Examples of new agents are: trastuzumab (Herceptin), a humanized monoclonal antibody that blocks the HER-2/neu proto-oncogene in combination with cytotoxic agents, is used in a percentage of breast cancer patients; signal transduction inhibitor of abl tyrosine kinase STI 571 (Glivec) has been shown to be an active treatment for chronic myeloid leukemia and GISTs; epidermal growth factor receptors in certain tumors have been targeted with agents such as C225 (Cetuximab) and ZD 1839 (IRESSA); an adenosine deaminase analogue of deoxyadenosine, Cladribine (2-chloro-2 deoxy-adenosine) has shown high effectiveness in hairy-cell leukemia and the multitargeted antifolate (Premetrexed) and several vaccines have been studied and are in clinical trials for resistant cancers.
ADA expression from these vectors was monitored in the ADA- human histiocytic lymphoma cell line DHL-9, and in the multipotential chronic myeloid leukemia cell line K562.