Cytotoxic activity of an anti-transferrin receptor immunotoxin on normal and leukemic human hematopoietic progenitors.

The process of cellular iron uptake involves a specific receptor for the plasma carrier transferrin and a pathway of receptor-mediated endocytosis. Transferrin receptor expression is closely related to the rate of cell proliferation, and conjugates between anti-transferrin receptor monoclonal antibodies and toxins have been shown to have potent cytotoxic activity. We have constructed an anti-transferrin receptor immunotoxin by conjugating the anti-transferrin receptor monoclonal antibody B3/25 to a ribosome-inactivating protein, the saporin-6 (SO6), which is derived from the seeds of the plant Saponaria officinalis. The immunotoxin B3/25-SO6 was tested for in vitro cytotoxic activity against the human cell lines K-562 and HL-60 and against normal human bone marrow hematopoietic progenitors and acute myeloid leukemia clonogenic cells. The immunotoxin proved to be an effective inhibitor of K-562 and HL-60 clonogenic cell growth, in vitro colony formation being completely inhibited at immunotoxin concentrations ranging from 10(-7) to 10(-10) M. B3/25-SO6 markedly reduced the recloning efficiency of HL-60 clonogenic cells at 10(-12) M. Exposure of HL-60 cells in suspension culture to 10(-9) M B3/25-SO6 for 48-72 h completely abolished their clonogenic potential. The immunotoxin was also found to be cytotoxic against normal human bone marrow progenitor cells (burst-forming unit-erythroid and colony-forming unit-granulocyte, macrophage) in a dose-dependent manner. However, exposure of normal colony-forming unit-granulocyte, macrophage in suspension culture to 10(-9) M B3/25-SO6 for 72 h resulted in only 50% suppression of their clonogenic potential. Finally, B3/25-SO6 was found to be a potent inhibitor of in vitro growth of acute myeloid leukemia clonogenic cells. The cytotoxic effects of B3/25-SO6 were shown to be specific, since both saporin alone and irrelevant immunotoxins did not have any effect in the cellular systems examined. We conclude that the immunotoxin B3/25-SO6 has dose-related cytotoxic effects on both normal and leukemic human hematopoietic progenitors. Since there are substantial differences between normal and leukemic progenitors with respect to the proportion of cycling cells and the expression of transferrin receptors, B3/25-SO6 or similar immunotoxins may have clinical application in bone marrow-purging procedures.

Cell kinetics in human malignancies studied with in vivo administration of bromodeoxyuridine and flow cytometry.

Bromodeoxyuridine (BrdUrd) is a pyrimidine analogue which is incorporated into the DNA of proliferating cells. When in vivo BrdUrd infusion is coupled with bivariate flow cytometry to measure cell BrdUrd incorporation and DNA content, both the percentage of DNA-synthesizing cells [BrdUrd-labeling index (LI)] and the DNA synthesis time (TS) can be determined on the same tissue sample. From experimentally determined LI and TS, the potential doubling time of the population and its cell production rate are calculated. To ascertain whether the BrdUrd infusion method is clinically feasible and if data are reliable, we studied patients with leukemia, refractory anemia, multiple myeloma, and brain and gastric tumors. The BrdUrd incorporation data were compared with those determined on duplicate samples with the techniques conventionally used for LI and TS values, i.e., 3H- and 14C-labeled thymidine autoradiography, respectively. The complete BrdUrd procedure takes 6-9 h, and no immediate toxicity from BrdUrd administration has been observed. In an 8-month period, 154 patients were studied. Successful LI and TS determinations were obtained in 78.9 and 59.7% of cases, respectively, more often in hematological than in solid tumors. The values for LI and TS assessed with the BrdUrd technique were very close to those found with 3H- and 14C-labeled thymidine autoradiography (r = 0.88, P less than 0.005, and r = 0.89; P less than 0.005, respectively). The potential doubling time and production rate were accordingly similar. These data indicate that in vivo BrdUrd infusion coupled with flow cytometry measurements can be performed in clinical settings and that this method is reliable. It could be used for kinetic studies in clinical trials aimed at evaluating the prognostic relevance of proliferative parameters and for planning radio- and/or chemotherapy.

