AFP binding to ErbB2 can also enhance MUC4 interactions with ErbB2, ErbB3, and neuregulin, increase the phosphorylation of the ErbB2 complex and result in enhancing cancer cell proliferation, migration, invasion and inhibition of apoptosis through activating ERK and AKT signaling pathways (74, 78, 79) (Figure 6). Here, MUC4 is linked to cancer.