ALTERATIONS OF RETINOBLASTOMA, P53, P16(CDKN2), AND P15 GENES IN HUMAN ASTROCYTOMAS

BACKGROUND. Alterations of the suppressor genes, such as the retinobla stoma (RE), p53, p16(CDKN2), and p15 genes, have been reported in huma n gliomas. These genes have been suggested as the cell cycle regulator y genes at the G(1)-S checkpoint. METHODS, Alterations of the RE, p53, p16(CDKN2), and p15 genes in human astrocytomas were screened by sing le strand conformation polymorphism analysis of polymerase chain react ion products (PCR-SSCP analysis) and then confirmed by dideoxy sequenc ing. In addition, the expression of RE and p16 protein was examined by Western blot analysis. RESULTS. Aberrations of the RE gene were found in 3 of 23 surgical astrocytoma specimens (13%). Mutations were found at codon 754 in exon 22 (Val-->Gly), codon 519 in exon 17 (Thr-->Pro) , and one base deletion at codon 903 resulting in stop codon at codon 905 in exon 26. These mutational locations were all near the regions a ssociated with the functional domains of the RE gene. Aberrations of t he p53 gene were found in 4 cases (17.4%). These mutations were found at codons 146 (Trp-->Gly) and 165 (Gln-->His) in exon 5, codon 73 (Val -->Glu) in exon 4, and codon 313 (Ser-->Asn) in exon 9. In addition, a lterations of the p16(CDKN2) gene were found, with 5 cases (21.7%) hav ing homozygous deletions, and 2 cases (8.7%) harboring point mutations . No p15 gene alteration was detected. The expression of p16 protein w as undetectable in 10 cases (43.5%) by Western blot analysis, demonstr ating an inverse correlation with the expression of RE protein. CONCLU SIONS, A few cases had overlapping alterations, and the incidence of o ne or more RE, p53, or p16(CDKN2) changes appeared to be relatively hi gh in human astrocytomas. These results suggest that cell cycle regula tory gene alterations may play an important role in the development of gliomas. (C) 1996 American Cancer Society.