Human Gene Therapy Subcommittee - 11/21-22/91 
These results were also obtained in an in vivo model. 
Dr. Sobol noted that although the results of these experiments are promising, there are 
disadvantages to using transduced tumor cells for this therapy. Tumor cells are often 
difficult to culture and transduce in vitro. Only a subset of patients will have tumors that 
can be grown effectively. In addition, this approach requires that tumor cells that have 
proliferative and metastatic capabilities would be readministered to the patients. 
Because of these problems, an alternative therapeutic approach was designed. Irradiated 
tumor cells will be used in place of viable tumor cells to eliminate their proliferative 
capacity. These tumor cells will be mixed with cells that have been transduced to 
express the target cytokine and to immunize patients and induce anti-tumor immunity. 
With the use of this approach, the likelihood of systemic toxicity is greatly reduced. This 
protocol obviates the need for intralesional injection because fibroblasts are readily 
cultured and transduced in vitro. Dr. Sobol introduced his collaborator, Dr. Fakhrai, to 
answer questions regarding the vector. 
Presentation-Dr. Fakhrai 
Dr. Fakhrai presented in vivo data using the retroviral vector, DCTK IL-2, that was 
developed in Dr. Eli Gilboa's laboratory. However, Dr. Fakhrai stated that since this 
vector did not provide sufficient levels of IL-2, he constructed new vectors that would 
secrete higher levels of cytokine. Dr. Miller asked why the animal experiments were 
performed using a vector that is different from the one that is being proposed in this 
protocol. Dr. Fakhrai explained that the new vector constructs, LNCX-IL2 and LXSN- 
IL2, produce significantly higher levels of IL-2 than DCTK IL-2. Dr. Neiman noted that 
the data were being presented for human embryonic fibroblasts, not skin fibroblasts. Dr. 
Fakhrai stated that the investigators are proposing to use LNCX-IL2 because it is the 
newest vector and produces the highest levels of IL-2 expression. Dr. Royston explained 
that the investigators are requesting the HGTS to grant approval for the use of both 
vectors, so that they have the option to use the vector that works the best. Dr. Royston 
stated that LNCX-IL2 is driven by a CMV promoter, and they have not established its 
efficacy in vivo. The LTR driven vector, LXSN-IL2, is more established in the in vivo 
system. 
Dr. Neiman asked Dr. Royston how many different primary fibroblast specimens have 
been transduced with LXSN? Dr. Royston responded that they have transduced two 
primary cultures. Dr. Fakhrai presented data in which mice were immunized on day 0 
with either 2.5 x 10 6 irradiated CT26 tumor cells alone, 2.5 x 10 6 CT26 tumor cells plus 2 
x 10 6 unmodified fibroblasts, or 2.5 x 10 6 CT26 cells plus 2 x 10 6 IL-2 expressing 
fibroblasts. A significant anti-tumor response was observed in animals receiving the 
irradiated tumor cells plus the IL-2 transduced fibroblasts. Dr. Miller stated that the 
responses appear the same with either modified or unmodified fibroblasts. Dr. Royston 
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Recombinant DNA Research, Volume 15 
