Cytoplasmic suppression of tumor progression in reconstituted cells

This report details studies of whether mouse NIH/3T3 TG^r karyoplasts that are exposed to benzo[a]pyrene epoxide(trans) (BPDE) can progress to tumorigenicity when they are rescued with either mouse B10mtJ CAP^r tumorigenic (experiment 1) or nontumorigenic (experiment 2) cytoplasts. The mitochondrial DNA of the B10mtJ cells has restriction fragment length differences that allow distinction from the mitochondrial DNA of the NIH/3T3 cells. The reconstructed clones in experiment 1 were all tumorigenic, while those from experiment 2 were all nontumorigenic. The clones in both experiments were passaged for an equivalent time. These findings reflect the presence of factors in mouse cytoplasm capable of suppressing the tumor phenotype of NIH/3T3-BPDE treated karyoplasts when rescued at an early stage of progression.