While there was a marked difference in tumor burden across the 2 groups 7 weeks postimplantation, extensive infiltration of GFP-positive shHDAC1 tumor cells was seen throughout the brain parenchyma compared with shNT tumor cells — demonstrating that HDAC1-deficient tumors displayed a more invasive phenotype in vivo (Figure 6, E and F). The gene discussed is HDAC1; the disease is neoplasm.