Phorbol diester-induced macrophage differentiation of leukemic blasts from patients with human myelogenous leukemia.

Phorbol esters, including 12-O-tetradecanoylphorbol 13-acetate (TPA), induce terminal macrophagelike differentiation of cells from human acute myelogenous leukemia lines. We report that myelogenous leukemia cells obtained from patients undergo macrophagelike differentiation after exposure to TPA. The myeloid leukemic cell cultured with TPA became adherent to charged surfaces with long filamentous pseudopodia; developed positive staining for alpha-napthyl acetate esterase, increased lysozyme secretion, reduced nitroblue tetrazolium, and acquired the ability to phagocytose candida. Cells from patients with lymphocytic leukemia did not become macrophagelike when cultured with TPA.

Effect of monocyte migration on low density lipoprotein transport across aortic endothelial cell monolayers.

Endothelial cell monolayers on polycarbonate filters present a barrier to low density lipoprotein (LDL) and albumin transport. These cells form a relatively tight monolayer as shown by measurements of electrical resistance across the monolayer (15 omega-cm2). Monocytes are able to migrate freely across the monolayers in response to chemotactic stimuli. Monocyte chemotaxis across the monolayer caused a marked increase in LDL and albumin transport across the monolayer in the direction of monocyte migration. However, transport in the opposite direction was not significantly increased. These results suggest that monocyte migration across the endothelium could lead to an increased LDL content of the intima.

Monocyte-chemotactic activity of defensins from human neutrophils.

We investigated the monocyte-chemotactic activity of fractionated extracts of human neutrophil granules. Monocyte-chemotactic activity was found predominantly in the defensin-containing fraction of the neutrophil granules. Purified preparations of each of the three human defensins (HNP-1, HNP-2, HNP-3) were then tested. HNP-1 demonstrated significant chemotactic activity for monocytes: Peak activity was seen at HNP-1 concentrations of 5 X 10(-9) M and was 49 +/- 20% (mean +/- SE, n = 9) of that elicited by 10(-8) M FMLP. HNP-2 (peak activity at 5 X 10(-9) M) was somewhat less active, yielding 19 +/- 10% (n = 11). HNP-3 failed to demonstrate chemotactic activity. Checkerboard analysis of monocyte response to HNP-1 and HNP-2 confirmed that their activity was chemotactic rather than chemokinetic. Neutrophils demonstrated a low level of response to defensins but this reaction was primarily chemokinetic. Defensins may play a role in the recruitment of monocytes by neutrophils into inflammatory sites.

Minimally modified low density lipoprotein-induced inflammatory responses in endothelial cells are mediated by cyclic adenosine monophosphate.

We have previously shown that minimally oxidized LDL (MM-LDL) activated endothelial cells to increase their interaction with monocytes but not neutrophils, inducing monocyte but not neutrophil binding and synthesis of monocyte chemotactic protein-1 and monocyte colony-stimulating factor (M-CSF). In the present studies we have examined the signaling pathways by which this monocyte-specific response is induced. Both induction of monocyte binding and mRNA levels for M-CSF by MM-LDL were not inhibited in protein kinase C-depleted endothelial cells. A number of our studies indicate that cAMP is the second messenger for the effects of MM-LDL cited above. Incubation of endothelial cells with MM-LDL caused a 173% increase in intracellular cAMP levels. Agents which increased cAMP levels, including cholera toxin, pertussis toxin, dibutyryl cAMP, and isoproterenol mimicked the actions of MM-LDL. Agents which elevated cAMP were also shown to activate NF kappa B, suggesting a role for this transcription factor in activation of monocyte-endothelial interactions. Although endothelial leukocyte adhesion molecule (ELAM) mRNA synthesis can be regulated by NF kappa B, ELAM was not expressed and ELAM mRNA was only slightly elevated in response to MM-LDL. We present evidence that induction of neutrophil binding by LPS is actually suppressed by agents that elevated cAMP levels.

Minimally modified low density lipoprotein stimulates monocyte endothelial interactions.

