PCNA and neoplasm: In addition, Eppk1-positive cells express PCNA (a proliferation marker), which plays an important role in transient amplification of cells [27], and Blagoev and others found that plakin identifies as one of the proteins binding to EGF receptor using proteomics, suggesting that Eppk1 involves in EGFR-related proliferation signal transduction in tumor cells [6].