Hedgehog signaling and gastrointestinal cancer

Hedgehog (Hh) signaling is critical for embryonic development and in differentiation, proliferation, and maintenance of multiple adult tissues. De-regulation of the Hh pathway is associated with birth defects and cancer. In the gastrointestinal tract, Hh ligands Sonic (Shh) and Indian (Ihh), as well as the receptor Patched (Ptch1), and transcription factors of Glioblastoma family (Gli) are all expressed during development. In the adult, Shh expression is restricted to the stomach and colon, while Ihh expression occurs throughout the luminal gastrointestinal tract, its expression being highest in the proximal duodenum. Several studies have demonstrated a requirement for Hh signaling during gastrointestinal tract development. However to date, the specific role of the Hh pathway in the adult stomach and intestine is not completely understood. The current review will place into context the implications of recent published data related to the biochemistry and cell biology of Hh signaling on the luminal gastrointestinal tract during development, normal physiology and subsequently carcinogenesis.

Interleukin-1beta promotes gastric atrophy through suppression of Sonic Hedgehog

BACKGROUND & AIMS

In both human subjects and rodent models, Helicobacter infection leads to a decrease in Shh expression in the stomach. Sonic Hedgehog (Shh) is highly expressed in the gastric corpus and its loss correlates with gastric atrophy. Therefore, we tested the hypothesis that proinflammatory cytokines induce gastric atrophy by inhibiting Shh expression.

METHODS

Shh-LacZ reporter mice were infected with Helicobacter felis for 3 and 8 weeks. Changes in Shh expression were monitored using beta-galactosidase staining and immunohistochemistry. Gastric acidity was measured after infection, and interleukin (IL)-1beta was quantified by quantitative reverse-transcription polymerase chain reaction. Mice were injected with either IL-1beta or omeprazole before measuring Shh mRNA expression and acid secretion. Organ cultures of gastric glands from wild-type or IL-1R1 null mice were treated with IL-1beta then Shh expression was measured. Primary canine parietal or mucous cells were treated with IL-1beta. Shh protein was determined by immunoblot analysis. Changes in intracellular calcium were measured by Fura-2.

RESULTS

All major cell lineages of the corpus including surface pit, mucous neck, zymogenic, and parietal cells expressed Shh. Helicobacter infection reduced gastric acidity and inhibited Shh expression in parietal cells by 3 weeks. IL-1beta produced during Helicobacter infection inhibited gastric acid, intracellular calcium, and Shh expression through the IL-1 receptor. Suppression of parietal cell Shh expression by IL-1beta and omeprazole was additive. IL-1beta did not suppress Shh expression in primary gastric mucous cells.

CONCLUSIONS

IL-1beta suppresses Shh gene expression in parietal cells by inhibiting acid secretion and subsequently the release of intracellular calcium.

Underrepresentation of underrepresented minorities in academic medicine: the need to enhance the pipeline and the pipe

The number of underrepresented minorities (URMs; black or African American, Hispanic or Latino, American Indian or Alaska Native, Native Hawaiian or other Pacific Islander) among US medical school faculty is markedly low when compared with their respective percent representation of the US population. Women URMs are doubly underrepresented, particularly as the academic rank advances from the instructor to the professor level, and gender discrepancies occur more prominently among white female faculty. Although the percent of white faculty has decreased over the past 5 years, the low percentage of black and Hispanic faculty has not changed proportionately. Furthermore, the 2008-2009 pipeline of URM trainees is unlikely to reverse the current trends. Several measures are suggested for consideration by medical schools and the National Institutes of Health, and recommendations that URM faculty and students may wish to consider are also discussed. The major issues to address include increasing the pipeline of predoctoral URMs, promoting the success and retention of junior URM faculty, enhancing the support of senior URM faculty to serve as needed mentors, and building a pool of URM and non-URM mentors for URM trainees. Therefore, issues pertaining to both the pipeline and the pipe need to be overcome.