The effect of minimally modified LDL (MM-LDL) on the ability of large vessel endothelial cells (EC) to interact with monocytes and neutrophils was examined. These LDL preparations, obtained by storage or by mild iron oxidation, were indistinguishable from native LDL to the LDL receptor and were not recognized by the scavenger receptor. Treatment of EC with as little as 0.12 micrograms/ml MM-LDL caused a significant increase in the production of chemotactic factor for monocytes (sevenfold) and increased monocyte binding (three- to fivefold). Monocyte binding was maximal after 4 h of EC exposure to MM-LDL, persisted for 48 h, and was inhibited by cycloheximide. In contrast, neutrophil binding was not increased after 1-24 h of exposure. Activity in the MM-LDL preparations was found primarily in the polar lipid fraction. MM-LDL was toxic for EC from one rabbit but not toxic for the cells from another rabbit or any human umbilical vein EC. The resistant cells became sensitive when incubated with lipoprotein in the presence of cycloheximide, whereas the sensitive strain became resistant when preincubated with sublethal concentrations of MM-LDL. We conclude that exposure of EC to sublethal levels of MM-LDL enhances monocyte endothelial interactions and induces resistance to the toxic effects of MM-LDL.

Minimally modified low-density lipoprotein induces monocyte adhesion to endothelial connecting segment-1 by activating beta1 integrin.

We have shown previously that treatment of human aortic endothelial cells (HAECs) with minimally modified low-density lipoprotein (MM-LDL) induces monocyte but not neutrophil binding. This monocyte binding was not mediated by endothelial E-selectin, P-selectin, vascular cell adhesion molecule-I, or intercellular adhesion molecule-I, suggesting an alternative monocyte-specific adhesion molecule. We now show that moncytic alpha4beta1 integrins mediate binding to MM-LDL-treated endothelial cells. We present data suggesting that the expression of the connecting segment-1 (CS-1) domain of fibronectin (FN) is induced on the apical surface of HAEC by MM-LDL and is the endothelial alpha4beta1 ligand in MM-LDL-treated cells. Although the levels of CS-1 mRNA and protein were not increased, we show that MM-LDL treatment causes deposition of FN on the apical surface by activation of beta1integrins, particularly those associated with alpha5 integrins. Activation of beta1 by antibody 8A2 also induced CS-1-mediated monocyte binding. Confocal microscopy demonstrated the activated beta1 and CS-1colocalize in concentrated filamentous patches on the apical surface of HAEC. Both anti-CS-1 and an antibody to activated beta1 showed increased staining on the luminal endothelium of human coronary lesions with active monocyte entry. These results suggest the importance of these integrin ligand interactions in human atherosclerosis.

Phorbol ester effect on differentiation of human myeloid leukemia cell lines blocked at different stages of maturation.

The control of differentiation by tumor-promoting phorbol diesters including 12-O-tetradecanoylphorbol-13-acetate (TPA) was investigated using cells from human myeloid leukemia lines and sublines that were blocked at different stages of maturation. The myeloid leukemia cells that were blocked at the myeloblast-promyelocyte stage of maturation (KG-1, HL-60, and ML-3) had a prominent response when cultured with TPA. The cells became adherent, developed pseudopodia, displayed macrophage characteristics by light microscopy, developed nonspecific acid esterase activity, phagocytized yeast, slightly reduced nitro blue tetrazolium, displayed Fc-immunoglobulin G receptors, and killed bacteria. Lysozyme secretion and enzyme activity for beta-glucuronidase and acid phosphatase increased 2- to 20-fold concomitant with macrophage differentiation. The myeloid leukemia cells that were blocked at the undifferentiated myeloid blast stage of maturation (KG-1a and K562) were completely resistant to TPA-induced macrophage differentiation. We examined ten macrophage functions in the myeloid cell lines and sublines after exposure to phorbol diesters. The leukemic lines blocked at the myeloblast-promyelocyte stage of maturation expressed almost all the macrophage-specific functions. Phorbol diesters probably induced differentiation through a common cellular mechanism because the macrophage-differentiated events could not be dissociated. In sharp contrast, the early myeloid blast cells (KG-1a and K562) were incapable of acquiring any of the macrophage-specific functions after exposure to phorbol diesters. The KG-1a variant, in particular, should provide a good model to help elucidate the regulatory mechanism controlling the expression of macrophage functions during exposure to phorbol diesters.

Bone marrow transplantation versus high-dose cytarabine-based consolidation chemotherapy for acute myelogenous leukemia in first remission.

