can be used to assess which tumors are likely to respond to therapy, by detecting the presence or elevated levels of the molecular target. chemical inhibitors tumor biology allows for a number of potential intracellular targets. many tumors are hormone dependent. the presence of hormone receptors can be used to determine if a tumor is potentially responsive to antihormonal therapy. one of the first therapies was the antiestrogen, tamoxifen, used to treat breast cancer. such hormone receptors can be detected by immunohistochemistry. imatinib, an intracellular tyrosine kinase inhibitor, was developed to treat chronic myelogenous leukemia, a disease characterized by the formation of a specific abnormal tyrosine kinase. imitanib has proven effective in tumors that express other tyrosine kinases, most notably kit. most gastrointestinal stromal tumors express kit, which can be detected by immunohistochemistry. monoclonal antibodies main article: monoclonal antibody therapy many proteins shown to be highly upregulated in pathological states by immunohistochemistry are potential targets for therapies utilising monoclonal antibodies. monoclonal antibodies, due to their size, are utilized against cell surface targets. among the overexpressed targets are members of the egfr family, transmembrane proteins with an extracellular receptor domain regulating an intracellular tyrosine kinase. of these, her2/neu (also known as erb-b2) was the first to be developed. the molecule is highly expressed in a variety of cancer cell types, most notably breast cancer. as such, antibodies against her2/neu have been fda approved for clinical treatment of cancer under the drug name herceptin. there are commercially available immunohistochemical tests, dako herceptest, leica biosystems oracle and ventana pathway. similarly, egfr (her-1) is overexpressed in a variety of cancers including head and neck and colon. immunohistochemistry is used to determine patients who may benefit from therapeutic antibodies such as erbitux (cetuximab). commercial systems to detect egfr by immunohistochemistry include the dako pharmdx. mapping protein expression immunohistochemistry can also be used for a more general protein profiling, provided the availability of antibodies validated for immunohistochemistry. the human protein atlas displays a map of protein expression in normal human organs and tissues. the combination of immunohistochemistry and tissue microarrays provides protein expression patterns in a large number of different tissue types. immunohistochemistry is also used for protein profiling in the most common forms of human cancer.