POLD1 and cancer: On the other hand, PPARδ activation in Hepa 1–6 induces the down-regulation of polymerase delta 1 catalytic subunit (Pold1, negatively correlated to the prognosis of HCC patients [48]), zinc finger and BTB domain containing 7A (Zbtb7a, promoter of cancer cells proliferation [49], [50]), and Dual specificity phosphatase 7 (Dusp7, known to be over-expressed in cancer [51]).