PURPOSE: Despite substantial progress in the treatment of acute myeloid leukemia (AML), fewer than 25% of patients survive free of leukemia for more than 5 years without allogeneic bone marrow transplantation (BMT). In this study we analyzed the results of one or more cycles of high-dose cytarabine-based consolidation chemotherapy as compared with allogeneic BMT in first remission. PATIENTS AND METHODS: The results in 28 adult patients, aged 16 to 45 years, who underwent a closely HLA-matched BMT for AML in first remission were compared with those in 54 consecutive, age-matched, adult patients treated with one or more cycles of high-dose, cytarabine-based consolidation chemotherapy. RESULTS: After a median follow-up of 4 years, the actuarial risk of leukemic relapse was considerably lower in the transplant group than in the group treated with consolidation chemotherapy (32% +/- 26% v 60% +/- 14%; P = .05). Treatment-related mortality, however, was much higher in the group treated with BMT (32% v 6%, P = .002). The actuarial disease-free survival at 5 years was not significantly different for the two groups (45% +/- 24% v 38% +/- 14%). CONCLUSIONS: Our results show that BMT in first remission AML did not offer a disease-free survival advantage over intensive postremission consolidation chemotherapy. Larger studies are needed to identify patients who might benefit most from BMT.

Minimally modified lipoproteins in diabetes.

Studies from several laboratories suggest that oxidized LDL may play an important role in atherogenesis. Our group previously showed that treatment of aortic endothelial cells with low levels of MM-LDL caused increased expression of MCP-1, M-CSF, tissue factor, and a monocyte-binding protein. In these studies MM-LDL was produced by storage of native LDL. We now show that cocultures of endothelial and smooth muscle cells can also produce MM-LDL from native LDL. This production of MM-LDL by cells is prevented by preincubating the LDL with probucol or vitamin E. However, addition of antioxidants to MM-LDL did not block its action. In past studies we also showed that endothelial cells exhibit differential sensitivity to the effects of MM-LDL. We report herein that in resistant cells there is no elevation of catalase, glutathione peroxidase, or copper-zinc-dependent SOD. However, manganese-dependent SOD is elevated in resistant cells. Ways in which MM-LDL production may be elevated in poorly controlled diabetics subjects are discussed.

Long-term outcome of autologous transplantation of peripheral blood progenitor cells as postremission management of adult acute myelogenous leukemia in first complete remission.

In order to improve leukemia-free survival (LFS) without the treatment-related morbidity of allogeneic bone marrow transplantation or multiple prolonged cycles of consolidation chemotherapy, we evaluated the long-term outcome of autologous transplantation of peripheral blood progenitor cells (PBPCs) as postremission therapy in 129 patients aged 18-71 years (median 49 years) with newly diagnosed acute myelogenous leukemia (AML) in first complete remission (CR1). The median follow-up from remission for surviving patients was 62.2 months (range 3.7-127.9 months). A total of 57 patients were alive and leukemia free at the end of the study. The LFS and overall survival 5 years from remission were 40.2% (+/-9.2%) and 41.4% (+/-9.4%), respectively. The median LFS and overall survival are 17.3 and 23.3 months, respectively. Multivariate analysis identified age as the most significant predictor for both LFS and overall survival. Karyotype was also found to be predictive of outcome. Our results show that autologous transplantation of PBPC procured after a single cycle of high-dose cytarabine-based consolidation chemotherapy for a population of adult patients with AML in CR1 produces a high likelihood of long-term LFS, offering a state of clinical minimal residual disease for the investigation of future therapeutic approaches.

Transplantation of IL-2-mobilized autologous peripheral blood progenitor cells for adults with acute myelogenous leukemia in first remission.

In order to improve leukemia-free survival we evaluated the feasibility and efficacy of autologous transplantation of interleukin-2 (IL-2)-mobilized peripheral blood progenitor cells for adult patients with acute myelogenous leukemia in first remission. Forty-nine consecutive patients (median age 49, range 21-70) with acute myelogenous leukemia in first remission were enrolled on a study of high-dose cytarabine/mitoxantrone consolidation chemotherapy with post-recovery IL-2 used as a method of in vivo purging for the purpose of autologous peripheral blood progenitor cell transplantation. A median of 2.08 x 10(6) CD34+ peripheral blood progenitor cells/kg were infused 1 day after preparative conditioning with 11.25 Gy total body irradiation and cyclophosphamide (120 mg/kg). Forty-one patients received myeloablative chemoradiotherapy followed by the infusion of IL-2-mobilized autologous peripheral blood progenitor cells. The median times to both neutrophil and platelet recovery were 16 days (range, 2-43) and 23 days (8-318+ days), respectively. Twenty-seven patients remain alive with 24 in continued first complete remission. Median remission duration for all eligible patients is 8 months, and actuarial leukemia-free survival is 49+/-15%. The actuarial risk of relapse is 43+/-16%. Toxicity of autologous peripheral blood progenitor cell transplant included treatment-related death in three patients and serious organ toxicity in 12. Advanced age was a negative prognostic factor for leukemia-free survival. Results were compared to an age-matched historical control treated with autologous transplantation of chemotherapy-mobilized progenitor cells; no significant difference in favor of IL-2 mobilization could be demonstrated. Our results demonstrate that autologous transplantation of IL-2-mobilized peripheral blood progenitor cells is feasible in an unselected population of adult patients with acute myelogenous leukemia in first remission with minimal toxicity but no clear evidence of benefit in leukemia-free survival.

