The tumor necrosis factor a (TNF-a) is a potent cytokine with antitumor activities including a direct cytotoxic effect on human cancer cells and the enhancement of a cytotoxic immune response against the tumor. However, its effectiveness in the human clinical trials is limited due to severe systemic toxicities. An alternative approach, that tumor cells are genetically engineered to secrete TNF-a locally to stimulate the immune system without systemic toxicities, is suggested as a form of gene therapy (tumor-cell-targeted lymphokine gene therapy). In this trial, cDNA encoding human TNF-a (TNF-NeoR) was introduced into five human gastric carcinoma cell lines using a retroviral vector to examine whether TNF-a gene could be transfected and expressed in gastric carcinoma cell lines in vitro. Successful transfer of TNF-a gene into five gastric csrcinoma cell lines was confirmed by polymerase chain reaction techniques. Supernatants (1: 2 dilution) from cultures of transduced gastric carcinoma cell lines demonstrated cytotoxicity to TNF-sensitive WEHI 164 cell lines in the range of 20-49%. TNF- transduced gastric carcinoma cell lines secreted TNF-a at the concetration of 479-8869 pg/10(6) cells-24 hours, whereas the parental cell lines did not secrete TNF-a. There were no differences in the growth rates between parental and TNF-transduced cell lines in vitro. The four TNF-transduced SNU cell lines showed the resistance to endogenous and exogenous TNF, except SNU-668 cell line. In conclusion, TNF-a gene was successfully transfected and expressed in gastric carcinoma cell lines in vitro. These data will be helpful in the development of tumor-cell-targeted lymphokine gene therapy for the treatment of advanced gastric carcinoma.
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