Two cell lines, MGR3 and HBT28, revealed hemizygous deletion of the p16 and p15 genes combined with indistinguishable rearrangements of the remaining p15-p16 locus that resulted in loss of exon 2 sequences for p15 and p16, but retention of p16 exon 1.     ///    "MGR2, which retained a single wild-type p15-p16 locus, showed expression of p16 transcript, but not of p16 protein as indicated by Western blot analysis. "