Vinblastine, bleomycin, and methotrexate chemotherapy plus extended-field radiotherapy in early, favorably presenting, clinically staged Hodgkin's patients: the Gruppo Italiano per lo Studio dei Linfomi Experience.

PURPOSE: To ascertain whether vinblastine, bleomycin, and methotrexate (VBM) (CT) combined with extended-field radiotherapy (EF RT) is effective enough to spare laparotomy in early, favorably presenting Hodgkin's disease (HD) patients. PATIENTS AND METHODS: Fifty patients with clinical stage IA or IIA HD with favorable histology and no bulky masses entered a prospective multicenter study started in January 1988. The median follow-up time was 38 months. RESULTS: All patients achieved a complete remission (CR). Five relapsed after 3 to 40 months and underwent successful salvage therapy. The actuarial remission rate was 0.89% at 3 years and 0.82% at 5 years. Two patients died in CR: one of severe pulmonary toxicity, the other of a second neoplasia (adenocarcinoma of the lung), 2 and 43 months after the end of therapy, respectively. The hematologic toxicity recorded during VBM CT was mild on the whole. Major toxicity was represented by pulmonary side effects and neurologic symptoms. Multiple regression analysis demonstrated that pulmonary toxicity was significantly related only to the amount of RT delivered to the mediastinum and not to the relative dose of bleomycin, to the dose-intensities of the three drugs in the regimen, or to patient age or sex. The same statistical technique showed that the only clinical factor related to grade of neurotoxicity was vinblastine dosage. CONCLUSION: VBM CT combined with EF RT is an effective treatment for early, clinically staged, favorable HD patients. However, the toxicity of this combination suggests that certain modifications should be evaluated.

Image-aided estimate of tumor burden in Hodgkin's disease: evidence of its primary prognostic importance.

PURPOSE: To explore a more direct method for evaluating tumor burden (TB) in Hodgkin's disease (HD) and to verify its prognostic importance. PATIENTS AND METHODS: The volume of TB at diagnosis was directly and retrospectively measured in 121 HD patients through images of the lesions recorded by computed tomographic (CT) scan of the thorax, abdomen, and pelvis for all deep sites of involvement and many superficial ones, and by ultrasonography (US) for the remaining superficial lesions. RESULTS: The TB, which was obtained from the sum of the volumes of all the lesions measured on CT scans and US and normalized to body-surface area (relative TB [rTB]), showed a median value of 102.6 cm(3)/m(2) (range, 2.2 to 582.8). At multivariate analysis for prognostic value, rTB was the parameter that statistically correlated best with time to treatment failure (P = 2.2 x 10(-6)), followed by erythrocyte sedimentation rate (ESR) (P =.0003), and serum fibrinogen (P =.0112). The prognostic discrimination allowed by rTB alone proved to be clearly superior to that obtained with the score of the International Prognostic Factor Project. The rTB was found to be correlated with many clinical staging parameters (bulky disease, number of involved lymph node regions, serum lactate dehydrogenase, ESR, hemoglobin, Karnofsky index), but its predictability from these variables was low (R(2) =.668). CONCLUSION: Relative TB is emerging as a strong prognostic factor in HD, more powerful than and largely independent of those hitherto known and used. Further studies are needed to confirm these results and exploit their clinical value, particularly the relationship among rTB, drug doses, and response.

Biological features of the clone involved in primary amyloidosis (AL).

Primary light chain-associated amyloidosis (AL) is a plasma cell dyscrasia that causes morbidity via systemic tissue deposition of monoclonal light chains in the form of fibrils (amyloid). It is the most common form of systemic amyloidosis in Western countries and is rapidly fatal. Knowledge of the pathobiology of the underlying B cell clone is of primary importance for the design and optimization of therapeutic strategies.

