SIRT1 and cancer: To determine the extent of AMPK pathway variation across the 21 cancers, we calculated ‘pathway scores’ for each of the 18,484 tumor samples by taking the mean transcript expression values of the 24 genes: SLC2A4, FOXO3, PPP2CB, PIK3CD, CAB39L, CCNA1, FBP1, FBP2, FOXO1, HMGCR, IRS2, PIK3R1, SIRT1, TBC1D1, PPARGC1A, PPP2R2C, MLYCD, PFKFB3, PPP2R2B, PRKAA2, LEPR, CAB39, IRS1 and PFKFB1. We observed interesting patterns when cancers were ranked from low to high, based on their median pathway scores (Fig. 2b).