The MAPK signaling pathway can induce multiple biologic events, such as cell proliferation, differentiation and survival, as well as stimulate cyclin D1 transcription in human cell lines.35 There are seven classes of MAPK signaling cascades, and three of them are essential for liver carcinogenesis, including ERK, JNK and p38 signaling cascades.36 Although Li et al.37 have observed simultaneous expression of MCM7, cyclin D1 and MAPKs in breast cancer cells, it was unclear whether MCM7 induced cyclin D1 expression through a MAPK-dependent mechanism in HCC. Here, MAPK8 is linked to breast cancer.