Fig. 1.

Role of the nucleus and mitochondria in the origin of tumors. This image summarizes the experimental evidence supporting a dominant role of the mitochondria in the origin of tumorigenesis as described previously (49). Normal cells are depicted in green with mitochondrial and nuclear morphology indicative of normal respiration and nuclear gene expression, respectively. Tumor cells are depicted in red with abnormal mitochondrial and nuclear morphology indicative of abnormal respiration and genomic instability. (1) Normal cells beget normal cells. (2) Tumor cells beget tumor cells. (3) Delivery of a tumor cell nucleus into a normal cell cytoplasm begets normal cells despite the persistence of tumor-associated genomic abnormalities. (4) Delivery of a normal cell nucleus into a tumor cell cytoplasm begets tumor cells or dead cells but not normal cells. The results suggest that tumors do not arise from nuclear genomic defects alone and that normal mitochondria can suppress tumorigenesis. Original diagram from Jeffrey Ling and Thomas N. Seyfried, with permission.