Minimal residual disease in acute leukemia: from experimental models to man.
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Water-soluble monoethers of sucrose and fatty acids were obtained from Trypanosoma lewisi and Astasia longa. The maximum tolerated dose of the preparations on their single intraperitoneal administration was more than 25 g/kg. The doses of 10--40 mg/kg were used repeatedly in therapy. Carcinoma 755, Lewis carcinoma, sarcoma 45, sarcoma 37 and sarcoma 180 were sensitive to the preparations. The preparations were inactive against experimental leukemia.
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Expression of genes, associated with leukemic transformation and called x-mla, was studied in cells of various types of experimental leukemia and in homologous normal cells. Augmentation of x-mla expression in malignant haemopoietic cells and lack or very low expression in normal tissues and non-haemopoietic tumors of mice and rats has been revealed. The involving of x-mla in proliferation control of leukemic but not normal cells has been shown. Product of x-mla--p46 was synthesized in cell-free translational system and purified. Its amino acid composition was determined and its mitogenic, RNAase activities, and ability to phosphorylation have been investigated.
Experimental and clinical evidence for persistence of polyclonal Philadelphia chromosome negative (Ph-) progenitors in chronic myelogenous leukemia (CML) patients has provided the rationale for autologous transplantation. Clinical trials of autologous transplantation suggest that this procedure can induce cytogenetic remissions in a subset of patients and may be associated with longer-than-expected patient survival. Most autologous transplant recipients, however, continue to have evidence of persistent leukemia. Recent reports indicating that it is possible to collect sufficient numbers of Ph- peripheral blood stem cells for autologous transplantation from most patients in complete cytogenetic remission on imatinib treatment have rekindled interest in autologous transplantation in CML. Additional approaches to eliminate residual disease in autografts and to sustain cytogenetic response after transplantation, however, will be required to achieve long-term restoration of Ph- hematopoiesis. Several promising methods to improve purging of the autograft and for more effective elimination of residual leukemia are being explored.
To determine the phenotype of target cells for bovine leukemia virus (BLV) infection in sheep, we analyzed blood lymphocytes from BLV-infected clinically healthy and leukemic sheep by use of monoclonal antibodies. In clinically healthy and leukemic sheep that were BLV-infected, the blood concentration of T lymphocytes was within normal values, but the number of B lymphocytes was increased in several cases. In addition, the number of blood lymphocytes expressing the BLV antigen correlated well with that of B lymphocytes. Double immunofluorescence staining demonstrated that lymphocytes expressing BLV antigens bore B-cell but not T-cell surface markers. Moreover, neoplastic cells in the lymph nodes of leukemic sheep were stained immunohistochemically with an anti-B monoclonal antibody but not with any of anti-T monoclonal antibody tested, indicating that tumor cells are of B-lymphocyte origin. Collectively, these results show that BLV antigen-positive cells obtained from BLV-infected sheep that have no clinical signs and BLV-induced lymphosarcoma cells belong to the B-lymphocyte lineage.
Experimental and clinical data suggest that Ph-negative myeloid progenitor cells are present, albeit suppressed, in the bone marrow of chronic myeloid leukemia (CML) patients. These residual Ph-negative cells might, in certain circumstances, regain their proliferative advantage over the leukemic Ph-positive clone. Treating CML patients with intensive chemotherapy might allow the harvest, in the early phase of recovery, of Ph-negative stem cells to be used as graft after myeloablative regimen. In our study, 6 CML patients were admitted to a program of autograft with circulating stem cells (CSC) collected after high-dose (5 or 7 g/m2) cyclophosphamide (HD-CY) mobilization. All were autografted, using busulphan 16 mg/kg and melphalan 60 mg/m2. As graft, 4 patients received CSC only, while 2 patients were also given bone marrow, as their peripheral blood CFU-GM yield was unsatisfactory. Two previously alpha-IFN-responding patients showed a slow hematologic recovery, but achieved a marked and further reduction of their Ph-positive metaphases post-graft. Moreover, in one of them, cytogenetic analyses performed on apheresis product showed a more pronounced reduction of his Ph-positive metaphases, as compared to bone marrow samples, suggesting a potential purging effect of the mobilization procedure.