Transplantation of autologous peripheral blood progenitor cells procured after high-dose cytarabine-based consolidation chemotherapy for adults with acute myelogenous leukemia in first remission.

The purpose of the study was to evaluate the feasibility and efficacy of high-dose cytarabine-anthracycline consolidation chemotherapy followed by autologous transplantation of chemotherapy/rHuG-CSF-mobilized peripheral blood progenitor cells for adult patients with acute myelogenous leukemia in first remission. Fifty-nine consecutive patients (median age 45, range 18-69) with acute myelogenous leukemia in first remission were enrolled on a study of high-dose cytarabine-mitoxantrone consolidation chemotherapy used as a method of in vivo purging for the purpose of autologous peripheral blood progenitor cell transplantation. A median of 7 x 10(8) peripheral blood mononuclear cells/kg were infused 1 day after preparative conditioning with 11.25 Gy total body irradiation and cyclophosphamide (120 mg/kg). Forty-six patients received myeloablative chemo-radiotherapy followed by the infusion of chemotherapy/rHu-G-CSF-mobilized autologous peripheral blood progenitor cells. The median time to both neutrophil and platelet recovery from transplant was 15 days (range, 11-36 and 5-253+ days, respectively). After a median follow-up of 27 months, 31 patients remain alive with 27 in complete remission. Median remission duration for all eligible patients is 12 months, and actuarial leukemia-free survival at 3 years is 42 +/- 14%. The actuarial risk of relapse is 54 +/- 15%. Toxicity of autologous peripheral blood progenitor cell transplant included treatment-related death in two patients and grade III/IV organ toxicity in six. Advanced age was a negative prognostic factor for leukemia-free survival. Our results demonstrate that autologous transplantation of chemotherapy-mobilized peripheral blood progenitor cells is feasible in an unselected population of adult patients with acute myelogenous leukemia in first remission producing improved leukemia-free survival with minimal toxicity.

Atherogenic diet and minimally oxidized low density lipoprotein inhibit osteogenic and promote adipogenic differentiation of marrow stromal cells.

In osteoporosis, the bone marrow stroma osteogenic cell population declines and adipocyte numbers increase. We recently showed that oxidized lipids inhibit differentiation of preosteoblasts. In this report, we assess the effect of minimally oxidized low density lipoprotein (MM-LDL) on osteoblastic differentiation of murine marrow stromal cells, M2-10B4. MM-LDL, but not native LDL, inhibited stromal cell osteoblastic differentiation as demonstrated by inhibition of alkaline phosphatase activity, collagen I processing, and mineralization, through a mitogen-activated protein kinase-dependent pathway. In addition, marrow stromal cells from C57BL/6 mice fed a high fat, atherogenic diet failed to undergo osteogenic differentiation in vitro. The ability of MM-LDL to regulate adipogenesis was also assessed. Treatment of M2-10B4 as well as 3T3-L1 preadipocytes with MM-LDL, but not native LDL, promoted adipogenic differentiation in the presence of peroxisome proliferator-activated receptor (PPAR) gamma agonist thiazolidinediones, BRL49653 and ciglitizone. Based on promoter-reporter construct experiments, MM-LDL may be acting in part through activating PPARalpha. These observations suggest that LDL oxidation products promote osteoporotic loss of bone by directing progenitor marrow stromal cells to undergo adipogenic instead of osteogenic differentiation. These data lend support to the "lipid hypothesis of osteoporosis."

A multicenter, randomized trial of fluconazole versus amphotericin B for empiric antifungal therapy of febrile neutropenic patients with cancer.