Hedgehog signaling in gastric physiology and cancer

The Hedgehog family of ligands was originally identified in mutagenesis screens of Drosophila embryos. Hedgehog signaling in multiple tissues is important during embryonic development. A common theme regarding Hedgehog expression in adult tissues is that tissue injury reactivates the developmental pattern of expression. In most instances, this appears to be important to initiate tissue repair. In the gastrointestinal (GI) tract, where epithelial cells are constantly replenished from progenitor populations, Hedgehog signaling also appears to be essential for regeneration. By contrast, reactivated Hedgehog signaling in adult tissues does not automatically predispose the tissue to transformation, but instead requires sustained tissue injury in the form of chronic inflammation. In this chapter, we review what is known about Hedgehog ligands and signaling during development of relevant organs, and discuss how the patterns of Hedgehog regulation are recapitulated in the GI tract during embryogenesis, adult homeostasis, and neoplastic transformation.

Paracrine Hedgehog signaling in stomach and intestine: new roles for hedgehog in gastrointestinal patterning

BACKGROUND & AIMS

Hedgehog signaling is critical in gastrointestinal patterning. Mice deficient in Hedgehog signaling exhibit abnormalities that mirror deformities seen in the human VACTERL (vertebral, anal, cardiac, tracheal, esophageal, renal, limb) association. However, the direction of Hedgehog signal flow is controversial and the cellular targets of Hedgehog signaling change with time during development. We profiled cellular Hedgehog response patterns from embryonic day 10.5 (E10.5) to adult in murine antrum, pyloric region, small intestine, and colon.

METHODS

Hedgehog signaling was profiled using Hedgehog pathway reporter mice and in situ hybridization. Cellular targets were identified by immunostaining. Ihh-overexpressing transgenic animals were generated and analyzed.

RESULTS

Hedgehog signaling is strictly paracrine from antrum to colon throughout embryonic and adult life. Novel findings include the following: mesothelial cells of the serosa transduce Hedgehog signals in fetal life; the hindgut epithelium expresses Ptch but not Gli1 at E10.5; the 2 layers of the muscularis externa respond differently to Hedgehog signals; organogenesis of the pyloric sphincter is associated with robust Hedgehog signaling; dramatically different Hedgehog responses characterize stomach and intestine at E16; and after birth, the muscularis mucosa and villus smooth muscle consist primarily of Hedgehog-responsive cells and Hh levels actively modulate villus core smooth muscle.

CONCLUSIONS

These studies reveal a previously unrecognized association of paracrine Hedgehog signaling with several gastrointestinal patterning events involving the serosa, pylorus, and villus smooth muscle. The results may have implications for several human anomalies and could potentially expand the spectrum of the human VACTERL association.

ZBP-89 reduces the cell death threshold in hepatocellular carcinoma cells by increasing caspase-6 and S phase cell cycle arrest

ZBP-89 inhibits the some tumor cells but its role in HCC is unknown. We investigated effect of ZBP-89 on cell death of 5 HCC cell lines with different status of p53. We found that ZBP-89 significantly induced cell death of all HCC cells particularly those with wild-type p53. The inhibition was well correlated with the induction of caspase-6 activity. The inhibition of caspase-6 abolished the effect of ZBP-89. ZBP-89 reduced the cells in G2-M but increased them in S phase. With the changes in caspase-6 and cell cycle, ZBP-89 greatly enhanced the killing effectiveness of 5-fluorouracil or staurosporine in HCC cells.

Sonic hedgehog in gastric physiology and neoplastic transformation: friend or foe?

PURPOSE OF REVIEW

To understand the role of sonic hedgehog (Shh) in normal gastric physiology and neoplastic transformation.

RECENT FINDINGS

Emerging evidence shows that gastric epithelial cells produce Shh ligand, which subsequently targets the mesenchyme. This paracrine signaling event is recapitulated by Shh-producing tumors that signal to the supporting stroma to encourage growth. Primary cilia contain components of the hedgehog signaling apparatus, and thus are typically found on responding stromal cells.

