NEUROFIBROMATOSIS-2 GENE IN HUMAN COLORECTAL-CANCER

Colon cancers commonly have allelic losses of chromosome 22q, which su ggests the presence of a tumor suppressor gene on 22q. The candidate t umor suppressor gene on 22q is the neurofibromatosis 2(NF2) gene. Usin g single strand conformation polymorphism (SSCP) analysis, we screened 24 pairs of colorectal cancer and adjacent normal mucosa, as well as 10 colon cancer cell lines from non-NF2 patients, for mutations in the coding sequence of the NF2 gene. Two SSCP variants, one in exon 14 an d another one in exon 16, were detected in two of the sporadic colorec tal cancers, but not in adjacent normal mucosa samples. Sequencing of these variants in one tumor detected an A-to-G transition in bp 1459 o f the NF2 cDNA, resulting in the change of Ile to Val at codon 487 of merlin, the NF2 protein product. The other tumor showed a 2-bp (CT) de letion in the intronic sequence of the alternatively spliced exon 16. These results suggest that the NF2 gene is probably involved in some c olorectal tumors, but is not the critical chromosome 22q tumor suppres sor gene involved in colon tumorigenesis.