MYC and lymphoma: Nepal et al. [10] showed that 90% of mature B-cell lymphomas (B220+ sIg+) overexpressed Mdm2, Arf, or p53 either alone or in combination, whereas none of the evaluated immature lymphomas in Eμ-c-Myc mice overexpressed Arf or p53 and only 27% overexpressed Mdm2.