Synergy between tumor suppressor APC and the beta-catenin-Tcf4 target Tcf1.

Mutations in APC or beta-catenin inappropriately activate the transcription factor Tcf4, thereby transforming intestinal epithelial cells. Here it is shown that one of the target genes of Tcf4 in epithelial cells is Tcf1. The most abundant Tcf1 isoforms lack a beta-catenin interaction domain. Tcf1(-/-) mice develop adenomas in the gut and mammary glands. Introduction of a mutant APC allele into these mice substantially increases the number of these adenomas. Tcf1 may act as a feedback repressor of beta-catenin-Tcf4 target genes and thus may cooperate with APC to suppress malignant transformation of epithelial cells.

Two members of the Tcf family implicated in Wnt/beta-catenin signaling during embryogenesis in the mouse.

Tcf transcription factors interact with beta-catenin and Armadillo to mediate Wnt/Wingless signaling. We now report the characterization of genes encoding two murine members of the Tcf family, mTcf-3 and mTcf-4. mTcf-3 mRNA is ubiquitously present in embryonic day 6.5 (E6.5) mouse embryos but gradually disappears over the next 3 to 4 days. mTcf-4 expression occurs first at E10.5 and is restricted to di- and mesencephalon and the intestinal epithelium during embryogenesis. The mTcf-3 and mTcf-4 proteins bind a canonical Tcf DNA motif and can complex with the transcriptional coactivator beta-catenin. Overexpression of Wnt-1 in a mammary epithelial cell line leads to the formation of a nuclear complex between beta-catenin and Tcf proteins and to Tcf reporter gene transcription. These data demonstrate a direct link between Wnt stimulation and beta-catenin/Tcf transcriptional activation and imply a role for mTcf-3 and -4 in early Wnt-driven developmental decisions in the mouse embryo.

All Tcf HMG box transcription factors interact with Groucho-related co-repressors.

Tcf/Lef family transcription factors are the downstream effectors of the Wingless/Wnt signal transduction pathway. Upon Wingless/Wnt signalling, beta-catenin translocates to the nucleus, interacts with Tcf (1-3) and thus activates transcription of target genes (4,5). Tcf factors also interact with members of the Groucho (Grg/TLE) family of transcriptional co-repressors (6). We have now tested all known mammalian Groucho family members for their ability to interact specifically with individual Tcf/Lef family members. Transcriptional activation by any Tcf could be repressed by Grg-1, Grg-2/TLE-2, Grg-3 and Grg-4 in a reporter assay. Specific interactions between Tcf and Grg proteins may be achieved in vivo by tissue- or cell type-limited expression. To address this, we determined the expression of all Tcf and Grg/TLE family members in a panel of cell lines. Within any cell line, several Tcfs and TLEs are co-expressed. Thus, redundancy in Tcf/Grg interactions appears to be the rule. The 'long' Groucho family members containing five domains are repressors of Tcf-mediated transactivation, whereas Grg-5, which only contains the first two domains, acts as a de-repressor. As previously shown for Drosophila Groucho, we show that long Grg proteins interact with histone deacetylase-1. Although Grg-5 contains the GP homology domain that mediates HDAC binding in long Grg proteins, Grg-5 fails to bind this co-repressor, explaining how it can de-repress transcription.

Antegrade revascularization for chronic mesenteric ischaemia.

OBJECTIVE: to evaluate the short- and long-term results, obtained after open revascularization for chronic mesenteric ischaemia as a reference in a field with growing interest for PTA and stenting. MATERIALS AND METHODS: we reviewed 14 patients with 15 antegrade revascularizations for chronic intestinal ischaemia, between 1996 and 2003: ten bypasses either to the celiac trunk or to the mesenteric artery and five bifurcated bypasses to both arteries were performed. There was one reimplantation for Wilki syndrome. Graft patency was monitored for a mean period of 24 months (range 1-84 months) by clinical examination and duplex scanning. MAIN RESULTS: one patient had recurrence of symptoms that disappeared after successful reoperation. There was one perioperative death All the other patients (84%) had a long-term symptom free survival. CONCLUSION: antegrade mesenterial revascularization through an upper abdominal approach is an excellent technique with good long-term results. It sets a high standard that will be difficult to obtain with mesenteric PTA and stenting. It remains the preferred method of revascularization in low-risk patients.

RasGRP1 overexpression in T-ALL increases basal nucleotide exchange on Ras rendering the Ras/PI3K/Akt pathway responsive to protumorigenic cytokines.

