RADIATION-INDUCED DELETION OF CHROMOSOMAL REGIONS CONTAINING TUMOR-SUPPRESSOR GENES IN HUMAN BRONCHIAL EPITHELIAL-CELLS

While several specific genetic alterations have been associated with m alignant transformation of human bronchial epithelial cells, they are not all present in every tumor and there is reason to believe that add itional genes important for loss of replication control in these cells remain to be identified. In an effort to develop a human bronchial ep ithelial cell model suitable for identification and functional analysi s of genes involved in loss of replication control, and for studying t he genetic basis of the multi-stage phenotypic changes associated with tumorigenesis, we treated multiple independent populations of the hum an papillomavirus (HPV)-immortalized human bronchial epithelial cell l ine BEP2D with ionizing radiation. Following irradiation, cell lines r epresenting the radiated populations were established from single soft agar-selected colonies. These lines-R2B5SA, R3B5DSA, R2H9S, R2H16S, R 2H18S and R3D7S-were compared cytogenetically to the parent cell line and found to have new chromosomal deletions involving putative or conf irmed tumor suppressor genes, including chromosome 13 in most R2B5SA c ells and all R3B5SA cells, chromosomes 11p and 22 in R216S, and 3p, 11 p and 22 in R2H18S. The R2B5SA cells that have lost one copy of chromo some 13 overgrow the culture but are not tumorigenic, suggesting that loss of a single copy of chromosome 13 confers growth advantage but no t tumorigenicity. The data confirm that ionizing radiation induces man y large chromosomal alterations including chromosomal loss, translocat ion and deletion and that following radiation it is possible to isolat e immortalized non-tumorigenic cell lines monosomic for regions known or suspected to contain tumor suppressor genes. The cell lines describ ed here provide powerful models for further investigation of putative tumor suppressor genes including identification, functional analysis a nd stage of transformation at which they are operative.