MAPK3 and hepatocellular carcinoma: Only in HCC patients with EGFRhigh, lenvatinib induces the feedback activation of EGFR and its downstream PAK2-ERK5 signaling pathway by inhibiting FGFR and downstream ERK1/2 (14), and simultaneously activates the downstream signaling pathway MEK1/2-ERK1/2, which is common with FGFR, resulting in strong proliferation ability of HCC cells while lenvatinib was administered.