Proliferation defects and genome instability in cells lacking Cul4A

The Cul4A gene, which encodes a core component of a cullin-based E3 ubiquitin ligase complex, is over-expressed in breast and hepatocellular cancers. In breast cancers, over-expression of Cul4A strongly correlates with poor prognosis. Also, Cul4A is required for early embryonic development. Early lethality of mouse embryos prevented a detailed analysis of the functions of Cul4A. Here, we used a strain of mice carrying floxed alleles of Cul4A to study its role in cell division, in vitro and in vivo. Embryonic fibroblasts exhibit a severe deficiency in cell proliferation following deletion of Cul4A. We observed that the Cul4A protein is abundantly expressed in brain, liver and in the mammary tissue of pregnant mice. Deletion of Cul4A in liver impairs hepatocyte proliferation during regeneration following carbon tetrachloride induced injury. The Cul4A-deleted cells are slow in entering S phase, and are deficient in progressing through early M phase. Several cell cycle regulators, including p53 and p27Kip1, are de-regulated in the Cul4A-deleted cells. Expression of a dominant negative mutant of p53 causes significant reversal of the proliferation defects in Cul4A-deleted cells. The Cul4A-deleted cells exhibit aberrant number of centrosome, multipolar spindles and micronuclei formation. Furthermore, those cells are sensitive to UV irradiation and exhibit reduced levels of unscheduled DNA synthesis. Together, our observations indicate that Cul4A is required for efficient cell proliferation, control of the centrosome amplification and genome stability.

The cost-effectiveness and budget impact of competing therapies in hepatic encephalopathy - a decision analysis

BACKGROUND

Treatment options for hepatic encephalopathy have disparate risks and benefits. Non-absorbable disaccharides and neomycin are limited by uncertain efficacy and common dose-limiting side effects. In contrast, rifaximin is safe and effective in hepatic encephalopathy, but is more expensive.

METHODS

We conducted a decision analysis to calculate the cost-effectiveness of six strategies in hepatic encephalopathy: (i) no hepatic encephalopathy treatment, (ii) lactulose monotherapy, (iii) lactitol monotherapy, (iv) neomycin monotherapy, (v) rifaximin monotherapy and (vi) up-front lactulose with crossover to rifaximin if poor response or intolerance of lactulose ('rifaximin salvage'). The primary outcome was cost per quality-adjusted life-year gained.

RESULTS

Under base-case conditions, 'do nothing' was least effective and rifaximin salvage was most effective. Lactulose monotherapy was least expensive, and rifaximin monotherapy was most expensive. When balancing cost and effectiveness, lactulose monotherapy and rifaximin salvage dominated alternative strategies. Compared to lactulose monotherapy, rifaximin salvage cost an incremental US$2315 per quality-adjusted life-year-gained. The cost of rifaximin had to fall below US$1.03/tab in order for rifaximin monotherapy to dominate lactulose monotherapy.

CONCLUSIONS

Rifaximin monotherapy is not cost-effective in the treatment of chronic hepatic encephalopathy at current average wholesale prices. However, a hybrid salvage strategy, reserving rifaximin for lactulose-refractory patients, may be highly cost-effective.

DNA methylation and histone modification regulate silencing of epithelial cell adhesion molecule for tumor invasion and progression

Epithelial cell adhesion molecule (Ep-CAM) is believed to have a critical role in carcinogenesis and cell proliferation. However, the association of Ep-CAM with cancer invasion and progression is less clear. We found that Ep-CAM was highly expressed on low-invasive cells compared with highly invasive cells. Forced expression of Ep-CAM decreased cancer invasiveness, and silencing Ep-CAM expression elevated cancer invasiveness. Ep-CAM expression was associated with promoter methylation. Treatment with a demethylating agent, and/or the histone deacetylase inhibitor reactivated Ep-CAM expression in Ep-CAM-negative cells and inhibited cancer invasiveness. Using a promoter-reporter construct, we demonstrated methylation of the promoter fragment drive Ep-CAM-silenced transcription. Additionally, silenced Ep-CAM gene in cancer cells was enriched for hypermethylated histone 3 lysine 9. When unmethylated and active, this promoter was associated with acetylated histone 3 lysine 9. Furthermore, we observed an increased association of Ep-CAM promoter with repression components as tumor invasiveness increased. In cancer tissues, Ep-CAM expression significantly correlated with tumor progression and associated with promoter methylation. Our data support the idea that modulation of Ep-CAM plays a pivotal role in tumor invasion and progression. Moreover, aberrant DNA methylation of Ep-CAM is implicated in enhancing invasive/metastatic proclivity of tumors.

