Background: Previous reports showed that mast cells can typically be found in the peritumoral stroma of cervix carcinomas as well as in many other cancers. Both histamine and TNF-alpha are potent preformed mast cell mediators and they can act simultaneously after release from mast cells. Thus, the effect of TNF-alpha and histamine on cervical carcinoma cell lines was studied.
Methods and results: TNF-alpha alone induced slight growth inhibition and cell cycle arrest at G0/G1 phase in SiHa cells, but increased their migration. Histamine alone had no effect on cells. In addition, TNF-alpha and histamine in combination showed no additional effect over that by TNF-alpha alone, although SiHa cells were even pretreated with a protein synthesis inhibitor. Furthermore, TNF-alpha-sensitive ME-180 carcinoma cells were also resistant to the combination effect of TNF-alpha and histamine. In comparison, TNF-alpha or histamine alone induced growth inhibition in a non-cytolytic manner in normal keratinocytes, an effect that was further enhanced to cell cytolysis when both mediators acted in combination. Keratinocytes displayed strong TNF receptor (TNFR) I and II immunoreactivity, whereas SiHa and ME-180 cells did not. Furthermore, cervix carcinoma specimens revealed TNF-alpha immunoreactivity in peritumoral cells and carcinoma cells. However, the immunoreactivity of both TNFRs was less intense in carcinoma cells than that in epithelial cells in cervical specimens with non-specific inflammatory changes.
Conclusion: SiHa and ME-180 cells are resistant to the cytolytic effect of TNF-alpha and histamine whereas normal keratinocytes undergo cytolysis, possibly due to the smaller amount of TNFRs in SiHa and ME-180 cells. In the cervix carcinoma, the malignant cells may resist this endogenous cytolytic action and TNF-alpha could even enhance carcinoma cell migration.