Experimental and clinical data demonstrate an antileukemia effect of acute graft-versus-host disease (aGVHD). In all, 58 pediatric patients with acute lymphoblastic leukemia (ALL) who had received an allogeneic bone marrow transplant (BMT) at our institution were retrospectively analyzed for a correlation between the development of aGVHD and leukemic relapse. Probability of relapse after 5 (3) years was 13% (7%) in patients developing grade II-IV aGVHD vs 30% in patients with grade 0 or I aGVHD. There was a trend for a difference of the point estimates at 3 years, but no overall significance because of an unusual late relapse. Moreover, we analyzed the impact of cyclosporin A (CsA) on aGVHD in a subgroup of 22 children who had received a matched sibling donor (MSD) BMT. An increased dose of CsA within the first 2 weeks after BMT led to decreased occurrence and severity of aGVHD (P=0.035). The cumulative CsA dose appeared to have more impact than the average CsA whole-blood levels within the first 2 weeks and than the CsA dose given from day 15 to 40. In this subgroup, no life-threatening aGVHD or death from aGVHD occurred. In all cases (6/22), leukemic relapse was the cause of death. We therefore suggest that there is a relation between dose of CsA and relapse rate in childhood ALL transplanted from a MSD.
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An optical polarizing microscope with a good coefficient of extinction permits the visualization of the cytoplasmic fibrillar body in living preparations and smears of leukemic cells (human leukemias and the L 5222 experimental leukemia). These inclusions are not visible by phase contrast microscopy nor in fixed and stained smears. The detection in living cells of fibrillar bodies makes it possible to study directly the conditions for their formation and their reaction to the effect of certain drugs.
Experimental studies in animals and recent preliminary clinical evidence raised the possibility that hypertransfusion might be capable of producing a beneficial effect on granulopoiesis recovery following irradiation or chemotherapy. This prompted us to design a study to determine the effect of hypertransfusion on the blood and marrow CFU-c of leukemic children during remission induction. Nineteen children with acute lymphoblastic leukemia have been randomized in pairs to normotransfused (Hb: 12-14 g/dl) and hypertransfused (Hb: 16-18 g/dl) groups. Anti-leukemic chemotherapy (vincristine and adriamycin weekly during 4 weeks and prednisone daily) was identical in all children. As expected, suppression of erythropoiesis was observed in the hypertransfused group. During the first three courses of chemotherapy, the number of marrow CFU-c remained very low in both groups. One week after the third course of chemotherapy the number of bone marrow CFU-c began to increase in both groups. One week after course four the CFU-c value was significantly larger in the hypertransfused group. We also observed that circulating CFU-c were almost absent before induction chemotherapy, whereas their number increased after course three and was higher in the hypertransfused group and remained higher after course four. These results show the kinetics of bone marrow recovery after chemotherapy and suggest that hypertransfusion increases the rate of recovery of granulopoiesis.
In preclinical investigations performed in mice, 2-amino-9-beta-D-ribofuranosyl purine-6-sulfinamide (sulfinosine), a novel derivative of 6-thioguanosine (6TGR), was active against six solid tumors and four strains of experimental leukemia. Sulfinosine penetrated the central nervous system more readily than did 6TGR and, when given repeatedly, was much more effective in the treatment of L1210 leukemia, being curative for some mice. Other findings of major interest to us were the different dosing characteristics of sulfinosine and 6TGR, the divergent efficiencies of the two drugs in generating cellular resistance, and the activity of sulfinosine against experimental leukemias refractory to 6TGR and other experimental or clinically used chemotherapeutic agents. The chemotherapeutic characterization of sulfinosine that evolved from these studies suggests that this agent may have unique properties that deserve clinical consideration. Both the dosing characteristics of the drug and its pronounced activity against thiopurine-resistant experimental leukemia favor the possibility that sulfinosine could be used to advantage in the treatment of human leukemia unresponsive to 6-mercaptopurine or 6-thioguanine.
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