NDUFB9 and Familial prostate cancer: NDUFB9 (NADH dehydrogenase (ubiquinone) 1 beta sub-complex, 9, 22kDa) is an accessory subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase (complex I), [11] and is encoded by a nuclear gene.[12] Mutation of NDUFB9 can lead to complex I deficiency, [13] which has been reported to promote tumor metastasis.[14, 15] Additionally, SNP (rs7830235) associated with prostate cancer risk is located in the NDUFB9 gene.[16]