Ras GTPases are activated by RasGEFs and inactivated by RasGAPs, which stimulate the hydrolysis of RasGTP to inactive RasGDP. GTPase-impairing somatic mutations in RAS genes, such as KRAS(G12D), are among the most common oncogenic events in metastatic cancer. A different type of cancer Ras signal, driven by overexpression of the RasGEF RasGRP1 (Ras guanine nucleotide-releasing protein 1), was recently implicated in pediatric T-cell acute lymphoblastic leukemia (T-ALL) patients and murine models, in which RasGRP1 T-ALLs expand in response to treatment with interleukins (ILs) 2, 7 and 9. Here, we demonstrate that IL-2/7/9 stimulation activates Erk and Akt pathways downstream of Ras in RasGRP1 T-ALL but not in normal thymocytes. In normal lymphocytes, RasGRP1 is recruited to the membrane by diacylglycerol (DAG) in a phospholipase C-γ (PLCγ)-dependent manner. Surprisingly, we find that leukemic RasGRP1-triggered Ras-Akt signals do not depend on acute activation of PLCγ to generate DAG but rely on baseline DAG levels instead. In agreement, using three distinct assays that measure different aspects of the RasGTP/GDP cycle, we established that overexpression of RasGRP1 in T-ALLs results in a constitutively high GTP-loading rate of Ras, which is constantly counterbalanced by hydrolysis of RasGTP. KRAS(G12D) T-ALLs do not show constitutive GTP loading of Ras. Thus, we reveal an entirely novel type of leukemogenic Ras signals that is based on a RasGRP1-driven increased in flux through the RasGTP/GDP cycle, which is mechanistically very different from KRAS(G12D) signals. Our studies highlight the dynamic balance between RasGEF and RasGAP in these T-ALLs and put forth a new model in which IL-2/7/9 decrease RasGAP activity.

TCF transcription factors: molecular switches in carcinogenesis.

Although originally cloned as lymphoid transcription factors, members of the T-cell factor (Tcf) family are now well recognized as key activators/repressors in many developmental processes. Transcriptionally inert Tcf factors become potent transactivators upon interaction with the Wnt signaling product beta-catenin or its Drosophila counterpart Armadillo. In contrast, Tcf proteins mediate repression when bound to members of the Groucho family of transcriptional repressors, CBP and CtBP. Recently, Tcf factors have been reported as tumor inducers, aberrantly activating their target genes as a result of elevated beta-catenin levels in many types of cancer. These abnormal beta-catenin levels are usually caused by stabilizing mutations in beta-catenin itself or truncating mutations in the adenomatous polyposis coli (APC) tumor suppressor gene. In this review, we will give a chronological overview of the Tcf factors and the phenotypes of Tcf mutant mice, as well as Tcf-binding partners. We will discuss Tcf signaling upon interaction with different partners, resulting in activator and repressor roles of Tcf factors in the light of carcinogenic events.

Differential expression of the Groucho-related genes 4 and 5 during early development of Xenopus laevis.

Recently, we demonstrated that the Xenopus Wnt effector XTcf-3 interacts with Groucho-related transcriptional repressors (Roose et al., 1998. Nature 395, 608-612). A long form of the Groucho-related genes, XGrg-4, was shown to repress axis formation in the Xenopus embryo, whereas a short form, XGrg-5, acted as a potentiator. In this study, the temporal and spatial expression of XGrg-4 and XGrg-5 is described in Xenopus laevis embryos. Both genes are maternally expressed. In the gastrula, transcripts of both genes are present in the animal as well as the vegetal region. At later stages, XGrg-4 and XGrg-5 show specific patterns of expression in the central nervous system (CNS), cranial ganglia, eyes, otic vesicles, stomodeal-hypophyseal anlage, cement gland, head mesenchyme, branchial arches, neural crest and derivatives, somites, pronephros, pronephric duct, heart and tailbud. Differences in the expression of XGrg-4 and XGrg-5 were found in the CNS, cranial ganglia, olfactory placodes, stomodeal-pharyngeal anlage, cement gland, head mesenchyme and ectoderm.

Differential expression of the HMG box transcription factors XTcf-3 and XLef-1 during early xenopus development.

The recent discovery that the HMG box transcription factor XTCF-3 is involved in early axis specification in Xenopus laevis (Molenaar, M., van de Wetering, M., Oosterwegel, M., Peterson-Maduro, J. Godsave, S., Korinek, V., Roose, J., Destree, O., Clevers, H., 1996. XTcf-3 transcription factor mediates beta-catenin-induced axis formation in Xenopus embryos. Cell 86, 391-399) led us to search for other members of the TCF/LEF family in this species. A newly identified HMG box factor was cloned with highest homology to human LEF-1, called XLEF-1. Unlike XTcf-3, XLef-1 is not expressed maternally, but its transcripts become detectable directly after the mid blastula transition (MBT). At later stages, both genes are expressed in the central nervous system (CNS), eyes, otic vesicles, head mesenchyme, neural crest and derivatives, branchial arches, developing heart, tailbud and limb buds. The expression pattern of Lef-1 during later stages of development is evolutionarily conserved.

dTcf antagonises Wingless signalling during the development and patterning of the wing in Drosophila.

