The exponentially growing acute lymphoblastic leukemia cell line, MOLT-4 cells, was cultured with or without a CDK2 inhibitor, GW8510 or Chk2 inhibitor II, for 6 h, and phosphorylation of pRB was evaluated by site-specific phospho-serine/threonine antibodies (Fig. 3B). The gene discussed is CHEK2; the disease is acute lymphoblastic leukemia.