The biology and pathogenesis of vulvar carcinoma are poorly understood at present. In order to understand this disease better, we have used recently developed squamous cell carcinoma lines of the vulva as models. Two cell lines originating from two individuals (UM-SCV-1A and UM-SCV-6) were cultured in vitro in 10% fetal calf serum. The effects of interleukins 10 and 13, interferons alpha and gamma, granulocyte/macrophage-growth-stimulating factor (GM-CSF), tumor necrosis factor alpha (TNF alpha), and transforming growth factor beta (TGFbeta) on the proliferation of the cells was investigated by using radioactively labelled uridine as tracer. In addition, an investigation on the molecular structure of extracted cellular DNA was carried out to investigate whether programmed cell death (apoptosis) would be inducible by any of the factors. In UM-SCV-1A cells, interleukin-10 (IL-10) and interleukin-13 (IL-13) caused an approximately 12-fold decrease in DNA synthesis in cells cultured for 72 h (P<0.001), while GM-CSF had no significant effect. TGFbeta showed a significant inhibitory effect on deoxyuridine incorporation (P<0.001), which was 2.0- and 4.2-fold at 48 h and 72 h, respectively. TFG alpha showed a 1.2-fold inhibitory effect on DNA synthesis at 48 h (P<0.01) and a 1.5-fold inhibition at 72 h (P<0.05). Interferon gamma (IFNgamma) showed an inhibitory effect on DNA synthesis (1.3-fold; P<0.01). In UM-SCV-6 cells, both IL-10 and IL-13 showed inhibitory effects on deoxyuridine incorporation (1.3- and 1.4-fold at 48 h, respectively; P<0.001) that were even more pronounced at 72 h (2.4- and 2.5-fold respectively; P<0.001). IFNgamma caused a 3.6-fold inhibition of DNA synthesis by UM-SCV-6 cells at 72 h (P<0.001). Both TFGbeta and TNF alpha inhibited uridine incorporation (3.0- and 1.6-fold at 48 h, respectively; 2.7-fold at 72 h for both factors). GM-CSF inihibited DNA synthesis by UM-SCV-6 cells 1.3- 2.0-fold at 48 h and 72 h, respectively. In dose/response analyses, the effect of INF alpha on DNA synthesis was inhibitory in both cell lines at 48 h, while stimulatory effects were observed at 72 h. Electrophoretic analyses of DNA isolated from cells cultured in the presence or absence of different factors did not reveal DNA fragmentation. All cytokines, with the exception of IFN alpha, showed inhibitory effects on DNA synthesis by vulvar carcinoma cells. Of the factors studied, the recently described interleukins 10 and 13 showed potent inhibition of cell growth, encouraging further investigation on the molecular mechanisms of the observed inhibition. Apoptosis does not seem to be induced in the two vulvar carcinoma cell lines by any of the cytokines studied.