Two naturally occurring Hsp90 inhibitors, geldanamycin and radicicol, we studied for their anti-cancer properties but their use was limited by severe hepatotoxicity (Samuni et al., 2010) and propensity to be derivatized into a biologically inactive form (Agatsuma et al., 2002; Zhou et al., 2010), respectively. Here, HSP90AB1 is linked to cancer.