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EphA2 Is a Therapy Target in EphA2-Positive Leukemias but Is Not Essential for Normal Hematopoiesis or Leukemia.

Charmsaz S, Beckett K, Smith FM, Bruedigam C, Moore AS, Al-Ejeh F, Lane SW, Boyd AW - PLoS ONE (2015)

Bottom Line: These studies showed that EphA2 does not have an obligatory role in normal hematopoiesis.We showed that treatment with EphA2 monoclonal antibody IF7 alone had no effect on tumorigenicity and latency of the MLL-AF9 leukemias, while targeting of EphA2 using EphA2 monoclonal antibody with a radioactive payload significantly impaired the leukemic process.Altogether, these results identify EphA2 as a potential radio-therapeutic target in leukemias with MLL translocation.

View Article: PubMed Central - PubMed

Affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.

ABSTRACT
Members of the Eph family of receptor tyrosine kinases and their membrane bound ephrin ligands have been shown to play critical roles in many developmental processes and more recently have been implicated in both normal and pathological processes in post-embryonic tissues. In particular, expression studies of Eph receptors and limited functional studies have demonstrated a role for the Eph/ephrin system in hematopoiesis and leukemogenesis. In particular, EphA2 was reported on hematopoietic stem cells and stromal cells. There are also reports of EphA2 expression in many different types of malignancies including leukemia, however there is a lack of knowledge in understanding the role of EphA2 in hematopoiesis and leukemogenesis. We explored the role of EphA2 in hematopoiesis by analyzing wild type and EphA2 knockout mice. Mature, differentiated cells, progenitors and hematopoietic stem cells derived from knockout and control mice were analyzed and no significant abnormality was detected. These studies showed that EphA2 does not have an obligatory role in normal hematopoiesis. Comparative studies using EphA2-negative MLL-AF9 leukemias derived from EphA2-knockout animals showed that there was no detectable functional role for EphA2 in the initiation or progression of the leukemic process. However, expression of EphA2 in leukemias initiated by MLL-AF9 suggested that this protein might be a possible therapy target in this type of leukemia. We showed that treatment with EphA2 monoclonal antibody IF7 alone had no effect on tumorigenicity and latency of the MLL-AF9 leukemias, while targeting of EphA2 using EphA2 monoclonal antibody with a radioactive payload significantly impaired the leukemic process. Altogether, these results identify EphA2 as a potential radio-therapeutic target in leukemias with MLL translocation.

No MeSH data available.


Related in: MedlinePlus

EphA2 knockout bone marrow repopulating potential in primary and secondary recipients.(A) Whole-blood chimerism at 4, 8, 12 and 16 weeks after transplantation of EphA2 knockout or wild type bone marrow cells into lethally irradiated CD45.1 recipients (n = 5). (B) Analysis of bone marrow and spleen chimerism in 16 weeks after primary transplantation. (C) Whole-blood chimerism of secondary transplant at 4, 8, 12, 16, 20 and 24 weeks after transplantation of EphA2 knockout or wild type primary bone marrow cells into lethally irradiated CD45.1 recipient (n = 5). (D) Bone marrow and spleen chimerism analysis 24 weeks after secondary transplantation. Each dot on panel A and C corresponds to mean and error from all wild type or knockout blood chimerism. Each dot on panel B and D corresponds to one individual mouse. The data presented as percentage of blood, bone marrow and spleen chimerism. The data represent mean ± SEM. Unpaired t test was performed for statistical analyses.
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pone.0130692.g003: EphA2 knockout bone marrow repopulating potential in primary and secondary recipients.(A) Whole-blood chimerism at 4, 8, 12 and 16 weeks after transplantation of EphA2 knockout or wild type bone marrow cells into lethally irradiated CD45.1 recipients (n = 5). (B) Analysis of bone marrow and spleen chimerism in 16 weeks after primary transplantation. (C) Whole-blood chimerism of secondary transplant at 4, 8, 12, 16, 20 and 24 weeks after transplantation of EphA2 knockout or wild type primary bone marrow cells into lethally irradiated CD45.1 recipient (n = 5). (D) Bone marrow and spleen chimerism analysis 24 weeks after secondary transplantation. Each dot on panel A and C corresponds to mean and error from all wild type or knockout blood chimerism. Each dot on panel B and D corresponds to one individual mouse. The data presented as percentage of blood, bone marrow and spleen chimerism. The data represent mean ± SEM. Unpaired t test was performed for statistical analyses.

Mentions: An increase in frequency of ST-HSCs in EphA2 knockout mice was observed which might indicate an altered stem cell dynamics. To verify these results, we carried out competitive bone marrow transplantation experiments using EphA2 knockout and wild type BM. No significant differences were observed between EphA2 knockout mice and congenic controls at 4, 8, 12 and 16 weeks after transplantation (Fig 3A). Bone marrow and spleen chimerism analysis also showed no statistical difference between EphA2 knockout and control mice at week 16 (Fig 3B). A secondary competitive transplantation was performed to assess whether there might be more subtle effects of EphA2 knockout on long-term stem cell self-renewal. In the secondary transplant, although some mice showed a very low percentage of chimerism, perhaps due to limiting numbers of LT-HSCs in the transplanted cell population, there were no significant differences between EphA2 knockout and control mice (Fig 3C and 3D).


