Western blot of lysed L428 cells using the MoAb Ki-S2 (B) after SDS-PAGE (gradient gel 5% to 10%). Ki-S2 detects a protein of about 100 kD. (A) Control experiment with an MoAb of the same isotype (IgG1) specific for topoisomerase-IIα (170 kD). (C) Control without primary antibody. Molecular weight standards are shown on the right (in kilodaltons).