NUMB and neoplasm: In Drosophila, during NB ASCD, Brat—along with Numb and the other main cell-fate determinant described in Drosophila, the transcription factor Prospero (PROX1 in humans)—represses self-renewal and induces differentiation in the daughter cell in which it is segregated, and all of them can induce tumor-like overgrowth when compromised in this context [44,73] (see also below).