DHFR and neoplasm: Sowers et al (2003) reported that E2F transcription factors may participate in the regulation of both TS and DHFR expression. We showed that a Spearman's correlation coefficient for TS/DHFR was 0.456 (P<0.001). Backus et al (2000) reported that low TS expression in vitro correlated with increased sensitivity to 5-FU. Several clinical studies have found that patients with low TS gene expression in primary GC correlate with a better tumour response and longer survival after 5-FU or S-1 treatment (Lenz et al, 1996; Ichikawa et al, 2004).