One of a group of proteins that help protect cells from stresses such as heat, cold, and low amounts of oxygen or glucose (sugar). Heat-shock proteins help other proteins function in normal cells and may be present at high levels in cancer cells. Blocking the activity of a heat-shock protein called HSP90 is being studied in the treatment of cancer. Other heat-shock proteins including HSP70 and gp96 are being studied in vaccines to treat cancer. Also called HSP and stress protein.