CPD and prostate carcinoma: SMS (EC:2.5.1.22, marked with 1 in Fig. 2) is adjacent to two differential metabolites (cpd:C00315, spermidine and cpd:C00750, spermine, marked 2 and 3 respectively) and participates in the polyamine synthesis pathway (Fig. 2), which is associated with prostate cancer metastasis30, 31, 38.