One human gene transfer and two human gene therapy clinical protocols are now underway in the Clinical Center. The gene transfer protocol involves the insertion of a marker gene (the NeoR gene carried in the retroviral vector LNL6) into tumor infiltrating lymphocytes (TIL). The purpose is to better understand TIL adoptive immunotherapy in the treatment of advanced cancer, specifically malignant melanoma. The first human gene therapy protocol was begun September, 1990. The goal is treatment of adenosine deaminase (ADA) deficiency (a cause of Severe Combined Immunodeficiency, a fatal disease of children) by inserting a normal ADA gene into the lymphocytes of patients. The second therapy protocol involves inserting the tumor necrosis factor (TNF) gene into TIL cells as an addition to TIL adoptive immunotherapy for the treatment of advanced cancer.