THY1 is a candidate tumour suppressor gene with decreased expression in metastatic nasopharyngeal carcinoma

Using oligonucleotide microarray analysis, THY1, mapping close to a previously defined 11q22-23 nasopharyngeal carcinoma (NPC) critical region was identified as showing consistent downregulated expression in the tumour segregants, as compared to their parental tumour-suppressing microcell hybrids (MCHs). Gene expression and protein analyses show that THY1 was not expressed in the NPC HONE1 recipient cells, tumour segregants, and other NPC cell lines; THY1 was exclusively expressed in the non-tumourigenic MCHs. The mechanism of THY1 gene inactivation in these cell lines was attributed to hypermethylation. Clinical study showed that in 65% of NPC specimens there was either downregulation or loss of THY1 gene expression. Using a tissue microarray and immunohistochemical staining, 44% of the NPC cases showed downregulated expression of THY1 and 9% lost THY1 expression. The frequency of THY1 downregulated expression in lymph node metastatic NPC was 63%, which was significantly higher than in the primary tumour (33%). After transfection of THY1 gene into HONE1 cells, a dramatic reduction of colony formation ability was observed. These findings suggest that THY1 is a good candidate tumour suppressor gene in NPC, which is significantly associated with lymph node metastases.     

Proving the value of simulation in laparoscopic surgery

OBJECTIVE: To assess the McGill Inanimate System for Training and Evaluation of Laparoscopic Skills (MISTELS) physical laparoscopic simulator for construct and predictive validity and for its educational utility. SUMMARY BACKGROUND DATA: MISTELS is the physical simulator incorporated by the Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) in their Fundamentals of Laparoscopic Surgery (FLS) program. MISTELS' metrics have been shown to have high interrater and test-retest reliability and to correlate with skill in animal surgery. METHODS: Over 200 surgeons and trainees from 5 countries were assessed using MISTELS in a series of experiments to assess the validity of the system and to evaluate whether practicing MISTELS basic skills (transferring) would result in skill acquisition transferable to complex laparoscopic tasks (suturing). RESULTS: Face validity was confirmed through questioning 44 experienced laparoscopic surgeons using global rating scales. MISTELS scores increased progressively with increasing laparoscopic experience (n = 215, P < 0.0001), and residents followed over time improved their scores (n = 24, P < 0.0001), evidence of construct validity. Results in the host institution did not differ from 5 beta sites (n = 215, external validity). MISTELS scores correlated with a highly reliable validated intraoperative rating of technical skill during laparoscopic cholecystectomy (n = 19, r = 0.81, P < 0.0004; concurrent validity). Novice laparoscopists were randomized to practice/no practice of the transfer drill for 4 weeks. Improvement in intracorporeal suturing skill was significantly related to practice but not to baseline ability, career goals, or gender (P < 0.001). CONCLUSION: MISTELS is a practical and inexpensive inanimate system developed to teach and measure technical skills in laparoscopy. This system is reliable, valid, and a useful educational tool.     

Off-pump myocardial revascularization is associated with less incidence of stroke in elderly patients

Several recent studies have highlighted the potential benefits of using off-pump coronary artery bypass (OPCAB) surgery, particularly in high-risk patients. The aim of this meta-analysis is to assess the effect of OPCAB on the incidence of stroke compared with coronary artery bypass grafting using cardiopulmonary bypass (CPB) in elderly patients. We performed a meta-analysis of all observational studies, published in MEDLINE between 1999 and 2002 and a comparison between the OPCAB and CPB techniques in elderly patients was performed with the outcome of interest being the incidence of stroke. Elderly patients were defined as those aged 70 years or older. Nine studies are included in the meta-analysis. The total number of subjects included was 4,475 patients, of which, 1,253 underwent OPCAB (28%) and 3,222 (72%) underwent CPB. The meta-analysis showed that the OPCAB technique was associated with significantly lower incidence of stroke in elderly patients compared with the CPB technique (1% vs 3%), with an odds ratio of 0.38% to 95% (CI, 0.22 to 0.65). We did not identify any significant heterogeneity and funnel plot asymmetry between the studies included in the meta-analysis. Meta-regression analysis including variables predicting stroke, mortality, and study characteristics did not show any associations affecting the calculated odds ratio of stroke. Despite the fact that this is a meta-analysis of observational studies and adjustment for differences in baseline risk factors between OPCAB and CPB patients was not possible, we believe that this study suggests that the OPCAB technique might be associated with reduced incidence of stroke in the elderly patients undergoing coronary artery bypass grafting.     

