1. Molecular target drug discovery.
Cancer is caused by genetic abnormalities: activation of oncogenes and functional inactivation of tumor-suppressor genes. Direct correction of these abnormalities should be the essential treatment for cancer; however, we have not developed any techniques to effectively fix the genome to date. Molecular biological analyses have demonstrated the cancer function of abnormal gene products, activated signal transduction pathways, and cancer-specific cell surface antigens. Molecular target drugs have been designed to suppress these molecules, important for maintaining cancer status, at stages of mRNA and protein. Some targets contributing to cancer progression are even within host cells such as angiogenic factor receptors. Differing from conventional chemotherapeutic agents screened and developed with cytotoxicity to tumor cells, molecular target drugs show higher specificity for cancer and sometimes simply stabilize the tumor. The effect of such drugs depends on the expression and functional importance of the target in cancer, and prediction of the effect using molecular techniques such as DNA microarray may be necessary for appropriate use.