Distribution of divalent metal transporter-1 in the monkey basal ganglia

An accumulation of iron occurs in the brain with age, and it is thought that this may contribute to the pathology of certain neurodegenerative diseases, including Parkinson's disease. In this study, we elucidated the distribution of divalent metal transporter-1 (DMT1) in the monkey basal ganglia by immunocytochemistry, and compared it with the distribution of ferrous iron in these nuclei by Turnbull's Blue histochemical staining. We observed a general correlation between levels of DMT1, and iron staining. Thus, regions such as the caudate nucleus, putamen, and substantia nigra pars reticulata contained dense staining of DMT1 in astrocytic processes, and were also observed to contain large numbers of ferrous iron granules. The exceptions were the globus pallidus externa and interna, which contained light DMT1 staining, but large numbers of ferrous iron granules. The thalamus, subthalamic nucleus, and substantia nigra pars compacta contained neurons that were lightly stained for DMT1, but few or no iron granules. The high levels of DMT1 expression in some of the nuclei of the basal ganglia, particularly the caudate nucleus, putamen, and substantia nigra pars reticulata, may account for the high levels of iron in these regions.

Neuronal localization and association of Niemann Pick C2 protein (HE1/NPC2) with the postsynaptic density

Niemann-Pick disease type C (NP-C) is an inherited disorder that is characterized biochemically by cellular cholesterol and glycolipid storage, and clinically by progressive neurodegeneration. Most cases of NP-C are caused by inactivating mutations of the npc1 gene, but about 5% are linked to npc2, which encodes a soluble cholesterol binding protein, previously identified as epididymal secretory glycoprotein 1 (HE1). The present study was carried out to investigate the immunocytochemical localization of HE1/NPC2 protein in the mouse brain. Using an antibody against recombinant HE1/NPC2, we found HE1/NPC2 to be localized predominantly in neurons in the brain. Immunoreactivity for HE1/NPC2 was observed in pyramidal or projection neurons in the cerebral cortex and amygdala, and Purkinje neurons in the cerebellum. Neurons in the thalamus, hypothalamus, and globus pallidus were lightly labeled, or unlabeled. This regional pattern of expression of HE1/NPC2 is similar to our previous findings with NPC1, with a low level of expression of both NPC1 and HE1/NPC2 proteins in regions derived from the diencephalon, such as the thalamus and hypothalamus. In contrast to NPC1, however, which is predominantly in astrocytes, HE1/NPC2 was observed mainly in neurons. Electron microscopic immunocytochemistry showed that HE1/NPC2 is present in the cytosol of dendrites and on post-synaptic densities (PSD). The occurrence of HE1/NPC2 in the PSD was confirmed by Western blots of PSD-enriched brain subcellular fractions that showed the presence of HE1/NPC2 together with the PSD-associated protein, PSD-95. These results suggest that NPC1 and HE1/NPC2 are differentially enriched in astrocytes and neurons, respectively, and that HE1/NPC2 may function in supporting the integrity of the PSD of neurons.

Closure of the subcutaneous dead space and wound disruption after Cesarean delivery

OBJECTIVE

To determine whether suture closure of subcutaneous dead space decreases wound disruption after Cesarean delivery.

METHODS

All patients undergoing Cesarean delivery at the New England Medical Center from September 1995 to June 1997 were eligible. One group (162 patients) was randomly assigned to have the subcutaneous fat layer closed with a running 3-0 plain suture. The other group (165 patients) had this layer left unclosed. Both groups had careful hemostasis of this layer with cautery and copious irrigation. All laboring and ruptured patients received prophylactic antibiotics. The patients were followed for 6 weeks after delivery for wound disruption.

RESULTS

No significant differences were noted between the two groups with respect to demographic, obstetric, or surgical characteristics or loss to follow-up. Excluding those lost to follow-up (27 closed vs. 22 unclosed), there was no difference in wound infection (11 (8.1%) closed vs. 13 (9.1%) unclosed, RR 0.90, 95% CI 0.14, 2.08). There were decreases in risk of skin separation (three (2.2%) vs. six (4.2%), RR 0.53, 95% CI 0.42, 1.93) and seroma or hematoma formation (two (1.5%) vs. seven (4.9%), RR 0.30, 95% CI 0.06, 1.43) that were not statistically significant. Decreases that were not statistically significant were also noted for any wound disruption (14 (10.4%) vs. 21 (14.7%), RR 0.71, 95% CI 0.37, 1.33) and non-infected wound complication (three (2.2%) vs. eight (5.6%), RR 0.40, 95% CI 0.11, 1.47). Increasing gravidity and parity, and Cesarean delivery performed for failure to progress were independent risk factors for any wound complication. Controlling for these factors did not alter the effect of subcutaneous closure.

CONCLUSIONS

Closure of the subcutaneous space does not increase and may protect against wound complications in patients undergoing Cesarean delivery.

Rupture of the renal pelvis associated with intravenous fluid bolus

Previously reported cases of spontaneous rupture of the kidney or ureter reflect underlying renal pathology and have been reported both spontaneously and in relationship to delivery, but not in relation to other operative procedures. A 27-year-old woman at 19 weeks' gestation developed severe right flank pain in the operating room immediately prior to cerclage placement. Postoperative renal ultrasound examination and intravenous pyelogram performed to evaluate persistent flank pain demonstrated renal pelvis rupture. No other renal abnormality was present. We postulated that increased urine flow from the fluid bolus for the spinal anesthetic precipitated the rupture.