Figure 3: Erlotinib treatment inhibits HSC regeneration in vivo after TBI.

(a) Schematic diagram of TBI and erlotinib (Erlot) treatment of C57BL/6 mice with evaluation of bone marrow (BM) progenitor cells and HSC repopulating capacity at day 14. (b) Bone marrow cellularity at day 14 in the erlotinib and water treatment groups. Scale bar, 250 μm. (c) Bone marrow CFCs (per 2 × 10⁴ cells) and bone marrow CFU-S12 in erlotinib- and water-treated mice at day 14. *P = 0.008, *P = 0.04 for CFCs and CFU-S12, respectively (means ± s.e.m., n = 3 experiments per group). (d) Percentage donor CD45.2⁺ cell, Mac-1/Gr-1, B220 and Thy1.2 cell engraftment in the peripheral blood of CD45.1⁺ mice at 12 weeks after competitive transplantation of 5 × 10⁵ bone marrow cells from irradiated mice treated with either erlotinib or water (controls) (n = 3–4 mice per group, means ± s.e.m.). *P = 0.007 for total CD45.2⁺ cell engraftment; *P = 0.04, *P = 0.003 for myeloid cell and T cell differences, respectively. Right, peripheral blood donor cell engraftment over time in mice transplanted with bone marrow from irradiated donors treated with erlotinib (red line) or water (black line). *P = 0.002, *P = 0.0002, *P = 0.007 at 4, 8 and 12 weeks, respectively (n = 3–4 mice per group). (e) Schematic diagram of irradiation and treatment of Tie2Cre; Bak1^−/−; Bax^flox/– mice with erlotinib or water. (f) Bone marrow KSL cells and CFU-S12 content at 2 h after TBI in erlotinib-treated and water-treated mice. *P = 0.02, *P = 0.046 for bone marrow KSL and CFU-S12, respectively (n = 2–5 experiments, means ± s.e.m.). (g) The percentage of bone marrow KSL cells with EGFR phosphorylation (pEGFR) in erlotinib-treated and water-treated mice (n = 2 experiments, means ± s.e.m.). (h) Percentage donor CD45.2⁺ cell, Mac-1/Gr-1, B220 and Thy1.2 cell engraftment in CD45.1⁺ mice at 12 weeks after competitive transplant of 3 × 10⁵ bone marrow cells from erlotinib-treated or water-treated mice. *P = 0.03, *P = 0.02 for CD45.2⁺ cell and T cell engraftment, respectively (means ± s.e.m., n = 4–6 mice per group). Donor CD45.2⁺ cell engraftment is also shown over time (right) in mice transplanted with bone marrow cells from erlotinib-treated (red line) or water-treated (black line) mice. *P = 0.009, *P < 0.0001, *P = 0.03 for differences at weeks 4, 8 and 12, respectively. A two-tailed t test was used for all statistical analyses.