When serum ST6GAL1 levels were compared in men with low grade and high grade prostate cancer (Gleason grade 6–7 compared to Gleason grade 8–9), levels of ST6GAL1 were found to be 6.7-fold higher in men with higher grade compared to men with lower grade disease (n = 200, unpaired t test, p < 0.0001) (Fig. 3b). Here, ST6GAL1 is linked to prostate cancer.