Importantly, by positional mapping of likely functional variants, we identified genes related to the immune system (CXCL6, MEF2C, ITPR3, UBE2D1, C7orf73, STIM1, PNP, CRK and SIRPB1), cancer and cell cycle (TERT, BAK1, CDK6, CDK10, SUFU, FANCI, MDFIC, JMJD1C, USP7, BIK) and mitochondrial function (MFN2, TFAM, DGUOK, USP30, CREB5, POLG) to be potentially involved in governing mtDNA abundance in blood (Fig. 3). This evidence concerns the gene CXCL6 and cancer.