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Expression of Fbxo7 in haematopoietic progenitor cells cooperates with p53 loss to promote lymphomagenesis.

Lomonosov M, Meziane el K, Ye H, Nelson DE, Randle SJ, Laman H - PLoS ONE (2011)

Bottom Line: Here we present new evidence in vitro and in vivo on the oncogenic potential of this regulatory protein in primary haematopoietic stem and progenitor cells (HSPCs).Increasing Fbxo7 expression in HSPCs suppressed their colony forming ability in vitro, specifically decreasing CD11b (Mac1) expression, and these effects were dependent on an intact p53 pathway.Furthermore, increased Fbxo7 levels enhanced the proliferative capacity of p53 HSPCs when they were grown in reduced concentrations of stem cell factor.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Cambridge, Cambridge, United Kingdom.

ABSTRACT
Fbxo7 is an unusual F box protein that augments D-type cyclin complex formation with Cdk6, but not Cdk4 or Cdk2, and its over-expression has been demonstrated to transform immortalised fibroblasts in a Cdk6-dependent manner. Here we present new evidence in vitro and in vivo on the oncogenic potential of this regulatory protein in primary haematopoietic stem and progenitor cells (HSPCs). Increasing Fbxo7 expression in HSPCs suppressed their colony forming ability in vitro, specifically decreasing CD11b (Mac1) expression, and these effects were dependent on an intact p53 pathway. Furthermore, increased Fbxo7 levels enhanced the proliferative capacity of p53 HSPCs when they were grown in reduced concentrations of stem cell factor. Finally, irradiated mice reconstituted with p53 , but not wild-type, HSPCs expressing Fbxo7 showed a statistically significant increase in the incidence of T cell lymphoma in vivo. These data argue that Fbxo7 negatively regulates the proliferation and differentiation of HSPCs in a p53-dependent manner, and that in the absence of p53, Fbxo7 expression can promote T cell lymphomagenesis.

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Fbxo7 expression alters the expression of markers of myeloid differentiation.FACS analysis of immunostaining for Mac1 (CD11b) on the x-axis and Gr1(Ly6C/G) on the y-axis for WT cells grown at 50 ng/mL (A) or 20 ng/mL (B) of SCF. FACS analysis of immunostaining for Mac1 (CD11b) and Gr1(Ly6C/G) for p53  cells grown at 50 ng/mL (C) or 20 ng/mL (D) of SCF. Table of percentages of either Mac1 (CD11b) or Gr1(Ly6C/G) positive cells for WT cells (E) and p53  cells (F).
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pone-0021165-g003: Fbxo7 expression alters the expression of markers of myeloid differentiation.FACS analysis of immunostaining for Mac1 (CD11b) on the x-axis and Gr1(Ly6C/G) on the y-axis for WT cells grown at 50 ng/mL (A) or 20 ng/mL (B) of SCF. FACS analysis of immunostaining for Mac1 (CD11b) and Gr1(Ly6C/G) for p53 cells grown at 50 ng/mL (C) or 20 ng/mL (D) of SCF. Table of percentages of either Mac1 (CD11b) or Gr1(Ly6C/G) positive cells for WT cells (E) and p53 cells (F).

Mentions: Fbxo7 expression had a strong suppressive effect on colony formation and proliferation of HSPCs, so we next wanted to determine whether its expression also affected their differentiation. Equal numbers of retrovirally infected FL-derived HSPCs were seeded and incubated under standard growth conditions. After 14 days, cells were harvested and immunostained for the expression of cell surface markers Ly6C/G (Gr1), which is a myeloid differentiation antigen whose expression increases during granulocyte differentiation, and CD11b (Mac-1), which is a macrophage differentiation factor. We observed that 55.64% of WT cells expressing the MSCV control were Ly6C/G+ CD11b+ (Figure 3A). As SCF levels can affect the differentiation of G/M progenitor cells and enhance their response to other cytokines [23], we also tested the effect of reducing the SCF concentration to 20 ng/mL, and this decreased the Ly6C/G+ CD11b+ population to 16.68% (Figure 3B). Fbxo7 expression in WT HSPCs strongly inhibited the appearance of the double positive population, which accounted for only 3.06% and 3.83% of the cells, at 50 and 20 ng/mL of SCF, respectively. We noted that the effect of Fbxo7 expression was attributable mainly to a decrease in CD11b expression as Ly6C/G was still expressed and even slightly enhanced when Fbxo7 was introduced (Figure 3A, B, E).


Expression of Fbxo7 in haematopoietic progenitor cells cooperates with p53 loss to promote lymphomagenesis.

