Irradiation Selects for p53-Deficient Hematopoietic Progenitors
Figure 2
Irradiation selects for p53−/− hematopoietic progenitors.
Freshly harvested WT BM was mixed with GFP Tg BM (WT control) or GFP Tg p53−/− BM at 7∶1 proportions and then transplanted into recipients that had been conditioned with 5 Gy irradiation (schemata in A). Each recipient received a total 8×106 BM cells. Six weeks post-transplantation, five WT control recipients and 14 p53−/− recipients were irradiated with 2.5 Gy, while five recipients from the WT control and nine recipients from the p53−/− groups were left untreated (control). (B) At 1, 2, and 4 wk post-irradiation peripheral blood was analyzed for the expression of GFP in MAC+ myeloid cells and B220+ B-cells. (C) At 7 wk post-irradiation, GFP expression in peripheral blood CD4+ and CD8+ T cells was analyzed. For B and C, the “GFP” control reflects analyses of GFP expression in the indicated lineages for peripheral blood from recipients transplanted with 100% GFP Tg BM. For B and C, p values are for t tests comparing means of base-line to 4 wk post-irradiation differences in GFP percentages between irradiated and control groups. (D) The same mice were followed for the development of hematopoietic malignancies. Mice were sacrificed when moribund at the indicated times post-BM transplantation (BMT). All sacrificed mice exhibited clear signs of GFP+ p53−/− thymomas or leukemias. Most mice exhibited greatly enlarged thymi almost entirely composed of CD4+CD8+ or CD4+ GFP+ blasted cells, together with infiltration of the spleen. The other sacrificed moribund mice exhibited a leukemic phenotype, with CD4+CD8+ or CD4+ GFP+ blast cell infiltration of the spleen and BM but without clear thymic enlargement. Kaplan-Meier curves for lymphoma-free survival are plotted. The p value indicates the result of log-rank test analysis.