TY - JOUR
T1 - Pediatric acute myelogenous leukemia cells express IL-6 receptors and are sensitive to a recombinant IL6-Pseudomonas exotoxin
AU - Boayue, K. B.
AU - Gu, L.
AU - Yeager, A. M.
AU - Kreitman, R. J.
AU - Findley, H. W.
N1 - Funding Information:
This work was supported by grants to HWF from CURE Childhood Cancer, Inc, and from the Parker Hughes Trust, Los Angeles, CA, the Winship Cancer Center of Emory University, and the National Cancer Institute, National Institutes of Health, Bethesda MD (R29 CA72020-01). The paper was presented in part at the annual meeting of the American Society for Hematology, December 1995. We would like to thank Dr Ira Pastan, Laboratory of Molecular Biology, National Cancer Institute, for supplying the recombinant toxins and for review of the manuscript. We also thank Dr Kevin Sullivan, Department of Biostatistics, Emory University School of Public Health, for performing the statistical analysis.
PY - 1998
Y1 - 1998
N2 - We have studied IL-6 receptor (IL-6R) expression on AML cells from 15 pediatric patients by immunocytochemistry/flow cytometry, reverse-transcription polymerase chain reaction, and Scatchard analysis. High-affinity IL-6R were detected on leukemic cells from 12 (80%) patients. Binding sites per cell ranged from 140 to 3580 (median 920; mean 1240), with dissociation constants of 0.26 to 0.71 nM. We therefore assessed the in vitro sensitivity of IL-6R+ AML cells to treatment with a recombinant IL6-Pseudomonas exotoxin fusion protein (IL6-PE(4E)), using the XTT cytotoxicity assay. Leukemic cells from eight patients had ID50 values (concentration of IL6-PE(4E) producing a 50% decrease in cell viability) of < 1000 ng/ml (median, 87 ng/ml; mean, 262 ng/ml). Sensitivity to IL6-PE(4E) correlated significantly with receptor number. Normal bone marrow mononuclear cells had undetectable IL6-R expression (< 20 receptors/cell) and were relatively resistant to IL6-PE(4E). To test the efficacy of IL6-PE(4E) for ex vivo purging in an autologous stem cell transplantation setting, we incubated primary IL-6R+ AML cells with 103 ng/ml IL6-PE(4E) for 24 h, followed by inoculation into SCID mice. Mice receiving treated cells showed no leukemic engraftment, while all mice receiving untreated or control-treated cells developed leukemia with a median presymptomatic interval of 55 days. In recipients of IL6-PE(4E) treated cells, no evidence of occult leukemia was detected by PCR analysis of blood and bone marrow cells at 185 days postinoculation. These data suggest that IL-6R are expressed on leukemic cells from a substantial percentage of pediatric AML patients. Furthermore, leukemic cells expressing high numbers of IL6-R may be sensitive to IL6-PE(4E) in an ex vivo purging protocol.
AB - We have studied IL-6 receptor (IL-6R) expression on AML cells from 15 pediatric patients by immunocytochemistry/flow cytometry, reverse-transcription polymerase chain reaction, and Scatchard analysis. High-affinity IL-6R were detected on leukemic cells from 12 (80%) patients. Binding sites per cell ranged from 140 to 3580 (median 920; mean 1240), with dissociation constants of 0.26 to 0.71 nM. We therefore assessed the in vitro sensitivity of IL-6R+ AML cells to treatment with a recombinant IL6-Pseudomonas exotoxin fusion protein (IL6-PE(4E)), using the XTT cytotoxicity assay. Leukemic cells from eight patients had ID50 values (concentration of IL6-PE(4E) producing a 50% decrease in cell viability) of < 1000 ng/ml (median, 87 ng/ml; mean, 262 ng/ml). Sensitivity to IL6-PE(4E) correlated significantly with receptor number. Normal bone marrow mononuclear cells had undetectable IL6-R expression (< 20 receptors/cell) and were relatively resistant to IL6-PE(4E). To test the efficacy of IL6-PE(4E) for ex vivo purging in an autologous stem cell transplantation setting, we incubated primary IL-6R+ AML cells with 103 ng/ml IL6-PE(4E) for 24 h, followed by inoculation into SCID mice. Mice receiving treated cells showed no leukemic engraftment, while all mice receiving untreated or control-treated cells developed leukemia with a median presymptomatic interval of 55 days. In recipients of IL6-PE(4E) treated cells, no evidence of occult leukemia was detected by PCR analysis of blood and bone marrow cells at 185 days postinoculation. These data suggest that IL-6R are expressed on leukemic cells from a substantial percentage of pediatric AML patients. Furthermore, leukemic cells expressing high numbers of IL6-R may be sensitive to IL6-PE(4E) in an ex vivo purging protocol.
KW - AML
KW - IL6-Pseudomonas exotoxin
KW - Interleukin-6 receptor
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U2 - 10.1038/sj.leu.2400914
DO - 10.1038/sj.leu.2400914
M3 - Article
C2 - 9519780
AN - SCOPUS:0031932142
SN - 0887-6924
VL - 12
SP - 182
EP - 191
JO - Leukemia
JF - Leukemia
IS - 2
ER -