HS-27, a fluorescently-tethered Hsp90 inhibitor, assays surface Hsp90 expression on intact tissue specimens. HS-27 is made up of the core elements of SNX-5422, an Hsp90 inhibitor, tethered via a PEG linker to a fluorescein derivative (fluorescein isothiocyanate or FITC), that binds to ectopically expressed Hsp90. HS-27 has potential use in a see-and-treat paradigm in breast cancer[1].
HS-27 labels all receptor subtypes of breast cancer, but not normal cells, and specifically binds to Hsp90 expressed on the surface of breast cancer cells before being internalized. HS-27 fluorescence is greater in tumor than non-tumor tissue[1].
[1]. Crouch BT, et al. Exploiting heat shock protein expression to develop a non-invasive diagnostic tool for breast cancer. Sci Rep. 2019 Mar 5;9(1):3461.