Human Renal Carcinoma Line Transfected With Interleukin-2 and/or Interferon Gene(s): Implications for Live Cancer Vaccines

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Abstract
Background : Combination therapy with systemically administered interleukin-2 (IL-2) and interferon α (IFN-α) has resulted in long-term objective remissions in 30% of patients with metastatic renal cell carcinoma (RCC), but toxic effects are clinically significant. Purpose : We have thus investigated an alternative therapeutic approach—continuous intratumoral production of IL-2 and/or IFN-α by a cytokine-transfected human RCC tumor cell line. Methods : Plasmid vectors were used to transfect the R11 RCC line with the genes for human IL-2 and/or IFN-α by the calcium phosphate precipitation method. Biologic characteristics of the cytokine-transfected tumor cells were determined by assays of thymidine incorporation and cytotoxicity, fluorescence-activated cell-sorter analysis, Northern blotting, and in vivo studies in C3Hf/Sed/Kam mice rendered T-cell deficient. Results : The transfected cell lines produced the following amounts of cytokine per 10 6 cells per day: R11-IL-2 (220 U), R11-IFN-α (10240 U), and R11-IL-2 + IFN-α (95-U + 1270 U, respectively). Gamma irradiation did not eliminate cytokine secretion. Morphology and growth rates were identical to those for the parental R11 cell line, except for IFN-α-producing clones, which showed significant growth inhibition. All cytokine-producing cells demonstrated increased susceptibility to cell killing by peripheral blood leukocytes (PBL). IFN-α producers exhibited enhanced HLA antigen expression and suppressed c-myc messenger RNA expression; when cocultured in vitro, they induced similar changes in parental R11 cells. IL-2 producers could stimulate growth and cytotoxicity of naive (i.e., freshly isolated, uncultured) and activated PBL. All cytokine-producing cells lost their tumorigenicity, as evidenced by failure to grow in the T-cell-depleted mice. When co-injected at a local site but not at a distant site, these cells prevented growth of parental R11 cells. Histologic examination of the injection sites revealed a substantial influx of macrophages. Intraperitoneal administration of IL-2 and/or IFN-α could not, however, prevent growth of the parental R11 tumors. Conclusion : Local production of high concentrations of IL-2 and IFN-α at the tumor site is more effective in preventing tumor growth than systemic administration. Implication : Continuous local delivery of cytokines via transfer of cytokine genes into tumor cells for use as live cancer vaccines is a novel strategy for manipulation of host-mediated antitumor immune response in patients with advanced RCC. [J Natl Cancer Inst 85:207–216, 1993]

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