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Loss of Ikaros DNA-binding function confers integrin-dependent survival on pre-B cells and progression to acute lymphoblastic leukemia.

Joshi I, Yoshida T, Jena N, Qi X, Zhang J, Van Etten RA, Georgopoulos K - Nat. Immunol. (2014)

Bottom Line: Deletion of the DNA-binding domain of the transcription factor Ikaros generates dominant-negative isoforms that interfere with its activity and correlate with poor prognosis in human precursor B cell acute lymphoblastic leukemia (B-ALL).Here we found that conditional inactivation of the Ikaros DNA-binding domain in early pre-B cells arrested their differentiation at a stage at which integrin-dependent adhesion to niches augmented signaling via mitogen-activated protein kinases, proliferation and self-renewal and attenuated signaling via the pre-B cell signaling complex (pre-BCR) and the differentiation of pre-B cells.Our results explain how normal pre-B cells transit from a highly proliferative and stroma-dependent phase to a stroma-independent phase during which differentiation is enabled, and suggest potential therapeutic strategies for Ikaros-mutant B-ALL.

View Article: PubMed Central - PubMed

Affiliation: Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.

ABSTRACT
Deletion of the DNA-binding domain of the transcription factor Ikaros generates dominant-negative isoforms that interfere with its activity and correlate with poor prognosis in human precursor B cell acute lymphoblastic leukemia (B-ALL). Here we found that conditional inactivation of the Ikaros DNA-binding domain in early pre-B cells arrested their differentiation at a stage at which integrin-dependent adhesion to niches augmented signaling via mitogen-activated protein kinases, proliferation and self-renewal and attenuated signaling via the pre-B cell signaling complex (pre-BCR) and the differentiation of pre-B cells. Transplantation of polyclonal Ikaros-mutant pre-B cells resulted in long-latency oligoclonal pre-B-ALL, which demonstrates that loss of Ikaros contributes to multistep B cell leukemogenesis. Our results explain how normal pre-B cells transit from a highly proliferative and stroma-dependent phase to a stroma-independent phase during which differentiation is enabled, and suggest potential therapeutic strategies for Ikaros-mutant B-ALL.

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Cooperation between integrin and growth factor signaling supports survival and proliferation of IkE5Δ/Δ pre-B cellsa, Effect of integrin and cytokine signaling on WT and IkE5Δ/Δ pre-B cell survival. Mean percent recovery ± s.d. of WT (left) and IkE5Δ/Δ (right) adherent pre-B cells after overnight incubation on plates coated with integrin ligands (fibronectin and collagen, FN+Col) or BSA, in the absence (None) or presence of cytokines (IL-7, SCF, or Both). Asterisks denote significant differences in the number of mutant pre-B cells recovered in the presence of cytokines with or without integrin ligand binding. The data shown is from two independent cultures with replicate testing in each (n=4; *P < 0.01, two-tailed Student's t-test). b, Effect of integrin and cytokine signaling on survival of IkE5Δ/Δ pre-B cells. The mean number ± s.d. of plate-bound and -unbound WT and IkE5Δ/Δ pre-B cells recovered after overnight incubation in plates coated with integrin ligands (FN+Col) in the presence of cytokines (IL-7, SCF, or Both) or without cytokines (None). The mean percent ± s.d. of viable cells in the bound and unbound fractions is shown on the right. Asterisks denote significant changes in number or survival of mutant pre-B cells under the different conditions (n=3; *P < 0.05, **P < 0.01, ***P <0.001, ****P <0.0001 two-tailed Student's t-test). c, Effect of integrin and cytokine signaling on proliferation of IkE5Δ/Δ pre-B cells. The mean percent ± s.d. of cycling cells (S+G2+M) in the bound and unbound fractions of IkE5Δ/Δ pre-B cells as described in Fig. 6b is shown. Asterisks denote significant differences in proliferation of mutant pre-B cells measured when bound or not bound to integrin ligands in the presence of different cytokines (n=3; *P < 0.05, two-tailed Student's t-test).
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Figure 7: Cooperation between integrin and growth factor signaling supports survival and proliferation of IkE5Δ/Δ pre-B cellsa, Effect of integrin and cytokine signaling on WT and IkE5Δ/Δ pre-B cell survival. Mean percent recovery ± s.d. of WT (left) and IkE5Δ/Δ (right) adherent pre-B cells after overnight incubation on plates coated with integrin ligands (fibronectin and collagen, FN+Col) or BSA, in the absence (None) or presence of cytokines (IL-7, SCF, or Both). Asterisks denote significant differences in the number of mutant pre-B cells recovered in the presence of cytokines with or without integrin ligand binding. The data shown is from two independent cultures with replicate testing in each (n=4; *P < 0.01, two-tailed Student's t-test). b, Effect of integrin and cytokine signaling on survival of IkE5Δ/Δ pre-B cells. The mean number ± s.d. of plate-bound and -unbound WT and IkE5Δ/Δ pre-B cells recovered after overnight incubation in plates coated with integrin ligands (FN+Col) in the presence of cytokines (IL-7, SCF, or Both) or without cytokines (None). The mean percent ± s.d. of viable cells in the bound and unbound fractions is shown on the right. Asterisks denote significant changes in number or survival of mutant pre-B cells under the different conditions (n=3; *P < 0.05, **P < 0.01, ***P <0.001, ****P <0.0001 two-tailed Student's t-test). c, Effect of integrin and cytokine signaling on proliferation of IkE5Δ/Δ pre-B cells. The mean percent ± s.d. of cycling cells (S+G2+M) in the bound and unbound fractions of IkE5Δ/Δ pre-B cells as described in Fig. 6b is shown. Asterisks denote significant differences in proliferation of mutant pre-B cells measured when bound or not bound to integrin ligands in the presence of different cytokines (n=3; *P < 0.05, two-tailed Student's t-test).