Recombinant gamma-interferon induces in vitro monocytic differentiation of blast cells from patients with acute nonlymphocytic leukemia and myelodysplastic syndromes.

gamma-Interferon (IFN-gamma) has previously been found to induce monocytic differentiation in established leukemic cell lines, such as HL-60 and U937. The aim of the present study was to evaluate the differentiative effect of highly purified recombinant (r)IFN-gamma on fresh bone marrow cells from patients with acute nonlymphocytic leukemia (n = 11) or myelodysplastic syndromes (n = 3). Blast cells were cultured in suspension in the presence or absence of rIFN-gamma (10-10(3) U/ml). While 6 out of 14 cases were unresponsive to rIFN-gamma in vitro, the remaining 8 patients showed a significant increase (0.05 greater than p greater than 0.001) in the percentage of cells expressing C3bi receptors, detected by OKM1 (median value in control cell, 9.5; median value in rIFN-gamma-treated cells, 31) and Mo1 (8.5 vs. 36), and in the percentage of cells expressing the monocytic antigens detected by Mo2 (8 vs. 28) and MY4 (6.5 vs. 32.5). In the responsive patients morphologic changes consistent with monocytic maturation, as well as a strong increase of alpha-naphthyl acetate esterase activity and of nitroblue tetrazolium reducing capability were observed upon culture with rIFN-gamma. We conclude that (a) rIFN-gamma may induce in vitro monocytic differentiation of blasts from acute nonlymphocytic leukemia and myelodysplastic syndrome patients, and that (b) this agent should be investigated for its capacity to be active in vivo.

Effects of desferrioxamine on normal and leukemic human hematopoietic cell growth: in vitro and in vivo studies.

The iron chelator desferrioxamine (DFO) has been previously shown to be an S-phase inhibitor of cell proliferation. To investigate its potential as an antileukemic drug, we first studied the effects of DFO on the in vitro growth of normal human hematopoietic progenitors (CFU-GM and BFU-E) and clonogenic cells from human leukemic cell lines. Then we evaluated the effects of DFO on progression of leukemia refractory to conventional therapy in two individuals. Micromolar concentrations of DFO determined a dose-dependent inhibition of normal progenitor growth, with inhibitory dose 50% (ID50) for CFU-GM and BFU-E being 6.7 and 5.5 microM/liter, respectively. Marked inhibitory effects were observed on clonogenic cells from HL-60 (ID50 = 1.4 microM/liter) and U-937 (ID50 = 3.6 microM/liter) human leukemic cell lines grown in semisolid medium. When DFO was given intravenously to a patient with lymphoid blast crisis of chronic myelogenous leukemia, a marked reduction in circulating blast count was observed. On the contrary, no in vivo effect was observed in a patient with acute nonlymphocytic leukemia having transfusional iron overload. We conclude that: (a) DFO is an inhibitor of both normal and leukemic myeloid cell proliferation in vitro; (b) our limited in vivo observations and a previous case study suggest that intravenous administration of DFO to patients with normal to low plasma iron may result in leukemic cytoreduction in vivo.

Tumor necrosis factor alpha modulates the messenger RNA expression of hematopoietic growth factor genes in fresh blast cells from patients with acute myeloblastic leukemia.

