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A radiolabeled antibody targeting CD123(+) leukemia stem cells - initial radioimmunotherapy studies in NOD/SCID mice engrafted with primary human AML.

Leyton JV, Gao C, Williams B, Keating A, Minden M, Reilly RM - Leuk Res Rep (2015)

Bottom Line: Radioimmunotherapy (RIT) with anti-CD123 monoclonal antibody CSL360 modified with nuclear translocation sequence (NLS) peptides and labeled with the Auger electron-emitter, (111)In ((111)In-NLS-CSL360) was studied in the prevalent NOD/SCID mouse AML engraftment assay.Significant decreases in CD123(+) leukemic cells and impairment of leukemic stem cell self-renewal were achieved with high doses of RIT.At low non-toxic treatment doses, (111)In-NLS-CSL360 demonstrated a trend towards improved survival associated with decreased spleen/body weight ratio, an indicator of leukemia burden, and almost complete eradication of leukemia from the bone marrow in some mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmaceutical Sciences, University of Toronto, Toronto, ON, Canada.

ABSTRACT
Radioimmunotherapy (RIT) with anti-CD123 monoclonal antibody CSL360 modified with nuclear translocation sequence (NLS) peptides and labeled with the Auger electron-emitter, (111)In ((111)In-NLS-CSL360) was studied in the prevalent NOD/SCID mouse AML engraftment assay. Significant decreases in CD123(+) leukemic cells and impairment of leukemic stem cell self-renewal were achieved with high doses of RIT. However, NOD/SCID mice were very radiosensitive to these doses. At low non-toxic treatment doses, (111)In-NLS-CSL360 demonstrated a trend towards improved survival associated with decreased spleen/body weight ratio, an indicator of leukemia burden, and almost complete eradication of leukemia from the bone marrow in some mice.

No MeSH data available.


Related in: MedlinePlus

(A) Kaplan–Meier survival curve for NOD/SCID mice engrafted with CD34+/CD38−/CD123+ sorted cells from specimen 080179 and treated with radioimmunoconjugates (2–3 MBq; 5–10 μg). (B) Effect of treatment with radioimmunoconjugates on the spleen/body weight ratio at the study end-point. Also shown are the spleen/body weight ratios for sublethally-irradiated but non-engrafted NOD/SCID mice and engrafted mice receiving no treatment. Bars represent the mean±SD and values for individual mice are shown. Significant differences (P<0.05) are indicated by an asterisk.
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f0015: (A) Kaplan–Meier survival curve for NOD/SCID mice engrafted with CD34+/CD38−/CD123+ sorted cells from specimen 080179 and treated with radioimmunoconjugates (2–3 MBq; 5–10 μg). (B) Effect of treatment with radioimmunoconjugates on the spleen/body weight ratio at the study end-point. Also shown are the spleen/body weight ratios for sublethally-irradiated but non-engrafted NOD/SCID mice and engrafted mice receiving no treatment. Bars represent the mean±SD and values for individual mice are shown. Significant differences (P<0.05) are indicated by an asterisk.

Mentions: The survival of NOD/SCID mice engrafted with sorted CD34+/CD38−/CD123+ cells from specimen 080179 was evaluated following treatment with reduced doses of 111In-NLS-CSL360 (2–3 MBq (5–10 μg). There was a trend towards longer survival in mice treated with 111In-NLS-CSL360 compared to mice receiving 111In-CSL360 or untreated mice (median survival of 125, 110 and 95 days, respectively; Fig. 3A). The median survival of mice treated with 111In-NLS-chIgG1 was similar to that for 111In-NLS-CSL360 treated mice, possibly indicating a beneficial effect of non-targeted radiation. Because the spleen is also an organ for leukemic cell engraftment, which is characterized by gross splenomegaly [11], we evaluated the leukemic burden by determining the spleen/body weight ratio. All radioimmunoconjugates decreased the spleen/body weight ratio compared to untreated engrafted mice (Fig. 3B). This was not completely unexpected as the NOD/SCID mouse exhibits very low circulating immunoglobulin levels which cause non-specific sequestration of human IgG1 by Fc receptors on spleen cells [11]. This would cause leukemia cells to be irradiated by splenic accumulation of 111In-NLS-chIgG1. Nonetheless, there was a trend towards lower spleen/body weight ratios in mice treated with 111In-NLS-CSL360. The spleen/body weight ratios were 2.9-, 2.3 and 1.8-fold lower compared to untreated AML-engrafted mice for 111In-NLS-CSL360, 111In-CSL360 and 111In-NLS-chIgG1, respectively. The spleen/body weight ratio was increased by 15-fold in mice engrafted with AML compared to sublethally irradiated but non-engrafted mice, demonstrating splenomegaly associated with leukemia involvement. In mice treated with 111In-NLS-CSL360, analysis of the BM of the two surviving mice showed only 0.04% and 0.03% hCD45+ cells, whereas non-surviving mice treated with 111In-NLS-CSL360 had 80.7% and 86.9% hCD45+ cells in their BM. The percentage of hCD45+ cells in the BM for untreated AML-engrafted mice ranged from 65.6% to 81.6%. These results are encouraging because they demonstrate that leukemia in mice inoculated with a high number (2.5×105 cells/mouse) of CD123+ LSCs could still be targeted and impaired by a single low radioactivity dose of 111In-NLS-CSL360 and in two cases, was almost completely eradicated from the BM.