Members of the Tcf family of HMG box-containing transcriptional regulators mediate Wnt signalling in the nucleus. Current models suggest that in the absence of Wnt signalling, Tcf interacts with the repressor protein Groucho and suppresses the expression of Wnt targets. Wnt signalling leads to increases in the level of cytoplasmic beta catenin, which enters the nucleus, displaces Tcf from Groucho and leads to transcriptional activation. In order to test this model we have studied the effects of Drosophila Tcf (dTcf) on signalling by Wingless, a Drosophila member of the Wnt family. We show that overexpression of wild-type dTcf during the development and patterning of the wing antagonises Wingless signalling. Furthermore, increases in the concentration of Armadillo, the Drosophila homologue of beta catenin, do not appear to be sufficient to trigger the change from antagonism to activation. This leads us to suggest that the inactivation of the repressive activity of dTcf requires the activity of Wingless in a manner that is independent of Armadillo. We observe that a Groucho molecule devoid of the WD40 repeats can interact with dTcf and acts as a dominant repressor of Wingless signalling in vivo and in vitro. Coexpression of this molecule with dTcf however, does not lead to enhancement of the repressive effects of dTcf alone. This observation suggests that repression by dTcf might not simply be mediated by an interaction with Groucho but that dTcf may have an intrinsic repressive activity that has to be antagonised by Wingless signalling.

The winged-helix transcription factor Trident is expressed in actively dividing lymphocytes.

We recently identified the winged-helix transcription factor Trident and described its expression pattern in synchronized fibroblasts. We have now studied Trident expression in cell lines, differentiating thymocytes and in lymphocytes derived from peripheral blood. During T cell differentiation, expression peaked in the actively dividing immature single positive cells. In peripheral blood lymphocytes, expression of Trident mRNA was absent, but could be induced upon stimulation with mitogens in vitro. These observations imply a function for Trident in dividing lymphocytes.

Polydioxanone suture material in growing vascular anastomoses. Experimental study.

We studied the growth of vascular anastomoses after use of absorbable suture material in 21 piglets. In six piglets, end-to-end anastomosis of the infrarenal aorta was performed with 5-0 continuous polypropylene suture; stenosis developed in two of these animals. In 15 piglets, continuous polydioxanone sutures were used for the anastomoses, and no stenosis developed. On the contrary, 14 of these anastomoses showed some degree of dilation at the anastomotic site. Burst testing to 300 mm Hg caused no disruption. On histologic examination, only scar tissue at media and intima with good degree of differentiation was noted. Growth of a vascular anastomosis after use of absorbable polydioxanone suture material seems to be perfectly possible without stricture formation. Because the growing process takes years instead of months in human beings, with obviously less stress at the anastomotic site, it is likely that dilatation at the level of the suture line will not occur in clinical use.

Fistula survival in single needle hemodialysis.

This study presents an average follow up per patient of 33.5 +/- 3.7 and 70.1 +/- 5.9 months (hospital and home dialysis) showing an actuarial fistula survival rate of 86.2% and 85.5% respectively after 5 years. The data suggest a satisfactory survival rate of the fistula when a single needle technique is used in comparison to the survival observed with the two needles technique.

Peritoneal lavage after abdominal trauma: indications, technique, results.

This study represents our experience with 1461 patients who were seen in the Emergency Room of the University Hospital in Ghent with multiple traumatic lesions, between 1978 and 1982. In 43% of these polytraumata, we did an explorative peritoneal lavage in order to obtain a quick evaluation of intrabdominal haemorrhage. In 65% of the patients, the lavage was negative; 221 positive lavages (35%) underwent abdominal exploration; in 85% of these there were evident positive findings. The remaining 15% showed either no lesions, or minor lesions not involving risk of life. The overall accuracy-rate of the technique described above is at least 93%.

[Surgical treatment of abdominal aortic occlusion (author's transl)]. / De chirurgische behandeling van de totale aortatrombose.

Forty-seven cases treated for atherosclerotic occlusion of the abdominal aorta are reported. The classical trans-abdominal approach used in all our cases is compared with alternative approaches. The reasons for this preference are discussed.

The true value of the carotid steal syndrome after the carotid subclavian by-pass. Human experimental study.

