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Treatment of acute lymphoblastic leukemia with an rGel/BLyS fusion toxin.

Parameswaran R, Yu M, Lyu MA, Lim M, Rosenblum MG, Groffen J, Heisterkamp N - Leukemia (2012)

Bottom Line: Here, we demonstrate that rGel/BLyS binds to ALL cells expressing BAFF receptor (BAFF-R) and upon internalization, it induces apoptosis of these cells and causes downregulation of survival genes even in the presence of stromal protection.Using an immunodeficient transplant model for human ALL, we show that rGel/BLyS prolongs survival of both Philadelphia chromosome-positive and negative ALL-bearing mice.Furthermore, we used AMD3100, a CXCR4 antagonist, to mobilize the leukemic cells protected in the bone marrow (BM) microenvironment and the combination with rGel/BLyS resulted in a significant reduction of the tumor load in the BM and complete eradication of ALL cells from the circulation.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular Carcinogenesis, Division of Hematology/Oncology and The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.

ABSTRACT
Acute lymphoblastic leukemia (ALL) is the most common malignancy affecting children and a major cause of mortality from hematopoietic malignancies in adults. A substantial number of patients become drug resistant during chemotherapy, necessitating the development of alternative modes of treatment. rGel (recombinant Gelonin)/BlyS (B-lymphocyte stimulator) is a toxin-cytokine fusion protein used for selective killing of malignant B-cells expressing receptors for B-cell-activating factor (BAFF/BLyS) by receptor-targeted delivery of the toxin, Gelonin. Here, we demonstrate that rGel/BLyS binds to ALL cells expressing BAFF receptor (BAFF-R) and upon internalization, it induces apoptosis of these cells and causes downregulation of survival genes even in the presence of stromal protection. Using an immunodeficient transplant model for human ALL, we show that rGel/BLyS prolongs survival of both Philadelphia chromosome-positive and negative ALL-bearing mice. Furthermore, we used AMD3100, a CXCR4 antagonist, to mobilize the leukemic cells protected in the bone marrow (BM) microenvironment and the combination with rGel/BLyS resulted in a significant reduction of the tumor load in the BM and complete eradication of ALL cells from the circulation. Thus, a combination treatment with the B-cell-specific fusion toxin rGel/BLyS and the mobilizing agent AMD3100 could be an effective alternative approach to chemotherapy for the treatment of primary and relapsed ALL.

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rGel/BLyS monotreatment prolongs survival in an ALL transplant model(A) Experimental outline. Treatment with saline or rGel/BLyS (3.75 mg/kg) was started 6 days after transplant. n= 5/group. Total amount of rGel/BLyS injected, 22.5 mg/kg (B) Survival of mice treated with saline (circles), or rGel/BLyS (squares). *p= 0.002, control compared with rGel/BLyS group. (C, D) Human leukemia cells in the peripheral blood (C) or bone marrow (D) of saline-treated mice at sacrifice compared to rGel/BLyS-treated mice, as detected by FACS analysis for human CD19 and CD10. (E) Representative FACS plot (left) and FACS analysis showing the percentage of BAFF-R positive CD19+ CD10+ gated cells in the bone marrow of rGel/BLyS treated group (right). Each bar represents a single mouse BM sample.
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Figure 4: rGel/BLyS monotreatment prolongs survival in an ALL transplant model(A) Experimental outline. Treatment with saline or rGel/BLyS (3.75 mg/kg) was started 6 days after transplant. n= 5/group. Total amount of rGel/BLyS injected, 22.5 mg/kg (B) Survival of mice treated with saline (circles), or rGel/BLyS (squares). *p= 0.002, control compared with rGel/BLyS group. (C, D) Human leukemia cells in the peripheral blood (C) or bone marrow (D) of saline-treated mice at sacrifice compared to rGel/BLyS-treated mice, as detected by FACS analysis for human CD19 and CD10. (E) Representative FACS plot (left) and FACS analysis showing the percentage of BAFF-R positive CD19+ CD10+ gated cells in the bone marrow of rGel/BLyS treated group (right). Each bar represents a single mouse BM sample.

Mentions: We next examined the ability of rGel/BLyS to suppress pre-B ALL growth in an in vivo NSG mouse model of human ALL. We transplanted US7 cells into NSG mice and allowed the cells to proliferate for 6 days to form an appreciable tumor burden, as detected by FACS analysis of PB (Suppl. Figure 2A). Then 3.75 mg/kg rGel/BLyS was administered bi-weekly for 3 weeks (Figure 4A). Mice not receiving treatment had to be sacrificed at around day 34 whereas mice treated with rGel/BLyS survived significantly (p=0.002) longer (Figure 4B). Remarkably, FACS analysis of PB from mice treated with rGel/BLyS, using human CD19 and CD10 antibodies, showed that the treatment had eliminated virtually all circulating leukemia cells (Figure 4C). However, the BM of these mice clearly contained leukemic cells (Figure 4D). We considered the possibility that the relapsed ALL cells in the BM were selected for loss of BAFF-R expression and thus escaped from rGel/BLyS-induced apoptosis. However, FACS analysis of the ALL cells in the BM of rGel/BLyS treated mice demonstrated that these cells uniformly expressed high levels of the BAFF-R (Figure 4E).


Treatment of acute lymphoblastic leukemia with an rGel/BLyS fusion toxin.

