The ErbB4 Q646C mutant inhibits clonogenic proliferation of several human cell lines, including the DU-145 and PC-3 human prostate tumor cell lines [43, 44], the SKBR3 and MCF7 human breast tumor cell lines, the MCF10A human breast epithelial cell line [42], and the CaPan-1, HPAC, MIA-PaCa2, and PANC-1 human pancreatic tumor cell lines [40]. Here, ERBB4 is linked to breast neoplasm.