SUMMARY

In the stomach, Shh is produced in epithelial cells and received by responding cells in the mesenchyme. In vitro, Shh enhances gastric acid secretion and induces mucin expression. It remains to be determined whether the canonical signaling pathway mediates the observed epithelial effects. Shh expression and signaling is reduced in chronic gastritis, and Shh(-/-) embryos exhibit hyperplasia and metaplastic changes in the gastric mucosa. After its loss in the corpus, Shh is re-expressed in some gastric carcinomas typically arising in the distal stomach or antrum, suggesting that it promotes tumor growth.

Somatostatin stimulates menin gene expression by inhibiting protein kinase A

Somatostatin is a potent inhibitor of gastrin secretion and gene expression. Menin is a 67-kDa protein product of the multiple endocrine neoplasia type 1 (MEN1) gene that when mutated leads to duodenal gastrinomas, a tumor that overproduces the hormone gastrin. These observations suggest that menin might normally inhibit gastrin gene expression in its role as a tumor suppressor. Since somatostatin and ostensibly menin are both inhibitors of gastrin, we hypothesized that somatostatin signaling directly induces menin. Menin protein expression was significantly lower in somatostatin-null mice, which are hypergastrinemic. We found by immunohistochemistry that somatostatin receptor-positive cells (SSTR2A) express menin. Mice were treated with the somatostatin analog octreotide to determine whether activation of somatostatin signaling induced menin. We found that octreotide increased the number of menin-expressing cells, menin mRNA, and menin protein expression. Moreover, the induction by octreotide was greater in the duodenum than in the antrum. The increase in menin observed in vivo was recapitulated by treating AGS and STC cell lines with octreotide, demonstrating that the regulation was direct. The induction required suppression of protein kinase A (PKA) since forskolin treatment suppressed menin protein levels and octreotide inhibited PKA enzyme activity. Small-interfering RNA-mediated suppression of PKA levels raised basal levels of menin protein and prevented further induction by octreotide. Using AGS cells, we also showed for the first time that menin directly inhibits endogenous gastrin gene expression. In conclusion, somatostatin receptor activation induces menin expression by suppressing PKA activation.

Hip1r is expressed in gastric parietal cells and is required for tubulovesicle formation and cell survival in mice

Huntingtin interacting protein 1 related (Hip1r) is an F-actin- and clathrin-binding protein involved in vesicular trafficking. In this study, we demonstrate that Hip1r is abundantly expressed in the gastric parietal cell, predominantly localizing with F-actin to canalicular membranes. Hip1r may provide a critical function in vivo, as demonstrated by extensive changes to parietal cells and the gastric epithelium in Hip1r-deficient mice. Electron microscopy revealed abnormal apical canalicular membranes and loss of tubulovesicles in mutant parietal cells, suggesting that Hip1r is necessary for the normal trafficking of these secretory membranes. Accordingly, acid secretory dynamics were altered in mutant parietal cells, with enhanced activation and acid trapping, as measured in isolated gastric glands. At the whole-organ level, gastric acidity was reduced in Hip1r-deficient mice, and the gastric mucosa was grossly transformed, with fewer parietal cells due to enhanced apoptotic cell death and glandular hypertrophy associated with cellular transformation. Hip1r-deficient mice had increased expression of the gastric growth factor gastrin, and mice mutant for both gastrin and Hip1r exhibited normalization of both proliferation and gland height. Taken together, these studies demonstrate that Hip1r plays a significant role in gastric physiology, mucosal architecture, and secretory membrane dynamics in parietal cells.

Induction of follistatin precedes gastric transformation in gastrin deficient mice

We previously showed that antral gastric tumors develop in gastrin-deficient (Gas(-/-)) mice. Therefore Gas(-/-) mice were studied sequentially over 12 months to identify molecular mechanisms underlying gastric transformation. Fundic atrophy developed by 9 months in Gas(-/-) mice. Antral mucosal hyperplasia developed coincident with the focal loss of TFF1 and Muc5AC. Microarray analysis of 12 month Gas(-/-) tumors revealed an increase in follistatin, an activin/BMP antagonist. We found that elevated follistatin expression occurred in the proliferative neck zone of hyperplastic antrums, in antral tumors of Gas(-/-) mice, and also in human gastric cancers. Follistatin induced cyclin D1 and the trefoil factors TFF1 and TFF2 in a gastric cancer cell line. We concluded that antral hyperplasia in Gas(-/-) mice involves amplification of mucous cell lineages due to follistatin, suggesting its role in the development of antral gastric tumors.

