 This study will also determine if insertion of a small piece of DNA a small piece of genetic material, makes these donor lymphocytes opened up and sensitive to the killing effects of the drug ganciclovir, but at the same time does not harm the lymphocytes ability to reduce the amount or size of the cancer in the recipient. The DNA to be inserted into the donor lymphocytes is transported into these cells by a type of virus called retrovirus vector. This retrovirus vector is made so the virus cannot divide cannot make more of itself, and cannot make cells or the recipient sick. Retroviruses do, however, allow for the gene DNA they are carrying, to be permanently inserted into the genetic material of the donor lymphocytes. Therefore, this inserted DNA will persist in the donor lymphocytes for the life of the lymphocytes. 