adjuvants such as BCG. 
Cell Therapy with Genetically Altered Tumor Vaccines 
Recently, new approaches have been developed in laboratory animal 
systems that modify tumor cells genetically so that they express new antigens 
or secrete certain cytokines. These studies began with Lindemann and Kline 
who showed that vaccination with influenza virus infected murine tumor cells 
generated enhanced systemic immune responses against a challenge with the 
original wild-type tumor cells. 45 
As newer techniques of gene transfer have been developed, infection with 
virus has been replaced with specific gene transfer systems in an attempt to 
regulate more carefully the nature of the genetic alteration in the tumor. A 
number of recent studies have used cytokine gene-modified tumor cells as tumor 
vaccines. Such studies have shown that transduction of some murine cancer 
cell lines with genes encoding IL-2, IL-4, interferon-gamma, IL-6, TNF-alpha, 
G-CSF, MCP-1, and IL-7 can lead to the rejection of the genetically modified 
cells by syngeneic hosts. 41-58 Moreover, additional studies indicated that 
cells expressing inteferon-gamma, IL-2 , TNF-alpha, or IL-4 also increase systemic 
immunity, since mice vaccinated with transduced cells reject a subsequent 
challenge by wild-type tumor cells, and in some cases, reject pre-existing 
tumor. 50 
Based on these pre-clinical studies, several investigators have received 
approval to initiate clinical protocols which involve the injection of 
genetically modified tumor cells into patients with advanced cancer. 
Investigators at the National Cancer Institute, for example, received approval 
to inject live autologous tumor cells engineered by retroviral mediated gene 
transfer to express either TNF-alpha or IL-2. Investigators at Memorial Sloan 
Kettering Cancer Center have recently received approval for clinical studies 
involving tumor cells engineered to express IL-2 in melanomas and renal cell 
carcinomas . 
The protocol described below, however, differs from those previous 
protocols in several ways. First, irradiated tumor cells, rather than live 
cells, will be administered to patients. This feature of the protocol reduces 
the risk of toxicities associated with the insertion of genetic material into 
the chromosomal DNA of the tumor cells. Second, low passage cultures of 
f reshly-explanted autologous tumor will be the targets for genetic 
modification, rather than established tumor cell lines. This feature of the 
protocol is designed to preserve any antigenic heterogeneity that may exist in 
the tumor, thereby maximizing the chance for eliciting a broad systemic anti- 
tumor immunity in vaccinated patients. Finally, tumor cells will be 
engineered to express GM-CSF, rather than TNF-alpha or IL-2, since our pre- 
clinical studies suggest that GM-CSF may be more potent than other gene 
products in inducing systemic anti-tumor immunity. 
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Recombinant DNA Research, Volume 17 
