Inactivation patterns of the p16 (INK4 alpha) gene in oral squamous cell carcinoma cell lines

To determine whether inactivation of the pld gene mapped to the chromosome 9p21 region is associated with the development of oral squamous cell carcin oma (SCC), we investigated the mutational states of two forms of alternativ e transcripts (alpha and beta) from the p16 gene in 14 oral SCC cell lines bq means of RT-PCR, PCR, direct sequencing and methylation analyses. Altera tions of the alpha transcript were detected in all of the cell lines examin ed: homozygous deletions in three lines; subtle mutations in exons 1 alpha or 2 in four lines; skipping of exon 2 in two lines; hypermethylation of th e 5' CpG island of the p16 gene in four lines; and an unknown mechanism in one line. On the other hand, abnormalities of the beta transcript were obse rved in seven of the 14 cell lines. Nonetheless, the mutations that essenti ally affect the function of the encoded protein were found only in five cel l lines, including three lines with homozygous deletion. There was no cell line having only beta transcript alterations. Thus, alteration of the alpha transcript of the p16 gene was a highly frequent event in oral SCC. Since this type of alteration resulted in gene inactivation through multiple path ways, it may play a major role in the process of oral SCC development. (C) 1999 Elsevier Science Ltd. All rights reserved.