CDK6 and hepatocellular carcinoma: While Western blot found EGFR-downstream effectors including MEK/ERK, G1/S phase-related proteins including CDK4, CDK6, cyclin D1, p-RB and E2F2 (but not E2F1 and E2F3) to be consistently up-regulated upon endogenous SPINK1 overexpression or when HCC cells were treated with recombinant SPINK1, cell proliferation-related proteins including MCM3, PCNA and Cyclin A2, and G1/S phase arrest was not altered (Fig. 8b, c).