Surface expression of heat shock proteins on human breast cells

The phenomenon of heat shock proteins on the plasma membrane has been described in a variety of malignant cells, but not in breast cancer. HSP are known to elicit an immune response when seen on the surface of cells. In this dissertation, both Hsp70 and gp96 were investigated to determine if they were important in human breast cell tumor biology. The two questions asked in this dissertation were: (1) Is this phenomenon of Hsp70 and gp96 plasma membrane surface expression seen in human breast cells and does it correlate with NK cytotoxicity? (2) How does Hsp70 arrive at the surface since there are no known mechanisms of Hsp70 surface expression?; Interesting Hsp70 plasma membrane surface expression was seen as a graded response on both malignant and nonmalignant cells. The stress protein gp96 was observed on the surface of malignant cells only. Previous experiments have relied on antibodies to detect Hsp70. In this dissertation, the putative Hsp70 molecule was isolated from membrane preparation and identied by peptide maps. The protein was identified as Hsp70. AU565 cells contain Hsp70 in the plasma membrane preparations; these results were confirmed by MALDI-TOF analysis, a non-antibody method.; Hsp70 surface expression was further investigated and was demonstrated to be a regulated process. In the human breast cells AU565, there was a two fold increase in Hsp70 surface expression after passive hyperthermia. As previously described for other cell types Hsp70 surface expression in human breast cells did not correlate with intracellular levels of Hsp70. While Hsp70 surface expression is increased with passive hyperthermia, passive hyperthermia is a pleiotrophic stimulus. The role of HSP40 in increased Hsp70 lends support to the role of co-chaperones in regulation of Hsp70 surface expression.; Other heat shock proteins observed on the surface of AU565 cells are UBP, HSP40 and gp96. The relative amounts of these heat shock proteins did not change when cells were treated with non-passive hyperthermia, or overexpressed Hsp70, HSP40, or Gam-1.; The final major finding of this dissertation was the role of gp96 in NK cytotoxicity in the breast cells lines tested. Hsp70 has been described as a target for NK cytotoxicity. Both Hsp70 and gp96 were targets for NK cells. (Abstract shortened by UMI.)...