Mentions: We then tested whether integrin-mediated adhesion was sufficient to support stromal-dependent survival and proliferation of IkE5Δ/Δ pre-B cells. The majority of IkE5Δ/Δ pre-B cells plated on fibronectin and collagen died after overnight incubation, indicating that integrin signaling alone could not support their survival (Fig. 7a). In sharp contrast, the majority of WT pre-B cells survived under these conditions.


Loss of Ikaros DNA-binding function confers integrin-dependent survival on pre-B cells and progression to acute lymphoblastic leukemia.

Joshi I, Yoshida T, Jena N, Qi X, Zhang J, Van Etten RA, Georgopoulos K - Nat. Immunol. (2014)

Cooperation between integrin and growth factor signaling supports survival and proliferation of IkE5Δ/Δ pre-B cellsa, Effect of integrin and cytokine signaling on WT and IkE5Δ/Δ pre-B cell survival. Mean percent recovery ± s.d. of WT (left) and IkE5Δ/Δ (right) adherent pre-B cells after overnight incubation on plates coated with integrin ligands (fibronectin and collagen, FN+Col) or BSA, in the absence (None) or presence of cytokines (IL-7, SCF, or Both). Asterisks denote significant differences in the number of mutant pre-B cells recovered in the presence of cytokines with or without integrin ligand binding. The data shown is from two independent cultures with replicate testing in each (n=4; *P < 0.01, two-tailed Student's t-test). b, Effect of integrin and cytokine signaling on survival of IkE5Δ/Δ pre-B cells. The mean number ± s.d. of plate-bound and -unbound WT and IkE5Δ/Δ pre-B cells recovered after overnight incubation in plates coated with integrin ligands (FN+Col) in the presence of cytokines (IL-7, SCF, or Both) or without cytokines (None). The mean percent ± s.d. of viable cells in the bound and unbound fractions is shown on the right. Asterisks denote significant changes in number or survival of mutant pre-B cells under the different conditions (n=3; *P < 0.05, **P < 0.01, ***P <0.001, ****P <0.0001 two-tailed Student's t-test). c, Effect of integrin and cytokine signaling on proliferation of IkE5Δ/Δ pre-B cells. The mean percent ± s.d. of cycling cells (S+G2+M) in the bound and unbound fractions of IkE5Δ/Δ pre-B cells as described in Fig. 6b is shown. Asterisks denote significant differences in proliferation of mutant pre-B cells measured when bound or not bound to integrin ligands in the presence of different cytokines (n=3; *P < 0.05, two-tailed Student's t-test).
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Figure 7: Cooperation between integrin and growth factor signaling supports survival and proliferation of IkE5Δ/Δ pre-B cellsa, Effect of integrin and cytokine signaling on WT and IkE5Δ/Δ pre-B cell survival. Mean percent recovery ± s.d. of WT (left) and IkE5Δ/Δ (right) adherent pre-B cells after overnight incubation on plates coated with integrin ligands (fibronectin and collagen, FN+Col) or BSA, in the absence (None) or presence of cytokines (IL-7, SCF, or Both). Asterisks denote significant differences in the number of mutant pre-B cells recovered in the presence of cytokines with or without integrin ligand binding. The data shown is from two independent cultures with replicate testing in each (n=4; *P < 0.01, two-tailed Student's t-test). b, Effect of integrin and cytokine signaling on survival of IkE5Δ/Δ pre-B cells. The mean number ± s.d. of plate-bound and -unbound WT and IkE5Δ/Δ pre-B cells recovered after