PURPOSE: To compare the efficacy and safety of fluconazole and amphotericin B as empiric antifungal therapy of febrile neutropenic patients with cancer. PATIENTS AND METHODS: A total of 317 neutropenic patients (<500 cells/mm3) with persistent or recrudescent fever despite 4 or more days of antibacterial therapy were randomly assigned to receive either fluconazole (400 mg intravenously once daily) or amphotericin B (0.5 mg/kg once daily). Patients were evaluated for the efficacy and safety of each drug by clinical criteria, frequent cultures and radiological procedures, and laboratory values. A response was classified as satisfactory at the end of therapy if the patient was afebrile, had no clinical or microbiological evidence of fungal infection, and did not require study termination due to lack of efficacy, drug toxicity, or death. RESULTS: A satisfactory response occurred in 68% of the patients treated with fluconazole (107 of 158 patients) and in 67% of patients treated with amphotericin B (106 of 159 patients). Progressive or new fungal infections during therapy occurred in 13 (8%) patients treated with fluconazole (8 with Candida, 5 with Aspergillus) and in 10 (6%) patients treated with amphotericin B (5 with Candida, 3 with Aspergillus, 2 with other fungi). Adverse events related to study drug (especially fever, chills, renal insufficiency, electrolyte disturbances, and respiratory distress) occurred more often in patients treated with amphotericin B (128 [81%] of 159 patients) than patients treated with fluconazole (20 [13%] of 158 patients, P = 0.001). Eleven (7%) patients treated with amphotericin B but only 1 (1%) patient treated with fluconazole were terminated from the study owing to an adverse event (P = 0.005). Overall mortality (27 [17%] patients treated with fluconazole versus 34 [21%] patients treated with amphotericin B) and mortality from fungal infection (7 [4%] patients treated with fluconazole versus 5 [3%] patients treated with amphotericin B) were similar in each study group. CONCLUSIONS: Intravenous fluconazole can be an effective and safe alternative to amphotericin B for empiric antifungal therapy in many febrile neutropenic patients. However, because fluconazole may be ineffective in the treatment of Aspergillus, patients at risk for that infection should be evaluated by chest radiograph, computed tomographic scanning, and cultures before the use of empiric fluconazole therapy.

Alveolar macrophage dysfunction in human bone marrow transplant recipients.

We studied the functional characteristics of alveolar macrophages obtained by segmental pulmonary lavage from allogeneic marrow transplant recipients without evidence of ongoing pulmonary infection. The macrophages were mostly of donor marrow origin as judged by Y body fluorescence and were morphologically normal, except for the intracellular accumulation of various amounts of heterogeneous foreign materials. Macrophage function of patients studied within four months after transplantation was impaired, as measured by chemotaxis, phagocytosis and killing of Candida pseudotropicalis, and killing of bacteria. In two patients studied six and 12 months after transplantation, macrophage functions returned toward normal except for a persistent defect in killing of C. pseudotropicalis. Cytomegalovirus was cultured from the lavaged cells of two patients, but the macrophage dysfunction was independent of the cytomegalovirus isolation. These results show that alveolar macrophage dysfunction occurs in marrow transplant recipients and may be associated with their increased risk for pulmonary infections.

Selective depletion of CD8+ cells for prevention of graft-versus-host disease after bone marrow transplantation. A randomized controlled trial.

We performed a prospective randomized, double-blind study to assess the efficacy of selective depletion of CD8+ bone marrow cells in preventing acute graft-versus-host disease (GVHD) in 38 patients undergoing HLA-identical sibling donor bone marrow transplantation for leukemia. All patients received CsA for GVHD prophylaxis. Nineteen patients received marrow depleted of CD8+ cells by ex vivo treatment with anti-leu2, an anti-CD8 mAb and complement; four patients had moderate (grade 1 or 2 acute GVHD) and the only patient who experienced grade 3 manifestations was a technical failure. The control group consisted of 19 patients who received unmodified bone marrow; one patient had grade 1, 4 patients had grade 2, and 10 had grade 3 or 4 acute GVHD. The actuarial incidence of grade > or = 2 acute GVHD was 20 +/- 20% in the CD8-depleted group compared with 80 +/- 18% in the controls (P = 0.004). Death in 5 of the control patients and the single patient in whom CD8 depletion was a technical failure was related to acute GVHD. Graft failure occurred in 2 patients in the CD8-depleted group and in none of the controls. Leukemic relapse occurred in 2 patients receiving CD8-depleted bone marrow and 2 patients in the control group. Seven patients receiving marrow depleted of CD8+ cells are alive and free of leukemia and 9 patients in the control group are alive, 7 of whom remain leukemia-free (P = 0.88). The 3-year actuarial leukemia-free survival is 37 +/- 22% of the CD8-depleted group and 36 +/- 22% for the control group. These results indicate that selective depletion of CD8+ cells from the bone marrow significantly reduces the incidence and severity of acute GVHD.

