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Microscopic adenoma in nonpolyposis coli: incidence and relation to basal cells and lymphoid follicles.

Six microscopic adenomas found in four patients of nonpolyposis coli (namely, not included in the group of familial polyposis coli) which had been detectable microscopically but not macroscopically, were examined by preparing complete serial section. With respect to the histogenesis of large-intestinal adenomas in nonpolyposis coli, they are considered to originate from the basal cells. As the background for this, a great number of adenomatous changes in basal cells were seen, and the microscopic adenomas showed a tendency of multiplicity (in the present study a total of 36 microscopic adenomas were detected). The above-described adenomatous changes in basal cells and development of microscopic adenomas are considered to be closely related to lymphoid follicles on the muscularis mucosa, with 20 (55.6 per cent) of 36 microscopic adenomas originating in the basal cell upon the lymphoid follicles.

Adenoma↗

Mammalian MutS homologue 5 is required for chromosome pairing in meiosis.

MSH5 (MutS homologue 5) is a member of a family of proteins known to be involved in DNA mismatch repair. Germline mutations in MSH2, MLH1 and GTBP (also known as MSH6) cause hereditary non-polyposis colon cancer (HNPCC) or Lynch syndrome. Inactivation of Msh2, Mlh1, Gtmbp (also known as Msh6) or Pms2 in mice leads to hereditary predisposition to intestinal and other cancers. Early studies in yeast revealed a role for some of these proteins, including Msh5, in meiosis. Gene targeting studies in mice confirmed roles for Mlh1 and Pms2 in mammalian meiosis. To assess the role of Msh5 in mammals, we generated and characterized mice with a null mutation in Msh5. Msh5-/- mice are viable but sterile. Meiosis in these mice is affected due to the disruption of chromosome pairing in prophase I. We found that this meiotic failure leads to a diminution in testicular size and a complete loss of ovarian structures. Our results show that normal Msh5 function is essential for meiotic progression and, in females, gonadal maintenance.

Animals↗

Expression of the APC gene after transfection into a colonic cancer cell line.

Mutations in the adenomatous polyposis coli (APC) gene cause the hereditary cancer syndrome familial adenomatous polyposis and are implicated in the early stages of sporadic colorectal carcinogenesis. APC is therefore a promising candidate for use in prophylactic gene therapy of intestinal tissues at high risk of becoming malignant. The aim of the study was to discover if functional full length APC gene can be introduced into somatic gut epithelial cells and to define the optimum conditions for such transfer. Copies of the normal APC gene were introduced into SW480 cells, a colonic epithelial cell line with an APC gene mutation, using plasmid DNA combined with liposomes. Reverse transcriptase polymerase chain reaction and restriction enzyme digestion allowed the endogenous gene to be distinguished from the transgene. It was shown that the normal APC gene is expressed at high levels for 72 hours after transfection and disappears within one week. This study shows that short-term expression of normal APC gene can be achieved after transfection with liposome-DNA complexes at sufficiently high levels to permit assessment of biological effects.

Base Sequence↗

[Genetics of colorectal cancer. II. Hereditary background of sporadic and familial colorectal cancer].

About 15% of patients with colorectal cancer have a positive family history: 5% have hereditary colorectal cancer (hereditary non-polyposis colorectal carcinoma (HNPCC), familial adenomatous polyposis (FAP) or some other hereditary syndrome), while in 10% no clear hereditary pattern can be recognized ('familial colorectal cancer'). In sporadic and in familial intestinal cancer, a demonstrable hereditary predisposition may undoubtedly exist. HNPCC is often characterized by microsatellite instability, i.e. an increased number of short DNA sequences in the DNA indicating a disorder in DNA repair and a mutation in a DNA 'mismatch repair' (MMR) gene. Indicative of hereditary bowel cancer on the basis of such an MMR gene mutation are: (a) presence of bowel cancer in > or = 3 relatives, (b) early age at the time of the diagnosis of 'bowel cancer', (c) multiple primary bowel tumours, (d) uterine cancer in the family and (e) bowel and uterine cancer in a woman. Recent data demand a new subdivision of hereditary bowel cancer, based upon both the clinical picture and the results of DNA-tests. The genetic alterations in colonic adenomas and carcinomas are known to a large extent. In future these insights may be important in clinical practice, such as a more individual determination of the patient's prognosis and accordingly, of the treatment and follow-up.

Adenoma↗