Experimental basis for the treatment of autoimmune diseases with autologous hematopoietic stem cell transplantation.

Preclinical research with autologous bone marrow transplantation has been performed in two models of autoimmune disease using Buffalo rats. In this strain, adjuvant arthritis develops as a chronic progressive systemic type of arthritis and experimental allergic encephalomyelitis as a chronic remitting relapsing disease. In these models, the influence of various treatment parameters was studied, among them the conditioning regimen, the composition of the graft and the effect of reimmunization of cured animals. Continued research in animal models is recommended to solve problems that have emerged from the experience with several hundreds of severely ill autoimmune patients treated thus far with autologous stem cells.

Experimental basis of hematopoietic stem cell transplantation for treatment of autoimmune diseases.

Experiments with animal models of autoimmune disease provided the rational and stimulus for the current, clinical studies of autologous stem cell transplantation for the treatment of a variety of severe, refractory, autoimmune diseases. The discoveries that led to the recognition of the key role of hematopoietic stem cells and the successful treatment of autoimmune diseases with bone marrow transplants are reviewed. The relevance of spontaneous and induced autoimmune disease models for the development of clinical treatment regimens is discussed. Most of the investigations with autologous stem cell transplantation have been performed with induced autoimmune disorders: in rats with adjuvant arthritis and in rats or mice with experimental, allergic encephalomyelitis, the current model for multiple sclerosis. The main aspects of this translational research were the conditioning regimens and the degree of T cell depletion of the graft as determinants of remission induction and the incidence of relapses. The emerging recommendations are compared with the outcome so far of the clinical studies.

The effects of fractionated gamma irradiation on induction of mammary carcinoma in normal and estrogen-treated rats.

The effects of dose fractionation on induction of mammary carcinoma were studied in normal and estrogen-treated female rats of the inbred WAG/Rij strain. Groups of 40 animals received total-body doses of 1 or 2 Gy of (137)Cs gamma radiation, administered in fractions of 2.5, 10 or 40 mGy with intervals of 12 h, or in fractions of 10 mGy with intervals of 2, 5 or 24 h. The irradiations were started at the age of 8 weeks. Estrogen treatment was accomplished by implantation of a pellet containing estrogen at the age of 6 weeks. All mammary tumors were resected and classified histologically as carcinoma or fibroadenoma. The age-specific incidence of mammary carcinoma was compared with that in control groups of unirradiated normal or estrogen-treated rats and was expressed as excess normalized risk, using lifetime statistical analysis with both parametric and nonparametric methods. The data were also compared to the results of single-dose experiments reported in previous papers. Fractionated irradiation increased the risk of mammary cancer in both normal and estrogen-treated rats compared to the corresponding unirradiated control group. The excess normalized risk per unit of total dose was approximately equal with or without estrogen treatment. Without estrogen treatment, the effects of the single-dose and fractionated irradiations were approximately equal. In estrogen-treated animals, however, single-dose irradiation was up to 15 times more carcinogenic than the fractionated exposures. This fractionation effect appeared to vanish for total doses below approximately 0.3 Gy. With estrogen treatment, the excess normalized risk was significantly higher for dose fractions of 40 mGy than for fractions of 10 mGy. The risk was also markedly higher for fractionation intervals of 2 or 5 h than for intervals of 12 or 24 h. The results of these experiments show that the effects of dose fractionation on the induction of mammary carcinoma may depend on hormonal status, the total dose delivered, the dose per fraction, and the fractionation interval.

Stem cell transplantation in experimental models of autoimmune disease.

A review of the experiments with animal models of autoimmune disease (AID) that have provided the rationale for the present clinical investigations on the use of autologous stem cells for treating patients with severe refractory AID. The various types of AID in laboratory animals and the recognition of the key-role of hematopoietic stem cells (HSC) in AID are discussed. Two animal models were employed for translational research on autologous bone marrow transplantation (BMT): adjuvant arthritis (AA) as model for rheumatoid arthritis (RA) and experimental allergic encephalomyelitis (EAE) as model for multiple sclerosis (MS). The principal aspects of the treatment, i.e., conditioning agents and doses and T cell depletion of the autograft, were investigated in relation to remission induction and the incidence of relapses.

Conditioning regimens for the treatment of experimental arthritis with autologous bone marrow transplantation.

Adjuvant induced arthritis (AA) in Buffalo rats is a chronic progressive disease that responds very well to treatment with myeloablation and rescue with autologous BM. These previous results were obtained by conditioning with a lethal single dose of TBI. In the present study various other conditioning regimens were compared with single dose TBI. Fractionated TBI using adjusted total dose was equally effective. CY and BU when used as single agents at the highest tolerated dose were less effective. Combinations of CY (2 x 60 mg/kg) with lower dose (4 Gy) TBI and of BU with CY were as beneficial as high-dose TBI. These results indicate that a very intense reduction of T lymphocytes, in the order of 3-4 log, is required for obtaining the highest rate of long-lasting complete remissions. A similar conclusion was reached from our studies of various conditioning regimens in rats suffering from experimental allergic encephalitis (EAE). If extrapolated to the clinic, such a degree of T lymphocyte eradication poses upper limits to the number of T lymphocytes that can be safely reintroduced with the autograft. The exact limits cannot be derived from these experiments because the addition of autologous T lymphocytes to the graft yielded different results in the two models of autoimmune disease (AID).