What lurks beneath: IL-11, via Stat3, promotes inflammation-associated gastric tumorigenesis

Chronic inflammation in the stomach induces cellular transformation and gastric cancer primarily in the distal stomach or antrum. In this issue of the JCI, a study in mice by Ernst et al. provides new insight into the role of IL-11 and its glycoprotein 130 (gp130) receptor in inflammation-associated gastric epithelial cell oncogenic transformation, which they show is mediated by and dependent on increased activation of Stat3 and, to a lesser extent, Stat1 (see the related article beginning on page 1727). Prior studies from this group have shown that Stat3 hyperactivity stimulates the TGF-beta inhibitor Smad7. Collectively, the studies suggest that an important pathway of oncogenic transformation in the stomach is through suppression of growth inhibitory signals, such as members of the TGF-beta family, that originate from the stroma.

Tissue stem cells and cancer stem cells: potential implications for gastric cancer

Gastric cancer remains the second leading cause of death in the world today, making the search for its molecular and cellular basis an important priority. Though recognition of the tight link between inflammation and tumorigenesis is centuries old, only recently are the pieces of the etiological puzzle beginning to fall together. Recent advances in gastric stem cell biology appear to be central to this slowly resolving puzzle. At least two types of stem cells may be important. Resident adult or tissue stem cells may, in a chronically inflamed environment, slowly acquire a series of genetic and epigenetic changes that lead to their emergence as ''cancer stem cells''. This scenario has not yet been proven experimentally, although the first step, prospective recognition of a gastric stem cell has recently been conquered. Alternatively, the setting of chronic inflammatory stress and injury may lead to loss of the indigenous gastric stem cells from their niches; bone marrow derived stem cells may then be recruited to and engraft into the gastric epithelium. Such recruited cells have the potential to contribute to the tumor mass. Indeed, evidence supporting this scenario has been published. Here, we review these recent findings and discuss implications for the future.

A role for CITED2, a CBP/p300 interacting protein, in colon cancer cell invasion

A thorough understanding of histone acetyltransferase CBP/p300-mediated regulation of gene expression and cell growth is essential to identify mechanisms relevant to the development of histone deacetylase (HDAC) inhibitor-based preventive and therapeutic strategies. We found that knockdown of CBP/p300 interacting coactivator with glutamic acid/aspartic acid-rich tail 2 (CITED2) increased colon cancer cell invasiveness in vitro. Gene expression profiling revealed that CITED2 knockdown induced matrix metalloproteinase-13 (MMP-13) gene expression in colon cancer cells. Butyrate, a naturally occurring HDAC inhibitor, induced CITED2 expression and downregulated MMP-13 expression in RKO cells. Additionally, ectopic expression of CITED2 arrested RKO cell growth. Thus, CITED2 regulates colon cancer invasion and might be a target for HDAC inhibitor-based intervention of colon cancer.

Prospective identification of a multilineage progenitor in murine stomach epithelium

BACKGROUND & AIMS

Epithelial stem cells in the stomach are responsible for constant renewal of the epithelium through generation of multiple gastric cell lineages that populate the gastric glands. However, gastric stem or progenitor cells have not been well-characterized because of the lack of specific markers that permit their prospective recognition. We identified an intestinal promoter that is active in a rare subpopulation of gastric epithelial cells and investigated whether these cells possess multilineage potential.

METHODS

A marked allele of the endogenous mouse villin locus was used to visualize single beta-galactosidase-positive cells located in the lower third of antral glands. A 12.4-kb villin promoter/enhancer fragment drives several transgenes (EGFP, beta-galactosidase, and Cre recombinase) in these cells in a pattern similar to that of the marked villin allele. Reporter gene activity was used to track these cells during development and to examine cell number in the context of inflammatory challenge while Cre activity allowed lineage tracing in vivo.

