NOTCH1 and acute lymphoblastic leukemia: We are grateful to Dennis Young of the University of California at San Diego Moores Cancer Center FACS facility for his expert assistance with FACS Aria analysis and sorting; Drs Mitchell B. Diccianni, Edward Kavalerchik, and Edward D. Ball for providing T-ALL patient samples and Ming Qiu and Qinghai Peng of the Oncology Research Unit at Pfizer Inc. for their technical assistance with hN1 antibody characterization.