The carcinogenic risk of high dose total body irradiation in non-human primates.

PURPOSE: High dose total body irradiation (TBI) in combination with chemotherapy, followed by rescue with bone marrow transplantation (BMT), is increasingly used for the treatment of haematological malignancies. With the increasing success of this treatment and its current introduction for treating refractory autoimmune diseases the risk of radiation carcinogenesis is of growing concern. Studies on tumour induction in non-human primates are of relevance in this context since the response of this species to radiation does not differ much from that in man. MATERIALS AND METHODS: Since the early sixties, studies have been performed on acute effects in Rhesus monkeys and the protective action of bone marrow transplantation after irradiation with X-rays (average total body dose 6.8 Gy) and fission neutrons (average dose 3.4 Gy). Of those monkeys, which were irradiated and reconstituted with autologous bone marrow, 20 animals in the X-irradiated group and nine animals in the neutron group survived more than 3 years. A group of 21 non-irradiated Rhesus monkeys of a comparable age distribution served as controls. All animals were regularly screened for the occurrence of neoplasms. Complete necropsies were performed after natural death or euthanasia. RESULTS: At post-irradiation intervals of 4-21 years an appreciable number of tumours was observed. In the neutron irradiated group eight out of nine animals died with one or more malignant tumours. In the X-irradiated group this fraction was 10 out of 20. The tumours in the control group, in seven out of the 21 animals, appeared at much older age compared with those in the irradiated cohorts. The histogenesis of the tumours was diverse with a preponderance of renal carcinoma, sarcomas among which osteosarcomas, and malignant glomus tumours in the irradiated groups. CONCLUSIONS: When corrected for competing risks, the carcinogenic risk of TBI in the Rhesus monkeys is similar to that derived from the studies of the Japanese atomic bomb survivors. The increase of the risk by a factor of 8, observed in the monkeys, indicates that patients are likely to develop malignancies more frequently and much earlier in life after TBI than non-exposed individuals. This finding underlines the necessity of regular screening of long-term surviving patients subjected to TBI and BMT.

Effectiveness and risks of total body irradiation for conditioning in the treatment of autoimmune disease with autologous bone marrow transplantation.

The results of experiments with the induced autoimmune diseases adjuvant arthritis and allergic encephalomyelitis in rats, which led to the discovery of the curative effect of autologous bone marrow transplantation following high-dose myeloablative treatment, are reviewed. The rationale is eradication of the autoreactive lymphocytes and memory cells, and the prevention of relapse due to transfer of lymphocytes with the autograft. Comparison of various conditioning regimens in the animal models indicates that a combination conditioning with low-dose total body irradiation (TBI) and high-dose cyclophosphamide is optimal. These findings were the basis for the conditioning currently employed in the treatment of polyarticular juvenile chronic arthritis (JCA) by the teams in Utrecht and Leiden, which consists of cyclophosphamide 50 mg/kg for 4 days, 4 Gy TBI and anti-thymocyte globulin (ATG). The use of TBI for the treatment of non-malignant disease is regarded as undesirable by many physicians in view of the risks, in particular, of growth inhibition in children and the induction of tumours. Experimental and clinical data show that a dose of 4 Gy does not cause significant inhibition of skeletal growth in infants. The risk of excess cancer due to TBI has been well established in quantitative terms and is compared with the expected risk of high-dose cyclophosphamide and the risk associated with the highly immunosuppressive regimens currently used for the treatment of JCA.

Intrinsic potential of phenotypically defined human hemopoietic stem cells to self-renew in short-term in vitro cultures.

In search for culture conditions that will facilitate hemopoietic stem cell (HSC) replication while preserving their primitive properties, we have made use of a multi-parameter FACS assay to define HSCs on basis of their phenotypic characteristics, i.e., CD34++CD33,38,71(-). Bone marrow and umbilical cord blood samples of CD34(+) cells from 31 donors were loaded with the membrane dye PKH26 and each exposed to various culture conditions for 6 days. The cells that retained the primitive CD34(++)CD33,38,71(-) phenotype were analysed for the number of cell replications they underwent, by measuring loss of PKH26 fluorescence after 6 days. A most striking observation was the large inter-sample variation in the proliferative response of cells that retained the CD34(++)CD33,38,71(-) phenotype. In general, samples could be characterised as either good- or poorly-replicating, according to the proliferation property of their CD34(++)CD33,38,71(-) subset. In comparison to this 'intrinsic' potential, the effects of the applied growth stimuli on CD34(++)CD33,38,71(-) cell replication were negligible. In contrast, the overall recovery of the CD34(++)CD33,38,71(-) cells was clearly dependent on the culture stimuli. Of the various conditions tested, serum-free cultures with pre-established stroma maintained the cells with this primitive phenotype most effectively. In cultures supplemented with various combinations of recombinant HGFs, HSC differentiation prevailed. These findings with phenotypically defined HSCs should assist in the design of systems for expansion and ex vivo gene therapy of early hemopoietic cells.

