S100A8 and coinfection: For this purpose, the MKN7 cells were incubated with live cagA and vacA negative Hp with or without NS-398 for 3, 6 and 24 h, exactly as in the case of experiments with Hp strain positive for cagA and vacA. In contrast to the HpcagA and vacA positive strain which caused a time-dependent rise in COX-2 expression, the signal for COX-2 mRNA did not change during co-infection of the MNK7 cells with HpcagA and vacA negative strain and this was confirmed by the ratio of mRNA for COX-2 over mRNA β-actin (Fig. 5, panels b and c).