Figure 2.

Metastatic tumors dictate a long-lived education of hematopoietic stem and progenitor cell differentiation toward myelopoiesis. (A) A schematic representation of the LSK and tumor cell co-implantation experiment is shown. LSK cells obtained from naïve GFP-expressing donor mice were coinjected with either met-low or met-high melanoma tumor cells to recipient mice. Control recipient mice (not shown) were injected either with LSK cells alone or with tumor cells alone. At end point, mice were sacrificed and tumors harvested. GFP+ progeny in tumors was assessed by flow cytometry (n=4–5 mice/group). (B) Tumor volumes at end point are presented. (C–F) The percentages of granulocytes (C), total macrophages (D), M1 macrophages (E), and M2 macrophages (F) in tumors were determined by flow cytometry on GFP+ gated cells. (G) A schematic representation of the tumor-educated LSK transplantation experiment is shown. LSK cells were obtained from the bone marrow of donor mice harboring met-low or met-high melanomas. The LSK cells (5×10³) were injected together with whole bone marrow supportive cells (1×10⁶) from naïve mice into lethally irradiated naïve recipient mice. Donor engraftment was monitored for 16 weeks after transplantation. GFP+ progeny in peripheral blood was assessed by flow cytometry. (H–I) Lineage distribution of myeloid-derived (H) and lymphoid-derived cells (I) is shown. (J–L) The percentage of GFP+ Ly6C^high monocytes (J), Ly6C^low monocytes (K), and GFP+ Ly6G+granulocytes (L) was gated from myeloid CD11b+ cells (n=5 mice/group). Statistical significance was assessed by one-way analysis of varaince, followed by Tukey post hoc test when comparing more than two groups or unpaired two-tailed t-test when comparing two groups. Asterisks represent significance from control, unless indicated otherwise in the figure. Significant p values are shown as *p<0.05; **p<0.01; ***p<0.001. LSK, Lin-Sca1+Kit+; met-high, high metastatic potential; met-low, low metastatic potential; WBM, whole bone marrow.