ARHGEF1 and neoplasm: Although for many a function in B cells is unknown, for others (namely Arhgef1, Gadd45g, Sh2b3, and Map2k7), tumor-suppressive and/or antiproliferative activity was described (Lu et al., 2001; Lv et al., 2017; Muppidi et al., 2014; Perez-Garcia et al., 2013; Thalheimer et al., 2014).