Cell cycle checkpoints and tumor suppressor gene functions appear to be required for the maintenance of a stable genome in proliferating cells. In this study chromosomal destabilization was monitored in relation to telomere structure, lifespan control and G2 checkpoint function. Replicative senescence was inactivated in secondary cultures of human skin ®broblasts by expressing the human papillomavirus type 16 (HPV-16) E6 oncoprotein to inactivate p53. Chromosome aberrations were enumerated during in vitro aging of isogenic control (F5neo) and HPV-16E6-expressing (F5E6) ®broblasts. We found that structural and numerical aberrations in chromosomes were signi®cantly increased in F5E6 cells during aging in vitro and¯uorescence in situ hybridization (FISH) analysis using chromosome-speci®c probes demonstrated the occurrence of rearrangements involving chromosome 4 and 6 in genetically unstable F5E6 cells. Flow cytometry and karyotypic analyses revealed increased polyploidy and aneuploidy in F5E6 cells only at passages 416, although these cells displayed defective mitotic spindle checkpoint function associated with inactivation of p53 at passages 5 and 16. G2 checkpoint function was con®rmed to be gradually but progressively inactivated during in vitro aging of E6-expressing cells. Aging of F5neo ®broblasts was documented during in vitro passaging by induction of a senescence-associated marker, pH 6.0 lysosomal b-galactosidase. F5E6 cells displayed extension of in vitro lifespan and did not induce b-galactosidase at high passage. Erosion of telomeres during in vitro aging of telomerase-negative F5neo cells was demonstrated by Southern hybridization and by quantitative FISH analysis on an individual cell level. Telomeric signals diminished continuously as F5neo cells aged in vitro being reduced by 80% near the time of replicative senescence. Telomeric signals detected by FISH also decreased continuously during aging of telomerasenegative F5E6 cells, but telomeres appeared to be stabilized at passage 34 when telomerase was expressed. Chromosomal instability in E6-expressing cells was correlated (P50.05) with both loss of telomeric signals and inactivation of G2 checkpoint function. The results suggest that chromosomal stability depends upon a complex interaction among the systems of telomere length maintenance and cell cycle checkpoints.

We have previously reported that a hypermetabolic state, resembling that produced by thyroid hormones, exists in the livers of animals treated chronically with ethanol. We propose that this alteration produces a relative hypoxia in the centrilobular zone of the liver which, if severe enough, leads to cellular death and to the production of hepatitis.Rats consuming ethanol for 30 days, given with a nutritionally adequate diet, and exposed to reduced oxygen tensions for only 6 hr, developed histological and biochemical evidence of hepatocellular necrosis and inflammatory lesions confined to the centrilobular zone. The severity was proportional to the degree of hypoxia. Pair-fed (nonalcohol) controls showed no such lesions. Treatment of the animals with propylthiouracil for 3-10 days abolished the hypermetabolic state of the liver in ethanolconsuming animals, and drastically reduced the histological and biochemical effects of hypoxia in them. These findings may have implications for pathogenesis and treatment of alcoholic hepatitis in man.Livers of rats chronically treated with ethanol utilize oxygen at higher rates than control livers (1-5). The hypermetabolic state results from increased utilization of ATP by the cell membrane (Na+K)-ATPase (ATP phosphohydrolase, EC 3.6.1.3), associated with an increase in the active transport of monovalent cations across the membrane (2, 6). We have also reported that the hypermetabolic state can be completely abolished by ouabain, an inhibitor of the (Na+K)-ATPase (2, 3).Similar changes in (Na+K)-ATPase activity, cation transport, and oxygen consumption occur in livers of animals treated with thyroid hormones, and can also be completely abolished by ouabain (3, 4, 7-10). We have also pointed out other similarities between the livers of animals chronically treated with ethanol and those treated with thyroid hormones (3, 4, 7). These similarities suggested that a functional hyperthyroid state exists in the livers of alcohol-treated animals (3, 7).In human alcoholic hepatitis (11,12), hepatocellular necrosis is most commonly seen in the central region of the hepatic lobule (zone 3 of Rappaport). Since the livers of ethanoltreated animals consume oxygen at higher rates (1-5), the possibility exists that the gradient of decreasing oxygen tension from the portal to the central venous end of the sinusoid is accentuated. We propose that, when the availability of oxygen is reduced, it is this accentuation of centrilobular hypoxia which leads to necrosis.Abbreviations: PTU, 6-propyl-2-thiouracil; SGOT, serum glutamic-oxalacetic transaminase [aspartate transferase]; SOCT, serum ornithine carbamyltransferase.To test this hypothesis we have exposed rats briefly to atmospheres with reduced oxygen tensions (5-11%). In animals treated chronically with ethanol, but not in controls, this period of hypoxia resulted in various degrees of centrilobular damage ranging from focal necrosis to massive confluent necrosis with accompanying inflammatory reaction. We have also found that a short pr...

