Activated Notch1 signaling promotes growth and survival of lymphoma cells.

(A) Proliferative responses of Notch1-expressing lymphoma cells after activation by Jagged1. After cocultivation for 24 hours, lymphoma cells were pulsed for another 20 hours with ³[H] thymidine and were harvested for scintillation counting. Results are shown as the mean of ³[H] thymidine incorporation (± SD) of 3 independent experiments. Counts of activated lymphoma cells (presence of Jagged1; −tet, black bars) are given relative to counts of nonactivated cells (absence of Jagged1; +tet, white bars) which were set arbitrarily at 100% for each cell line. (B) Proliferative responses of Notch1-expressing lymphoma cells after activation by soluble Jagged1. Counts of activated lymphoma cells (presence of soluble hJagged1; black bars) are given relative to counts of nonactivated cells (white bars), which were set arbitrarily at 100% for each cell line. *P < .05; **P < .001; n.s., not significant using the Student t test. (C) Activated Notch1 signaling inhibits the apoptosis of HRS cells. After cocultivation of lymphoma cells in the presence (−tet, black bars) or absence (+tet, white bars) of Jagged1, apoptosis was induced by 10 μM arsenite. Counts of apoptotic cells were determined and are given in percentages. *P < .05.