The mammosphere phenotype in PB2 KO cells was restored by overexpression of the full-length PLXNB2 and to a lesser extent by overexpressed dECTO PB2 mutant, suggesting that the extracellular domain of PLXNB2 is necessary for its functions in promoting self-renewal of tumor cells (Supplementary Fig. S6i-j). The gene discussed is PLXNB2; the disease is neoplasm.