Changes in the tumorigenic and metastatic properties of murine melanoma cells treated with a triazene derivative.

Treatment of B16/BL6 murine melanoma cells in vitro with the 'xenogenizing' agent potassium p-(3-methyl-1-triazeno)benzoate (MM-COOK) had a profound impact on the tumorigenic and metastatic properties of the tumor, an effect that was only detectable in immunologically intact hosts. The treated tumor cells gave rise to a considerably smaller number of experimental and spontaneous pulmonary metastases and displayed an impaired growth rate in vivo, but were highly tumorigenic and metastatic in irradiated recipients. Moreover, the drug-treated cells retained the in vitro growth pattern and plating efficiency of the parent line, and were able actively to immunize intact hosts. Studies aimed at clarifying the mechanisms responsible for the decreased metastatic potential of the cells treated with MM-COOK indicated the involvement of host immune responses largely mediated by cells in the T-dependent compartment with no major contribution of natural immunity effector mechanisms.