injected intravenously only 2% of the TNF dose required to mediate antitumor 
effects in the mouse can be administered to man. 
Because of the unique effectiveness of TNF in the treatment of a variety 
of murine malignancies, we have sought means to selectively increase the local 
concentration of TNF at the tumor site. Because TIL can traffic directly to 
tumor deposits and concentrate at those sites we have hypothesized that TIL 
that are producing large amounts of TNF may generate very high TNF concentra- 
tions in the local tumor microenvironment and this has substantially increased 
antitumor effects compared to normal TIL. We are thus proposing to introduce 
the gene coding for TNF into human TIL prior to TIL therapy. The gene we are 
using is identical to the gene used to produce the recombinant TNF we have 
administered to patients. 
It has thus far not been possible to test this hypothesis directly using 
gene transduction of murine TIL in experimental therapy models. We and many 
other groups have expended substantial effort trying to introduce genes into 
murine cytolytic T lymphocytes or TIL by a variety of techniques including 
retroviral gene transduction, DNA-calcium phosphate precipitation, electro- 
poration and liposome mediated transfection. These techniques have all been 
unsuccessful in introducing genes into short term murine TIL although we have 
been able to Introduce the TNF gene Into a single noncytotoxic long term murine 
T cell line that had previously lost therapeutic activity. As an alternate 
means to test the hypothesis that the local production of TNF might impact on 
tumor growth we have been successful in using retroviral vectors to introduce 
the gene coding for TNF into both mouse and human cancer cell lines. When the 
mouse MCA-207 cancer cell line bearing the TNF gene (and secreting TNF) was 
injected subcutaneously into mice these tumors grew and then regressed com- 
pletely leading to the cure of the majority of mice. Similar experiments 
utilizing human melanoma transduced with the gene for TNF and injected into 
Recombinant DNA Research, Volume 14 
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