Heat shock proteins (HSPs) are a family of highly conserved proteins that are expressed, either constitutively or regulated inductively, in response to a wide range of physiological and environmental insults, such as heat shock. According to molecular weight, mammalian HSPs are classified into four subfamilies, including HSP90 (90 kDa), HSP70 (70 kDa), HSP60 (60 kDa) and small HSPs (15 to 30 kDa), among which HSP90 and HSP70 are two of the most studied stress-inducible HSPs. HSP90 is a highly abundant chaperone protein characterized by containing three relevant domains, including the N-terminal domain, the charged middle linker region and the C-terminal dimerization domain; while HSP70 is an ATP-dependent chaperone protein characterized by containing two distinct functional domains, including a peptide binding domain (PBD) and the amino-terminal ATPase domain (ABD). Collectively HSPs play a fundamental role in maintaining the stability of other cellular proteins.