude mice and EF24 was given i.p. EF24 significantly suppressed the growth of colon cancer tumor xenografts. Immunostaining for CD31 showed that there was a lower number of microvessels in the EF24-treated animals coupled with decreased cyclooxygenase-2, interleukin-8, and vascular endothelial growth factor mRNA and protein expression. Western blot analyses also showed decreased AKT and extracellular signal-regulated kinase activation in the tumors. Taken together, these data suggest that the novel curcumin-related compound EF24 is a potent antitumor agent that induces caspase-mediated apoptosis during mitosis and has significant therapeutic potential for gastrointestinal cancers.

Granulocyte macrophage colony-stimulating factor ameliorates DSS-induced experimental colitis

Background: Sargramostim, granulocyte macrophage colony‐stimulating factor (GM‐CSF), a hematopoietic growth factor, stimulates cells of the intestinal innate immune system. Clinical trials show that sargramostim induces clinical response and remission in patients with active Crohns disease. To study the mechanism, we examined the effects of GM‐CSF in the dextran sulfate sodium (DSS)‐induced acute colitis model. We hypothesized that GM‐CSF may work through effects on dendritic cells (DCs). Methods: Acute colitis was induced in Balb/c mice by administration of DSS in drinking water. Mice were treated with daily GM‐CSF or phosphate‐buffered saline (PBS). To probe the role of plasmacytoid DCs (pDCs) in the response to GM‐CSF, we further examined the effects of monoclonal antibody 440c, which is specific for a sialic acid‐binding immunoglobulin (Ig)‐like lectin expressed on pDCs. Results: GM‐CSF ameliorates acute DSS‐induced colitis, resulting in significantly improved clinical parameters and histology. Microarray analysis showed reduced expression of proinflammatory genes including TNF‐&agr; and IL1‐&bgr;; the results were further confirmed by real‐time reverse‐transcriptase polymerase chain reaction and serum Bio‐plex analysis. GM‐CSF treatment significantly expands pDCs and type 1 IFN production. Administration of mAb 440c completely blocked the therapeutic effect of GM‐CSF. GM‐CSF is also effective in RAG1−/− mice, demonstrating activity‐independent effects on T and B cells. IFN‐&bgr; administration mimics the therapeutic effect of GM‐CSF in DSS‐treated mice. GM‐CSF increases systemic and mucosal type 1 IFN expression and exhibits synergy with pDC activators, such as microbial cytosine‐phosphate‐guanosine (CpG) DNA. Conclusions: GM‐CSF is effective in the treatment of DSS colitis in a mechanism involving the 440c+ pDC population.

Translation regulatory factor RBM3 is a proto-oncogene that prevents mitotic catastrophe

RNA-binding proteins play a key role in post-transcriptional regulation of mRNA stability and translation. We have identified that RBM3, a translation regulatory protein, is significantly upregulated in human tumors, including a stage-dependent increase in colorectal tumors. Forced RBM3 overexpression in NIH3T3 mouse fibroblasts and SW480 human colon epithelial cells increases cell proliferation and development of compact multicellular spheroids in soft agar suggesting the ability to induce anchorage-independent growth. In contrast, downregulating RBM3 in HCT116 colon cancer cells with specific siRNA decreases cell growth in culture, which was partially overcome when treated with prostaglandin E2, a product of cyclooxygenase (COX)-2 enzyme activity. Knockdown also resulted in the growth arrest of tumor xenografts. We have also identified that RBM3 knockdown increases caspase-mediated apoptosis coupled with nuclear cyclin B1, and phosphorylated Cdc25c, Chk1 and Chk2 kinases, implying that under conditions of RBM3 downregulation, cells undergo mitotic catastrophe. RBM3 enhances COX-2, IL-8 and VEGF mRNA stability and translation. Conversely, RBM3 knockdown results in loss in the translation of these transcripts. These data demonstrate that the RNA stabilizing and translation regulatory protein RBM3 is a novel proto-oncogene that induces transformation when overexpressed and is essential for cells to progress through mitosis.

An open-labelled study of granulocyte colony-stimulating factor in the treatment of active Crohn's disease

Background : Immunodeficiency syndromes associated with a Crohns‐like illness suggest innate immune defects may lead to Crohns disease. Anecdotal cases using haemopoietic colony‐stimulating factors report improvement in intestinal disease associated with these syndromes.

