Consistent with POLG1 expression data (Fig 1), we observed variability in copy number (both amplification and deletion) of POLG1 gene in several human cancers including breast, lung, ovary, pancreas, stomach, melanoma, ovary, uterine, cervical, colorectal, prostate, head & neck, bladder and renal carcinoma (Figs 2A and 3A). Here, POLG is linked to cancer.