A preparation of lymphocytes harvested from a patient and genetically modified ex vivo for use in gene therapy for the patient's cancer. Ex vivo, the lymphocytes are transduced with the N2 retroviral vector, which is modified to express a gene whose protein product either kills tumor cells or elicits specific anti-tumor immunity. Genetically modified lymphocytes are infused back into the patient from whom they were harvested, locate to the tumor site, and express the candidate protein that kills tumor cells or stimulates host anti-tumor immunity. (NCI04) [ ]