maximum of about 2 x 10 9 cells (or a 2 cm nodule) before they are excised. 2 
x 10 9 cells will make about 30 ug of IL-2 (90,000 Cetus units) for 24 hours. 
We and others have previously shown that 70 kg patients can tolerate 
approximately 700 ug IL-2 iv every 24 hours (8-10/ug/kg) . Thus for a 70 kg 
human, the amount of IL-2 being produced by these gene modified cells would be 
about l/25th the amount of IL-2 already shown to be well tolerated by 
patients. It should be emphasized, however, that it is not expected that 
these tumor cells will grow based on experimental animal models. Further, if 
patients do develop signs of toxicity due to IL-2 exposure then it will be 
possible to excise the local nodules in the anterior thigh. If tumor spreads 
from the local site, however, it may not be possible to remove all of the IL-2 
producing tumor. If IL-2 toxicity does occur, this toxicity may be partially 
abrogated by steroid therapy. 
5. Risk from murine retrovirus . Exposure of the cancer patient to 
retrovirus could theoretically pose a risk of insertional mutagenesis. It 
should be emphasized, however, that careful tests will be conducted to assure 
that the patient is not exposed to replication competent virus. The 
retrovirus derived from the Moloney murine leukemia virus has been modified so 
that it no longer contains any intact viral genes and thus cannot produce the 
envelope proteins necessary to package its RNA into an intact infectious virus 
(36,37,41,43,44). To assemble the retrovirus, a retrovirus packaging cell 
line was used that contained a second defective retrovirus which expresses the 
viral structural proteins. This packaging cell line does not produce 
replication competent retrovirus because of multiple modifications made to the 
second retrovirus that prevent its replication, including removal of signals 
required for RNA encapsidation, reverse transcription, and integration (37). 
Multiple assays will be performed on the final producer cell line, the 
retroviral vector supernatant as well as on the TIL prior to infusion to 
insure that no replication competent virus is present. These tests will 
include S+L- assays including 3T3 amplification, PCR assays for the envelope 
gene, and assays for reverse transcriptase (41,42). Any supernatants or TIL 
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