Retroviral infection accelerates tumor onset and increases clonal complexity in MYC/Runx2 mice. A, Tumor free survival of MYC/Runx2 (o; n=41) and MYC/Runx2 infected with MLV (•; n=27) mice. B, Tumor involvement in thymus, spleen and lymph nodes was scored on a scale of 0-3 in MYC/Runx2 (filled columns; -MLV (n=28) and MYC/Runx2 infected (hatched columns; +MLV (n=19)) mice. C, Southern analysis of genomic DNA from MLV infected MYC/Runx2 mice and uninfected littermate control (C) DNA digested with EcoRI or EcoRV and probed with a viral specific U3-LTR (upper panel) and Pim1 3′UTR (lower panel) specific probes. *; rearranged Pim1 allele detected in a single MLV-infected MYC/Runx2 mouse, M; high molecular weight DNA markers