marked at relapse, then this would constitute the first definitive evidence that 
marrow contamination with malignant cells contributes to relapse after ABMT. 
The approach would also provide a means of assessing the efficacy of any 
purging regimen chosen. 51,52 
As part of the justification for this proposal, we studied the transduction 
efficiency of LNL6 into neuroblastoma cells from patients. By modifying cell 
culture techniques and using autologous marrow stromal cell cultures, we were 
able to grow and subsequently select NEO R gene transduced neuroblastoma cell 
lines from >70% of the patients. Transduction of these cells with an IL-2- 
NEO r containing construct would provide cells suitable for the proposed 
investigation. 
3.6 Rationale For Current Proposal 
Feasibility and efficacy data from a variety of animal systems provide strong 
rationale for an immunotherapeutic approach using cytokine transduction of 
tumor cells (including neuroblastoma). 18 ' 45 However, as yet there is no 
evidence that such an approach will be effective against primary tumors in 
man. The value of this approach ultimately can only be assessed clinically, as 
it is not possible in animal models to replicate the effects of a stimulated 
human immune system on primary human tumors. We believe that further 
exploration of the approach can legitimately take place in patients with 
relapsed neuroblastoma for the following reasons; 
1) The pre-clinical and early clinical studies described above indicate that 
the immune system can contribute to control of human tumors, 
including advanced neuroblastoma. 
2) Neuroblastoma cell lines can be generated and transduced in most 
patients, allowing systematic analysis in vitro of any anti-tumor response 
generated in vivo , even in the absence of apparent clinical benefits in 
patients with advanced disease. 
3) Relapsed/resistant disease is essentially incurable by conventional 
approaches. 
3.7 Rationale For Choosing IL-2 as Cytokine For Transduction 
We have chosen IL-2 primarily because of evidence that it has in vivo and in 
vitro immunomodulatory effects that would benefit neuroblastoma patients and 
because animal model data suggest it augments tumor immunogenicity across 
a broad tumor range which includes the murine C1300 neuroblastoma 
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Recombinant DNA Research, Volume 15 
