Sunitinib enhances engraftment in immunocompetent hosts but does not enhance engraftment in KIT^W/Wv mice. (A-B) C57Bl/6 CD45.2 recipients received 4 daily doses of sunitinib or vehicle followed by transfer of 5 × 10⁶ congenic CD45.1 TCD BM cells on days 0 and 1. Organs were harvested and analyzed by FACS on day 28. (A) Representative flow cytometry plots of Lin⁻-gated thymocytes from vehicle- (left) versus sunitinib- (right) treated recipients. (B) Sunitinib recipients showed significantly increased Lin⁻ thymic and splenic T-cell engraftment compared with vehicle controls. (C) C57BL/6 × C3H.SW (H-2^b) (F1) recipients received 4 daily doses of sunitinib or vehicle followed by transfer of 5 × 10⁶ congenic CD45.1 TCD BM cells on days 0 and 1. Organs were harvested and analyzed by FACS on day 28. Sunitinib significantly increased BM multipotent progenitor (P = .03) and peripheral T-cell (P = .03) engraftment; n = 4 mice per group. (D) C57Bl/6 CD45.2 recipients received 4 daily doses of sunitinib or vehicle followed by total body irradiation with the doses indicated on day 0 and transfer of 5 × 10⁶ congenic CD45.1 TCD BM cells on days 0 and 1. On day 28, sunitinib-treated mice show increased BM engraftment compared with vehicle controls. This difference was significant at 400 cGy; n = 5 mice/group. (E) KIT^W/Wv recipients received 4 daily doses of sunitinib or vehicle followed by transfer of 5 × 10⁶ CD45.1 TCD BM cells on days 0 and 1. Sunitinib did not significantly increase the frequency of BM cells (P = .93), splenocytes (P = .70), or thymocytes (P = .69) 28 days after BMT. Data represent pooled results from 2 independent experiments; n = 13 or 14 mice/group. *P < .05. ***P < .001.