Optimization of cardiac preload during laparoscopic donor nephrectomy: A preliminary study of central venous pressure versus esophageal doppler monitoring

Background: While the popularity of laparoscopic donor nephrectomy (LDN) has increased, concern persists about the potential deleterious effects of pneumoperitoneum on renal function. Thus, preload optimization with vigorous intravenous hydration has been recommended. The purpose of this study was to compare central venous pressure (CVP) monitoring with a noninvasive measure of cardiac preload (esophageal Doppler) during LDN. Methods: Thirteen patients were studied. Following induction of general anesthesia, a Doppler probe was inserted in the lower third of the esophagus to measure flow time corrected for heart rate (FTc), which is an index of preload. In 10 patients, a catheter was placed in the right internal jugular vein and CVP measured. CVP and FTc were measured at baseline in the supine and right lateral decubitus positions, then 15 and 60 min after the establishment of CO₂ pneumoperitoneum (12–15 mmHg). IV fluids were increased if the FTc fell below 300 msec. Results are expressed as means (±SD). Data were analyzed using repeated measures ANOVA. Results: Lateral positioning and pneumoperitoneum significantly increased CVP from baseline (p < 0.01), while the FTc did not change (p = 0.57). After 60 min of pneumoperitoneum, the FTc was <300 msec in only one patient. Conclusion: CVP is not an accurate guide for administration of IV fluids during LDN. Esophageal Doppler monitoring can be used to noninvasively follow changes in preload during LDN and is worthy of further study. Presented at the annual meeting of the Society of American Gastrointestinal Endoscopic Surgeons (SAGES), Los Angeles, CA, USA, March 2003 Financial Disclosure. This work was supported by an unrestricted educational grant from Tyco Healthcare.     

Fine mapping of the 11q22-23 tumor suppressive region and involvement of TSLC1 in nasopharyngeal carcinoma

Previous studies transferring an intact chromosome 11 into HONE1 cells demonstrated the functional significance of chromosome regions, 11q13 and 11q22-23, in nasopharyngeal carcinoma (NPC) development. In our study the 11q22-23 region was comprehensively re-investigated by detailed microsatellite and single nucleotide polymorphism genotyping and by fluorescence in situ hybridization to map precisely the regions containing tumor suppressive activity. We observed 3 chromosomal intervals within 11q22-23 that were commonly lost in the tumor segregants derived from HONE1/chromosome 11 hybrids. One critical region of 0.36 Mb was mapped near the marker D11S2000 and a second 0.44 Mb region was located around the markers D11S1300 and D11S1391. In a third region high allelic loss was also observed at marker D11S4484, where a newly cloned tumor suppressor gene, TSLC1 (tumor suppressor in lung cancer 1), is located. The gene expression analysis showed absence or low expression levels of TSLC1 mRNA in 4 highly tumorigenic NPC cell lines. In addition, the methylation study results show that the TSLC1 promoter region was hypermethylated in all 4 NPC cell lines and re-expression of the gene occurs in HONE1 cells after 5-aza-2'-deoxycytidine treatment. Hence, the mode of silencing of this candidate TSG in NPC may be attributed to promoter hypermethylation. We have obtained functional evidence for multiple critical tumor suppressive regions in 11q22-23 by fine deletion mapping and for inactivation of TSLC1 being one of these candidate TSGs in NPC development.     