Tumor necrosis factor alpha (TNF-alpha) has been previously shown to modulate the expression of hematopoietic growth factor genes in monocytes and other mesenchymal cells. As acute myeloblastic leukemia (AML) blasts can express and produce hematopoietic growth factors, the influence of TNF-alpha on the accumulation of mRNAs for c-myc, interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF), G-CSF, IL-6 and IL-1 beta was evaluated in fresh blasts from 13 patients with AML. Total cellular RNA was extracted from blast cells cultured for 24 hours with or without TNF-alpha (500 U/ml). The c-myc transcript level was decreased by TNF-alpha treatment in 9/13 cases, and increased in only one case. Among the growth factor genes, the GM-CSF gene was more often and consistently influenced by TNF-alpha, increased levels of its transcript being observed in 6/13 cases following treatment with the cytokine; in no case was there a reduction of GM-CSF mRNA. G-CSF and IL-6 transcripts were more heterogeneously influenced, whereas the IL-3 transcript was never detected in our AML samples. The IL-1 beta message was present in 8/13 untreated and in 13/13 TNF-alpha treated samples. Moreover, in untreated cells, GM-CSF, G-CSF and IL-6 expression was always associated with IL-beta expression. These findings indicate that TNF-alpha can modulate the levels of growth factor transcripts in AML blasts, and raise questions about the effects of TNF-alpha on leukemic hematopoiesis, considering that TNF-alpha, IL-1 and GM-CSF can synergistically stimulate the growth of AML clonogenic cells.

Splenectomy for patients with myelofibrosis with myeloid metaplasia: pretreatment variables and outcome prediction.

Since according to the early studies, the outcome after splenectomy in the individual patient with myelofibrosis with myeloid metaplasia (MMM) is unpredictable, we assessed retrospectively the pre-intervention characteristics that best predicted adverse events, hematological consequences, and survival in 71 splenectomized MMM patients. The findings indicate that the operative risk of splenectomy for both mortality (8.4%) and morbidity (39.3%) was unpredictable. New hemorrhagic or thrombotic complications occurred in 16.9% of surviving patients and were predicted by age < 50 years, a normal to high platelet count (> 200 x 10(9)/l) and huge splenomegaly (> 16 cm from the costal margin). Massive liver enlargement occurred in 24% of patients and has to be expected in patients splenectomized for transfusion-dependent anemia. Anemia improved substantially in 45% and 52% of patients at 3 months and at 1 year, respectively, and was predicted by severe anemia, low platelet count (< 100 x 10(9)/l) or normal to high white blood cell (WBC) count (> 4 x 10(9)/l). Survival from splenectomy was superior in patients < 45 years with WBC < 10 x 10(9)/l count. An unexpectedly high rate of blastic transformation was observed. It accounted for 42.8% of the deaths. The results suggest trials for prophylactic cytoreductive treatment in young patients and when platelet count is normal to increased. Further study is needed for elucidating the possible role played by splenectomy in inducing blastic transformation.

Effects of a new aminodiphosphonate (aminohydroxybutylidene diphosphonate) in patients with osteolytic lesions from metastases and myelomatosis. Comparison with dichloromethylene diphosphonate.

We have compared in an open trial the clinical and biochemical effects of a new aminodiphosphonate, aminohydroxybutylidene diphosphonate, with those of dichloromethylene diphosphonate, which has been proved effective. The patients presented extensive and symptomatic bone involvement from multiple myeloma, breast cancer, and other metastatic tumors. The treatment consisted of aminohydroxybutylidene diphosphonate, 2.5 mg/d intravenously for five days, or dichloromethylene diphosphonate, 300 mg/d intravenously for seven days, followed by 100 mg/d intramuscularly for ten days. Twelve patients treated with aminohydroxybutylidene diphosphonate and 16 patients treated with dichloromethylene diphosphonate were assessable and were followed up for one to six months. Therapy with aminohydroxybutylidene diphosphonate showed a quicker action in reducing bone pain and reduced significantly more the serum calcium level than did therapy with dichloromethylene diphosphonate. Aminohydroxybutylidene diphosphonate therapy also affected urinary calcium levels and hydroxyproline excretion more markedly than did dichloromethylene diphosphonate, although the differences are not statistically significant. However, the biochemical indexes rebounded more quickly in patients treated with aminohydroxybutylidene diphosphonate, indicating that the loading amount (only 12.5 mg) used in this preliminary study is insufficient to sustain a prolonged effect. The effectiveness and lack of side effects render aminohydroxybutylidene diphosphonate an attractive treatment for malignant bone resorption.

