Human Gene Therapy Subcommittee - 11/21-22/91 
exogenous production of IL-2 by fibroblasts will lead to the same augmentation of 
immunological response that occurs when the IL-2 gene is inserted into viable tumor 
cells. The investigators hypothesize that irradiation of the tumor cells will alleviate 
safety concerns about growth and possible metastasis of tumor cells. The scientific 
concern is whether having IL2 produced locally in a different cell type will produce the 
same biological effects as having the EL-2 produced by the tumor cells. 
Dr. Parkman cited data submitted by the investigators demonstrating that human IL-2 
can be expressed in both human embryonic fibroblasts as well as murine fibroblasts. 
However, there is a significant twofold difference between the amount of IL-2 that is 
produced depending on the cell type that is transduced. Another factor to consider is 
that the experimental data have been derived using embryonic fibroblasts. The proposed 
study will use primary skin or dermal fibroblasts. Dr. Parkman inquired whether the 
production of IL-2 is the same between the different cell types. Is the biologically active 
IL-2 immunochemically detectable by Enzyme-Linked-Immunosorbent Assay (ELISA)? 
The investigators have observed stimulation by supernatants of non-modified fibroblasts 
that may indicate that there is a feeder effect. Is the stimulatory effect on modified cells 
due to IL-2, or are there other consequences to transduction that could result in the 
stimulation of CTL by molecules other than IL-2? What is the evidence that the 
stimulatory effect is due to IL-2 and not other factors? What percentage of the selected 
fibroblasts are actively producing human IL-2? 
Dr. Parkman stated that his greatest concern was whether the introduction of tumor cells 
plus fibroblasts produces biologically active IL-2 equivalent to tumor cells into which the 
IL-2 gene has been directly inserted. Data indicate that there is a statistically significant 
difference in the amount of IL-2 expressed by transduced viable tumor cells alone versus 
irradiated tumor cells in combination with transduced fibroblasts. Since these data were 
derived from a single experiment, he inquired if these data were reproducible. Have the 
investigators analyzed IL-2 expression in tumor cells plus unmodified fibroblasts versus 
tumor cells plus modified fibroblasts? How long do the fibroblasts continue to produce 
IL-2? It is not clearly outlined in the protocol how the investigators are going to 
determine between IL-2 produced by the patient versus IL-2 produced by the local 
injection of the modified cells. Will there be a change in IL-2 serum levels? 
Dr. Parkman noted that there is no reference to patient biopsy to determine the 
persistence of these fibroblasts. How long will these cells persist? How long will they 
make IL-2? Is it critical that these fibroblasts continue to produce IL-2 for a long period 
of time? Many of these experimental questions could have been answered using a 
murine model. Primary murine fibroblasts could be transduced and returned to the 
mice. The mice could then be biopsied and analyzed by ELISA for murine IL-2 
expression. This experiment would answer the question regarding detectable circulating 
levels of IL-2 that are derivative of the local injection. This question cannot be 
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Recombinant DNA Research, Volume 15 