Expression of the Regenerating Gene Family in Inflammatory Bowel Disease Mucosa: Reg Iα Upregulation, Processing, and Antiapoptotic Activity

Background The pathophysiology of inflammatory bowel disease (IBD) reflects a balance between mucosal injury related to an ongoing inflammatory process and mucosal reparative mechanisms. Proreparative mucosal factors may offer new therapeutic paradigms. Transcriptional profiling can be applied to identify candidate gene products involved in colonic mucosal regeneration. Methods Resection specimens from patients who underwent colonic resection for IBD or non-IBD indications were analyzed by performing Affymetrix GeneChip hybridization (Affymetrix, Inc., Santa Clara, Calif) and histopathologic scoring. Expression and physiologic processing of Reg Iα, the most highly expressed member of the regenerating (Reg) gene family, was further studied by performing specific immunohistochemistry, protein sequencing, and mass spectroscopy. Results Foregut-derived tissues normally express human Reg proteins with minimal expression in the colon. In the setting of tissue injury associated with IBD, Reg Iα, Reg Iβ, and Reg III mRNA were highly expressed in colonic mucosa. Paired histopathologic scoring demonstrated that Reg expression was not related to the presence or the degree of mucosal inflammation. Studies of the Reg Iα protein revealed evidence of proteolytic cleavage at the N-terminus. In IBD, intact Reg Iα protein was expressed by the metaplastic Paneth granular cell population. Whereas Reg Iα cleaved at the N-terminus, it was also deposited throughout the lamina propria. Reg Iα treatment was shown to reduce epithelial apoptosis that occurred in response to treatment with hydrogen peroxide. Conclusion Ectopic expression, physiologic processing, and directed tissue deposition of Reg Iα are components of the colonic mucosal regenerative response in IBD. Reg Iα may serve to reduce epithelial apoptosis in inflammation.

Is Crohn's Disease an Immunodeficiency?

The current hypothesis for the etiology of Crohns disease proposes an excessive immune response, largely T-cell driven, possibly against endogenous bacteria. Standard therapy is therefore directed towards suppression of this immune response. An alternative theory of pathogenesis accounts for epidemiologic and pathophysiologic observations that have been hitherto underemphasized, namely, (1) genetic disorders with deficiencies in neutrophil function can give rise to a clinical and pathologic syndrome indistinguishable from Crohns; (2) abnormal neutrophil function is well described in Crohns disease; (3) a group of bacteria implicated in other chronic inflammatory disorders causes impairment of neutrophil function; and (4) 20th century environmental risk factors for Crohns disease may directly suppress neutrophil function and may have led to a shift in the dominant gut flora with similar effects. We propose that some cases of Crohns disease result from the interaction of environmental and genetic influences leading to impaired mucosal neutrophil function, resulting in failure to effectively clear intramucosal microbes effectively. While encompassing existing data, this hypothesis proposes a proximate defect in the mucosal immune response. If this paradigm were correct, new therapeutic approaches might involve strategies to alter intestinal flora and stimulate neutrophil function.

Delayed hepatocellular mitotic progression and impaired liver regeneration in early growth response-1-deficient mice.

The early growth response-1 transcription factor (Egr-1) is induced as part of the immediate-early gene expression response during early liver regeneration. In the studies reported here the functional significance of EGR-1 expression during liver regeneration was examined by characterizing the hepatic regenerative response to partial hepatectomy in Egr-1 null mice. The results of these studies showed that liver regeneration in Egr-1 null mice is impaired. Although activation of interleukin-6-STAT3 signaling, regulation of expression of hepatic C/ebpα, C/ebpβ, cyclin D, and cyclin E and progression through the first wave of hepatocellular DNA synthesis occurred appropriately following partial hepatectomy in Egr-1 null mice, subsequent signaling events and cell cycle progression after the first round of DNA synthesis were deranged. This derangement was characterized by increased activation of the p38 mitogen-activated protein kinase and inhibition of hepatocellular metaphase-to-anaphase mitotic progression. Together these observations suggest that EGR-1 is an important regulator of hepatocellular mitotic progression. In support of this, microarray-based gene expression analysis showed that induction of expression of the cell division cycle 20 gene (Cdc20), a key regulator of the mitotic anaphase-promoting complex, is significantly reduced in Egr-1 null mice. Taken together these data define a novel functional role for EGR-1 in regulating hepatocellular mitotic progression through the spindle assembly checkpoint during liver regeneration.