Postremission chemotherapy in adult acute non-lymphoblastic leukaemia including intensive or non-intensive consolidation therapy.

From October 1983 to December 1988, 84 consecutive adult patients with acute non-lymphoblastic leukaemia (ANLL; median age = 51 yr) were uniformly treated to induce remission (CR) with intravenous vincristine and cytarabine sequentially followed by daunomycin and infusion cytarabine. From October 1983 to December 1985 consolidation was non-intensive (2 courses with the same drugs used for induction) (protocol ANLL83: 27 patients, median age = 45). From January 1986 to December 1988 consolidation was intensive (4 courses of vincristine and cytarabine sequentially followed by etoposide plus thioguanine or amsacrine) (protocol ANLL86: 57 patients, median age = 57). Excluding early deaths, the CR rate was 71.6%. Median CR, responsive patient survival and overall survival were 11.1, 15.3 and 8.5 mo, respectively. For protocol ANLL83 and ANLL86, median CR was 8.7 and 13.2 mo (P less than 0.05) and median survival was 13.1 and 16.9 mo (P less than 0.05) for responders and 8.0 and 9.2 mo (P not significant) for all patients. Intensive consolidation including drugs not previously used for induction seems to prolong CR duration and responder survival in adult ANLL.

Changing clinical presentation of multiple myeloma.

We compared the presentation features of three series of patients with multiple myeloma diagnosed between 1960 and 1971 (Kyle R, Mayo Clin Proc, 1975, 50, 29, n = 869), 1972 and 1986 (Clinica Medica, University of Pavia, n = 345) and 1987 and 1990 (Cooperative Group for Study and Treatment of Multiple Myeloma, n = 341). In the most recently diagnosed patients, the percentage of those who had symptoms related to multiple myeloma (i.e. any of bone pain, systemic symptoms, disturbances related to hypercalcemia, neurological involvement and hyperviscosity) was reduced (90 vs. 86 vs. 66%) (P less than 0.001), while the percentage of asymptomatic patients diagnosed by chance was increased (not reported, and 14 vs. 34%). In the most recent series, a lower percentage of spontaneous bone pain (68 vs. 60 vs. 37%, P less than 0.001) paralleled a lower incidence of advanced bone disease (osteolyses and pathological fractures, 60 vs. 64 vs. 34%), and renal failure (serum creatinine greater than 1.2 mg/dl) was also less common (56 vs. 44 vs. 33%, P less than 0.01), at least partially due to a decreased incidence of both hypercalcemia (30 vs. 20 vs. 18%, P less than 0.001) and of hyperuricemia (serum uric acid greater than 7 mg/dl, 47 vs. 32 vs. 26%, P less than 0.01). Systemic symptoms (weakness, infections, fever or weight loss) were reported more seldom by recently diagnosed patients, due to a decreased frequency of anaemia (haemoglobin less than 12 g/dl), leukopenia and thrombocytopenia, as well as of the systemic effects of bone pain and of renal insufficiency. These data indicate that multiple myeloma is diagnosed earlier now than in the past, and this must be taken into account when comparing survival data in treated series.

Response to first-line chemotherapy and long-term survival in patients with multiple myeloma: results of the MM87 prospective randomised protocol.

