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Title: Modulation of the androgen receptor by hyperthermia in human prostate cancer cell lines
Author: Hocken, Alison
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1994
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Many types of tumour cells are more sensitive to elevated temperatures than normal cells. This observation and the accessibility of the prostate gland to an external heat source has led to the development of thermotherapy as a treatment for prostate disease. One possible problem with this type of therapy is the development of thermotolerance. Thermotolerance is the acquisition of a resistance to a thermokilling temperature by pre-exposure of the cell to a sublethal dose of heat and is due to an increased level of a group of proteins known as heat shock proteins (hsp). One of the members of the hsp family is hsp90. Hsp90 is associated with steroid receptors and forms part of the unactivated 8S receptor. Work described in this thesis has shown that thermotolerance in three prostate cancer cell lines (LNCaP, DU145 and PCS) is a transient property which can be established by pre-exposing the cells to 39°C for 2 hours. This temperature has been shown to induce hsp90 synthesis in prostate cell lines, shown using immunoprecipitation of hsp90 after incorporation of S³⁵ methionine and Western blotting. The androgen sensitive prostate cell line LNCaP is not normally growth inhibited by the antiandrogen HO-Flut. However if the cells are treated with hyperthermia therapy (2 hours at 39°C and 42°C) before exposure to HO-Flut the cells exhibit an increased cell kill. This increased sensitivity to cell kill was shown to be maximised 12 hours after heat shock and had fallen by 72 hours to control levels. Re-establishment of both thermotolerance and the increased cell kill in conjunction with antiandrogens can be achieved by a further heat shock administration. Thus, induction of thermotolerance in the prostate cancer cells may not be too serious for patients or clinicians because these cells may now be more sensitive to cell kill by antiandrogens. Androgen receptor ligand binding assays were used to study the effect of heat shock on the binding affinity of androgen receptors in LNCaP and DU145 cells. A gradual increase (0.232±0.050 - 0.513±0.019) in the disassociation constant (Kd) of the type I binding site was seen during the first 12 hours following heat shock. To answer the question of whether this change in Kd reflects some underlying change in the composition of the androgen receptor following heat shock sucrose density gradient analysis was used to investigate the possible changes in the androgen receptor complex composition and the ratio of 8S:4S receptor types. After heat shock a temporal shift in favour of the 8S receptor complex was seen, the time course for this mimics that of the acquisition and loss of thermotolerance as shown by cell survival to exposure to normally lethal temperatures. An additional peak around 11S can be seen between 10-12 hours after heat shock. A model is presented to provide a molecular basis for these observations.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available