Recombinant DNA Advisory Committee - 2/10-11/92 
, progress. 
I 
Dr. Economou stated that clinical responses would not be expected from biological therapy 
alone. There is some suggestion of in vivo tumor specificity, but there is no understanding 
of the biology or mechanism of antitumor action. One cannot predict which patients will 
respond, and there is the outstanding question of whether TILs provide a truly effective 
antitumor therapy. Therefore, the investigators decided to conduct the gene marking study 
that has been superimposed on the current clinical trials. The hypothesis is that TILs have 
special properties, either in terms of specificity, better cytokine production, or 
I proliferation. Most importantly, these cells may have a better in vivo lifespan. A 
fundamental question is whether the TILs preferentially accumulate at tumor sites and 
generate an antitumor response, or are present via the circulation. The only way to 
address this issue is to compare TILs with PBL. PBL would not be expected to exhibit 
these special in vivo properties. 
Dr. Economou will retrieve TIL and PBL from patients; expand them ex vivo in IL-2; 
transduce them with two different but related retroviral vectors containing the neomycin 
phosphotransferase gene; conduct large-scale expansion in IL-2; combine them; and infuse 
them into the patient. The bulk TIL and PBL will be examined, as well as the 
subpopulations. The CD8( + ) and CD4(+) subpopulations of TIL and PBL will be 
examined in the same manner. Five melanoma patients will be treated per group. 
The protocol includes infusion of IL-2 for melanoma patients, and IL-2 plus subcutaneous 
IFNaA for renal cell carcinoma patients. The experimental design describes TIL and PBL 
subpopulations to be administered at certain ratios, e.g., 1:1. The TIL and PBL must be 
detectable by PCR in tumor biopsies. If the ratio is still 1:1, it is unlikely that there is 
specific accumulation or localization of those cells. However, if the input ratio is 1:1 and 
there is an 8:1 ratio of TIL to PBL at eight weeks, this result would strongly suggest that 
there is localization of TIL at the tumor site. 
Dr. Economou presented data demonstrating the ability to detect a single copy of LNL6 
and GIN in l(r cells. Dr. Economou described PCR amplifications of the combination of 
LNL6 to GIN. The DNA ratios shown were 1:1, 1:251, 1:661, 2:51, and 3:31. When the 
ratios were plotted, the results were actually better than one would have predicted for 
PCR, especially at low copy number; however, these were idealized conditions. All of 
these results were repeatable. The introduction of the neomycin resistance gene does not 
affect the proliferation of TIL; the infection rate remains at approximately 5%, under the 
conditions described. 
Dr. Economou then described mixing experiments in which transduced TILs were mixed 
with cells obtained from normal tissues. The DNA would be isolated, and quantitative and 
Recombinant DNA Research, Volume 15 
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