RESULTS

We show that these rare epithelial cells are normally quiescent, but multiply in response to interferon gamma. Lineage tracing studies confirm that these cells give rise to all gastric lineages of the antral glands. In the embryo, these cells are located basally in the stomach epithelium before completion of gastric gland morphogenesis.

CONCLUSIONS

We have identified a rare subpopulation of gastric progenitors with multilineage potential. The ability to prospectively identify and manipulate such progenitors in situ represents a major step forward in gastric stem cell biology and has potential implications for gastric cancer.

Re-expression of sonic hedgehog and reduction of CDX2 after Helicobacter pylori eradication prior to incomplete intestinal metaplasia

Loss of Sonic Hedgehog (Shh) and aberrant CDX2 expression are early changes correlating with the presence of intestinal metaplasia that occur in the gastric mucosa prior to neoplastic transformation. The aim of this study was to compare the improvement in corpus gastritis with Shh and CDX2 expression after H. pylori eradication between subjects at high risk for gastric cancer and controls. The usefulness of serum pepsinogen levels as a predictor of resolved corpus gastritis was also examined. Seventy patients with endoscopic resection for early gastric cancer and 30 controls were studied. Expression of Shh and CDX2 were evaluated by immunostaining. Serum levels of pepsinogen I before eradication in the patients scored as having improvement of corpus atrophy were significantly higher than in the patients without improvement (<0.01). Residual inflammation at the corpus lesser curve was more frequently detected in the cancer group than in the controls (OR 4.6 95% C.I. 1.6-13.5) and in the mucosa with incomplete intestinal metaplasia rather than in those without incomplete intestinal metaplasia (OR 7.6 95% C.I. 2.4-24.3). Atrophy, expression of Shh and CDX2 at the corpus lesser curve significantly improved in mucosa without incomplete intestinal metaplasia (p < 0.01), but not in mucosa with incomplete intestinal metaplasia. In conclusion, H. pylori eradication prior to development of incomplete intestinal metaplasia improves corpus gastritis and may prevent gastric cancer. Pepsinogen I may be a useful marker in patients with a residual higher risk of gastric cancer after H. pylori eradication.

Sumoylation-dependent control of homotypic and heterotypic synergy by the Kruppel-type zinc finger protein ZBP-89

The Krüppel-like transcription factor ZBP-89 is a sequence-specific regulator that plays key roles in cellular growth and differentiation especially in endodermal and germ cell lineages. ZBP-89 shares with other members of the Sp-like family an overlapping sequence specificity for GC-rich sequences in the regulatory regions of multiple genes. Defining the mechanisms that govern the intrinsic function of ZBP-89 as well as its competitive and non-competitive functional interactions with other regulators is central to understand how ZBP-89 exerts its biological functions. We now describe that post-translational modification of ZBP-89 by multiple small ubiquitin-like modifier (SUMO) isoforms occurs at two conserved synergy control motifs flanking the DNA binding domain. Functionally sumoylation did not directly alter the ability of ZBP-89 to compete with other Sp-like factors from individual sites. At promoters bearing multiple response elements, however, this modification inhibited the functional cooperation between ZBP-89 and Sp1. Analysis of the properties of ZBP-89 in cellular contexts devoid of competing factors indicated that although on its own it behaves as a modest activator it potently synergizes with heterologous activators such as the glucocorticoid receptor. Notably we found that when conjugated to ZBP-89, SUMO exerts a strong inhibitory effect on such synergistic interactions through a critical conserved functional surface. By regulating higher order functional interactions, sumoylation provides a reversible post-translational mechanism to control the activity of ZBP-89.

