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Recombinant toxins containing human granulocyte-macrophage colony-stimulating factor and either pseudomonas exotoxin or diphtheria toxin kill gastrointestinal cancer and leukemia cells.

Abstract：

:The granulocyte-macrophage colony-stimulating factor receptor (GM-CSFR) is a potential target for toxin-directed therapy, because it is overexpressed on many leukemias and solid tumors and apparently not on stem cells. To investigate the potential therapeutic use of GM-CSF toxins, we fused human GM-CSF to truncated forms of either Pseudomonas exotoxin (PE) or diphtheria toxin (DT) and tested the cytotoxicity of the resulting GM-CSF-PE38KDEL and DT388-GM-CSF on human gastrointestinal (GI) carcinomas and leukemias. Toward gastric and colon cancer cell lines, GM-CSF-PE38KDEL was much more cytotoxic than DT388-GM-CSF, with IC50s (concentration resulting in 50% inhibition of protein synthesis) of 0.5 to 10 ng/mL compared with 4 to 400 ng/mL, respectively. In contrast, toward leukemia lines and fresh bone marrow cells DT388-GM-CSF was more cytotoxic than GM-CSF-PE38KDEL. The cytotoxicity of both GM-CSF-PE38KDEL and DT388-GM-CSF toward the human cells was specific, because it could be competed by an excess of GM-CSF. Binding studies indicated that human GM-CSF receptors were present on all of the human GI and leukemic cell lines tested, at levels of 540 to 3,700 sites per cell (kd = 0.2 to 2 nmol/L), and the number of sites per cell did not correlate with the cell type. A similar pattern of cytotoxicity was found with recombinant immunotoxins binding to the transferrin receptor, in that anti-TFR(Fv)-PE38KDEL was much more cytotoxic than DT388-anti-TFR(Fv) toward GI cells, but both were similar in their cytotoxic activity toward leukemia cells. The fact that PE is more effective than DT in killing GI but not leukemic tumor cells targeted by GM-CSF indicates a fundamental difference in the way PE or DT gains access to the cytosol in these cells. GM-CSF-PE38KDEL and DT388-GM-CSF deserve further evaluation as possible treatments for selected tumors.

journal_name

Blood

journal_title

Blood

authors

Kreitman RJ,Pastan I

subject

Has Abstract

pub_date

1997-07-01 00:00:00

pages

252-9

issue

eissn

0006-4971

issn

1528-0020

journal_volume

pub_type

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Recombinant toxins containing human granulocyte-macrophage colony-stimulating factor and either pseudomonas exotoxin or diphtheria toxin kill gastrointestinal cancer and leukemia cells.