Microcell-mediated transfer of chromosome 4 into HeLa cells suppresses telomerase activity

Telomerase activity can be detected in most human cancers and immortal cell lines. In contrast, the lack of telomerase activity in normal diploid fibroblasts has been correlated with progressive reduction of telomere lengths to critically short sizes followed by the cessation of cell division and the onset of senescence. Several investigators have provided evidence for the localization of a telomerase suppressor gene on chromosome 3. The aim of our study was to determine whether other chromosomes are involved in telomerase repression. Beside human chromosome 3 (serving as positive control), chromosomes 4, 6, and 11 were introduced into HeLa cells via microcell-mediated chromosome transfer. Telomerase activity from different hybrid cell lysates was determined at an early time point after fusion using a Telomerase ELISA kit. Strong repression of telomerase activity was only found in a subset of HeLa hybrids in which chromosome 3 or chromosome 4 had been introduced. Telomerase suppression induced by chromosome 3 or 4 transfer was paralleled by a high frequency (30% or 43%, respectively) of a senescent-like phenotype. Chromosomes 6 and 11, the functional loss of which is also implicated in cervical cancer, had no effect. These results indicate that normal human chromosomes 3 and 4 carry a gene or genes that suppress telomerase activity and induce cellular senescence in HeLa cells.Copyright 2001 Wiley-Liss, Inc.     

Effect of tumour and chemoradiotherapy on oesophageal motility

Background The contribution of dysmotility to dysphagia in oesophageal cancer is unclear. Aim To examine oesophageal motility in patients with oesophageal carcinoma and to assess the effect of chemoradiotherapy on motility. Methods Stationary manometry and 24-hour pH-metry were performed in 12 patients with oesophageal carcinoma and one week following completion of chemoradiotherapy using 5-fluorouracil (5-FU), cisplatin and 40Gy radiotherapy. Results All patients had abnormal motility prior to treatment. Peristalsis was impaired in 11 patients with a mean (SD) of 25% (9) of waves normally propagated. Eight patients had 20% or more simultaneous waves. Following chemoradiotherapy, the percentage of waves normally propagated increased from 25% (9) to 52% (10) (p < 0.03) and normal peristalsis was restored in four patients. The percentage of simultaneous waves decreased from 38% (11) to 21.6% (10) (p=0.129) while the percentage of dropped or increased waves decreased from 20% (11) to 8.3% (4) (p=0.264). Conclusions Oesophageal motility is disturbed in oesophageal cancer. Dysphagia in oesophageal cancer may be partly explained by oesophageal dysmotility. This is improved by chemotherapy.     

Differential gene expression in tumorigenic and nontumorigenic HeLa x normal human fibroblast hybrid cells

Fusion of tumorigenic HeLa cells with human skin fibroblasts results in chromosomally stable hybrids that are nontumorigenic and no longer express the HeLa tumor-associated marker intestinal alkaline phosphatase (IAP). Previous studies of spontaneous tumorigenic segregants from the nontumorigenic hybrids implicated the loss of one copy of human fibroblast chromosome 11 in the concomitant reexpression of tumorigenicity. In an attempt to identify genes involved in the control of tumorigenic expression, we performed differential display screening of nontumorigenic hybrid cells and tumorigenic segregants. Subsequent northern blot analyses reproducibly showed 17 differentially expressed genes, eight of which were expressed differentially in the nontumorigenic hybrids and nine of which were expressed differentially in the tumorigenic hybrids. The former were genes for 80K-L protein (a substrate of protein kinase C), AXL/UFO (a receptor tyrosine kinase), insulin-like growth factor binding protein 3, apolipoprotein AI regulatory protein, collagen type I alpha-2 chain, transforming growth factor-beta-induced gene product 3 (BIGH3), pregnancy-specific beta-1-glycoprotein, and fibroblast activation protein alpha. The latter nine genes were genes for serum/glucocorticoid-regulated kinase (SGK; a serine/threonine protein kinase), PTPCAAX1 (a tyrosine phosphatase), CXCR-4 (a G-protein-coupled membrane receptor), L-kynurenine hydrolase, beta-1, 4-galactosyltransferase, keratin 8, keratin 17, and H19 and a novel gene. The differential expression of these genes provided several interesting candidates for regulation of tumorigenic expression, including those involved in signal transduction and the extracellular matrix, cytoskeletal proteins, cell-surface enzyme, and the H19 gene.