ACTB and glioblastoma: Finally, to evaluate therapeutic tractability in GBM models, we applied a small molecule inhibitor of Hsp90, radicicol (Sharma et al., 1998), to multiple GBM-derived human cell cultures with differing published expression levels of Hsp90 from highest to lowest relative to β-actin: LN-229 > U-251 > U-87 (Belkacemi and Hebb, 2014).