Oral squamous cell carcinomas induced in rats by 4-nitroquinoline-1-oxide (NQO) show substantial overexpression of cyclooxygenase-2 (COX-2) when compared with adjacent phenotypically normal oral tissues. By contrast, neither 5-lipoxygenase (LOX) nor 12-LOX is overexpressed in rat oral cancers. Two chemoprevention studies were done to test the resulting hypothesis that COX-2 is a useful target for oral cancer chemoprevention in the rat. In both studies, male F344 rats received drinking water exposure to NQO (20 ppm) for 10 weeks, followed by administration of chemopreventive agents from week 10 until study termination at week 26. In the first study, groups of rats were fed basal diet (control), or basal diet supplemented with the selective COX-2 inhibitor celecoxib (500 or 1,500 mg/kg diet), the nonselective COX inhibitor piroxicam (50 or 150 mg/kg diet), or the 5-LOX inhibitor zileuton (2,000 mg/kg diet). In the second study, rats were fed basal diet (control) or basal diet supplemented with nitric oxide-naproxen (180 or 90 mg/kg diet), a nonselective COX inhibitor that shows reduced gastrointestinal toxicity. When compared with dietary controls, celecoxib decreased oral cancer incidence, cancer invasion score, and cancer-related mortality. Piroxicam decreased cancer-related mortality and cancer invasion score, whereas nitric oxide-naproxen decreased oral cancer incidence and cancer invasion score. By contrast, zileuton showed no chemopreventive activity by any parameter assessed. These data show that both selective and nonselective inhibitors of COX-2 can prevent NQO-induced oral carcinogenesis in rats. The chemopreventive activity of COX inhibitors may be linked to overexpression of their enzymatic target in incipient oral neoplasms. Cancer Prev Res; 3(1); 73-81. ©2010 AACR.

The measurement of late-night salivary cortisol is a mainstay in the diagnosis of Cushing syndrome. Furthermore, the measurement of salivary cortisol is useful in assessing the cortisol awakening response. Because the salivary glands express 11-β-hydroxysteroid dehydrogenase, the measurement of salivary cortisone may improve the performance of salivary corticosteroid measurements. We measured salivary cortisol by enzyme immunoassay (EIA) and salivary cortisol and cortisone by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in only 50 µL of saliva sampled from 54 healthy subjects (aged 20 to 64 years). We allowed patients to sample at their normal bedtime (2025 to 2400 hours) to answer a common question as to whether sampling at the normal bedtime is equivalent to the standard required sampling at 2300 to 2400 hours. We found that the salivary cortisol and cortisone results by LC-MS/MS correlated well with salivary cortisol measured with the US Food and Drug Administration-cleared EIA. Furthermore, the upper limit of normal of salivary cortisol by EIA for bedtime samples was lower than the previously published upper limit of normal with sampling required at 2300 to 2400 hours. There were no significant effects of age or sex on any of the salivary steroid measurements. We conclude that (i) salivary cortisol and cortisone can be reliably measured by LC-MS/MS in small volumes of saliva and (ii) that patients can be evaluated using saliva sampled at their normal bedtime, rather than being required to stay awake until 2300 to 2400 hours.

Context Late-night salivary cortisol (LNSC) measured by enzyme immunoassay (EIA-F) is a first-line screening test for Cushing’s syndrome (CS) with a reported sensitivity and specificity of >90%. However, liquid chromatography-tandem mass spectrometry, validated to measure salivary cortisol (LCMS-F) and cortisone (LCMS-E), has been proposed to be superior diagnostically. Objective, Setting, and Main Outcome Measures Prospectively evaluate the diagnostic performance of EIA-F, LCMS-F, and LCMS-E in 1453 consecutive late-night saliva samples from 705 patients with suspected CS. Design Patients grouped by the presence or absence of at least one elevated salivary steroid result and then subdivided by diagnosis. Results We identified 283 patients with at least one elevated salivary result; 45 had an established diagnosis of neoplastic hypercortisolism (CS) for which EIA-F had a very high sensitivity (97.5%). LCMS-F and LCMS-E had lower sensitivity but higher specificity than EIA-F. EIA-F had poor sensitivity (31.3%) for ACTH-independent CS (5 patients with at least one and 11 without any elevated salivary result). In patients with Cushing’s disease (CD), most non-elevated LCMS-F results were in patients with persistent/recurrent CD; their EIA-F levels were lower than in patients with newly diagnosed CD. Conclusions Since the majority of patients with ≥1 elevated late-night salivary cortisol or cortisone result did not have CS, a single elevated level has poor specificity and positive predictive value. LNSC measured by EIA is a sensitive test for ACTH-dependent Cushing’s syndrome but not for ACTH-independent CS. We suggest that neither LCMS-F nor LCMS-E improves the sensitivity of late-night EIA-F for CS.