Neuroblastoma is the most common extracranial solid tumor of childhood, and has an annual incidence of one per 
7000 children under age 15. Neuroblastomas differ markedly in their clinical behavior. Sixty percent of patients are 
at high-risk for developing progressive and ultimately fatal disease. In high-risk patients 5 year survival rates are 
low (40%) even with use of intensive chemotherapy followed by BMT (62,68,71). Therefore, additional therapeutic 
strategies are required to improve the outcome in high-risk neuroblastoma. 
In contrast to many other solid tumors, neuroblastoma cells grow readily in vitro. In fact, the ability of a human 
neuroblastoma to form a cell line is strongly associated with a poor prognosis (Fig. 12). Thus, neuroblastoma is an 
excellent candidate for gene ther£q)y. The advantages of neuroblastoma include: i) ability to grow cells in vitro, ii) 
ability to achieve minimal residual disease with standard therapy, and iii) the high and rapid relapse rate. 
One commonly used strategy in tumor immunotherapy involve the induction of tumor antigens in the context of 
MHC. Antigen loaded MHC molecules are the prefen^ target antigens for T-cell mediated reactions. They serve to 
focus T lymphoctyes on those host cells that have foreign antigen on their surface. Class I MHC molecules (HLA 
A, B, C) are expressed on all nucleated cells and are recognized by cytotoxic T cells, whereas class II molecules (DP, 
DQ, DR) are typically confined to cells involved in immune responses (B cells, antigen presenting cells, thymus 
epithelial cells) and are recognized by helper T-cells. Immunogenicity of tumor cells may be potentially augmented 
f in an antigen-specific manner by stimulation of the MHC class I molecules. Costimulation of T-cells by the 
[ CD28/CTLA4 ligand(s), B7/BB 1, B7-2, may provide the antigen-nonspecific signal required for an immune response 
I (68,69). y-IFN has also been shown to augment B7 expression on some antigen presenting cells (Nadler L, personal 
I communication). 
Most neuroblastoma cells have reduced expression of class I and II MHC antigens (66,70,75). Therefore, if 
neuroblastoma cells can be genetically engineered to synthesize and secrete specific cytokines, effective tumor 
j immunity may be induced by local secretion of these factors. ylFN has been found to have stimulating effects on 
I expression of MHC class-I and II antigens on neuroblastoma (28,75). Most class I MHC genes have promoter 
j sequences which are responsive to interferon (76). Antitumor effects have been observed with transduction of y-IFN 
; into mouse fibrosarcoma, and neuroblastoma cells (28,30): y-IFN secretion by tumor cells decreased their 
tumorigenicity and induced p>ersistent antitumor immunity. Furthermore, administration of y-IFN transduced tumor 
cells into tumor bearing animals also resulted in substanti^ reduction of metastatic disease (82). 
We will use a MoMLV-based retroviral y-IFN vector to transduce neuroblastoma cell lines. We will then measure 
■ the expression of cytokine genes, alterations in MHC-I and II antigen expression, NAAg’s, immunogenicity, and 
doubling time. The goal of these studies is to use retroviral vectors to render neuroblastoma cells immunogenic so 
that the transduced cells can be used as tumor vaccines, and to develop in vitro correlates of immunogenicity in 
neuroblastoma. 
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, Recombinant DNA Research, Volume 19 
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