Role of the mitochondrial stress response in human cancer progression

Mitochondria are important organelles that are responsible for cellular energy metabolism, cellular redox/calcium homeostasis, and cell death regulation in mammalian cells. Mitochondrial dysfunction is involved in various diseases, such as neurodegenerative diseases, cardiovascular diseases, immune disorders, and cancer. Defective mitochondria and metabolism remodeling are common characteristics in cancer cells. Several factors, such as mitochondrial DNA copy number changes, mitochondrial DNA mutations, mitochondrial enzyme defects, and mitochondrial dynamic changes, may contribute to mitochondrial dysfunction in cancer cells. Some lines of evidence have shown that mitochondrial dysfunction may promote cancer progression. Here, several mitochondrial stress responses, including the mitochondrial unfolded protein response and the integrated stress response, and several mitochondrion-derived molecules (reactive oxygen species, calcium, oncometabolites, and others) are reviewed; these pathways and molecules are considered to act as retrograde signaling regulators in the development and progression of cancer. Targeting these components of the mitochondrial stress response may be an important strategy for cancer treatment. Impact statement Dysregulated mitochondria often occurred in cancers. Mitochondrial dysfunction might contribute to cancer progression. We reviewed several mitochondrial stresses in cancers. Mitochondrial stress responses might contribute to cancer progression. Several mitochondrion-derived molecules (ROS, Ca2+, oncometabolites, exported mtDNA, mitochondrial double-stranded RNA, humanin, and MOTS-c), integrated stress response, and mitochondrial unfolded protein response act as retrograde signaling pathways and might be critical in the development and progression of cancer. Targeting these mitochondrial stress responses may be an important strategy for cancer treatment.