LONP1 and cancer: Indeed, Lon downregulation leads to loss of mitochondrial function, early embryonic lethality, reduced cell proliferation, and apoptosis.10, 11, 12, 13 Lon upregulation is critical for cancer cell survival and tumorigenesis by regulating stress responses induced by oxidative condition.11, 12 Lon is a stress protein and induced by a number of stresses such as hypoxia and oxidative and mitochondrial unfolded protein stress,11, 14, 15, 16, 17 which are common stress phenotypes of cancer cells.