GAPDH and neoplasm: As shown in Fig 7D, RT-PCR, using primer pairs for Krt10 in combination with MmuPV1, we detected a chimeric MmuPV1-Krt10 RNA of the expected size from total RNA extracted from a MmuPV1 tumor tissue (Fig 7D gel panel, lane 3), but not a negative control Gapdh RNA (Fig 7D gel panel, lane 2).