Reduced pepsin A processing of sonic hedgehog in parietal cells precedes gastric atrophy and transformation

Sonic hedgehog (Shh) is not only essential to the development of the gastrointestinal tract, but is also necessary to maintain the characteristic acid-secreting phenotype of the adult stomach. Gastrin is the only hormone capable of stimulating gastric acid and is thus required to maintain functional parietal cells. We have shown previously that gastrin-null mice display gastric atrophy and metaplasia prior to progression to distal, intestinal-type gastric cancer. Because reduced levels of Shh peptide correlate with gastric atrophy, we examined whether gastrin regulates Shh expression in parietal cells. We show here that gastrin stimulates Shh gene expression and acid-dependent processing of the 45-kDa Shh precursor to the 19-kDa secreted peptide in primary parietal cell cultures. This cleavage was blocked by the proton pump inhibitor omeprazole and mediated by the acid-activated protease pepsin A. Pepsin A was also the protease responsible for processing Shh in tissue extracts from human stomach. By contrast, extracts prepared from neoplastic gastric mucosa had reduced levels of pepsin A and did not process Shh. Therefore processing of Shh in the normal stomach is hormonally regulated, acid-dependent, and mediated by the aspartic protease pepsin A. Moreover parietal cell atrophy, a known pre-neoplastic lesion, correlates with loss of Shh processing.

H pylori infection causes chronic pancreatitis in Mongolian gerbils

AIM: To investigate whether chronic H pylori infection has the potential to induce pancreatitis in the Mongolian gerbil model, and whether it is dependent on an intact type IV secretion system.

METHODS: Mongolian gerbils were infected with wild type (WT) H pylori typeIstrain B128 or its isogenic mutant B128 ΔcagY (defective type IV secretion). After seven months of infection, H pylori was reisolated from antrum and corpus and H pylori DNA was analyzed by semi-nested polymerase chain reaction (PCR). Inflammation and histological changes were documented in the gastric antrum, corpus, and pancreas by immunohistochemistry. Cytokine mRNA, gastric pH, plasma gastrin, amylase, lipase, and glucose levels were determined.

RESULTS: The H pylori infection rate was 95%. Eight infected animals, but none of the uninfected group, developed transmural inflammation and chronic pancreatitis. Extensive interstitial fibrosis and inflammation of the pancreatic lobe adjacent to the antrum was confirmed by trichrome stain, and immuno-histochemically. Pro-inflammatory cytokine mRNA was significantly increased in the antral mucosa of all infected gerbils. In the corpus, only cytokine levels of WT-infected animals and those developing transmural inflammation and pancreatitis were significantly increased. Levels of lipase, but not glucose or amylase levels, were significantly reduced in the pancreatitis group. H pylori DNA was detected in infected antral and corpus tissue, but not in the pancreas.

CONCLUSION: H pylori infection is able to induce chronic pancreatitis in Mongolian gerbils independently of the type IV secretion system, probably by an indirect mechanism associated with a penetrating ulcer.

ATM phosphorylates ZBP-89 at Ser202 to potentiate p21waf1 induction by butyrate

Histone deacetylase inhibitors (HDACi) induce growth arrest and differentiation, particularly in the colon where they are potential chemotherapeutic agents. A key mediator of HDACi action is the cyclin dependent kinase (CDK) inhibitor p21(waf1). HDACi treatment of colonic cells promotes the formation of an ATM/ZBP-89/p300 complex on p21(waf1) proximal promoter, and this multi-molecular complex plays an important role in HDACi induction of p21(waf1) expression in vitro and mucosal protection in vivo. Here we found that ZBP-89 is phosphorylated by ATM kinase in vitro and in vivo. Disruption of the ATM phosphorylation motif (202)SQ within the zinc finger domain of ZBP-89 attenuated its ability to enhance p21(waf1) activation by butyrate. Moreover, disruption of the ATM phosphorylation site abrogated the ability of ZBP-89 to potentiate butyrate induction of endogenous p21(waf1) expression. These results demonstrate that ATM phosphorylation of ZBP-89 contributes to HDACi induction of p21(waf1) gene expression.