In this study we evaluated whether a good response to conventional chemotherapy, i.e. a significant tumour reduction, is a prerequisite for improved survival in multiple myeloma (MM). Between January 1987 and March 1990, 341 consecutive previously untreated patients with MM received chemotherapy within the prospective, multicentre, randomised Protocol MM87. Of these, 258 patients were evaluable for both response and long-term survival and 244 (94.6%) have died. The median survival of all patients was 40 months (6-162 months). The median survival did not differ between patients who had complete response (CR) (50 months (9-162 months)), partial response (PR) (46 months (8-147 months)) or stable disease (SD) (41 months (7-135 months)). The median survival was shorter (13.6 months (6-135 months)) (P<0.0001) in patients whose disease progressed while they were receiving first induction chemotherapy. Causes of death were more frequently (P=0.04) related to MM in patients who had progressive disease (PD) than in patients who had a CR or PR or SD. The main clinical and laboratory characteristics were similar in the four groups. These data indicate that patients who maintain SD during first-line chemotherapy have a prognosis similar to that of patients who attain a response. Only patients whose disease progresses have a distinctly worse outcome.

Cigarette-smoking effect on platelet function.

The immediate effect of cigarette-smoking on ADP-induced platelet aggregation and on platelet adhesiveness was investigated in 12 normal subjects aged 20 to 40, in 10 normal subjects aged 43 to 72 and in 10 patients with cerebrovascular disease aged 45 to 75. All the subjects were heavy smokers (more than 20 cigarettes a day). After smoking 2 cigarettes a significant increase in ADP aggregation and platelet adhesiveness was found in the group of young heavy smokers, while in the old subjects with or without cerebrovascular disease the increase in platelet activity was never significant. These data were discussed and some hypotheses for this higher reactivity of platelets from young people were suggested.

Synoviorthesis versus synovectomy in the treatment of recurrent haemophilic haemarthrosis: long-term evaluation.

The authors report a long-term evaluation of the effects of chemical and surgical synovectomies performed in two groups of patients which were comparable as regards number of haemarthrosis per year and joint mobility. The results obtained indicated that both synovectomy and synoviorthesis were effective in reducing the bleeding episodes; however, while synovectomy stopped almost completely the recurrence of haemarthrosis, synoviorthesis in 3 patients younger than 12 years did not modify it and in one case it even increased the bleeding tendency. Moreover, the occurrence of arthritic pain was observed in 6 knees treated by synoviorthesis and only in 3 knees treated by synovectomy. Finally, the joint function was significantly reduced in the synoviorthesis group as compared to the synovectomy group. In conclusion, synovectomy gave better results than synoviorthesis but the latter treatment has a number of economical and technical advantages and should therefore be considered in patients older than 12 year of age with good joint function and without evident radiological changes, in whom full dose replacement therapy has had no effect on the recurrence of haemarthrosis.

Enhanced antithrombotic mechanisms in patients with maturity-onset diabetes mellitus without thromboembolic complications.

Some haemostatic parameters have been evaluated in a group of rigorously selected patients with maturity-onset diabetes mellitus without thromboembolic complications and in apparently normal subjects of the same age before and after the venous occlusion test (VOT). In basal conditions diabetics had higher levels of AT III as biological activity and higher fibrinolytic and antifibrinolytic activities than controls. After VOT, F VIII R:Ag increased significantly in both groups, more markedly in controls than in diabetics, while F VIII: C showed no modification. Also AT III R:Ag increased after the test, but such variation was significant only in diabetics; on the contrary, the biological activity of AT III was always significantly decreased after the test. After VOT there were also in both groups highly significant increases in the fibrinolytic and antifibrinolytic activities. Finally, HbA1c levels directly correlated with AT III as biological activity before VOT, but with no other parameter either before or after the test. These data suggest the existence in patients with diabetes mellitus without thromboembolic complications of an activated protective mechanism against intravascular clotting.

UV-induced DNA repair in hairy cell leukaemia patients.

We analysed by liquid scintillation counting and by autoradiography the DNA repair synthesis induced by UV irradiation in mononucleated cells from peripheral blood of 'hairy cell leukaemia' patients. In 9 out of 12 patients the repair activity values obtained in repeated assays were found to be significantly lower than those of healthy donors.

Cancer chemotherapy-related thrombotic thrombocytopenic purpura: biological evidence of increased nitric oxide production.

