Western blot analysis of p21 in primary ALL.

Protein was extracted by the SDS/boiling method from (A) infant ALL; (B) B-precursor ALL; and (C) T-ALL cells treated with AN-9 as indicated. SJ SA-1 osteosarcoma cells, known to express p21, were used as the positive control. Western blot analysis was performed using a p21 antibody at 0.5 μg/mL. Equal amounts of protein in each lane were verified by probing the blot with a β-actin antibody at 2 μg/mL. U indicates untreated (0.1% DMSO); C, positive control for p21; pt, patient. AN-9 IC₅₀ in the infant ALL was 13 μM in a ³H-thymidine uptake assay.