Nitric oxide of human colorectal adenocarcinoma cell lines promotes tumour cell invasion

The present study investigates the role of nitric oxide and the involvement of nitric oxide synthase H isoform on the invasion of human colorectal adenocarcinoma cell lines HRT-18 and HT-29. HRT-18 cells, which constitutively express nitric oxide synthase II mRNA were three-fold more invasive in a Matrigel((R)) invasion assay than nitric oxide synthase II mRNA negative HT-29 cells. Treatment of HT-29 cells with the nitric oxide donor Deta NONOate (50 nM) as well as induction of nitric oxide synthase II mRNA and production of endogenous nitric oxide by inflammatory cytokines (IFN-gamma and IL-1alpha) increased the invasiveness of HT-29 cells by approximately 40% and 75%, respectively. In HT-29 cells nitric oxide synthase II mRNA was also induced in co-culture with human monocytes. The invasiveness of HRT-18 cells and stimulated HT-29 cells was partly inhibited by the nitric oxide synthase II inhibitor 1400 W. These results show that nitric oxide increases the invasion of human colorectal adenocarciroma cell lines HRT-18 and HT-29, and the involvement of nitric oxide synthase II isoform in tumour cell invasion. Therefore, the production of nitric oxide and secretion of pro-inflammatot-gamma cytokines by tumour-assocated macrophages, which in turn induce nitric oxide synthase II isoform in tumour cells, promotes tumour cell invasiveness. (C) 2002 Cancer Research UK.