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Title: Transglutaminase apoptosis and tumour progression
Author: Johnson, Timothy Scott
ISNI:       0000 0001 3591 4564
Awarding Body: Nottingham Trent University
Current Institution: Nottingham Trent University
Date of Award: 1995
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Reduced expression of the tissue transglutaminase in both murine and human tumours has been consistently associated with tumour growth and progression. This study confirms that this reduction in transglutaminase activity may, in part, be due to the expression of an inactive transglutaminase that results from perturbations at the translational or post translational level. To investigate the functional effects of transglutaminase expression, the pharmacological agents all-trans retinoic acid and dexamethasone were initially used to modulate transglutaminase activity in hamster fibrosarcoma and 'normal' cell lines. Retinoic acid causes de novo synthesis of transglutaminase resulting in increased activity in both the highly metastatic hamster fibrosarcoma cell line Met B and the 'normal' cell line BHK-21. In addition, retinoic acid causes an increase in the number of detergent insoluble bodies (apoptotic bodies) within a cell population. A range of hamster fibrosarcoma cells (Met B, D and E), BHK-21 hamster fibroblast cells and the human malignant melanoma cell line BI6 were treated with dexamethasone. This resulted in a powerful, dose dependent, but mRNA independent increase in transglutaminase activity that could be correlated to dexamethasone responsive receptor numbers in each cell line. In addition, increasing the number of dexamethasone responsive receptors by transfection of the HG I glucocorticoid receptor protein caused increases in transglutaminase activity that was proportional to the level of transfected receptor. In all experiments levels of detergent insoluble bodies were measured to demonstrate cellular increases in transglutaminase product. Correlation between transglutaminase activity and apoptotic bodies was noted. To provide a more permanent increase in transglutaminase expression without the non specific effects of pharmacological agents a constitutive human tissue transglutaminase expression construct was transfected into a highly malignant hamster fibrosarcoma cell line Met B. Transglutaminase transfected clones exhibited no significant differences in anchorage dependent growth rate in vitro, cell morphology or levels of spontaneous apoptosis measured by the determination of detergent insoluble apoptotic envelopes, but showed an increased adherence to tissue culture plastic and fibronectin coated surfaces when compared to transfected and non transfected control cells. When transglutaminase transfected fibrosarcoma cells were returned to the in vivo situation by subcutaneous injection, these cells exhibited both an increased time for tumour development and a reduced incidence of primary tumour formation, but no alteration in tumour growth rate was observed. Assay of developing tumours indicated loss of transglutaminase expression at the mRNA level, although the transglutaminase cDNA insert remained within the tumour cell genome. A gradual increase in transglutaminase expression was observed compared to controls on return of the tumour cells to the in vitro environment. When transglutaminase transfected fibrosarcoma cells were subcutaneously injected into Balb C (nu+ \ nu+) mice, no differences in primary tumour formation or tumour development time compared to controls was observed. In addition, injection of transglutaminase transfected fibrosarcoma cells into hamsters pre immunised with irradiated transglutaminase transfected cells demonstrated an increases in tumour development time compared to controls. These results suggest transglutaminase expression in the tumour cell may have an effect on tumour cell immunogenicity. The data clearly demonstrates a suppressive effect of tissue transglutaminase on tumour growth and confirms its importance in the phenotypic changes associated with the cancer process.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Fibrosarcoma; Cancer