Rc3h1 targets the mRNA of Icos and Ox40 in follicular helper T cells, cell cycle-promoting genes in breast cancer cell lines, and Tfr1 in HAP1, HUVEC, L-M, and MEF cell lines 16,26,27, suggesting Rc3h1 controls the abundance of mRNA in a cell-specific manner. This evidence concerns the gene ICOS and breast carcinoma.