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AHI-1 interacts with BCR-ABL and modulates BCR-ABL transforming activity and imatinib response of CML stem/progenitor cells.

Zhou LL, Zhao Y, Ringrose A, DeGeer D, Kennah E, Lin AE, Sheng G, Li XJ, Turhan A, Jiang X - J. Exp. Med. (2008)

Bottom Line: Conversely, RNAi-mediated suppression of AHI-1 in BCR-ABL-transduced lin(-)CD34(+) human cord blood cells and primary CML stem/progenitor cells reduces their growth autonomy in vitro.Interestingly, coexpression of Ahi-1 in BCR-ABL-inducible cells reverses growth deficiencies exhibited by BCR-ABL down-regulation and is associated with sustained phosphorylation of BCR-ABL and enhanced activation of JAK2-STAT5.Moreover, we identified an AHI-1-BCR-ABL-JAK2 interaction complex and found that modulation of AHI-1 expression regulates phosphorylation of BCR-ABL and JAK2-STAT5 in CML cells.

View Article: PubMed Central - PubMed

Affiliation: Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver V5Z 1L3, BC, Canada.

ABSTRACT
Chronic myeloid leukemia (CML) represents the first human malignancy successfully treated with a tyrosine kinase inhibitor (TKI; imatinib). However, early relapses and the emergence of imatinib-resistant disease are problematic. Evidence suggests that imatinib and other inhibitors may not effectively eradicate leukemic stem/progenitor cells, and that combination therapy directed to complimentary targets may improve treatment. Abelson helper integration site 1 (Ahi-1)/AHI-1 is a novel oncogene that is highly deregulated in CML stem/progenitor cells where levels of BCR-ABL transcripts are also elevated. Here, we demonstrate that overexpression of Ahi-1/AHI-1 in murine and human hematopoietic cells confer growth advantages in vitro and induce leukemia in vivo, enhancing effects of BCR-ABL. Conversely, RNAi-mediated suppression of AHI-1 in BCR-ABL-transduced lin(-)CD34(+) human cord blood cells and primary CML stem/progenitor cells reduces their growth autonomy in vitro. Interestingly, coexpression of Ahi-1 in BCR-ABL-inducible cells reverses growth deficiencies exhibited by BCR-ABL down-regulation and is associated with sustained phosphorylation of BCR-ABL and enhanced activation of JAK2-STAT5. Moreover, we identified an AHI-1-BCR-ABL-JAK2 interaction complex and found that modulation of AHI-1 expression regulates phosphorylation of BCR-ABL and JAK2-STAT5 in CML cells. Importantly, this complex mediates TKI response/resistance of CML stem/progenitor cells. These studies implicate AHI-1 as a potential therapeutic target downstream of BCR-ABL in CML.

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Overexpression of Ahi-1 induces a lethal leukemia in vivo and these effects can be enhanced by cotransduction of BCR-ABL. (A) Survival curves of NOD/SCID-β2M−/− mice injected with 5 × 106 BaF3 cells transduced with MIY, Ahi-1, BCR-ABL, and Ahi-1 plus BCR-ABL. 8–10 mice were used per each group. (B) Spleen (top) and liver (bottom) weight of mice injected with MIY control cells, Ahi-1–transduced cells, BCR-ABL–transduced cells, and cells cotransduced with Ahi-1 and BCR-ABL. (C) FACS profiles of YFP+ BM cells isolated from a representative moribund mouse with leukemia, after injection of Ahi-1–transduced cells and showing expression by the YFP+ cells of Gr-1/Mac-1, B220, CD4/CD8, Ter119, Sac-1, and c-kit.
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fig1: Overexpression of Ahi-1 induces a lethal leukemia in vivo and these effects can be enhanced by cotransduction of BCR-ABL. (A) Survival curves of NOD/SCID-β2M−/− mice injected with 5 × 106 BaF3 cells transduced with MIY, Ahi-1, BCR-ABL, and Ahi-1 plus BCR-ABL. 8–10 mice were used per each group. (B) Spleen (top) and liver (bottom) weight of mice injected with MIY control cells, Ahi-1–transduced cells, BCR-ABL–transduced cells, and cells cotransduced with Ahi-1 and BCR-ABL. (C) FACS profiles of YFP+ BM cells isolated from a representative moribund mouse with leukemia, after injection of Ahi-1–transduced cells and showing expression by the YFP+ cells of Gr-1/Mac-1, B220, CD4/CD8, Ter119, Sac-1, and c-kit.

