Fresh or thawed newly diagnosed T-ALL blasts were transplanted into NOD-Scid mice. Three routes of transplantation were used: IVI (10⁷ cells), intraperitoneum (10⁷ cells), or IBI (1.5-2.5 × 10⁵ cells) for M18, M22, and M30, whereas the other samples were injected either IVI (M61, M66) or IBI (M29, M34, M40, M52, M53). Analysis of engraftment was performed when mice showed signs of sickness. Secondary and tertiary transplantations were done using total cells from the spleen, bone marrow (BM), or lymph nodes of engrafted mice using the same route of transplantation as primary mice. A mouse was considered positive when ≥ 0.1% CD45⁺ human cells were detected. In the most engrafted and sick mice, we observed a severe BM aplasia and few human cells, whereas spleen was massively infiltrated with blasts. Shown are engraftment levels in the mouse BM. T-ALL samples were cocultured with MS5-GFP or MS5-DL1 cells, with or without γ -secretase inhibitor (GSI). Proliferation and phenotype analysis were done weekly.

− indicates no cell recovered from the culture; +, no amplification of cell number; +++, amplification (≥ 4 times) of cell number; nd, not done; μ, T-ALL samples with a notch1 mutation detected; and nd, no mutation detected.

Positive/total mouse.

Percentage of CD45⁺ cells.

Time of analysis.