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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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FAK inhibition interferes with survival of IkE5Δ/Δ pre-B cellsa-b.In vitro effects of FAK inhibition on pre-B cell stromal adhesion and survival. The mean percentage ± s.d. of adherent cells (left) and % inhibition of adhesion ± s.d. (right), are shown in (a). The percentage of viable adherent and non-adherent cells recovered in the presence of FAK inhibitor is shown in (b). The data in (a) are from two independent cultures with replicate testing (n=4). For Annexin staining described in (b) replicates were pooled. c-d,In vivo effect of FAK inhibition on IkE5Δ/Δlarge pre-B cells. c, The mean number ± s.d. of pro-B-large pre-B cells (CD19+CD43+) per leg (femur + tibia) of WT (n=2) and IkE5Δ/ΔCD19-Cre (n=3) mice is shown after 3-5 doses of FAK inhibitor (WT, n=3; IkE5Δ/ΔCD19-Cre, n=6) or vehicle control (WT, n=2; IkE5Δ/ΔCD19-Cre, n=3). The effect of FAK inhibitor treatment on total BM B cells (CD19+) in WT mice is also shown. d, Percent of apoptotic cells (mean ± s.d.) of BM cells from panel c. Asterisks in a, c, and d denote significant changes in adhesion, cellularity or survival of WT and mutant large pre-B cells in the presence of the FAK inhibitor vs. control (*P < 0.05, **P < 0.01, ***P <0.001, two-tailed Student's t-test).
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Figure 6: FAK inhibition interferes with survival of IkE5Δ/Δ pre-B cellsa-b.In vitro effects of FAK inhibition on pre-B cell stromal adhesion and survival. The mean percentage ± s.d. of adherent cells (left) and % inhibition of adhesion ± s.d. (right), are shown in (a). The percentage of viable adherent and non-adherent cells recovered in the presence of FAK inhibitor is shown in (b). The data in (a) are from two independent cultures with replicate testing (n=4). For Annexin staining described in (b) replicates were pooled. c-d,In vivo effect of FAK inhibition on IkE5Δ/Δlarge pre-B cells. c, The mean number ± s.d. of pro-B-large pre-B cells (CD19+CD43+) per leg (femur + tibia) of WT (n=2) and IkE5Δ/ΔCD19-Cre (n=3) mice is shown after 3-5 doses of FAK inhibitor (WT, n=3; IkE5Δ/ΔCD19-Cre, n=6) or vehicle control (WT, n=2; IkE5Δ/ΔCD19-Cre, n=3). The effect of FAK inhibitor treatment on total BM B cells (CD19+) in WT mice is also shown. d, Percent of apoptotic cells (mean ± s.d.) of BM cells from panel c. Asterisks in a, c, and d denote significant changes in adhesion, cellularity or survival of WT and mutant large pre-B cells in the presence of the FAK inhibitor vs. control (*P < 0.05, **P < 0.01, ***P <0.001, two-tailed Student's t-test).

Mentions: The role of integrin signaling in supporting stromal adhesion and survival of IkE5Δ/Δ pre-B cells was validated by treatment with a small molecule inhibitor (PF-431396) that blocks the kinase activity of FAK (Ptk2) and the related kinase Ptk2b (ref. 38), which together serve as major signaling effectors of the integrin pathway. FAK-Ptk2b inhibitor treatment greatly reduced stromal adhesion not only in IkE5Δ/Δ but also in WT pre-B cells (Fig. 6a). However, the loss in adhesion preceded an increase in apoptosis only in IkE5Δ/Δ pre-B cell and not in WT pre-B cells (Fig. 6b).


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)

FAK inhibition interferes with survival of IkE5Δ/Δ pre-B cellsa-b.In vitro effects of FAK inhibition on pre-B cell stromal adhesion and survival. The mean percentage ± s.d. of adherent cells (left) and % inhibition of adhesion ± s.d. (right), are shown in (a). The percentage of viable adherent and non-adherent cells recovered in the presence of FAK inhibitor is shown in (b). The data in (a) are from two independent cultures with replicate testing (n=4). For Annexin staining described in (b) replicates were pooled. c-d,In vivo effect of FAK inhibition on IkE5Δ/Δlarge pre-B cells. c, The mean number ± s.d. of pro-B-large pre-B cells (CD19+CD43+) per leg (femur + tibia) of WT (n=2) and IkE5Δ/ΔCD19-Cre (n=3) mice is shown after 3-5 doses of FAK inhibitor (WT, n=3; IkE5Δ/ΔCD19-Cre, n=6) or vehicle control (WT, n=2; IkE5Δ/ΔCD19-Cre, n=3). The effect of FAK inhibitor treatment on total BM B cells (CD19+) in WT mice is also shown. d, Percent of apoptotic cells (mean ± s.d.) of BM cells from panel c. Asterisks in a, c, and d denote significant changes in adhesion, cellularity or survival of WT and mutant large pre-B cells in the presence of the FAK inhibitor vs. control (*P < 0.05, **P < 0.01, ***P <0.001, two-tailed Student's t-test).
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Figure 6: FAK inhibition interferes with survival of IkE5Δ/Δ pre-B cellsa-b.In vitro effects of FAK inhibition on pre-B cell stromal adhesion and survival. The mean percentage ± s.d. of adherent cells (left) and % inhibition of adhesion ± s.d. (right), are shown in (a). The percentage of viable adherent and non-adherent cells recovered in the presence of FAK inhibitor is shown in (b). The data in (a) are from two independent cultures with replicate testing (n=4). For Annexin staining described in (b) replicates were pooled. c-d,In vivo effect of FAK inhibition on IkE5Δ/Δlarge pre-B cells. c, The mean number ± s.d. of pro-B-large pre-B cells (CD19+CD43+) per leg (femur + tibia) of WT (n=2) and IkE5Δ/ΔCD19-Cre (n=3) mice is shown after 3-5 doses of FAK inhibitor (WT, n=3; IkE5Δ/ΔCD19-Cre, n=6) or vehicle control (WT, n=2; IkE5Δ/ΔCD19-Cre, n=3). The effect of FAK inhibitor treatment on total BM B cells (CD19+) in WT mice is also shown. d, Percent of apoptotic cells (mean ± s.d.) of BM cells from panel c. Asterisks in a, c, and d denote significant changes in adhesion, cellularity or survival of WT and mutant large pre-B cells in the presence of the FAK inhibitor vs. control (*P < 0.05, **P < 0.01, ***P <0.001, two-tailed Student's t-test).
Mentions: The role of integrin signaling in supporting stromal adhesion and survival of IkE5Δ/Δ pre-B cells was validated by treatment with a small molecule inhibitor (PF-431396) that blocks the kinase activity of FAK (Ptk2) and the related kinase Ptk2b (ref. 38), which together serve as major signaling effectors of the integrin pathway. FAK-Ptk2b inhibitor treatment greatly reduced stromal adhesion not only in IkE5Δ/Δ but also in WT pre-B cells (Fig. 6a). However, the loss in adhesion preceded an increase in apoptosis only in IkE5Δ/Δ pre-B cell and not in WT pre-B cells (Fig. 6b).

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