Mentions: To investigate effects of overexpression of Ahi-1 on the ability of transduced cells to induce leukemias in vivo, we injected transduced cells into sublethally irradiated NOD/SCID–β2 microglobulin (β2m)−/− mice. Strikingly, mice injected intravenously with Ahi-1–transduced BaF3 cells had a lethal leukemia within 70 d (5 × 106 cells/per mouse; Fig. 1 A). Disease latency was shortened to 40 d with BCR-ABL–transduced cells alone. Leukemogenic activity was further increased by introduction of cotransduced Ahi-1 and BCR-ABL cells, producing a latency of 26 d (P < 0.05; Fig. 1 A). Mice injected with either parental BaF3 cells or vector control cells had no evidence of disease after 120 d. Leukemic mice injected with either Ahi-1 or BCR-ABL–transduced cells developed splenomegaly and hepatomegaly, with 50–90% of YFP+/Ahi-1+, GFP+/BCR-ABL+, or both YFP+GFP+ cells detectable in these tissues (Fig. 1 B). As expected, larger spleens and livers were observed in mice injected with both Ahi-1 and BCR-ABL–transduced cells (Fig. 1 B and Table I). Interestingly, despite the apparently homogeneous pro–B cell phenotype of BaF3 cells transplanted, the leukemias generated from Ahi-1–transduced cells revealed multilineage features that included the production of Gr-1+Mac-1+ (myeloid), Ter119+ (erythroid), B220+ (B-lineage), and CD4+CD8+ (T-lineage; Fig. 1 C), suggesting that overexpression of Ahi-1 induces abnormal differentiation (including lineage switching) in hematopoietic cells. This was also observed in mice injected with Ahi-1 and BCR-ABL cotransduced cells. In addition, YFP+/Ahi-1+ or GFP+/BCR-ABL+ cells purified from BM cells of diseased mice showed increased proliferation and reduced apoptosis compared with control BaF3 cells; these effects were enhanced in Ahi-1– and BCR-ABL–cotransduced cells (Fig. S2 available at http://www.jem.org/cgi/content/full/jem.20072316/DC1). Thus, overexpression of Ahi-1 alone in IL-3–dependent hematopoietic cells has strong transforming activity in vitro and in vivo, and this is additive with the effects of BCR-ABL.


AHI-1 interacts with BCR-ABL and modulates BCR-ABL transforming activity and imatinib response of CML stem/progenitor cells.

Zhou LL, Zhao Y, Ringrose A, DeGeer D, Kennah E, Lin AE, Sheng G, Li XJ, Turhan A, Jiang X - J. Exp. Med. (2008)

Overexpression of Ahi-1 induces a lethal leukemia in vivo and these effects can be enhanced by cotransduction of BCR-ABL. (A) Survival curves of NOD/SCID-β2M−/− mice injected with 5 × 106 BaF3 cells transduced with MIY, Ahi-1, BCR-ABL, and Ahi-1 plus BCR-ABL. 8–10 mice were used per each group. (B) Spleen (top) and liver (bottom) weight of mice injected with MIY control cells, Ahi-1–transduced cells, BCR-ABL–transduced cells, and cells cotransduced with Ahi-1 and BCR-ABL. (C) FACS profiles of YFP+ BM cells isolated from a representative moribund mouse with leukemia, after injection of Ahi-1–transduced cells and showing expression by the YFP+ cells of Gr-1/Mac-1, B220, CD4/CD8, Ter119, Sac-1, and c-kit.
© Copyright Policy
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC2571939&req=5