overnight incubation in plates coated with integrin ligands (FN+Col) in the presence of cytokines (IL-7, SCF, or Both) or without cytokines (None). The mean percent ± s.d. of viable cells in the bound and unbound fractions is shown on the right. Asterisks denote significant changes in number or survival of mutant pre-B cells under the different conditions (n=3; *P < 0.05, **P < 0.01, ***P <0.001, ****P <0.0001 two-tailed Student's t-test). c, Effect of integrin and cytokine signaling on proliferation of IkE5Δ/Δ pre-B cells. The mean percent ± s.d. of cycling cells (S+G2+M) in the bound and unbound fractions of IkE5Δ/Δ pre-B cells as described in Fig. 6b is shown. Asterisks denote significant differences in proliferation of mutant pre-B cells measured when bound or not bound to integrin ligands in the presence of different cytokines (n=3; *P < 0.05, two-tailed Student's t-test).
Mentions: We then tested whether integrin-mediated adhesion was sufficient to support stromal-dependent survival and proliferation of IkE5Δ/Δ pre-B cells. The majority of IkE5Δ/Δ pre-B cells plated on fibronectin and collagen died after overnight incubation, indicating that integrin signaling alone could not support their survival (Fig. 7a). In sharp contrast, the majority of WT pre-B cells survived under these conditions.

Bottom Line: Deletion of the DNA-binding domain of the transcription factor Ikaros generates dominant-negative isoforms that interfere with its activity and correlate with poor prognosis in human precursor B cell acute lymphoblastic leukemia (B-ALL).Here we found that conditional inactivation of the Ikaros DNA-binding domain in early pre-B cells arrested their differentiation at a stage at which integrin-dependent adhesion to niches augmented signaling via mitogen-activated protein kinases, proliferation and self-renewal and attenuated signaling via the pre-B cell signaling complex (pre-BCR) and the differentiation of pre-B cells.Our results explain how normal pre-B cells transit from a highly proliferative and stroma-dependent phase to a stroma-independent phase during which differentiation is enabled, and suggest potential therapeutic strategies for Ikaros-mutant B-ALL.

View Article: PubMed Central - PubMed

Affiliation: Cutaneous Biology Research Center, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts, USA.

ABSTRACT
Deletion of the DNA-binding domain of the transcription factor Ikaros generates dominant-negative isoforms that interfere with its activity and correlate with poor prognosis in human precursor B cell acute lymphoblastic leukemia (B-ALL). Here we found that conditional inactivation of the Ikaros DNA-binding domain in early pre-B cells arrested their differentiation at a stage at which integrin-dependent adhesion to niches augmented signaling via mitogen-activated protein kinases, proliferation and self-renewal and attenuated signaling via the pre-B cell signaling complex (pre-BCR) and the differentiation of pre-B cells. Transplantation of polyclonal Ikaros-mutant pre-B cells resulted in long-latency oligoclonal pre-B-ALL, which demonstrates that loss of Ikaros contributes to multistep B cell leukemogenesis. Our results explain how normal pre-B cells transit from a highly proliferative and stroma-dependent phase to a stroma-independent phase during which differentiation is enabled, and suggest potential therapeutic strategies for Ikaros-mutant B-ALL.

Show MeSH
Related in: MedlinePlus