Heat shock protein 90 (Hsp90) is a chaperone protein that protects proteins from heat stress, aids in the correct folding of other proteins and assists in protein degradation. It also stabilizes several proteins required for tumor growth, which is why Hsp90 inhibitors are investigated as anti-cancer drugs. The inhibition of Hsp90 causes cell death, as it induces the ubiquitin-proteasome system to eliminate the incorrectly folded proteins within the tumor cells, whose proliferation is induced by the inhibition of Hsp90. Another important role of Hsp90 in cancer is the stabilization of mutant proteins, it seems that Hsp90 can intervene to maintain the correct folding of the less stable proteins produced by DNA mutations, making the effect of these mutations phenotypically less relevant.