A preclinical human cancer xenotransplantation platform has been recently developed in zebrafish to inform therapeutic decisions in T-ALL patients (Fig. 2a).5 The authors previously tested the in vitro sensitivity of three T-ALL cell lines, with specific mutations in PTEN and NOTCH1 genes, to three different inhibitors (targeting mTOR, AKT, and NOTCH1) and demonstrated that the same cell lines were sensitive to the same drugs upon xenotransplantation in the zebrafish embryos. The gene discussed is MTOR; the disease is acute lymphoblastic leukemia.