Identification of additional complementation groups that regulate genomic instability.

By somatic cell hybridization, amplification has been found to be a recessive genetic trait in three tumor cell lines examined. Studies with transgenic mice have shown that amplification frequency can be altered by a lack of wild-type TP53 (p53) activity. Other factors may regulate this phenotype in tumor cell lines possessing both wild-type p53 activity and amplification ability. Complementation analysis of somatic cell hybrids was performed to delineate groups of tumor cell lines that share a common defect that modulates the ability to amplify. The amplification frequencies of three normal fibroblast x tumor hybrids were suppressed 10-100-fold from parental tumor values, extending the observation that amplification is a recessive genetic characteristic in these cell lines. Analysis of tumor x tumor hybrids revealed at least two complementation groups. Defects in these groups differed from TP53 and implicate multiple variables in the regulation of gene amplification.