It is also worth noting that targeting seed factors is not always effective, for example, to determine whether metastatic cancers that overexpress Her-2 (a gene found in both normal cells and cancer cells) or CEA (a protein present mostly in cancer cells) can be treated effectively with lymphocytes (white blood cells) that have been genetically engineered to contain an anti-Her-2 protein or anti-CEA protein. This evidence concerns the gene ERBB2 and cancer.