Tales from the crypts: regulatory peptides and cytokines in gastrointestinal homeostasis and disease

The gastrointestinal (GI) tract is composed of a diverse set of organs that together receive extracorporeal nutrition and convert it to energy substrates and cellular building blocks. In the process, it must sort through all that we ingest and discriminate what is useable from what is not, and having done that, it discards what is "junk." To accomplish these many and varied tasks, the GI tract relies on endogenous enteric hormones produced by enteroendocrine cells and the enteric nervous system. In many instances, the mediators of these tasks are small peptides that home to the CNS and accessory gut organs to coordinate oral intake with digestive secretions. As the contents of ingested material can contain harmful agents, the gut is armed with an extensive immune system. A breach of the epithelial barrier of the GI tract can result in local and eventually systemic disease if the gut does not mount an aggressive immune response.

Helicobacter pylori-induced atrophic gastritis progressing to gastric cancer exhibits sonic hedgehog loss and aberrant CDX2 expression

BACKGROUND

The loss of sonic hedgehog is an early change that occurs in the mucosa prior to neoplastic transformation and correlates with the type of intestinal metaplasia. Aberrant expression of CDX has also been shown to correlate with the development of intestinal metaplasia.

AIM

To examine CDX2 expression in the non-cancerous mucosa of patients with gastric cancer and compared it to CDX2 expression in controls with intestinal metaplasia.

METHODS

Sixty patients who had undergone endoscopic mucosal resection for early gastric cancer and 60 gender- and age-matched controls were studied. Two specimens each were obtained from the greater and lesser curves of the corpus and from the greater curve of the antrum. Expression of CDX2 and sonic hedgehog were evaluated by immunostaining.

RESULTS

Gastric cancer was associated with a higher frequency of incomplete intestinal metaplasia (OR = 8.3; 95%CI, 3.7-18.9, P < 0.001). CDX2 negatively correlated with sonic hedgehog expression, however, multivariate analysis revealed that CDX2 correlated with the intestinal metaplasia scores. Sonic hedgehog indices were lower and CDX2 staining in the corpus lesser curve was higher in the cancer group than in the controls. Sonic hedgehog indices in the corpus decreased and CDX2 indices in both areas increased in patients in the ascending order of those without intestinal metaplasia, those with complete intestinal metaplasia and those with incomplete intestinal metaplasia (P < 0.001).

CONCLUSIONS

Loss of sonic hedgehog expression and aberrant expression of CDX2 correlates with the type of intestinal metaplasia and may play a role in carcinogenesis.

Inhibition of Growth Hormone Receptor Gene Expression by Saturated Fatty Acids: Role of Krüppel-Like Zinc Finger Factor, ZBP-89

The expression and function of the GH receptor is critical for the actions of pituitary GH in the intact animal. The role of systemic factors in the reduced expression of the GH receptor and consequent GH insensitivity in pathological states such as sepsis, malnutrition, and poorly controlled diabetes mellitus is unclear. In the current study, we demonstrate that saturated (palmitic and myristic; 50 μm) fatty acids (FA) inhibit activity of the promoter of the major (L2) transcript of the GH receptor gene; unsaturated (oleic and linoleic) FA (200 μm) do not alter activity of the promoter. Comparable effects with palmitic acid and the nonmetabolizable analog bromo-palmitic acid, and failure of triacsin C to abrogate palmitic acids effects on GH receptor expression indicate that this effect is due to direct action(s) of FA. Palmitic acid, but not the unsaturated FA linoleic acid, decreased steady-state levels of endogenous L2 mRNA and GHR protein in 3T3-L1 preadipocytes. The effect of FA was localized to two cis elements located approximately 600 bp apart on the L2 promoter. EMSA and chromatin immunoprecipitation assays established that both these cis elements bind the Krüppel-type zinc finger transcription factor, ZBP-89. Ectopic expression of ZBP-89 amplified the inhibitory effect of FA on L2 promoter activity and on steady-state levels of endogenous L2 mRNA in 3T3-L1 preadipocytes. Mutational analyses of the two ZBP-89 binding sites revealed that both the sites are essential for palmitic acid’s inhibitory effect on the L2 promoter and for the enhancing effect of ZBP-89 on palmitic acid-induced inhibition of the L2 promoter. Our results establish a molecular basis for FA-induced inhibition of GH receptor gene expression in the pathogenesis of acquired GH insensitivity in pathological states such as poorly controlled diabetes mellitus and small for gestational age.

