Genetic modification of a murine fibrosarcoma to produce interleukin 7 stimulates host cell infiltration and tumor immunity

Cancer Res. 1992 Jul 15;52(14):3931-7.

Abstract

Retroviral-mediated gene transfer was used to introduce and express the gene for murine interleukin 7 (IL-7) in a fibrosarcoma tumor (FSA). The tumorigenicity of these genetically modified FSA cells was greatly decreased in immunologically intact syngeneic mice but was unaltered in T-cell-deprived mice. IL-7-infected tumors that did grow in intact animals from large size inocula did so slowly and had a high incidence of spontaneous regression. Furthermore, mice that had rejected tumors became specifically immune to challenge with uninfected parental tumor cells. IL-7-infected FSA growing in intact mice were heavily infiltrated with host T-cells that were presumably responsible for slow growth and tumor regression, and tumor cells were in the minority. Fluorescence-activated cell sorter analysis showed that there was a 530% increase in T-cells in IL-7-infected FSA compared with control tumors. CD8+ T-cells were particularly elevated, but CD4+ lymphocytes were also increased in number, as were eosinophils and basophils. The CD4+:CD8+ ratio in IL-7-infected FSA was 1:1.7 in comparison to 1:0.6 in control tumors. Lymphocytes isolated from IL-7-producing tumors had greatly enhanced cytotoxicity towards uninfected, parental FSA cells. Killing of non-cross-reacting fibrosarcoma line was also increased but to a much lesser extent. Injection of recombinant human IL-7 directly into established FSA tumors slowed their growth and, in a significant number of instances, caused complete regression. Mice that had rejected tumor became specifically immune. The dose that was needed for this effect was, however, somewhat large: 20 micrograms twice daily for 10 days. This result contrasts with the efficacy of IL-7 gene infection in stimulating responses to the same tumor. These considerations make IL-7 a good candidate for tumor-directed cytokine gene therapy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Female
  • Fibrosarcoma / genetics*
  • Fibrosarcoma / immunology
  • Genetic Therapy
  • Graft Rejection
  • Interleukin-7 / biosynthesis
  • Interleukin-7 / genetics*
  • Lymphocytes, Tumor-Infiltrating / immunology*
  • Mice
  • Mice, Inbred C3H
  • Neoplasm Regression, Spontaneous
  • RNA, Messenger / analysis
  • Transfection* / immunology

Substances

  • Interleukin-7
  • RNA, Messenger