SLC25A28 and breast cancer: Furthermore, Ni et al. showed that iron supplementation increases the proliferation rate of osteosarcoma cells by increasing the mitochondrial iron level in a manner dependent on MFRN1 and MFRN2 expression [57], while Sandoval-Acuna et al. showed that depleting mitochondrial iron abrogates breast cancer invasion in vitro and metastasis in vivo [15].