fig1: Overexpression of Ahi-1 induces a lethal leukemia in vivo and these effects can be enhanced by cotransduction of BCR-ABL. (A) Survival curves of NOD/SCID-β2M−/− mice injected with 5 × 106 BaF3 cells transduced with MIY, Ahi-1, BCR-ABL, and Ahi-1 plus BCR-ABL. 8–10 mice were used per each group. (B) Spleen (top) and liver (bottom) weight of mice injected with MIY control cells, Ahi-1–transduced cells, BCR-ABL–transduced cells, and cells cotransduced with Ahi-1 and BCR-ABL. (C) FACS profiles of YFP+ BM cells isolated from a representative moribund mouse with leukemia, after injection of Ahi-1–transduced cells and showing expression by the YFP+ cells of Gr-1/Mac-1, B220, CD4/CD8, Ter119, Sac-1, and c-kit.
Mentions: To investigate effects of overexpression of Ahi-1 on the ability of transduced cells to induce leukemias in vivo, we injected transduced cells into sublethally irradiated NOD/SCID–β2 microglobulin (β2m)−/− mice. Strikingly, mice injected intravenously with Ahi-1–transduced BaF3 cells had a lethal leukemia within 70 d (5 × 106 cells/per mouse; Fig. 1 A). Disease latency was shortened to 40 d with BCR-ABL–transduced cells alone. Leukemogenic activity was further increased by introduction of cotransduced Ahi-1 and BCR-ABL cells, producing a latency of 26 d (P < 0.05; Fig. 1 A). Mice injected with either parental BaF3 cells or vector control cells had no evidence of disease after 120 d. Leukemic mice injected with either Ahi-1 or BCR-ABL–transduced cells developed splenomegaly and hepatomegaly, with 50–90% of YFP+/Ahi-1+, GFP+/BCR-ABL+, or both YFP+GFP+ cells detectable in these tissues (Fig. 1 B). As expected, larger spleens and livers were observed in mice injected with both Ahi-1 and BCR-ABL–transduced cells (Fig. 1 B and Table I). Interestingly, despite the apparently homogeneous pro–B cell phenotype of BaF3 cells transplanted, the leukemias generated from Ahi-1–transduced cells revealed multilineage features that included the production of Gr-1+Mac-1+ (myeloid), Ter119+ (erythroid), B220+ (B-lineage), and CD4+CD8+ (T-lineage; Fig. 1 C), suggesting that overexpression of Ahi-1 induces abnormal differentiation (including lineage switching) in hematopoietic cells. This was also observed in mice injected with Ahi-1 and BCR-ABL cotransduced cells. In addition, YFP+/Ahi-1+ or GFP+/BCR-ABL+ cells purified from BM cells of diseased mice showed increased proliferation and reduced apoptosis compared with control BaF3 cells; these effects were enhanced in Ahi-1– and BCR-ABL–cotransduced cells (Fig. S2 available at http://www.jem.org/cgi/content/full/jem.20072316/DC1). Thus, overexpression of Ahi-1 alone in IL-3–dependent hematopoietic cells has strong transforming activity in vitro and in vivo, and this is additive with the effects of BCR-ABL.

Bottom Line: Conversely, RNAi-mediated suppression of AHI-1 in BCR-ABL-transduced lin(-)CD34(+) human cord blood cells and primary CML stem/progenitor cells reduces their growth autonomy in vitro.Interestingly, coexpression of Ahi-1 in BCR-ABL-inducible cells reverses growth deficiencies exhibited by BCR-ABL down-regulation and is associated with sustained phosphorylation of BCR-ABL and enhanced activation of JAK2-STAT5.Moreover, we identified an AHI-1-BCR-ABL-JAK2 interaction complex and found that modulation of AHI-1 expression regulates phosphorylation of BCR-ABL and JAK2-STAT5 in CML cells.

View Article: PubMed Central - PubMed

Affiliation: Terry Fox Laboratory, British Columbia Cancer Agency, Vancouver V5Z 1L3, BC, Canada.

ABSTRACT
Chronic myeloid leukemia (CML) represents the first human malignancy successfully treated with a tyrosine kinase inhibitor (TKI; imatinib). However, early relapses and the emergence of imatinib-resistant disease are problematic. Evidence suggests that imatinib and other inhibitors may not effectively eradicate leukemic stem/progenitor cells, and that combination therapy directed to complimentary targets may improve treatment. Abelson helper integration site 1 (Ahi-1)/AHI-1 is a novel oncogene that is highly deregulated in CML stem/progenitor cells where levels of BCR-ABL transcripts are also elevated. Here, we demonstrate that overexpression of Ahi-1/AHI-1 in murine and human hematopoietic cells confer growth advantages in vitro and induce leukemia in vivo, enhancing effects of BCR-ABL. Conversely, RNAi-mediated suppression of AHI-1 in BCR-ABL-transduced lin(-)CD34(+) human cord blood cells and primary CML stem/progenitor cells reduces their growth autonomy in vitro. Interestingly, coexpression of Ahi-1 in BCR-ABL-inducible cells reverses growth deficiencies exhibited by BCR-ABL down-regulation and is associated with sustained phosphorylation of BCR-ABL and enhanced activation of JAK2-STAT5. Moreover, we identified an AHI-1-BCR-ABL-JAK2 interaction complex and found that modulation of AHI-1 expression regulates phosphorylation of BCR-ABL and JAK2-STAT5 in CML cells. Importantly, this complex mediates TKI response/resistance of CML stem/progenitor cells. These studies implicate AHI-1 as a potential therapeutic target downstream of BCR-ABL in CML.

Show MeSH
Related in: MedlinePlus