PLK4 and hepatocellular carcinoma: Meanwhile, PLK-4 expression level was negatively associated with miR-126 expression (R = −0.237, P < 0.0001) (Fig. 3g) and positively related to the expression of Ki67, a proliferation marker of HCC cells27 (R = 0.7731, P < 0.0001) (Fig. 3h).