A radiolabeled antibody targeting CD123(+) leukemia stem cells - initial radioimmunotherapy studies in NOD/SCID mice engrafted with primary human AML.

Leyton JV, Gao C, Williams B, Keating A, Minden M, Reilly RM - Leuk Res Rep (2015)

(A) Kaplan–Meier survival curve for NOD/SCID mice engrafted with CD34+/CD38−/CD123+ sorted cells from specimen 080179 and treated with radioimmunoconjugates (2–3 MBq; 5–10 μg). (B) Effect of treatment with radioimmunoconjugates on the spleen/body weight ratio at the study end-point. Also shown are the spleen/body weight ratios for sublethally-irradiated but non-engrafted NOD/SCID mice and engrafted mice receiving no treatment. Bars represent the mean±SD and values for individual mice are shown. Significant differences (P<0.05) are indicated by an asterisk.
© Copyright Policy - CC BY-NC-ND
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4588397&req=5

f0015: (A) Kaplan–Meier survival curve for NOD/SCID mice engrafted with CD34+/CD38−/CD123+ sorted cells from specimen 080179 and treated with radioimmunoconjugates (2–3 MBq; 5–10 μg). (B) Effect of treatment with radioimmunoconjugates on the spleen/body weight ratio at the study end-point. Also shown are the spleen/body weight ratios for sublethally-irradiated but non-engrafted NOD/SCID mice and engrafted mice receiving no treatment. Bars represent the mean±SD and values for individual mice are shown. Significant differences (P<0.05) are indicated by an asterisk.
Mentions: The survival of NOD/SCID mice engrafted with sorted CD34+/CD38−/CD123+ cells from specimen 080179 was evaluated following treatment with reduced doses of 111In-NLS-CSL360 (2–3 MBq (5–10 μg). There was a trend towards longer survival in mice treated with 111In-NLS-CSL360 compared to mice receiving 111In-CSL360 or untreated mice (median survival of 125, 110 and 95 days, respectively; Fig. 3A). The median survival of mice treated with 111In-NLS-chIgG1 was similar to that for 111In-NLS-CSL360 treated mice, possibly indicating a beneficial effect of non-targeted radiation. Because the spleen is also an organ for leukemic cell engraftment, which is characterized by gross splenomegaly [11], we evaluated the leukemic burden by determining the spleen/body weight ratio. All radioimmunoconjugates decreased the spleen/body weight ratio compared to untreated engrafted mice (Fig. 3B). This was not completely unexpected as the NOD/SCID mouse exhibits very low circulating immunoglobulin levels which cause non-specific sequestration of human IgG1 by Fc receptors on spleen cells [11]. This would cause leukemia cells to be irradiated by splenic accumulation of 111In-NLS-chIgG1. Nonetheless, there was a trend towards lower spleen/body weight ratios in mice treated with 111In-NLS-CSL360. The spleen/body weight ratios were 2.9-, 2.3 and 1.8-fold lower compared to untreated AML-engrafted mice for 111In-NLS-CSL360, 111In-CSL360 and 111In-NLS-chIgG1, respectively. The spleen/body weight ratio was increased by 15-fold in mice engrafted with AML compared to sublethally irradiated but non-engrafted mice, demonstrating splenomegaly associated with leukemia involvement. In mice treated with 111In-NLS-CSL360, analysis of the BM of the two surviving mice showed only 0.04% and 0.03% hCD45+ cells, whereas non-surviving mice treated with 111In-NLS-CSL360 had 80.7% and 86.9% hCD45+ cells in their BM. The percentage of hCD45+ cells in the BM for untreated AML-engrafted mice ranged from 65.6% to 81.6%. These results are encouraging because they demonstrate that leukemia in mice inoculated with a high number (2.5×105 cells/mouse) of CD123+ LSCs could still be targeted and impaired by a single low radioactivity dose of 111In-NLS-CSL360 and in two cases, was almost completely eradicated from the BM.

Bottom Line: Radioimmunotherapy (RIT) with anti-CD123 monoclonal antibody CSL360 modified with nuclear translocation sequence (NLS) peptides and labeled with the Auger electron-emitter, (111)In ((111)In-NLS-CSL360) was studied in the prevalent NOD/SCID mouse AML engraftment assay.Significant decreases in CD123(+) leukemic cells and impairment of leukemic stem cell self-renewal were achieved with high doses of RIT.At low non-toxic treatment doses, (111)In-NLS-CSL360 demonstrated a trend towards improved survival associated with decreased spleen/body weight ratio, an indicator of leukemia burden, and almost complete eradication of leukemia from the bone marrow in some mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmaceutical Sciences, University of Toronto, Toronto, ON, Canada.

ABSTRACT
Radioimmunotherapy (RIT) with anti-CD123 monoclonal antibody CSL360 modified with nuclear translocation sequence (NLS) peptides and labeled with the Auger electron-emitter, (111)In ((111)In-NLS-CSL360) was studied in the prevalent NOD/SCID mouse AML engraftment assay. Significant decreases in CD123(+) leukemic cells and impairment of leukemic stem cell self-renewal were achieved with high doses of RIT. However, NOD/SCID mice were very radiosensitive to these doses. At low non-toxic treatment doses, (111)In-NLS-CSL360 demonstrated a trend towards improved survival associated with decreased spleen/body weight ratio, an indicator of leukemia burden, and almost complete eradication of leukemia from the bone marrow in some mice.

No MeSH data available.


Related in: MedlinePlus