Between 1964 and 1978 sixteen patients underwent a carotid subclavian by-pass in the Akademisch Ziekenhuis of Gent. Most of these patients were submitted to tests to evaluate the importance of the carotid steal effect. The patency of the vertebral artery was found to influence these tests. Two of the three patients with an occluded vertebral artery had cerebral symptoms when the peripheral resistance was lowered in the involved limb. No positive tests could be found in the twelve patients with a patient vertebral artery. These results indicate that the carotid subclavian artery by-pass performed in the presence of an occluded vertebral artery does not protect the patient from the carotid steal effect.

[Parenteral nutrition "à la carte" in major abdominal surgery with mixtures of Totamine concentrate and Vintène. A clinical study based on nitrogen balance]. / Parenterale voeding "à la carte" in maieure abdominale heelkunde met gebruik van Totamine concentre en Vintène. En klinische studie aan de hand van de stikstofbalansen.

The authors present a series of thirty patients who underwent major abdominal surgery. Each patient received preoperative total parenteral nutrition (TPN) during bowel preparation. After the operation the TPN was continued immediately, even if reanimation was necessary. The dosages of nitrogen and calories were individually adapted in function of the daily calculated nitrogen-balances. So the authors were able to administer a TPN "à la carte" using eight solutions mixed in a single bag, containing amino-acids (varying between 6 and 20 g of nitrogen), glucose (ad 150 Kcal/gN) lipids (constituting 40% of the calorie-intake), ions, vitamins and oligoelements. With a follow-up of minimum 10 days, the study proves the possibility of creating positive nitrogen-balances in 87% of the cases and an acceptable deviation in the daily measured glycemia and plasma-ionograms.

[The McVay technic for inguinal hernia cure. Results of treatment in a teaching center (author's transl)]. / Resultaten van de behandeling van hernia inguinalis volgens McVay in een opleidingscentrum.

Over a 20 year period 390 adults underwent 454 operations for inguinal hernia using the technique of McVay. The recurrence rate after primary repair was 7.61% and 18.33% for secondary hernias. This was usually early in the postoperative period. These results must be interpreted taking into a ccount that the operations were performed at a teaching institution.

Bronchial rupture after direct chest trauma in a child.

Tracheobronchial injuries are rare in trauma patients, and most often occur after motor vehicle accidents. Occasionally, other mechanisms cause airway disruption. The pliability of the chest wall in children greatly adds to the differences in injuries when compared with adult trauma patients. We present the case of a six-year old girl with an isolated right-sided bronchial rupture after direct trauma to the chest.

Cost-benefit analysis of endovascular versus open abdominal aortic aneurysm treatment.

OBJECTIVE: To compare the costs and benefits of open versus endovascular repair of abdominal aortic aneurysm (AAA). METHODS: A consecutive series of 29 elective patients (open treatment, N = 20 and endovascular treatment, N = 9) were compared retrospectively. RESULTS: Operating time was significantly shorter for endovascular treatment (mean 90 vs. 125 min, p = 0.026). No endovascular procedure was converted to open surgery; one early endoleak was seen which sealed spontaneously. Endovascular treatment resulted in a shorter ICU and hospital stay (0 days vs. 2 days, p. 0.001 and 5 days vs. 11 days, p = 0.01 respectively). Mean total cost did not differ 361,938 BEF (9,048 Euro) vs. 382,995 BEF (9,575 Euro), p = 0.46. Endovascular treatment generated significantly less hospitalization costs (73,162 BEF or 1,829 Euro vs. 18,2740 BEF or 4,568 Euro, p = 0.001) but required a more expensive implant (153,293 BEF or 3,832 Euro vs. 38,296 BEF or 957 Euro, p = 0.001). Mean total cost for the patient was significantly higher in the endovascular treatment group (66,309 BEF or 1,658 Euro vs. 24,969 BEF or 624 Euro, p = 0.003). CONCLUSION: Our experience confirms the feasibility and safety of endovascular AAA treatment. It is associated with a shorter ICU and hospital stay and less morbidity. Overall cost for society does not differ significantly as the benefit, of lower hospitalization costs is undone by the high cost of the endovascular graft.

[Indications, method and results of autotransfusion in trauma and vascular surgery (author's transl)]. / Indikaties, methodiek en uitslagen van de autotransfusie in vasculaire en traumachirurgie

The authors have used the Bentley Ats 100 system, a disposable autotransfusion unit, in 31 cases of trauma and major vascular surgery. An original method of anticoagulation consisting in heparine (1 mg/kg bodyweight) and priming and flushing of the succion unit with ACD is described. The effect of the autotransfusion on the coagulation and the recent problems and advances are discussed.