CD8A and hepatocellular carcinoma: In HBV patients, a lower level of serum mtDNA content is related to an increased risk of HCC development, indicating that circulating mtDNA may be a potential noninvasive marker of HCC risk.25 Extensive mitochondrial gene dysregulation and global downregulation of mitochondrial function have been observed in HBV‐specific CD8 T cells from patients with chronic infection.