The aim of this study was to examine the antitumor effect of irradiated granulocyte macrophage-colony-stimulating factor (GM-CSF)-gene-transduced hamster pancreatic cancer cells and its relationship to the amount of GM-CSF produced by transduced tumor cells. Hamster pancreatic adenocarcinuma cells, HPD1NR, which spontaneously secrete 15.0 ± 0.4pg/106 cells per 24h of GM-CSF, and HPD2NR cells, which do not secrete GM-CSF, were used. When these cells were infected with recombinant adenovirus harboring the GM-CSF gene, HPD1NR and HPD2NR secreted 624.2 ± 9.9 and 157.8 ± 5.7pg/106 cells per 24h. respectively. Vaccination with irradiated GM-CSF-secreting HPD2NR completely protected syngeneic hamsters challenged with live parental cells. On the other hand, vaccination with irradiated HPD1NR protected 60% of hamsters from tumor development after challenge with parental cells. None of the tumor-free hamsters initially vaccinated with irradiated GM-CSF-producing HPD2NR cells developed tumor upon repeated challenge with parental cells during the entire observation period. Irradiated GM-CSF-gene-transduced hamster pancreatic cells are promising as a novel adjuvant cancer therapy after surgery for primary and metastatic pancreatic cancer. The results indicate the necessity for a therapeutic strategy for cancer based on the cytokine status of tumors.
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