Induction of mammary tumors in rats by single-dose gamma irradiation at different ages.

The effect of age at exposure on induction of mammary tumors was studied in female rats of the inbred WAG/Rij strain. Groups of 40 animals were exposed to a single total-body dose of 1 or 2 Gy of 137Cs gamma radiation at ages of 8, 12, 16, 22, 36 or 64 weeks and were observed for life. Mammary tumors, identified as nodules persisting and growing for 6 weeks, were resected and classified histologically as carcinoma or fibroadenoma. The age-specific incidence of mammary carcinoma was compared with that in a group of 120 unirradiated control rats, using lifetime statistical analysis with both parametric and nonparametric methods. The excess normalized risk of carcinoma was 0.9 for 1 Gy and 2.2 for 2 Gy in age groups 8-36 weeks, with no significant differences between the age groups. However, irradiation at 64 weeks yielded fewer carcinomas than in the controls, the excess normalized risk being -0.7 and -0.3 for 1 and 2 Gy, respectively. The occurrence of one or more fibroadenomas did not influence the incidence of carcinoma. The present data agree closely with the results reported previously for rats irradiated at age 8 or 17 weeks with a dose of 1.2 Gy. The reduced risk of radiation exposure at midlife is consistent with the available epidemiological data for exposed women. Although our findings have been obtained with a single total-body dose that is several orders of magnitude higher than the multiple doses delivered to the mammary gland during mammography, it is suggested that radiological screening for mammary cancer after the age of menopause will not increase the normal incidence of breast cancer.

The influence of estrogen treatment on induction of mammary carcinoma in rats by single-dose gamma irradiation at different ages.

The effect of age at exposure on induction of mammary carcinoma was studied in female rats of the inbred WAG/Rij strain that were treated with estrogen. Groups of 40 animals were exposed to a single total-body dose of 1 or 2 Gy of 137Cs gamma radiation at age 8, 10, 12, 15, 22, 36 or 64 weeks. Hormone levels in the animals were increased by implantation of a pellet containing Estradiol-17beta 2 weeks prior to irradiation. Animals were killed when moribund. All mammary tumors were resected and classified histologically as carcinoma or fibroadenoma. The age-specific incidence of mammary carcinoma was compared with that in control groups of unirradiated estrogen-treated rats using lifetime statistical analysis with both parametric and nonparametric methods. The excess normalized risk of carcinoma was 7.7 for both 1 and 2 Gy in the age groups 8-15 weeks, with no significant differences between the age groups. However, in the age groups 22-64 weeks, the excess normalized risk decreased with increasing age at exposure. Irradiation at 64 weeks yielded fewer carcinomas than in the controls, with an excess normalized risk of -0.6 for both 1 and 2 Gy. The excess normalized risk was 10-80 in estrogen-treated controls compared to untreated rats. The present data agree with the results reported previously for estrogen-treated rats irradiated at ages 8 or 17 weeks with doses of 0.3 or 1.2 Gy. The reduced risk of radiation exposure at midlife observed in this study in hormone-treated rats has also been reported for animals not treated with estrogens. The present findings support the earlier conclusion that radiological screening for mammary cancer after the age of menopause will not increase the normal incidence of breast cancer. Estrogen treatment at midlife may increase the risk of breast cancer in women using replacement estrogens during and after menopause.

IL-1/IL-3 gene therapy of non-small cell lung cancer (NSCLC) in rats using 'cracked' adenoproducer cells.

Cytokine gene therapy was studied in established L42 tumours in syngeneic rats. L42 is a transplantable non-immunogenic non-small cell lung cancer (NSCLC). Genes coding for human interleukin-1 alpha and for rat interleukin-3 beta were transferred by injecting producer cells of recombinant adenovirus vectors into the tumour in attempts to achieve high concentrations of the cytokines inside the tumor without systemic toxicity. Limited tumour growth delay was obtained with viable producer cells. For logistic reasons stocks of pooled frozen producer cells allowed intensive treatment of groups of tumour bearing rats. The cells were lysed by thawing before administration. Ten daily injections of such 'cracked' producer cells induced reproducible tumour responses. These were due to local release of cytokines, not to systemic effects. Growth retardation also occurred in contralateral tumours which were not injected. When rats carrying established tumours were vaccinated with lysates of tumours collected during treatment with 'cracked' producer cells, significant tumour growth retardation was obtained. We speculate that both cytokines, if produced at sufficiently high concentrations in tumours, induce inflammation which in turn initiates an immune response against tumours growing at a distant site. These findings seem to justify further exploration of IL-1 and IL-3 gene transfer for the treatment of cancers.