Mitochondria are essential organelles as they produce most ATP to support cellular activities, synthesize critical metabolic factors and are involved in lipid and phospholipid metabolism as well as calcium signalling. The oxidative phosphorylation (OXPHOS) system, present at the inner mitochondrial membrane, plays role in regulation of cellular metabolism and survival of cancer cells. Recent studies show importance of OXPHOS in growth of cancer cells via regulation of the de novo pyrimidine synthesis pathway. Dihydroorotate dehydrogenase (DHODH), a flavoprotein localized in the inner mitochondrial membrane, converts dihydroorotate (DHO) to orotate within the de novo pyrimidine synthesis pathway, generating electrons that are transferred, via redox- cycling of ubiquinone, to complex III (CIII) of respiratory chain. Since DHODH is functionally linked to CIII activity, impairment of respiration results in reduced activity of DHODH and pyrimidine synthesis. Therefore, mitochondrial damage or mutation in mitochondrial DNA (mtDNA) leads to decreased respiration, cancer cell proliferation and delay of tumour growth. As a compensation for damaged mitochondria, horizontal transfer of functional mitochondria from donor somatic cells to the mitochondria-damaged tumour cells was demonstrated. This...

(EN) Mitochondria are the principal intracellular organelles responsible for fuel generation; however, they are not just cell powerhouses but are involved in a range of other intracellular functions including cell metabolism, proliferation, death, and immune responses. Loss of function in mitochondria will result in oxidative stress, which is one of the underlying causal factors for a variety of diseases including cancer. Cancer cells can predominantly produce energy by glycolysis even in the presence of oxygen. This alternative metabolic behavior is known as the "Warburg Effect." Linked to this, cancer cell mitochondria can switch between glycolysis and oxidative phosphorylation (OXPHOS) for their energy requirements and survival. The electron transport chain (ETC) function is pivotal for mitochondrial respiration, which is also needed for dihydroorotate dehydrogenase (DHODH) activity that is essential for de novo pyrimidine synthesis. In our research, we have used respiration-deficient cancer cells to challenge the dogma that mitochondria with their DNA are constrained within cells in the body. Our results document that mitochondria move from normal cells within the tumor stroma to tumor cells without mitochondrial DNA (mtDNA), resulting in long-lasting recovery of mitochondrial functions and,...