Biochemical and immunological roles of heat shock proteins in human cancer

Abstract

Found in every cell of every organism, heat shock proteins (hsps) participate in a wide range of cellular processes and primarily function as molecular chaperones that mediate the activity of other cellular proteins. Hsps are required for a range of fundamental mechanisms used by cancer cells and they have consequently been identified as valid targets in the treatment of cancer. It was the aim of this thesis to further investigate these roles in breast cancer and melanoma using novel approaches from a biochemical and immunological perspective. In a preliminary study, breast cancer tissues (n = 30) were demonstrated by Western immunoblotting to widely express hsps 90 and 70. Two-dimensional gel electrophoresis indicated that a number of proteins were differentially expressed in tumour and healthy breast tissue from the same patient. These results suggest that a number of possibly unidentified proteins may play important roles in breast cancer and thus have use as therapeutic targets or biomarkers. The role of hsp90 and associated client proteins in breast cancer was further investigated by non-denaturing immunoprecipitation followed by elution with geldanamycin, a specific inhibitor of hsp90. Geldanamycin-sensitive hsp90 client proteins were observed in seven of 11 protein extracts from breast cancer patients and one healthy individual. Immunoprecipitation, Western immunoblotting and LC-MS identified hsps 40, 56/FKBP52, 60, 70, 105 and lumican as potential hsp90 client proteins. These proteins may thus assist breast cancer progression alongside hsp90. In one patient sample, a cancer-specific group of proteins was identified, while in all experiments geldanamycin resistance was observed. The results of this study may have relevance for the future of breast cancer research and clinical treatment.