JAK2 and neoplasm: These included genes encoding known tumor suppressors, namely Arhgef1, a RhoA-specific guanine nucleotide exchange factor frequently lost in GC B cell–derived lymphomas (Muppidi et al., 2014); the cytokine-regulated Gadd45g, required in hematopoietic stem cell differentiation and lineage selection (Lu et al., 2001; Thalheimer et al., 2014); and the U3 ubiquitin ligase Sh2b3 that regulates JAK2 stability, which is frequently lost in acute lymphoblastic leukemia (Lv et al., 2017; Perez-Garcia et al., 2013).