Fig. 5.

Xbp1 function is critical for the survival and proliferation of normal and NRAS^G12D transformed pre-B cells. (A) Xbp1 mRNA levels were measured in Xbp1^fl/fl NRAS^G12D ALL cells transduced with EV control or 4-OHT–inducible retroviral Cre (Cre) after 48 h of 4-OHT treatment by qRT-PCR (n = 3). (B) Xbp1^fl/fl NRAS^G12D ALL were transduced with GFP-tagged EV control or 4-OHT–inducible GFP-tagged Cre (Cre) and the relative fraction of GFP⁺ cells was measured (n = 3). (C) Apoptosis was assessed by Annexin-V and 7AAD staining in Xbp1^fl/fl NRAS^G12D ALL cells with EV and Cre after 1, 4, and 7 d of treatment with 4-OHT (n = 3). (D) Xbp1^fl/fl NRAS^G12D ALL cells with EV and Cre were stained with BrdU and 7AAD and the percentages of cells in the G_0/1, S, and G₂/M cell cycles are indicated after 5 d of 4-OHT treatment and shown in a bar graph (n = 3). (E) Apoptosis was assessed by Annexin-V and 7AAD FACS staining in IL-7–dependent Xbp1^fl/fl pre-B cells with (Cre) or without (EV) deletion of Xbp1 after 1, 2, and 5 d of treatment with 4-OHT (n = 3). (F) IL-7–dependent Xbp1^fl/fl pre-B cells with EV and Cre were stained with BrdU and 7AAD and the percentages of cells in the G_0/1, S, and G₂/M cell cycles are indicated after 5 d of 4-OHT treatment and shown in bar graph (n = 3).