Amplification of MMTV-like env gene sequences in lung samples. Agarose gel electrophoresis of the 665-bp PCR product using primers 1-3 (top panel). The 595-bp PCR product using the 5L-3L primers (middle panel). As a PCR control, we used G3PDH primers to amplify a 452-bp product (bottom panel). Lane M contains a marker; lane 1 is INER51; lane 2 is INER6; lane 3 is IN-9; lane 4 is HZ-14; lane 5 is HZ-19; and lane 6 is HZ-101.