Nonactivated macrophage-induced nitric oxide production by tumor cells differing in tumorigenic and spontaneous...

The ability of nonactivated peritoneal macrophages to induce nitric oxide (NO) secretion in transformed and tumor cells of the same origin differing in tumorigenic (TGA) and spontaneous metastatic activities (SMA) was examined. Low tumorigenic and nonmetastatic spontaneously transformed in vitro hamster embryo cells of the STHE strain in contact with macrophages, or their non-purified soluble product were the highest producers of NO. In vivo selected STHE cell variants characterized by middle or high TGA demonstrated low, or no NO production, respectively (independently of SMA- or SMA+). Two highly tumorigenic RSV-SR (v-src) transformed cell strains (SMA- and SMA+) were both negative in NO production. Thus, NO production by tumor cells appeared to be inversely correlated with TGA level and less dependent on SMA.