Inhibition of LMP7 is sufficient to cause an antitumor effect in Δβ5 HS-Sultan cells. (A) HS-Sultan cells transduced with a control shRNA-expressing (ctl) or β5-targeting shRNA vector (Δβ5) were profiled for LMP7 and β5 expression. Control (■) or Δβ5 (□) HS-Sultan cells were treated with a 1-hour pulse dose escalation of IPSI (B) or carfilzomib (C), and cell viability was measured at 24 hours. Mean ± SD are shown (n = 24). For IPSI (B), the dotted line represents the LMP7-selective dose (0.27 μM) described in Figure 3.