were coated in 96-well ELISA plates at 10 mg/mL. Purified hN1 mAb was added to the wells at the indicated concentrations. Graph of mean O.D. 450 value in ELISA binding assays demonstrates control mAb and antiNOTCH1-NRR mAb specificity for human NOTCH1 receptor versus NOTCH2 receptor. NOTCH1 luciferase reporter assays utilized DLL4-coated plates. Graph depicts mean luciferase activity in BSA, DLL4, DLL4+control mAb and DLL4+ hN1 mAb treated wells. Mouse weight monitoring during dosing time demonstrates that hN1 mAb treatment was well-tolerated in the engrafted mice. No significant weight loss was detected throughout the 3-week dosing period. Statistical Analysis All statistical tests were performed for two sided p values. Continuous variables for each comparison group were assessed for distribution through univariate statistics. If the assumption of normal distribution could be supported, then the Student’s t-test was performed for comparison of two samples with assessment of equality of variance with an F statistic. If the assumption of normal distribution was not supported, nonparametric testing was performed with the two sample Wilcoxon test using the t approximation for samples with N of less than 20. Supporting Information Self-renewing LIC activate NOTCH1. Graph of mean thymic weight in primary and secondary NOTCH1Mutated T-ALL LIC transplant recipients compared with no transplant control mice . Graph of mean splenic weight PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/22202440 in 1u and 2u T-ALL LIC transplant recipients compared with no transplant control mice . Normalized NOTCH1 transcript levels to HPRT in engrafted human CD34+ cells following transplantation of NOTCH1Mutated T-ALL, NOTCH1High T-ALL, and NOTCH1WT T-ALL samples compared with normal human cord blood CD34+ cells. This experiment was repeated 3 times. hN1 mAb treatment inhibits NOTCH1High LIC self-renewal. Graph of HPRT-normalized q-RT-PCR results showing NOTCH1 transcript levels in normal cord blood CD34+ cells compared with engrafted T-ALL CD34+ cells from serially transplanted LIC from a NOTCH1High patient sample. This experiment was repeated 3 times. Graph of percent human CD34+ cell engraftment determined by FACS analysis in marrow, spleen and thymus of secondary transplant recipients of T-ALL NOTCH1High LIC. Representative photographs depicting characteristics of serially transplanted mouse bone marrows derived from control mAb and hN1 mAb treated NOTCH1High LIC engrafted mice. FACS analysis demonstrating CD34+CD45+ LIC engraftment in bone marrow following serial transplantation of control mAb and hN1 mAb treated NOTCH1High LIC. NOTCH1 Inhibition in T-ALL Initiating Cells Human cell infiltration in the tertiary CD34+CD2+CD7+ cells transplanted mouse brain. 30 000 CD34+CD38+CD2+CD7+Lin2 cells sorted from T-ALL patient 11 with the aid of FACS were intrahepatically transplanted into neonatal RAG22/2gc2/2 mice, and serial transplantation were done by 50 000 mouse BM cells. Tertiary transplanted mouse brain was fixed in 4% PFA and 30% CC 4047 sucrose overnight, separately, and then embedded in OCT for 
section with the thickness of 16 mm. Mouse brain sections were stained with antihuman CD45 antibody, mounted with prolong gold. Images were taken under the Fluoview FVi10 confocal microscope. H & E staining of the mouse ventricular area. Scale bar is 100 mm. Human CD45 Immunostaining of no transplant control mouse brain. DAPI detects the mouse cell nuclei. Scale bar is 20 mm. Human CD45 Immunostaining of 3u transplant mouse bra