Interestingly, we observed that mono-allelic expression of Hdac2 in Hdac1-deficient Eμ-myc B cells (Hdac1Δ/Δ; Hdac2Δ/+) resulted in delayed tumor development, whereas complete Hdac1 and Hdac2 deletion (Hdac1Δ/Δ; Hdac2Δ/Δ) prevented tumorigenesis altogether (Fig. 2A). This evidence concerns the gene HDAC1 and neoplasm.