Heat shock protein 90 (Hsp90) chaperone complex, molecular model. Hsp90 is a molecular chaperone and a member of the heat shock protein (HSP) family. HSPs are a group of proteins whose levels increase when cells are exposed to raised temperatures or other stress. Hsp90 is one of the most abundant proteins in cells where it is essential for the creation, maintenance, and destruction of proteins. Under normal functioning it is critical to maintaining the health of cells, whereas its dysregulation may contribute to carcinogenesis. It is therefore being researched as a possible target for anti-cancer drugs.