(a) Slot blots of mouse EGF-R cDNA, exon 1α fragment for p16INK4a/p19ARF, and a nonamplified chromosome 19 murine genomic DNA fragment. Of note, there is a mild increase in EGF-R cDNA in some samples (arrows). C, WT/WT; TG, EGF-R transgenic mouse. (b) Methylation-specific PCR for p16INK4a. No p16INK4a promoter methylation was observed in 9 informative samples. Sp6 lung cancer cells were used as a positive control. U, uninformative; N, normal; S, Sp6 lung.