Figure 1.

(A) ALL cells are sensitive to VLX1570. Pre-B, B-cell and T-cell ALL lines were incubated in the indicated concentrations of VLX1570 for 72 hours and viability was determined by the MTT assay. (B) ALL cell lines were exposed to the indicated concentrations of VLX1570 for 6 hours. Cell extracts were prepared and subjected to immunoblotting using antibodies to K48-linked ubiquitin, HSP70B’ and β-actin as indicated. HSP70B’ is the inducible form of Hsp70 (HSPA6). (C) Four ALL cell lines with different sensitivities to VLX1570 were treated for 6 h with the indicated drug concentrations, extracts prepared and transferred to the same filter. Note that although the accumulation of polyubiquitinated proteins was dose-dependent, there was no correlation between the extent of accumulation and VLX1570 sensitivity (MOLT-4 IC₅₀ 180 nM; Reh IC₅₀ 68 nM; T-ALL IC₅₀ 100 nM; SUP-B15 IC₅₀ 68 nM).