Mitochondria are essential for cancer cell survival and growth, contrary to conventional wisdom. While mitochondrial gene mutations are common in cancer, they do not inactivate mitochondrial energy metabolism but alter its bioenergetic and biosynthetic state. These changes communicate with the nucleus through mitochondrial retrograde signaling, modulating signal transduction, transcription, and chromatin structure to support cancer cell needs. Cancer cells reprogram adjacent stromal cells to optimize their environment, activating programs important for development, stress response, and metabolism. Otto Warburg's observation that cancer cells exhibit aerobic glycolysis has been revisited, with recent evidence showing that mitochondrial oxidative phosphorylation (OXPHOS) is not impaired in cancer cells. Instead, mitochondrial dysfunction leads to altered bioenergetics and metabolism, which influence nuclear functions and stromal cell behavior. Mitochondrial DNA (mtDNA) mutations are prevalent in various cancers, including renal, colon, breast, and ovarian cancers. These mutations can affect mitochondrial function, leading to changes in energy production, redox status, and apoptosis. Mutations in genes such as succinate dehydrogenase (SDH), fumarate hydratase (FH), and isocitrate dehydrogenase (IDH1/IDH2) are associated with cancer. These mutations alter metabolic pathways, leading to changes in histone and DNA methylation, and epigenetic dysregulation. For example, IDH1 and IDH2 mutations produce (R)-2-hydroxyglutarate, which can activate or inhibit hypoxia-inducible factor 1 alpha (HIF1α), affecting tumor growth and metabolism. Mitochondrial ROS production and redox balance are crucial for cancer cell survival and proliferation. ROS can induce apoptosis or promote neoplastic transformation, depending on the cellular context. Mitochondrial dysfunction also affects calcium homeostasis, which is essential for cell signaling and apoptosis. The reverse Warburg effect describes how cancer cells alter the metabolic environment of surrounding stromal cells, promoting glycolysis and lactate production, which can enhance FDG uptake in imaging. This intercellular metabolic coupling is a key aspect of cancer progression. In conclusion, mitochondrial function is essential for cancer cells, but different cancer types exhibit varied bioenergetic adaptations. Understanding mitochondrial biology and its interactions with the nucleus and stromal cells is crucial for developing targeted cancer therapies. Further research is needed to explore the genetic and biochemical mechanisms underlying mitochondrial dysfunction in cancer.Mitochondria are essential for cancer cell survival and growth, contrary to conventional wisdom. While mitochondrial gene mutations are common in cancer, they do not inactivate mitochondrial energy metabolism but alter its bioenergetic and biosynthetic state. These changes communicate with the nucleus through mitochondrial retrograde signaling, modulating signal transduction, transcription, and chromatin structure to support cancer cell needs. Cancer cells reprogram adjacent stromal cells to optimize their environment, activating programs important for development, stress response, and metabolism. Otto Warburg's observation that cancer cells exhibit aerobic glycolysis has been revisited, with recent evidence showing that mitochondrial oxidative phosphorylation (OXPHOS) is not impaired in cancer cells. Instead, mitochondrial dysfunction leads to altered bioenergetics and metabolism, which influence nuclear functions and stromal cell behavior. Mitochondrial DNA (mtDNA) mutations are prevalent in various cancers, including renal, colon, breast, and ovarian cancers. These mutations can affect mitochondrial function, leading to changes in energy production, redox status, and apoptosis. Mutations in genes such as succinate dehydrogenase (SDH), fumarate hydratase (FH), and isocitrate dehydrogenase (IDH1/IDH2) are associated with cancer. These mutations alter metabolic pathways, leading to changes in histone and DNA methylation, and epigenetic dysregulation. For example, IDH1 and IDH2 mutations produce (R)-2-hydroxyglutarate, which can activate or inhibit hypoxia-inducible factor 1 alpha (HIF1α), affecting tumor growth and metabolism. Mitochondrial ROS production and redox balance are crucial for cancer cell survival and proliferation. ROS can induce apoptosis or promote neoplastic transformation, depending on the cellular context. Mitochondrial dysfunction also affects calcium homeostasis, which is essential for cell signaling and apoptosis. The reverse Warburg effect describes how cancer cells alter the metabolic environment of surrounding stromal cells, promoting glycolysis and lactate production, which can enhance FDG uptake in imaging. This intercellular metabolic coupling is a key aspect of cancer progression. In conclusion, mitochondrial function is essential for cancer cells, but different cancer types exhibit varied bioenergetic adaptations. Understanding mitochondrial biology and its interactions with the nucleus and stromal cells is crucial for developing targeted cancer therapies. Further research is needed to explore the genetic and biochemical mechanisms underlying mitochondrial dysfunction in cancer.