Utilization of interleukin-2 gene transfer in local immunotherapy of cancer.

It has been previously found that local administration of Balb/c plasmacytoma cells transformed and made non-tumorigenic by insertion of the cloned murine interleukin-2 (IL-2) gene induced regressions of a variety of murine tumours including the original Balb/c plasmacytoma X63-Ag8.653 growing in syngeneic mice. The tumour-inhibitory effect of the plasmacytoma cells transformed by IL-2 cDNA and designated as X63-m-IL-2 was due to their high constitutive production of IL-2. Here we show that admixture of syngeneic spleen cells to the X63-m-IL-2 transformants substantially (P < 0.025) increased the antitumour efficacy of the transformants. Balb/c spleen cells co-cultivated with X63-m-IL-2 cells in vitro yielded predominantly Thy 1.2+, CD3+, LFA-1+ lymphocytes, cytolytic for the X63-Ag8.653 plasmacytoma as well as for other murine tumours, including the X63-m-IL-2 target cells.