Fig 1: Ex vivo analysis of GCH-1, SPR, QDPR, and DHFR in normal mucosa and colon adenocarcinoma human tissue samples. (A–D) Representative sections of whole tissue sections analyzed for normal and tumor tissue by a pathologist as shown in Supporting Information Figure 5 . In the bar graphs, GCH-1, SPR, and QDPR expression levels from five patient samples and for DHFR from three patient samples were measured for each tumor stage and normalized to DAPI. These values were subsequently compared to normal tissue expression set to 1. Relative expression is shown for each enzyme at different stages of tumor progression. Values are shown as ± SD, and unpaired t-test was used to determine statistical significance (*p<0.05).