Cell and molecular biology of gastrointestinal tract cancer.

The gene for familial adenomatous polyposis coli (APC or FAP), which has previously been linked to chromosome 5q21 has been identified. The APC gene has been found to be altered by point mutations in the germ line of both adenomatous polyposis coli and Gardner's syndrome patients and somatically in tumors from sporadic colorectal cancer patients. During the hunt for the APC gene, the closely linked MCC (mutated in colorectal cancer) gene was identified and found to be altered somatically in tumors from sporadic cancer patients. These data suggest that more than one gene on chromosome 5q21 may contribute to colorectal carcinogenesis and that mutations at the APC gene can cause both adenomatous polyposis coli and Gardner's syndrome. The identification of these genes should aid in the counseling of patients with genetic predispositions to colorectal cancer. Progress has also been made in identifying specific genetic changes that occur in other gastrointestinal cancers. A mutational "hotspot" in the p53 gene in human hepatocellular carcinomas has been identified that could reflect exposure to a specific carcinogen, one candidate being aflatoxin B1.     

A translational repression assay procedure (TRAP) for RNA–protein interactions in vivo

RNA–protein interactions are central to many aspects of cellular metabolism, cell differentiation, and development as well as the replication of infectious pathogens. We have devised a versatile, broadly applicable in vivo system for the analysis of RNA–protein interactions in yeast. TRAP (translational repression assay procedure) is based on the translational repression of a reporter mRNA encoding green fluorescent protein by an RNA-binding protein for which a cognate binding site has been introduced into the 5′ untranslated region. Because protein binding to the 5′ untranslated region can sterically inhibit ribosome association, expression of the cognate binding protein causes significant reduction in the levels of green fluorescent protein fluorescence. By using RNA–protein interactions with affinities in the micromolar to nanomolar range, we demonstrate the specificity of TRAP as well as its ability to recover the cDNA encoding a specific RNA-binding protein, which has been diluted 500,000-fold with unrelated cDNAs, by using fluorescence-activated cell sorting. We suggest that TRAP offers a strategy to clone RNA-binding proteins for which little else than the binding site is known, to delineate RNA sequence requirements for protein binding as well as the protein domains required for RNA binding, and to study effectors of RNA–protein interactions in vivo.     

Is the structure of anatomy curriculum adequate for safe medical practice?

IntroductionAnatomy has been considered a core subject within the medical education curriculum. In the current setting of ever-changing diagnostic and treatment modalities, the opinion of both students and trainers is crucial for the design of an anatomy curriculum which fulfils the criteria required for safe medical practice.MethodsMedical students, trainees and specialist trainee doctors and specialists from the London (England) area were surveyed to investigate the how curriculum changes have affected the relevance of anatomical knowledge to clinical practice and to identify recommendations for optimum teaching methods. The survey employed 5-point Likert scales and multiple-choice questions. Where the effect of training level was statistically significant (p < 0.05), post-hoc analysis was carried out using Mann–Whitney U tests. Significance levels were modified according to the Bonferroni method.ResultsTwo hundred and twenty-eight individuals completed the survey giving a response rate of 53%. Medical students, trainees and specialists all agreed (mean Likert score 4.51, 4.79, 4.69 respectively) that knowledge of anatomy is important for medical practice. Most of the trainees (88.4%) and specialists (81.3%) used dissection to learn anatomy, but only 61.4% of medical students used this approach. Dissection was the most commonly recommended approach for learning anatomy across all the groups (41.7%–69.3%).ConclusionsKnowledge of anatomy is perceived to be important for safe clinical practice. Anatomy should be taught with other relevant system or clinical modules. Newer tools for anatomy teaching need further validation before incorporation into the curriculum.     

Abrogation of the radiation-induced G2 checkpoint by the staurosporine derivative UCN-01 is associated with radiosensitisation in a subset of colorectal tumour cell lines

Ionising radiation is commonly used in the treatment of colorectal cancer. Tumour cells with mutant p53 undergo cell cycle arrest at G2/M after ionising radiation and evidence suggests that abrogation of this G2 arrest can lead to a premature, aberrant mitosis, thus enhancing ionising radiation-induced cell killing. The G2 checkpoint inhibitor UCN-01 was thus investigated to determine whether it would abrogate the G2 checkpoint induced by 5 Gy ionising radiation in a range of colorectal tumour cell lines. Data presented show that, at doses that are alone non-toxic to the cells, UCN-01 inhibits the ionising radiation-induced G2 checkpoint in five colorectal tumour cell lines with mutant p53. The ability of UCN-01 to sensitise cells to ionising radiation-induced growth inhibition and apoptosis was also investigated and UCN-01 was found to radiosensitise two out of five cell lines. These results were confirmed by long-term colony forming efficiency studies. These results demonstrate that abrogation of the ionising radiation-induced G2 checkpoint is not necessarily associated with sensitisation to ionising radiation, however, some colorectal tumour cell lines can be radiosensitised by UCN-01. Although the mechanism of radiosensitisation is not clear, this may still be an important treatment strategy.     

Self-citations in six anaesthesia journals and their significance in determining the impact factor

Self-citation of a journal may affect its impact factor. We investigated self-citations in the 1995 and 1996 issues of six anaesthesia journals by calculating the self-citing and self-cited rates for each journal. Self-citing rate relates a journal's self- citations to its total number of references. We defined self-cited rate as the ratio of a journal's self-citations to the number of times it is cited by the six anaesthesia journals. We also correlated self-citing rates with the impact factor of the six journals for 1997. Citations among the six journals differed significantly (P < 0.0001). Anesthesiology had the highest self-citing rate (57%). Anaesthesia, Anesthesia and Analgesia, British Journal of Anaesthesia, Canadian Journal of Anaesthesia and the European Journal of Anaesthesiology had self-citing rates of 28%, 28%, 30%, 11% and 4% respectively. The self- cited rates were 31%, 35%, 34%, 27%, 31% and 17% for Anaesthesia, Anesthesiology, Anesthesia and Analgesia, British Journal of Anaesthesia, Canadian Journal of Anaesthesia and the European Journal of Anaesthesiology, respectively. North America journals cited the North America literature. This also occurred, to a lesser extent, in the European anaesthesia journals. A significant correlation between self-citing rates and impact factors was found (r = 0.899, P = 0.015). A high self-citing rate of a journal may positively affect its impact factor.      

Increased p53-dependent apoptosis by the insulin-like growth factor binding protein IGFBP-3 in human colonic adenoma-derived cells

We investigated the expression of insulin-like growth factor binding protein 3 (IGFBP-3) in normal human colonic epithelium and whether IGFBP-3 is involved in the induction of apoptosis in colonic epithelial cells. A gradient of IGFBP-3 protein expression was observed within the normal colonic crypt, and increased IGFBP-3 expression was coincident with the region of increased differentiation and apoptosis. Treatment of human colonic tumor cell lines with IGFBP-3 alone was shown to have no effect on growth. However, an increase in p53-dependent apoptosis was observed in the presence of 100 ng/ml IGFBP-3 24 h after the induction of DNA damage by gamma-irradiation. These results suggest that IGFBP-3 enhances the p53-dependent apoptotic response of colorectal cells to DNA damage.