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Title: The cell kinetics of human breast cancer
Author: Stanton, Peter David
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1995
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Tumour growth has been studied for many years in the hopes of gaining prognostic information, guiding cancer therapy, and better understanding the control of cellular proliferation within tumours. Recent methods have applied the technology of flow cytometry, using its ability to characterise many cells in a short space of time. This thesis examines the potential for two of these techniques to contribute to the study of tumour cell kinetics in the context of breast cancer, one of the commonest tumours, one of the most studied, and yet one where patient outcome has improved little in recent years. The first method involves staining of tumour nuclei with fluorescent stoichiometric DNA dyes in order to obtain a frequency distribution of DNA contents within the tumour cell population. From this, the amount of nuclear DNA of the tumour cells relative to the norm (tumour ploidy), and the proportion of cells in the S phase of the cell cycle (the S phase fraction, SPF) can be estimated. These parameters have been described as being of prognostic significance in breast cancer. In 293 cases studied here, there was a non-statistically significant worse prognosis for aneuploid tumours relative to diploid (relative hazard in multivariate analysis 1.20, 95%CI 0.81-1.76), whilst SPF shows an also non-significant trend toward poor survival associated with high SPF (relative hazards 1.31, 95%CI 0.87-1.98). In view of theoretical and logistical shortcomings of the methodology, studies of the reproducibility of the SPF were carried out, indicating very large variations in repeated estimates (95% Cl for estimates of +40% or more). This may contribute to the limited prognostic power of this parameter. The second technique, which also provides information about the rate of cell cycle transit, involves the administration of the DNA precursor bromodeoxyuridine prior to tumour biopsy. Staining of nuclear suspensions for both DNA content as above, and for bromodeoxyuridine content, analysed by multiparameter flow cytometry, allows estimation of the proportion of cells in S phase (the bromodeoxyuridine labelling index, BLI), the length of that phase (Ts), and the potential doubling time (Tppot) of the tumour. This information has been gained in 84 women, out of 89 labelled. This has demonstrated that the technique can be successfully applied to most breast cancers. Median values for the three parameters were: LI- 3.2%, Ts- 12.7hrs, Tpot- 14.6days. Prognostic information is not yet available, but the relationship to other prognostic factors. Kinetics were closely related to histological grade, but not tumour size or nodal status. Although oestrogen receptor status was known for only a minority of tumours, within this group ER negative tumours showed significantly higher BLI. In terms of reproducibility, this method emerges as superior to the estimation of SPF (95%CI for estimations of BLI +30%). Its own limitations are considered, principally the inability to allow for ceil loss within tumours, or to deal with variation in kinetic parameters in different areas of tumour. The potential to use this technique as a means of exploring tumour biology was addressed in a further study of type I growth factor expression in the same group of breast tumours. Two members of this family of cell surface proteins were studied, the epidermal growth factor receptor (EGFR) and the c-erbB-2 oncoprotein. Both are known to be expressed in a signigicant minority of breast cancers, and in each case expression has been shown to be associated with poorer prognosis. This has led to the hypothesis that they act to give growth advantage to tumours in which they are overexpressed, which was tested here by looking at the relationship between expression and cell kinetics. In the case of erbB-2, there was a trend toward higher ELI in positive tumours, but this was not statistically significant (p=0.28). For the study of EGFR, a quantitative immunohistochemical method not previously used in breast cancers was used. This involves application of radio-iodinated antibody to tissue sections, the binding of which is demonstrated by covering the slide with autoradiographic emulsion. Quantification is possible by counting the number of grains developed in the emulsion, using an image analysis system. In all, 105 tumours were studied this way, as well as 9 normal breast controls. This demonstrated that 97% of tumours had levels of EGFR expression lower than that in normal breast. Tumours with preserved expression of any degree did have significantly higher BLI (rank correlation, p=0.019), and lower Tpot (p=0.039).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available