Palbociclib (S1116), abemaciclib (S7158), and ribociclib (S7440) were purchased from Selleck Chemicals. CR-1–31-B and silvestrol were synthesized as described previously (26 (link), 27 (link)). Antibodies against HSP90 (H-114), Cyclin D1 (M20), Cyclin D3 (DCS28), Cyclin A2 (BF683), Cyclin E1 (HE12), Cyclin E2 (A-9), CDK2 (D-12), CDK4 (DCS-35), CDK6 (C-21), p16 (C-20), p21 (H164), and p27 (C-19) were purchased from Santa Cruz Biotechnology; p-RB (S795) and Cyclin D2 (D52F9) were purchased from Cell Signaling Technology; RB (554136) was purchased from BD Pharmingen; and eIF4A1 (ab31217) was purchased from Abcam.