ACE and neoplasm: Considering that ACE inhibition eventually increases kinin availability, that activation of B1 receptor has been reported to inhibit cell migration in normal cells [31], and the fact that the B1 receptor is also a Gαq protein coupled receptor, similar to the metastatic suppressor receptor GPR54, we hypothesized that B1 receptor activation, in the absence of B2 receptor activation, could play a host protective role in tumor progression.