Fludarabine with pharmacokinetically guided IV busulfan is superior to fixed-dose delivery in pretransplant conditioning of AML/MDS patients.

We hypothesized that IV busulfan (Bu) dosing could be safely intensified through pharmacokinetic (PK-) dose guidance to minimize the inter-patient variability in systemic exposure (SE) associated with body-sized dosing, and that this should improve outcome of AML/MDS patients undergoing allogeneic stem cell transplantation. To test this hypothesis, we treated 218 patients (median age 50.7 years, male/female 50/50%) with fludarabine 40 mg/m2 once daily x4, each dose followed by IV Bu, randomized to 130 mg/m2 (N=107) or PK-guided to average daily SE, AUC of 6000 µM min (N=111), stratified for remission status and allo-grafting from HLA-matched donors. Toxicity and GvHD rates in the groups were similar; the risk of relapse or treatment-related mortality remained higher in the fixed-dose group throughout the 80-month observation period. Further, PK-guidance yielded safer disease control, leading to improved overall and PFS, most prominently in MDS patients and in AML patients not in remission at allogeneic stem cell transplantation. We conclude that AML/MDS patients receiving pretransplant conditioning treatment with our 4-day regimen may benefit significantly from PK-guided Bu dosing. This could be considered an alternative to fixed-dose delivery since it provides the benefit of precise dose delivery to a predetermined SE without increasing risk(s) of serious toxicity and/or GvHD.

Intratumor murine interleukin-12 gene therapy suppressed the growth of local and distant Ewing's sarcoma.

We evaluated the effect of interleukin-12 (IL-12) gene therapy using an Ewing's sarcoma animal model in T-cell-deficient nude mice. Subcutaneous injection of TC71 cells resulted in tumor development by day 5. Mice were treated with a single intratumor injection of adenovirus beta-galactosidase (Ad.beta-gal) or adenovirus murine IL-12 (Ad.mIL-12) (2 x 10(9) PFU) and killed 1-7 days later. Reverse transcriptase-polymerase chain reaction analysis of tumor tissue demonstrated peak expression of IL-12 p35 and p40 at 48 h, which persisted up to 7 days. For in vivo therapy, mice received intratumor Ad.beta-gal or Ad.mIL-12 twice weekly for 2.5 weeks starting on day 6. Ad.mIL-12-treated tumors were significantly smaller (median volume, 19.7 mm3; range, 3.41-159.5 mm3) than Ad.beta-gal-treated tumors (median volume, 3214.9 mm3; range 1679.9-5909.8 mm3, P<0.003) on day 31. The weight of Ad.mIL-12-treated tumors was also lighter than the Ad.beta-gal-treated tumors (median, 2 mg; range, 1-5 mg versus median, 1960 mg; range 1640-5230 mg, P<0.01). Ad.mIL-12 therapy significantly prolonged the survival time and also inhibited the growth of an untreated tumor on the contralateral side. Immunohistochemistry analysis of the IL-12-treated tumors demonstrated IL-12 expression with increased Fas, Fas ligand and tumor cell apoptosis. CD31 and vascular endothelial growth factor expression were decreased. These data suggest that IL-12 gene therapy may be useful in the treatment of Ewing's sarcoma.

Interferon-alpha after autologous stem cell transplantation in pediatric patients with advanced Hodgkin's lymphoma.

Thirteen children with refractory or recurrent Hodgkin's lymphoma (HL) received high-dose chemotherapy and autologous hematopoietic stem cell transplant (ASCT). After hematologic recovery, 10 patients were given interferon-alpha (IFN-alpha) as adjuvant therapy, starting at a dose of 0.5 x 10(6) U/m2 subcutaneously, three times a week. The dose was escalated as tolerated. Patients were treated for a median of 12 (4-24) months. Transient myelosuppression was the most common toxicity and led to temporary treatment interruption in five patients. The IFN-alpha dose was increased in nine patients, to a median final dose of 3.5 x 10(6) U/m2/week. With a median follow-up of 67 (range 25-114) months, nine of the 10 patients are alive and in continuous remission. One patient relapsed. Three patients were not treated with IFN-alpha initially, two because of rapidly progressive disease. One patient received IFN-alpha for treatment of relapse after transplant, and is alive in remission 10 years later. IFN-alpha has activity in children with advanced HL, and prolonged, low-dose treatment given after ASCT can be tolerated. Its therapeutic effect as a post-transplant adjuvant warrants further investigation.

Total body irradiation, fludarabine, melphalan, and allogeneic hematopoietic stem cell transplantation for advanced pediatric hematologic malignancies.

We evaluated the efficacy and toxicity of adding 9 Gy of total body irradiation (TBI), in three single daily fractions of 3 Gy, to the reduced intensity regimen of fludarabine 30 mg/m2 i.v. x 4 days and melphalan 140 mg/m2 i.v. x 1 day in advanced pediatric hematologic malignancies. Twenty-two acute lymphoblastic leukemia (ALL), six acute myeloid leukemia (AML), and one non-Hodgkin lymphoma patients were transplanted. Of these, 13 were beyond second remission, and five had prior hematopoietic stem cell transplant (HSCT). Twenty-one donors were unrelated, of which 19 were from cord blood (CB) units. Three of the eight related donors were genotypically disparate. Oral mucositis and diarrhea were the most common toxicities. Twenty-seven patients achieved neutrophil engraftment (median 16 days), and 23 had platelet engraftment (median 42 days). One patient had primary graft failure. Seven patients died of non-relapse causes in the first 100 days. With a median follow-up of 52 months, seven of 22 ALL, five of six AML, and one of one lymphoma patients are alive and in remission. The regimen of TBI, fludarabine, and melphalan allows the engraftment of allogeneic hematopoietic stem cells (including mismatched CB). It was fairly well tolerated in pediatric patients, even for second transplants. Its efficacy requires further evaluation.