Parameswaran R, Yu M, Lyu MA, Lim M, Rosenblum MG, Groffen J, Heisterkamp N - Leukemia (2012)

rGel/BLyS monotreatment prolongs survival in an ALL transplant model(A) Experimental outline. Treatment with saline or rGel/BLyS (3.75 mg/kg) was started 6 days after transplant. n= 5/group. Total amount of rGel/BLyS injected, 22.5 mg/kg (B) Survival of mice treated with saline (circles), or rGel/BLyS (squares). *p= 0.002, control compared with rGel/BLyS group. (C, D) Human leukemia cells in the peripheral blood (C) or bone marrow (D) of saline-treated mice at sacrifice compared to rGel/BLyS-treated mice, as detected by FACS analysis for human CD19 and CD10. (E) Representative FACS plot (left) and FACS analysis showing the percentage of BAFF-R positive CD19+ CD10+ gated cells in the bone marrow of rGel/BLyS treated group (right). Each bar represents a single mouse BM sample.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3376225&req=5

Figure 4: rGel/BLyS monotreatment prolongs survival in an ALL transplant model(A) Experimental outline. Treatment with saline or rGel/BLyS (3.75 mg/kg) was started 6 days after transplant. n= 5/group. Total amount of rGel/BLyS injected, 22.5 mg/kg (B) Survival of mice treated with saline (circles), or rGel/BLyS (squares). *p= 0.002, control compared with rGel/BLyS group. (C, D) Human leukemia cells in the peripheral blood (C) or bone marrow (D) of saline-treated mice at sacrifice compared to rGel/BLyS-treated mice, as detected by FACS analysis for human CD19 and CD10. (E) Representative FACS plot (left) and FACS analysis showing the percentage of BAFF-R positive CD19+ CD10+ gated cells in the bone marrow of rGel/BLyS treated group (right). Each bar represents a single mouse BM sample.
Mentions: We next examined the ability of rGel/BLyS to suppress pre-B ALL growth in an in vivo NSG mouse model of human ALL. We transplanted US7 cells into NSG mice and allowed the cells to proliferate for 6 days to form an appreciable tumor burden, as detected by FACS analysis of PB (Suppl. Figure 2A). Then 3.75 mg/kg rGel/BLyS was administered bi-weekly for 3 weeks (Figure 4A). Mice not receiving treatment had to be sacrificed at around day 34 whereas mice treated with rGel/BLyS survived significantly (p=0.002) longer (Figure 4B). Remarkably, FACS analysis of PB from mice treated with rGel/BLyS, using human CD19 and CD10 antibodies, showed that the treatment had eliminated virtually all circulating leukemia cells (Figure 4C). However, the BM of these mice clearly contained leukemic cells (Figure 4D). We considered the possibility that the relapsed ALL cells in the BM were selected for loss of BAFF-R expression and thus escaped from rGel/BLyS-induced apoptosis. However, FACS analysis of the ALL cells in the BM of rGel/BLyS treated mice demonstrated that these cells uniformly expressed high levels of the BAFF-R (Figure 4E).

Bottom Line: Here, we demonstrate that rGel/BLyS binds to ALL cells expressing BAFF receptor (BAFF-R) and upon internalization, it induces apoptosis of these cells and causes downregulation of survival genes even in the presence of stromal protection.Using an immunodeficient transplant model for human ALL, we show that rGel/BLyS prolongs survival of both Philadelphia chromosome-positive and negative ALL-bearing mice.Furthermore, we used AMD3100, a CXCR4 antagonist, to mobilize the leukemic cells protected in the bone marrow (BM) microenvironment and the combination with rGel/BLyS resulted in a significant reduction of the tumor load in the BM and complete eradication of ALL cells from the circulation.

View Article: PubMed Central - PubMed

Affiliation: Section of Molecular Carcinogenesis, Division of Hematology/Oncology and The Saban Research Institute, Children's Hospital Los Angeles, Los Angeles, CA 90027, USA.

ABSTRACT
Acute lymphoblastic leukemia (ALL) is the most common malignancy affecting children and a major cause of mortality from hematopoietic malignancies in adults. A substantial number of patients become drug resistant during chemotherapy, necessitating the development of alternative modes of treatment. rGel (recombinant Gelonin)/BlyS (B-lymphocyte stimulator) is a toxin-cytokine fusion protein used for selective killing of malignant B-cells expressing receptors for B-cell-activating factor (BAFF/BLyS) by receptor-targeted delivery of the toxin, Gelonin. Here, we demonstrate that rGel/BLyS binds to ALL cells expressing BAFF receptor (BAFF-R) and upon internalization, it induces apoptosis of these cells and causes downregulation of survival genes even in the presence of stromal protection. Using an immunodeficient transplant model for human ALL, we show that rGel/BLyS prolongs survival of both Philadelphia chromosome-positive and negative ALL-bearing mice. Furthermore, we used AMD3100, a CXCR4 antagonist, to mobilize the leukemic cells protected in the bone marrow (BM) microenvironment and the combination with rGel/BLyS resulted in a significant reduction of the tumor load in the BM and complete eradication of ALL cells from the circulation. Thus, a combination treatment with the B-cell-specific fusion toxin rGel/BLyS and the mobilizing agent AMD3100 could be an effective alternative approach to chemotherapy for the treatment of primary and relapsed ALL.

Show MeSH
Related in: MedlinePlus