EphA2 Is a Therapy Target in EphA2-Positive Leukemias but Is Not Essential for Normal Hematopoiesis or Leukemia.

Charmsaz S, Beckett K, Smith FM, Bruedigam C, Moore AS, Al-Ejeh F, Lane SW, Boyd AW - PLoS ONE (2015)

EphA2 knockout bone marrow repopulating potential in primary and secondary recipients.(A) Whole-blood chimerism at 4, 8, 12 and 16 weeks after transplantation of EphA2 knockout or wild type bone marrow cells into lethally irradiated CD45.1 recipients (n = 5). (B) Analysis of bone marrow and spleen chimerism in 16 weeks after primary transplantation. (C) Whole-blood chimerism of secondary transplant at 4, 8, 12, 16, 20 and 24 weeks after transplantation of EphA2 knockout or wild type primary bone marrow cells into lethally irradiated CD45.1 recipient (n = 5). (D) Bone marrow and spleen chimerism analysis 24 weeks after secondary transplantation. Each dot on panel A and C corresponds to mean and error from all wild type or knockout blood chimerism. Each dot on panel B and D corresponds to one individual mouse. The data presented as percentage of blood, bone marrow and spleen chimerism. The data represent mean ± SEM. Unpaired t test was performed for statistical analyses.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4470658&req=5

pone.0130692.g003: EphA2 knockout bone marrow repopulating potential in primary and secondary recipients.(A) Whole-blood chimerism at 4, 8, 12 and 16 weeks after transplantation of EphA2 knockout or wild type bone marrow cells into lethally irradiated CD45.1 recipients (n = 5). (B) Analysis of bone marrow and spleen chimerism in 16 weeks after primary transplantation. (C) Whole-blood chimerism of secondary transplant at 4, 8, 12, 16, 20 and 24 weeks after transplantation of EphA2 knockout or wild type primary bone marrow cells into lethally irradiated CD45.1 recipient (n = 5). (D) Bone marrow and spleen chimerism analysis 24 weeks after secondary transplantation. Each dot on panel A and C corresponds to mean and error from all wild type or knockout blood chimerism. Each dot on panel B and D corresponds to one individual mouse. The data presented as percentage of blood, bone marrow and spleen chimerism. The data represent mean ± SEM. Unpaired t test was performed for statistical analyses.
Mentions: An increase in frequency of ST-HSCs in EphA2 knockout mice was observed which might indicate an altered stem cell dynamics. To verify these results, we carried out competitive bone marrow transplantation experiments using EphA2 knockout and wild type BM. No significant differences were observed between EphA2 knockout mice and congenic controls at 4, 8, 12 and 16 weeks after transplantation (Fig 3A). Bone marrow and spleen chimerism analysis also showed no statistical difference between EphA2 knockout and control mice at week 16 (Fig 3B). A secondary competitive transplantation was performed to assess whether there might be more subtle effects of EphA2 knockout on long-term stem cell self-renewal. In the secondary transplant, although some mice showed a very low percentage of chimerism, perhaps due to limiting numbers of LT-HSCs in the transplanted cell population, there were no significant differences between EphA2 knockout and control mice (Fig 3C and 3D).

Bottom Line: These studies showed that EphA2 does not have an obligatory role in normal hematopoiesis.We showed that treatment with EphA2 monoclonal antibody IF7 alone had no effect on tumorigenicity and latency of the MLL-AF9 leukemias, while targeting of EphA2 using EphA2 monoclonal antibody with a radioactive payload significantly impaired the leukemic process.Altogether, these results identify EphA2 as a potential radio-therapeutic target in leukemias with MLL translocation.

View Article: PubMed Central - PubMed

Affiliation: QIMR Berghofer Medical Research Institute, Brisbane, Australia.

ABSTRACT
Members of the Eph family of receptor tyrosine kinases and their membrane bound ephrin ligands have been shown to play critical roles in many developmental processes and more recently have been implicated in both normal and pathological processes in post-embryonic tissues. In particular, expression studies of Eph receptors and limited functional studies have demonstrated a role for the Eph/ephrin system in hematopoiesis and leukemogenesis. In particular, EphA2 was reported on hematopoietic stem cells and stromal cells. There are also reports of EphA2 expression in many different types of malignancies including leukemia, however there is a lack of knowledge in understanding the role of EphA2 in hematopoiesis and leukemogenesis. We explored the role of EphA2 in hematopoiesis by analyzing wild type and EphA2 knockout mice. Mature, differentiated cells, progenitors and hematopoietic stem cells derived from knockout and control mice were analyzed and no significant abnormality was detected. These studies showed that EphA2 does not have an obligatory role in normal hematopoiesis. Comparative studies using EphA2-negative MLL-AF9 leukemias derived from EphA2-knockout animals showed that there was no detectable functional role for EphA2 in the initiation or progression of the leukemic process. However, expression of EphA2 in leukemias initiated by MLL-AF9 suggested that this protein might be a possible therapy target in this type of leukemia. We showed that treatment with EphA2 monoclonal antibody IF7 alone had no effect on tumorigenicity and latency of the MLL-AF9 leukemias, while targeting of EphA2 using EphA2 monoclonal antibody with a radioactive payload significantly impaired the leukemic process. Altogether, these results identify EphA2 as a potential radio-therapeutic target in leukemias with MLL translocation.

No MeSH data available.


Related in: MedlinePlus