Figure 1.

Representative results of methylation-specific polymerase chain reaction (PCR) and direct DNA sequencing analysis of p16INK4a CpG islands from epithelial cells in seven patients with pterygia. A: Lanes M and U show products obtained with primers specific for methylated and unmethylated DNA, respectively. DNA templates P1-6 were prepared from epithelial cells of various patients. Templates from Calu-1 cells served as positive controls for methylated and unmethylated reactions, whereas distilled water was used as a templates for N (negative control). B: CpG-methylated cytosines remained as cytosines, whereas 5-methylcytosines were unaltered in this example (star). C: p16INK4a unmethylated cytosines changed to thymidines in the PCR products.