Specifically, both short hairpin RNA (shRNA)-mediated abrogation of HSP90 isoforms (HSP90ɑ and HSP90β) and pharmacologic inhibition of HSP90 by PU-H71 and STA-9090 resulted in decreased PKD2 protein levels and enhanced apoptosis in lung, pancreatic, and breast cancer cell lines [45]. This evidence concerns the gene HSP90AB1 and breast cancer.