A two-dimensional gel electrophoretic study of proteins in tumours of the lung and breast

Sammanfattning: Defining differences in gene expression between benign and malignant cells is an important aspectof cancer research, and has been the object of a large number of studies. Such studies are aimed atdefining tumour markers to be used in prognostic studies, and to understand mechanisms leading touncontrolled growth and tumour metastasis. In this thesis two-dimensional polyacrylamide gelelectrophoresis (2-DE) of polypeptides was used to document patterns of gene expression in humanbreast and lung carcinomas. Applying 2-DE to the analysis of human material is not trivial, sinceserum proteins and extracellular matrix components frequently obscure the patterns and impair gelquality. Techniques therefore had to be established for the preparation of clinical tumour material for2-De. These methods allowed the characterisation of polypeptide expression in breast and lungtumours. The levels of a number of polypeptides with known identity were determined in carcinomas. Wefound that the expression of high molecular weight tropomyosin polypeptides (TMI-3) were down-regulated in both lung and breast tumours. The expression of cytokeratins 8 and 18 were lower inbreast carcinomas compared to fibroadenomas. This result should be considered when interpretingexperiments where cytokeratins are used as markers for breast cancer cells (gating cells for flowcytometry, staining for carcinoma cells in bone marrow). The levels of some members of the heatshock protein family were found to be elevated in high malignant carcinomas. A number of potential polypeptide markers were detected in lung carcinomas. One of thesemarkers (TA02) was studied in some detail. The overall pattern of polypeptide expression was studiedwith the aid of the 2-DE PDQUEST software. By pairwise comparisons of 2-DE patterns derivedfrom different tumours, we concluded that malignant breast carcinomas are highly heterogeneouswith respect to their patterns of gene expression. In contrast, polypeptide profiles from different partsof a tumour or from a tumour and its metastasis showed large similarities. These studies that 2-DEoffers an alternative to nucleic acid based techniques in studies show gene expression in humantumours .Key Words:Two-dimensional gel electrophoresis, protein analysis, sample preparation, mammary tumour, lungcarcinomas, heterogeneity, diagnostic markers.

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