Page 115 - 2019_10 resto del Mondo_web

TNFSF13 is a positive regulator of AML cells
lation and T-cell biology.12,13 No change in white blood cell count, red blood cell count, or platelet levels was observed in Tnfsf13-/- mice (Online Supplementary Table S4). We then characterized their HSPC compartment and the lineage distribution in the BM and PB (Online Supplementary Figure S4A and B). Whereas long- and short-term HSC numbers were not affected, a significant decrease in granulocyte and macrophage progenitor (GMP) cells, accompanied by reduced numbers of monocytes, and a trend towards lower levels of granulocytes, was observed (Figure 4A-D, Online Supplementary Table S4 and Online Supplementary Figure S4A and B). Moreover, a skewing towards more B cells and fewer T cells was detected in the BM, whereas in the PB, only T cells were significantly altered (Online Supplementary Table S4). These data indicate that TNFSF13 supports the formation of GMP cells and that it favors myeloid and T-cell development relative to B cells.
TNFSF13 is a ligand for two cell-surface receptors: TNF receptor superfamily member 13B (TNFRSF13B) and 17 (TNFRSF17).17 Whereas TNFRSF17 was expressed on c- Kit+ leukemia cells, these cells were devoid of TNFRSF13B expression (Figure 4E and F). On normal HSPC, and in mature lineages of the BM and PB, TNFRSF17 was more broadly expressed than TNFRSF13B (Figure 4G and H and Online Supplementary Figure S4C-G). TNFRSF17 expression was detected in several mature blood cell lineages and multiple progenitor cell populations, with the lowest expression detected on long-term HSC (Figure 4G and H and Online Supplementary Figure S4C and D). These data suggest that TNFRSF17 is the primary receptor for
TNFSF13 on murine AML cells and a putative receptor for TNFSF13 on normal murine myeloid progenitor cells and monocytes.
TNFSF13 promotes acute myeloid leukemia initiation by suppressing apoptosis and promoting active cell cycle progression
To assess whether TNFSF13 supports leukemia-initia- tion and progression in vivo, c-Kit+ Tnfsf13-/- BM cells were transduced with a gamma retroviral vector expressing MLL-AF9 and transplanted into sublethally irradiated Tnfsf13+/+ or Tnfsf13-/- recipient mice (Figure 5A). A 2.1- fold-lower (P<0.01) leukemic burden was detected in the PB of Tnfsf13-/- recipient mice six weeks post transplanta- tion, but no significant survival difference was observed between the two groups (Figure 5B and C and Online Supplementary Figure S5A and B). To study whether TNFSF13 supports AML maintenance in vivo, 10,000 or 1,000 leukemia cells harvested from spleens of primary recipients of each group were transplanted into correspon- ding Tnfsf13+/+ or Tnfsf13-/- secondary recipient mice (Figure 5A). Interestingly, while no significant difference in sur- vival was observed between the groups when transplant- ing 10,000 leukemia cells (Online Supplementary Figure S5C), Tnfsf13-/- recipients showed an extended survival compared to Tnfsf13+/+ recipients when 1,000 leukemia cells were transplanted (mean of 28.5 vs. 34.5 days; P=0.0235) (Figure 5D). These data indicate that TNFSF13 supports AML initiation and maintenance under physio- logical conditions.
ABCD
EFGH
Figure 4. Tnfsf13-/- mice have myelopoiesis defects and acute myeloid leukemia cells express TNFRSF17. Frequency of (A) long-term hematopoietic stem cells (LT- HSC), (B) granulocyte and macrophage progenitor (GMP) cells, (C) monocytes, and (D) granulocytes in the bone marrow of Tnfsf13+/+ (n=14) and Tnfsf13-/- (n=13) mice. Flow cytometric analysis showing (E) TNFRSF17 (purple) and (F) TNFRSF13B (green) expression on c-Kit+ MLL-AF9 leukemic cells. Isotype control is shown in light gray. TNFRSF17 geometric mean fluorescent intensity (gMFI) expression within (G) hematopoietic stem and progenitor cells (HSPC) (n=5) and (H) lineage pop- ulations (n=10) in the bone marrow of normal mice, after subtracting the signal using matching isotype control antibodies. Values are means±Standard Deviation. *P<0.05; ****P<0.0001. WBC: white blood cells.
haematologica | 2019; 104(10)
2011