NOTCH1 and acute lymphoblastic leukemia: However, NOTCH1 seems dispensable for BCP-ALL; none of the 31 leukemia cell lines studied previously expressed the NOTCH1 protein, and we were unable to detect NOTCH1 in any leukemia cell line supernatant (Figs. 5D, E and S14A, B) [33, 50, 59–61].