Finally, although 70–80% depletion of UPF1 is thought to be sufficient for inhibiting the NMD machinery both in microsatellite instable cell lines[15] as well as in microsatellite stable gastric cancer cell lines[35], with correlation with downregulation of the UPF1 protein, we cannot exclude the possibility that in this case the treatment was insufficient. This evidence concerns the gene UPF1 and gastric cancer.