Pathogenesis of atherosclerosis.

The earliest lesion in the development of an atherosclerotic plaque is the fatty streak. This chronic inflammatory reaction results from a sequence of events that begins with the trapping of low density lipoprotein (LDL) in the subendothelial space of the artery wall. The trapped LDL is seeded with oxidative species released by the overlying endothelium, and lipid oxidation is initiated within the LDL particle. Some of the lipids that result lead to the activation of NFkB-like transcription factors that cause the expression of genes whose protein products mediate monocyte binding, monocyte chemotaxis into the subendothelial space, and conversion into macrophages. At least 1 major gene modulates the oxidation of LDL lipids and/or the biologic response to these lipids. The inverse relation between high density lipoprotein (HDL) and atherosclerotic events may in part be due to enzymes associated with HDL that destroy the biologically active lipids generated in LDL.

HTLV-I-associated myelopathy following allogeneic bone marrow transplantation.

A 39-year-old polytransfused patient with aplastic anemia acquired transfusion-associated HTLV-I infection shortly before transplantation. The patient underwent allogeneic bone marrow transplantation and developed HTLV-I associated myelopathy 3 years later. Clinical abnormalities and a host of atypical findings are presented in the context of previous reports describing uncommon features of the disease.

Localized radiation increases morbidity and mortality after TBI-containing autologous stem cell transplantation in patients with lymphoma.

The purpose of this study is to assess the relationship between involved field radiation therapy (IFRT) and treatment-related morbidity and mortality in patients receiving high-dose chemotherapy (HDC), total body irradiation (TBI) and autologous peripheral stem cell transplant (PSCT) for Hodgkin's and non-Hodgkin's lymphoma. Between January 1994 and May 2002, 156 patients underwent HDC, TBI and autologous PSCT. Localized external beam radiation therapy was given to 21 patients for consolidation, or to achieve control of symptomatic or active disease prior to or after transplant. Among patients who had IFRT prior to autologous PSCT, five treatment-related deaths were observed, compared to seven deaths in 135 patients who had autologous PSCT without IFRT (P<0.01). Most deaths were attributable to sepsis and multiorgan failure. A higher incidence of pneumonitis was also noted in patients exposed to mediastinal irradiation. No adverse impact on long-term survival could be demonstrated. Involved field radiation prior to TBI is associated with higher treatment-related mortality in lymphoma patients undergoing autologous peripheral stem cell transplant, necessitating careful monitoring.

Phase I-II study of busulfan and cyclophosphamide conditioning for transplantation in advanced multiple myeloma.

We evaluated a non-radiation containing preparative regimen for persons with myeloma receiving bone marrow (BM) or blood cell transplants. Twenty-three adults with advanced multiple myeloma (15 responsive to chemotherapy, 8 resistant) received cyclophosphamide 120 mg/kg and busulfan 14-16 mg/kg followed by the infusion of BM or blood progenitor cells. Patients were followed for response by monthly skeletal radiographs, urine and serum monoclonal paraprotein measurement, BM evaluation and beta 2-microglobulin. Three of 18 evaluable patients achieved complete response, 13 patients achieved partial response and two a minimal response. Actuarial 1 year survival post-transplant for all patients is 63% (95% confidence interval, 40-86%). Disease stage and response to chemotherapy pre-transplant correlated with survival post-transplant. Actuarial survival for patients with resistant disease was 38% (4-72%); for patients with chemotherapy-responsive disease, it was 78% (48-100%, p = 0.02). Regimen-related toxicity consisted of five early deaths, three from veno-occlusive disease, one from infection and one from multiorgan failure. Fatal and non-fatal hepatic and renal toxicities were related to busulfan dose with most complications occurring at 16 mg/kg. Our studies suggest that busulfan and cyclophosphamide are an effective conditioning regimen in multiple myeloma. Toxicity precludes increasing the total dose of busulfan beyond 14 mg/kg.