PDE1B and breast cancer: In the analysis of MR association between the target gene expressions in blood and overall BC risk, we identified significant associations for five genes including P4HA1, SLC12A2, KCNJ11, CA12 and PDE1B, but only the association for SLC12A2 was significant after Bonferroni correction (0.05/23 = 2.2 × 10–3) (Table 1).