Molecular biology of malignant brain tumors

Molecular genetic analyses have revealed that the genesis and progression of tumors are the result of accumulated changes in positive and negative growth regulatory genes. Several sequential genetic alterations are considered to be required to direct cells toward the malignant phenotype. Recent studies have demonstrated that glial oncogenesis is also involved in multiple, but relatively consistent genetic alterations. The most frequent chromosomal alterations observed in astrocytic tumors include amplification of chromosome 7 and losses on chromosomes 9p, 10, and 17p. The p53 gene and the CDKN2/p16 gene have been indicated as target genes for losses of chromosome 17p and 9p, respectively. The biochemical characters of these tumor suppressor proteins are discussed in this review.