An immunohistochemical study of beta-catenin in HNPCC colon tumours

Includes bibliographical references (leaves 49-55).Beta-catenin is normally complexed with adenomatous polyposis coli (APC) protein and E-cadherin adhesion molecule, and localized on the cell membrane. If APC/beta-catenin is disrupted, beta-catenin transfers into the nucleus, where it functions as a transcriptional activator, causing unregulated cell proliferation. The localisation of beta-catenin in H NPCC adenomas has not been studied but a shift in beta-catenin to the nucleus has been previously demonstrated in a range of col 0 recta I cancers, including those in HNPCC. The aim of the first part of the study was to determine whether there is a beta-catenin shift occurring as an early event in HNPCC tumours. Coded sections of tumours were immunohistochemically stained with antibody against beta-catenin and counterstained in haematoxylin. 14 HNPCC adenomas, 13 HNPCC carcinomas, 10 FAP adenomas, 10 FAP carcinomas, 10 sporadic adenomas and carcinomas and 10 juvenile polyps -three with dysplasia and seven without- were studied. A score was given for loss of membrane staining (0-1), presence of cytoplasmic staining (0-2) or nuclear staining (0- 2) and a total out of five obtained. An shift in beta-catenin was demonstrated at the adenoma phase in HNPCC. HNPCC, tumours were compared with sporadic tumours and a statistically significant similarity in prevalence of beta-catenin shift found in adenomas and carcinomas. The early shift in beta-catenin in HNPCC led to the second part of the study evaluating the "down-stream" effects of this shift in HNPCC tumours. TheHNPCC sections were immunohistochemically stained with E-cadherin, cmyc and cyclin 01. The results showed a positive correlation between Ecadherin loss, increased cyclin 01 and a shift in beta-catenin. No significant change in c-myc or correlation between c-myc and a shift of beta-catenin was found. In conclusion the study indicates that disruption of the APC/beta-catenin pathway plays a similar role in HNPCC tumours to that in sporadic tumours. A notable exeption is the effect on c-myc and further study is needed in this regard

Oesophageal squamous cell carcinogenesis : a study of cell cycle regulatory proteins by immunohistochemistry

Oesophageal squamous cell carcinoma (OSCC) is a highly malignant tumour that has a poor prognosis and shows marked regional variation in its incidence, implicating environmental factors. South Africa is one of several countries that has areas of high incidence. The exact aetiopathogenesis of OSCC is not well understood. Current environmental risk factors include alcohol, tobacco, human papillomavirus (HPV) infection and nutritional factors including; low intake of Vitamins A, C and riboflavin, lack of fruit and vegetables, ingestion of fungal contaminated foods and consumption of extremely hot beverages. This study was a retrospective immunohistochemical study done on paraffin embedded tissues. The histopathology, grading and staging of all resected squamous cell carcinomas over a twenty one year period from 1982 to 2002, were reviewed. Sixty eight patients were identified; all had an oesophagectomy for OSCC at Groote Schuur Hospital, a tertiary referral centre. Clinical details regarding gender, race, age, smoking or alcohol usage and survival data were collected. Survival data was updated to 23 June 2003. Two paraffin blocks representing OSCC and normal mucosa for each patient were retrieved from the archives in the Division of Anatomical Pathology. In addition, 16 cases of reflux oesophagitis were included for comparison. Initial immunohistochemical staining for HPV (Dako- clone KlH8) was undertaken but the negative results necessitated a shift in the focus of this study to that of cell cycle regulatory proteins. The tissues were evaluated for p53 (Dako - clone D0-7), p2l (Novocastro - clone 4Dl0), cyclin DI (Dako - clone DCS-6) and cyclin E (Novocastro - clone 13A3). Expression was interpreted as positive if 10% or more of the tumour cell population stained. Expression was also stratified into three levels (1, 2 and 3) depending on the percentage positive staining. Normal mucosa did not stain for any of the cell cycle regulators. OSCC stained as follows: 61.8% for p53, 27.9% for p21, 22.1 % for cyclin E and 44.1% for cyclin Dl. Reflux oesophagitis stained as follows: 31.2% for cyclin DI, 12.5% for p21 and 0% for both p53 and cyclin E. Subsequent statistical analysis failed to reveal any prognostic significance to the expression of cell cycle regulators, nor could expression or level of expression be associated with stage, grade, age, gender or alcohol use. There was however a significant relationship between cyclin DI and smoking. In addition, expression of p53 discriminated between malignant and reactive oesophageal lesions. Advancing age proved to be associated with an increased risk of mortality. Lastly, histopathological staging proved to be the most significant prognostic factor in this study

Role of BRCA2 in DNA repair

Master'sMASTER OF SCIENC