Intestinal overexpression of ZNF148 suppresses ApcMin/+ neoplasia

ZNF148 (ZBP-89, Zfp148) is a multifunctional transcription factor expressed at low levels in most tissues. When overexpressed in gastrointestinal cancer cell lines, ZNF148 inhibits cellular proliferation and induces apoptosis. We sought to determine whether intestinal ZNF148 overexpression would abrogate adenoma development in the ApcMin/+ mouse, i.e., whether ZNF148 is a tumor suppressor. The 13-kb villin promoter was spliced upstream of the ZNF148 cDNA to generate transgenic villin-ZNF148 (ZNF148TgVZ) mice. Intestinal mucosal ZNF148 expression was elevated in four of five ZNF148(TgVZ) lineages and correlated with increased caspase-3 expression and activation. In addition, DNA fragmentation was increased in ZNF148TgVZ mice relative to wild-type littermates. These results suggested that increased intestinal ZNF148 expression induces apoptosis. ZNF148TgVZ mice were crossed with ApcMin/+ mice to assess the biological significance of intestinal ZNF148 overexpression. The presence of the ZNF148TgVZ allele in ApcMin/+ mice correlated with reduced gastrointestinal bleeding at 5 weeks, a 50% reduction in adenoma burden at 20-22 weeks, and prolonged survival (median survival of 33.5 days vs. 21.5 days), relative to nontransgenic littermates. These data suggest that enhanced ZNF148 expression activates intestinal apoptosis and thereby mitigates disease burden in ApcMin/+ mice. They also suggest that ZNF148 is a therapeutic target to inhibit colon cancer development.

Recruitment of ataxia-telangiectasia mutated to the p21(waf1) promoter by ZBP-89 plays a role in mucosal protection

BACKGROUND & AIMS

Histone deacetylase inhibitors (HDACi) induce growth arrest, apoptosis, and differentiation, particularly in colon cancer cells where they are potential chemopreventive agents. HDACi induction of the cyclin-dependent kinase inhibitor p21(waf1) has been shown to require ataxia-telangiectasia mutated (ATM). Nevertheless, how ATM participates in p21(waf1) gene expression has not been defined.

METHODS

In vivo protein complexes forming in response to butyrate were studied using co-immunoprecipitation and mass spectroscopy. DNA elements in the p21(waf1) promoter were analyzed in vivo by chromatin immunoprecipitation and in vitro DNA affinity precipitation assays. The expression of p21(waf1) was analyzed by immunoblots and reporter assays.

RESULTS

Reduction of ZBP-89 or ATM with small interfering RNAs blocked HDACi-induced p21(waf1) expression. Chromatin immunoprecipitation and DNA affinity precipitation assays showed that both ZBP-89 and ATM are recruited to the GC-rich DNA elements of the p21(waf1) promoter with HDACi treatment. Co-immunoprecipitation revealed that ATM associates with ZBP-89 in an HDACi-dependent manner. Serial deletions revealed that ATM interacts with both the N-terminal and DNA binding domains of ZBP-89. Moreover, we found that immunodepletion of ZBP-89 prevented recruitment of ATM to the p21(waf1) promoter in vitro. Silencing of ZBP-89 expression blocked HDACi-induced phosphorylation of ATM(Ser1981) and p53(Ser15). ATM(Ser1981) phosphorylation in the colons of mutant mice expressing an N-terminally truncated form of ZBP-89 was not observed after ingestion of dextran sodium sulfate and correlated with exacerbation of the mucosal injury.

CONCLUSIONS

ZBP-89 interacts with ATM in a butyrate-dependent manner and is essential for colonic homeostasis in the setting of acute mucosal injury.