VARS2 and inborn mitochondrial metabolism disorder: Several mutations in VARS2 have been associated with mitochondrial diseases such as complex I defect, early onset of mitochondrial encephalomyopathies and encephalocardiomyopathies,35 and cancer risks including breast cancer, colon and lung cancer.36, 37, 38 Here, we propose VARS2 as a causal gene only for lung cancer.