We have found that there is a striking difference between normal, diploid cells and tumorigenic ell in their ability to amplify a given endogenous gene. Amplification frequency is high in tumorigenic cells (10-3), lower in nontumorigenic, preneoplastic cells (10-5) and undetectable in normal, diploid cells (lessor10-9). To investigate the genetic control of gene amplification, amplification frequency was measured in hybrids formed between tumorigenic cells and normal, diploid cells. The ability to amplify an endogenous gene behaved as a recessive genetic trait. Amplification frequency in the hybrid cells was suppressed by over five orders of magnitude (10-3 to lessor10-8). We observed that diploid cells that had not detectable frequency of gene amplification are arresting in the cell cycle when placed in the metabolic inhibitor, PALA. Tumorigenic cells do not arrest but proceed to make a choice between growth (containing amplified target genes) or suicide, the activation of apoptosis. In this application we wish to address two questions. 1) is there a functional connection between the metabolic growth arrest in normal cells and their ability to amplify? and 2) is apoptosis the default alternative? We will approach these goals by examining the relationship between growth arrest and amplification using flowcytometry as a method of detection we can determine if the cellular arrest generates amplification intermediates. We will also examine amplification of genes that are not directly connected to the production of nucleotide precursors. Finally, we will ask if genes that suppress amplification ability suppress apoptosis. We will use the somatic cell hybrids we have characterized for these purposes.
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