The origin of isochromosomes and their significance in tumorigenesis of human lung cancer

Frequent hypomethylation in Wilms tumors of pericentromeric DNA in chromosomes 1 and 16

Rearrangements in the pericentromeric heterochromatin of chromosome 1 or 16 are often found in many types of cancers, including Wilms tumors, and have been suggested to contribute to oncogenesis or tumor progression. The oncogenic potential of these rearrangements has been ascribed to the resulting chromosome arm imbalances affecting the dosage of tumor suppressor genes or protooncogenes. Because DNA hypomethylation has been linked to rearrangements in the pericentromeric regions of chromosome 1 and 16 in two types of non-cancer cell populations, we examined methylation of normally highly methylated satellite DNA sequences in these regions in Wilms tumors. Hypomethylation was found to be frequent in juxtacentromeric (satellite 2) sequences and, especially, in centromeric (satellite alpha) sequences of chromosome 1. Hypomethylation of satellite 2 DNA of chromosome 16 showed a high degree of concordance with that of satellite 2 DNA of chromosome 1. We discuss the relationship of this satellite DNA hypomethylation in Wilms tumors to chromosome aberrations, as determined by assays for loss of heterozygosity.

Cytogenetic study of twenty-three primary squamous cell carcinomas of the lung

Fifty-seven primary squamous cell carcinomas of the lung were analyzed cytogenetically. Karyotyping was possible in seven cases, and chromosome counting without detailed analysis was possible in 16 other cases. The results suggested that structural chromosome rearrangements related to the short arms of chromosomes 1(5/7), 9(3/7), and 11(6/7), and the long arms of chromosomes 6(4/7) and 7(6/7) may be the primary and non-random chromosome defects which are closely associated with human lung squamous cell carcinoma. These primary and non-random chromosome defects are believed to confer a proliferative advantage to cells carrying them, and to be involved in the pathogenesis of human lung squamous cell carcinoma.