The occurrence of thrombotic thrombocytopenic purpura (TTP) in cancer patients receiving chemotherapy has been well established; although this entity is rare, its clinical importance seems to be growing. We describe 3 cases of TTP developing in cancer patients receiving different chemotherapeutic regimens. Using a sensitive high-performance liquid chromatographic method, we evaluated the stable nitric oxide end products, nitrite and nitrate, in the plasma of these patients. Nitric oxide is one of the key components involved in maintaining the normal nonthrombogenicity of the vascular endothelium. In our 3 patients, we found increased nitrate titers that were substantially higher than those observed in patients with de novo TTP. The observed increased release of nitrate could be interpreted as the consequence of massive disruption of endothelial integrity, with consequent passive nitric oxide release in vivo, or an adaptive mechanism of the endothelium to compensate for diffuse microvascular occlusion. The 2 mechanisms may both be involved, but the normal titers of nitric oxide end products in de novo TTP suggest that the former mechanism is more important, at least in cancer chemotherapy-related TTP.

Immunocytochemical detection of factor XIII A--subunit in acute leukemia.

Factor XIII (FXIII) is a plasma pro-transglutaminase consisting of A and B subunits in a tetrameric structure. A cellular form of FXIII consisting exclusively of A subunits exists in platelets and monocytes: monocyte FXIII may be involved in connective tissue organization. To evaluate the expression and diagnostic significance of FXIII A subunit (FXIIIA) in acute leukemia, we performed an immunocytochemical study (PAP technique) with rabbit antiserum against FXIIIA on leukemic blasts of 48 cases. FXIIIA was detected only in myelomonocytic (M4), monocytic (M5) and megakaryocytic (M7) cases: in M4 and M5 samples the amount of blast cytoplasmic FXIIIA was closely correlated with the expression of monocyte-specific antigenic and cytochemical markers. Our data show immunocytochemical detection of FXIIIA to be useful for acute leukemia characterization.

Circulating progenitor cell release and functional characterization after topotecan plus G-CSF and erythropoietin in small cell lung cancer patients.

Topotecan is a new antineoplastic agent active in ovarian cancer, with promising activity in small cell lung cancer and predictable toxicity. As a part of our ongoing attempt to optimize the use of disease-specific drugs as circulating progenitor cell (CPC) priming in solid tumors, we have evaluated the effects on CPC release of single-agent Topotecan followed by granulocyte colony-stimulating factor (G-CSF) + human recombinant erythropoietin (rhEPO), together with the cell cycle status of the collected CD34+ cells. Ten pretreated patients with small cell lung cancer received Topotecan (1 mg/m2, i.v. for 5 consecutive days) followed by G-CSF (5 microg/kg/day, s.c.) + rhEPO (10,000 I.U. daily, s.c.), starting 24 h after Topotecan. The combination was well tolerated and no relevant side-effects were recorded. On day +10 (range +9 to +11) after the last dose of Topotecan, the median WBC count and the CD34+ cell peak were 8.2 x 10(3) microl (range 4.9-13.9) and 55 microl (range 28-75), respectively. Using flow cytometry, a detailed cell cycle analysis was performed on these CD34+ cells. The cell cycle distribution was determined by DNA content coupled with bromodeoxyuridine incorporation analysis. Apoptosis was evaluated by quantitating DNA strand breaks. The percentage of CD34+ cells in active S-phase was 10.2+/-5%, while early apoptotic CD34+ cells were detected in a low percentage (5.5+/-3%). Topotecan followed by G-CSF + rhEPO mobilizes CPCs effectively. This sequence exerts a stimulation on CD34+ cell cycle with a protective effect from chemotherapy-induced apoptosis. Taken together, these data could be of value for the incorporation of Topotecan, as well as of the combination of G-CSF and rhEPO, into high-dose chemotherapy programs with CPC support.