SLC12A2 and breast cancer: By using two-sample MR, we found BC risk was negatively associated with expression of SLC12A2, and ER+BC risk was positively associated with expression of PDE1B. Therefore, expression modulation of SLC12A2 and PDE1B via antihypertensive drug usage (in addition to possible impacts through SLC12A2-DT) was associated respectively with increased and decreased risk of BC.