ESR1 and cancer: In cancer,Hsp90 has been shown to play a key role in the stabilization and activationof various oncogenic proteins such as kinases (e.g., AKT, MEK, STAT3,and mTOR) and transcription factors (e.g., estrogen receptor, androgenreceptor) involved in all hallmarks of cancer.11,16−19 Since many tumor-promoting factors depend on Hsp90, proliferationof cancer cells is highly dependent on Hsp90 function, leading totheir addiction to Hsp90.