Lomonosov M, Meziane el K, Ye H, Nelson DE, Randle SJ, Laman H - PLoS ONE (2011)

Fbxo7 expression alters the expression of markers of myeloid differentiation.FACS analysis of immunostaining for Mac1 (CD11b) on the x-axis and Gr1(Ly6C/G) on the y-axis for WT cells grown at 50 ng/mL (A) or 20 ng/mL (B) of SCF. FACS analysis of immunostaining for Mac1 (CD11b) and Gr1(Ly6C/G) for p53  cells grown at 50 ng/mL (C) or 20 ng/mL (D) of SCF. Table of percentages of either Mac1 (CD11b) or Gr1(Ly6C/G) positive cells for WT cells (E) and p53  cells (F).
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3117880&req=5

pone-0021165-g003: Fbxo7 expression alters the expression of markers of myeloid differentiation.FACS analysis of immunostaining for Mac1 (CD11b) on the x-axis and Gr1(Ly6C/G) on the y-axis for WT cells grown at 50 ng/mL (A) or 20 ng/mL (B) of SCF. FACS analysis of immunostaining for Mac1 (CD11b) and Gr1(Ly6C/G) for p53 cells grown at 50 ng/mL (C) or 20 ng/mL (D) of SCF. Table of percentages of either Mac1 (CD11b) or Gr1(Ly6C/G) positive cells for WT cells (E) and p53 cells (F).
Mentions: Fbxo7 expression had a strong suppressive effect on colony formation and proliferation of HSPCs, so we next wanted to determine whether its expression also affected their differentiation. Equal numbers of retrovirally infected FL-derived HSPCs were seeded and incubated under standard growth conditions. After 14 days, cells were harvested and immunostained for the expression of cell surface markers Ly6C/G (Gr1), which is a myeloid differentiation antigen whose expression increases during granulocyte differentiation, and CD11b (Mac-1), which is a macrophage differentiation factor. We observed that 55.64% of WT cells expressing the MSCV control were Ly6C/G+ CD11b+ (Figure 3A). As SCF levels can affect the differentiation of G/M progenitor cells and enhance their response to other cytokines [23], we also tested the effect of reducing the SCF concentration to 20 ng/mL, and this decreased the Ly6C/G+ CD11b+ population to 16.68% (Figure 3B). Fbxo7 expression in WT HSPCs strongly inhibited the appearance of the double positive population, which accounted for only 3.06% and 3.83% of the cells, at 50 and 20 ng/mL of SCF, respectively. We noted that the effect of Fbxo7 expression was attributable mainly to a decrease in CD11b expression as Ly6C/G was still expressed and even slightly enhanced when Fbxo7 was introduced (Figure 3A, B, E).

Bottom Line: Here we present new evidence in vitro and in vivo on the oncogenic potential of this regulatory protein in primary haematopoietic stem and progenitor cells (HSPCs).Increasing Fbxo7 expression in HSPCs suppressed their colony forming ability in vitro, specifically decreasing CD11b (Mac1) expression, and these effects were dependent on an intact p53 pathway.Furthermore, increased Fbxo7 levels enhanced the proliferative capacity of p53 HSPCs when they were grown in reduced concentrations of stem cell factor.

View Article: PubMed Central - PubMed

Affiliation: Department of Pathology, University of Cambridge, Cambridge, United Kingdom.

ABSTRACT
Fbxo7 is an unusual F box protein that augments D-type cyclin complex formation with Cdk6, but not Cdk4 or Cdk2, and its over-expression has been demonstrated to transform immortalised fibroblasts in a Cdk6-dependent manner. Here we present new evidence in vitro and in vivo on the oncogenic potential of this regulatory protein in primary haematopoietic stem and progenitor cells (HSPCs). Increasing Fbxo7 expression in HSPCs suppressed their colony forming ability in vitro, specifically decreasing CD11b (Mac1) expression, and these effects were dependent on an intact p53 pathway. Furthermore, increased Fbxo7 levels enhanced the proliferative capacity of p53 HSPCs when they were grown in reduced concentrations of stem cell factor. Finally, irradiated mice reconstituted with p53 , but not wild-type, HSPCs expressing Fbxo7 showed a statistically significant increase in the incidence of T cell lymphoma in vivo. These data argue that Fbxo7 negatively regulates the proliferation and differentiation of HSPCs in a p53-dependent manner, and that in the absence of p53, Fbxo7 expression can promote T cell lymphomagenesis.

Show MeSH
Related in: MedlinePlus