INFREQUENT CDKN2 MUTATION IN HUMAN DIFFERENTIATED THYROID CANCERS

We examined the frequency of cyclin-dependent kinase (CDK) N2 alterati ons in differentiated and anaplastic thyroid cancers to assess the inv olvement of CDKN2 in the development of these cancers. The CDKN2 gene, which encodes the cell-cycle regulator p16, was recently shown to be mutated or deleted in many tumor cell lines. Its role in the genesis o f primary tumors is uncertain, however. Tumor and corresponding normal DNAs were prepared by microdissection of paraffin-embedded tissue blo cks or from frozen surgical specimens of 15 papillary, 15 follicular, and five anaplastic thyroid carcinomas. The entire CDKN2 coding region was screened by single-strand conformational variant analysis and dir ect sequencing of variants. The presence of homozygous deletions was e valuated by multiplex polymerase chain reaction (PCR) analysis. Loss o f heterozygosity (LOH) in the CDKN2 region was assessed by using flank ing polymorphic markers. Two somatic missense mutations were found amo ng the 35 thyroid cancers, one in a follicular tumor and one in an ana plastic tumor. Multiplex PCR suggested the presence of homozygous dele tion in one anaplastic tumor and hemizygous deletions in four tumors. LOH studies revealed loss of 9p sequences in four follicular (27%) and two anaplastic (50%) cancers. Our data suggest that alterations in CD KN2 played a role in a minority of thyroid cancers (three of 35). LOH in the region of CDKN2 is seen in a significant proportion of follicul ar and anaplastic but not papillary cancers. Loss of 9p sequences sugg ests a role for a tumor suppressor gene in the development of follicul ar and anaplastic thyroid cancers. (C) 1996 Wiley-Liss, Inc.