ERBB2 and breast neoplasm: HER2 and fibroblast growth factor-inducible 14-kDa protein (Fn14) are frequently co-expressed in human breast tumors, and HER2 directly induces increase in Fn14 expression, therefore sensitizing tumor cells to an immunotoxin generated by fusing Fn14 antibodies to recombinant gelonin (designated hSGZ) [8].