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Title: Gene expression in human breast cancer
Author: Thompson, Alastair Mark
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1991
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Evidence exists which suggests that the expression of certain genes is associated with the development of human malignancy. The aims of the work reported in this thesis were (i) to quantitate accurately the expression (ie transcription) of selected important genes in human breast cancer, to relate this to clinical and pathological factors and to other genetic changes in the tumours and (ii) to develop a xenograft model in which to study the effect of an anticancer agent on breast tumour gene expression in vivo and thus to establish whether these approaches migh have therapeutic implications. The particular approach used to achieve these objectives was the development of molecular techniques to measure gene expression and loss of genetic material at the nucleic acid level. Gene expression was measured in primary breast cancers from 80 female patients and compared to that in normal control tissues from other patients who had surgical removal of normal breast tissue. Ribonucleic acid (RNA) was extracted from the tumours and probed with radiolabelled gene probes. Gene expression (messenger RNA) was then quantified using laser densitometry on the resultant Northern blots. Increased expression of three oncogenes (p53, c-myc, c-erbB-2), a growth factor gene (TGF-beta) and an oestrogen regulated mRNA (pS2) was detected in varying proportions of the tumours. Overexpression of individual genes was found to correlate significantly to different clinical and pathological parameters. Since the loss of specific regions of deoxyribonucleic acid (DNA) is associated with oncogenesis, DNA was also extracted from the paired venous blood and tumour tissue of each patient. Allele loss specific to the tumour DNA was then determined using Southern blots probed with radiolabelled DNA. The p53 gene is located near the tip of the short arm of chromosome 17 at 17p13 and so this region was examined for loss of genetic material. Specific DNA loss in this region was demonstrated in 64% of tumours. Loss close to, but not including, the p53 locus correlated with p53 overexpression. Using the polymerase chain reaction, exons 5 and 6 of the p53 gene were selectively amplified and subsequently sequencing suggested the overexpressed p53 may be mutant and oncogenic in at least some tumours. These results suggest that chromosome 17p is important in breast cancer. Lack of normal p53 tumour suppressor gene expression or deletion of a nearby regulatory locus resulting in overexpression of mutant p53 are proposed as key events in the pathogenesis of breast cancer. It is concluded that the use of molecular approaches, such as those employed in this work, will help not only to elucidate the pathogenesis of breast cancer, but also clarify the mechanisms by which anticancer therapy is mediated and lead to new therapeutic approaches.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available