Southwestern Internal Medicine Conference: clinical use of hematopoietic growth factors

Effect of recombinant human granulocyte colony-stimulating factor (rhG-CSF) on leukocyte count and survival rate of dogs with parvoviral enteritis

Dogs with clinical signs consistent with parvoviral enteritis and leukopenia (total leukocyte count < 5.0 x 10(9) l(-1)) were included in this randomised double-blind study (treatment group: n = 22; control group: n = 21). The dogs in the treatment group received a subcutaneous daily injection of 10 microg kg(-1) of recombinant human granulocyte colony-stimulating factor (rhG-CSF) for 5 days. Clinical and blood investigations were performed prior to the first injection, daily during the treatment period and on the day after treatment ended, and then once more, 26 days after the first injection. During the study, no significant differences were found between the two groups with respect to survival rate (treatment group: 68 per cent; control group: 71 per cent, P > 0 4, Fisher-Test) and other clinical findings. Similarly the total leukocyte count, neutrophil count and other haematologic and biochemical parameters did not differ significantly between the groups, based on differences from initial values (P > 0 05). Consequently, the use of rhG-CSF in the treatment of dogs with parvoviral enteritis cannot be recommended.

Effective acute desensitization for immediate-type hypersensitivity to human granulocyte-monocyte colony stimulating factor

BACKGROUND

Granulocyte-monocyte colony stimulating factor (GM-CSF) is the treatment of choice for patients with life threatening neutropenias. Hypersensitivity to GM-CSF may lead to cessation of treatment. Acute desensitization is an alternative mode of managing drug hypersensitivity, especially when other common modes like substitution of offending drug or premedication with antihistamines and/or corticosteroids are not available or fail.

CASE REPORT

A 42-year-old woman with a 17-year history of severe chronic mucocutaneous candidal infections became resistant to all common antifungal drugs. As her disorder was associated with defective functions of monocytes and granulocytes, GM-CSF treatment was started yielding a very good clinical effect. After a short period of treatment, however, the patient developed anaphylactic reactions which could not be abolished by preadministration of antihistamines and/or corticosteroids. Replacement of therapy by G-CSF caused identical hypersensitivity phenomena.

METHODS

Prick skin tests with 100, 200, or 400 microg/mL of GM-CSF or G-CSF, using also negative and positive controls, were performed on the patient and three healthy control subjects. A positive local reaction was observed only in patient at the prick point of 200 microg/mL GM-CSF or 400 microg/mL G-CSF. Acute desensitization to GM-CSF was initiated adopting a protocol used for parenteral desensitization to penicillin.

RESULTS

The patient tolerated the desensitization procedure very well and we could resume the administration of GM-CSF. For the past 30 months the patient has been treated uneventfully by subcutaneous administration of GM-CSF, 500 microg twice weekly, and is free of candidal infections. Skin prick tests were repeated 1 month postdesensitization and resulted in a very weak response to GM-CSF compared with the predesensitization response.

CONCLUSIONS

Acute desensitization can be utilized in patients who develop drug hypersensitivity reactions to GM-CSF. As GM-CSF is a very unique agent and in most cases cannot be replaced by another one, acute desensitization may play a very important role in managing failure of GM-CSF treatment due to hypersensitivity reactions.

Accelerated recovery from cyclophosphamide-induced leukopenia in mice administered a Japanese ethical herbal drug, Hochu-ekki-to

The effect of a Japanese ethical herbal drug, Hochu-ekki-to (HOT), on recovery from leukopenia induced by cyclophosphamide (CY) was investigated. Daily oral administration of 1000 mg/kg HOT into CY-treated mice significantly prevented decrease of leukocyte numbers in the peripheral blood and accelerated recovery from leukopenia. Ginsenoside Rgl extracted from Ginseng radix, a major herb of HOT, was one of the active ingredients. HOT increased numbers of neutrophils and monocytes in the peripheral blood compared with CY-treated control. Moreover, HOT augmented the resistance against Pseudomonas aeruginosa infection. The number of colony-forming units in the spleen (CFU-S) also increased in HOT-treated mice. The frequencies of IL-3-, GM-CSF- and IFN-gamma-producing cells increased in the spleen, bone marrow, liver and IEL on HOT treatment, and HOT clearly augmented the expressions of IL-3, GM-CSF and IFN-gamma mRNA in the spleen, bone marrow, liver and IEL except IL-3 and IFN-gamma mRNA in the IEL. These results suggest that HOT enhances the production of hematopoietic lymphokines, stimulates the proliferation of hematopoietic progenitor cells and consequently accelerates recovery from leukopenia in CY-treated mice. Additionally, IFN-gamma which HOT-augmented the production may contribute the protective effect against the bacterial infection by activating of phagocyte cells.

Recombinant Toxins Containing Human Granulocyte-Macrophage Colony-Stimulating Factor and Either Pseudomonas Exotoxin or Diphtheria Toxin Kill Gastrointestinal Cancer and Leukemia Cells

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.

Recombinant Toxins Containing Human Granulocyte-Macrophage Colony-Stimulating Factor and Either Pseudomonas Exotoxin or Diphtheria Toxin Kill Gastrointestinal Cancer and Leukemia Cells

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.

Prolonged expression of therapeutic levels of human granulocyte colony-stimulating factor in rats following gene transfer to skeletal muscle

Gene transfer to skeletal muscle was examined as a means of gene therapy for neutropenia. A recombinant retrovirus containing a human granulocyte colony-stimulating factor (G-CSF) gene was introduced into primary human or rat myoblasts, which were then shown to produce biologically active G-CSF. Transplantation of G-CSF-producing rat myoblasts into the muscle of syngeneic rats resulted in a 15-fold increase in absolute neutrophil counts. This increase correlated with detection of circulating human G-CSF protein throughout the 6-month duration of the experiment. These results clearly demonstrate long-term production of therapeutically relevant amounts of a human protein by normal cells in vivo.

Apoptosis in the pathogenesis and treatment of disease

In multicellular organisms, homeostasis is maintained through a balance between cell proliferation and cell death. Although much is known about the control of cell proliferation, less is known about the control of cell death. Physiologic cell death occurs primarily through an evolutionarily conserved form of cell suicide termed apoptosis. The decision of a cell to undergo apoptosis can be influenced by a wide variety of regulatory stimuli. Recent evidence suggests that alterations in cell survival contribute to the pathogenesis of a number of human diseases, including cancer, viral infections, autoimmune diseases, neurodegenerative disorders, and AIDS (acquired immunodeficiency syndrome). Treatments designed to specifically alter the apoptotic threshold may have the potential to change the natural progression of some of these diseases.