Methylation status of the p16^INK4a exon 1 in NHL analyzed by PCR and comparison with the results of the protein expression by Western blot analysis (WB). Products of p16^INK4a exon 1 and the internal control β-globin are indicated. The amplification of exon 1 after digestion with SmaI indicates that this restriction site was methylated. Cases with p16^INK4a exon 1 amplification showed loss of protein expression by Western blot whereas protein expression was detected in cases in which p16^INK4a exon 1 was not amplified.