The discovery analysis of 1793 plasma proteins with a cis-pQTL from the deCODE study, which was also available in our bladder cancer GWAS, showed that higher plasma levels of glutathione S-transferase mu 1 (GSTM1) and mu 4 (GSTM4), instrumented by the same variant close to GSTM1, were associated with a reduced risk of bladder cancer (Figure 2 and Table S5). Here, GSTM1 is linked to urinary bladder cancer.