Fibrosarcoma cells transduced with the IL-6 gene exhibited reduced tumorigenicity, increased immunogenicity, and decreased metastatic potential.

Murine fibrosarcoma cell lines transduced with retroviral vectors containing the murine interleukin 6 (IL-6) gene constitutively secreted IL-6. When injected s.c. into normal mice these IL-6-secreting tumors exhibited reduced tumorigenicity. This reduced tumorigenicity was not seen in nude or irradiated mice, implicating a T-cell-dependent, radiosensitive host response activated by the cytokine. Subcutaneous IL-6-secreting tumor did not retard the growth of distant deposits of wild-type tumor in the same host. However, animals rejecting IL-6-secreting tumors exhibited resistance to later challenge with wild-type tumor. When injected i.v. in an experimental metastasis model the IL-6-secreting tumors failed to or were extremely inefficient in giving rise to pulmonary nodules; this was observed in both normal and immunoincompetent mice, implicating a second, nonimmune mechanism affecting the growth of the tumor modified to secrete IL-6.