Recombinant DNA Advisory Committee - 06/1-2/92 
Dr. Brenner addressed Dr. Leventhal's question concerning the immunogenicity of 
irradiated cells versus non-irradiated. The current literature regarding the 
immunogenicity of irradiated cells has been disputed by a number of investigators. In 
addition, Dr. Brenner said his data demonstrates that irradiation kills neuroblastoma 
cells within 24 hours; therefore, IL-2 secretion would be too minimal to generate an in 
vivo immune response. When neuroblastoma cells were irradiated at a lower dose to 
allow for prolonged survival and secretion of IL-2, the radiation resistant cells grew back 
within two weeks. This result represented no advantage over using non-irradiated cells. 
Regarding Dr. Leventhal's question about the use of the word window, Dr. Brenner 
stated that if subsequent injections are administered after the first two injections, it will 
be as a continued window therapy. Only those patients who exhibit a response or have 
stable disease will continue on this protocol. Patients that demonstrate disease 
progression will receive alternative therapy. 
Dr. Brenner addressed Dr. D. Miller's question regarding the selection of 150 picograms 
per 10 6 cells in 24 hours as the acceptable level of IL-2 expression in this cell population. 
Dr. Brenner stated that this decision was based on experimental results generated in his 
laboratory. Data suggests that the optimal activated killer cell response occurs at 
between 1 and 10 units of IL-2. Dr. Brenner stated that a level of two units (150 
picograms) was chosen because it was over the minimum level. Dr. D. Miller asked if a 
similar level of response was observed with a level of 150 picograms per 10 6 cells in 24 
hours. Dr. Brenner stated that a cytotoxic response was observed at this level. Dr. 
Geiduschek asked Dr. Brenner if the cell lines generated from these patients will 
produce IL-2 at these levels. 
Dr. Brenner stated that 12 of the 15 cell lines that have been established to date, 
produce detectable levels of IL-2. The lines which produce lower levels of IL-2 can be 
cloned in order to select for cells which produce higher levels. The investigators have 
not encountered any problems in generating clones which can produce the required 
levels of IL-2. Since the injected cells will be derived from clones, IL-2 production levels 
should remain relatively constant. 
Dr. Geiduschek inquired if it is possible to select for neuroblastoma cells which are 
secreting high levels of IL-2, and suggested that the investigators should increase the 
requirement for IL-2 expression in this protocol. Dr. Brenner stated that while it would 
be easy to obtain clones which produce four times the 150 picogram level, there is no 
evidence that more is better. 
Dr. Brenner explained that the protocol is designed to include a dose escalation of IL-2 
by increasing the number of IL-2 secreting cells from 10 5 to 10 6 . Clones will be chosen 
which produce equal to or greater than 150 picograms per 10 6 cells in 24 hours. 
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Recombinant DNA Research, Volume 15 
