Our subsequent inspection of this apparent tumor-suppressive behavior exerted in vitro and in vivo by MB made use of CRISPR/Cas9-engineered MB-deficient breast cancer cells, in comparison to MB-proficient controls, and of spontaneous breast cancers, formed with and without MB, in two different mouse models (see: a) Aboouf, M. A., et al., Pro-apoptotic and anti-invasive properties underscore the tumor suppressing impact of myoglobin on subset of human breast cancer cells. Here, MB is linked to neoplasm.