Phosphorylation of ornithine decarboxylase at both serine and threonine residues in the ODC-overproducing, Abelson virus-transformed RAW264 cell line.

Expression of ornithine decarboxylase (ODC), the initial enzyme is polyamine biosynthesis, is essential for cell growth. The Abelson virus-transformed, murine macrophage-derived RAW264 cell line, overexpresses ODC activity and enzyme protein at a level 100-1000-fold greater than in normal cells. Expression of ODC was completely dependent on extracellular stimulants and followed a temporally discrete pattern similar to that in normal cells. ODC was present in RAW264 cells as two major and one minor isoelectric forms. Analysis of ODC isolated from [32P]orthophosphate metabolically radiolabeled cells demonstrated that the basic isoelectric enzyme form was unphosphorylated, the two more acidic forms were phosphorylated, and both phosphoserine and phosphothreonine residues were present in the phosphorylated ODC. Therefore, in the RAW264 cell line, ODC is overexpressed and phosphorylated at multiple sites on the enzyme molecule.

Interleukin (IL)-12 and IL-12 gene transfer up-regulate Fas expression in human osteosarcoma and breast cancer cells.

Expression of Fas (CD95, APO-1), a cell surface receptor capable of inducing ligand-mediated apoptosis, is involved in tissue homeostasis and elimination of targeted cells by natural killer and T cells. Corruption of this pathway, such as reduced Fas expression, can allow tumor cells to escape elimination and promote metastatic potential. In this study, the status of Fas expression has been examined in the parental SAOS human osteosarcoma cells that do not metastasize and in selected variants that cause lung metastases in 16 weeks (LM2) or 8 weeks (LM6) after i.v. injection into nude mice. Fas expression correlated with the metastatic potentials of the three cell lines. Northern and fluorescence-activated cell-sorting analyses indicated that LM6 cells expressed Fas at a lower level than seen in the parental cells. Infection of the LM6 cells with an adenoviral vector containing the murine interleukin (IL)-12 gene (AD:mIL-12) or treatment with recombinant murine IL-12 resulted in a dose-dependent up-regulation of FAS: The up-regulation of Fas by IL-12 was also demonstrated in human etoposide-resistant MDA-MB-231 breast cancer cells. [(3)H]Thymidine growth inhibition studies indicated that the cell surface Fas induced after IL-12 exposure was functional and able to mediate cell death on cross-linking with anti-FAS: We also demonstrate that this effect is independent of IFN-gamma. Whereas these cell lines are sensitive to IFN-gamma, incubation with IFN-gamma does not increase susceptibility to Fas-mediated cell death, nor do these cells produce IFN-gamma with or without IL-12 treatment. We hypothesize that expression of Fas may play a role in the elimination of metastatic tumor cells in the lung, an organ in which Fas ligand is expressed. The antitumor activity of IL-12 may be secondary in part to its ability to up-regulate Fas expression on tumor cells, which subsequently increases immune-mediated destruction of osteosarcoma cells.

Intranasal therapy with an adenoviral vector containing the murine interleukin-12 gene eradicates osteosarcoma lung metastases.

The purpose of these studies was to determine the effect of adenovirus-mediated interleukin-12 (IL-12) gene transfer on the growth and development of osteosarcoma (OS) lung metastases in nude mice. A nude mouse model was produced by repetitive cycling of human SAOS OS cells through the lung. The resultant SAOS-LM6 cell line produced microscopic lung metastases by 5-6 weeks after i.v. injection of the tumor cells, with visible lung metastases present 8 weeks after injection. Transfection of SAOS-LM6 cells with a plasmid containing the murine IL-12 gene resulted in a decrease in metastatic potential. Animals injected with IL-12-transfected clones had fewer metastases compared with mice injected with SAOS-LM6 cells transfected with a control plasmid. Furthermore, nasal delivery of an adenoviral vector containing the murine IL-12 gene resulted in the inhibition of pulmonary metastases. Together, these data indicate that IL-12 may be an effective agent against OS and that nasal delivery may offer a unique way to deliver the gene to the local tumor environment, potentially decreasing systemic toxic effects.

9-Nitrocamptothecin liposome aerosol treatment of melanoma and osteosarcoma lung metastases in mice.

The response rates of relapsed osteosarcoma and melanoma pulmonary metastases to traditional i.v. chemotherapeutic regimens have been disappointing. Direct drug delivery of chemotherapy to the lungs could increase the drug concentration in the tumor area and may offer a new therapeutic approach for these patients. Previous studies demonstrated that drugs delivered to the respiratory tract in liposomal formulation resulted in high pulmonary drug concentration, reduced systemic toxicity, and reduced dosage requirements compared with parenteral and oral administration. To determine whether this approach has utility against pulmonary metastases, the efficacy of aerosol therapy with liposome-encapsulated 9-nitrocamptothecin (L-9NC) was determined using two different experimental lung metastasis models. C57BL/6 mice were treated the day after the i.v. injection of B16 melanoma cells with aerosol L-9NC for 1 h (153 microg 9-nitrocamptothecin/kg) for 5 days per week for up to 3 weeks. Aerosol L-9NC treatment resulted in a reduction in lung weights (P = 0.005) and number of tumor foci (P < 0.001). Visible tumor nodules were fewer and smaller in the 9-nitrocamptothecin-treated group than in untreated control mice (P < 0.001). Using a newly developed human osteosarcoma experimental metastasis model in nude mice, we demonstrated that aerosol L-9NC was also effective against established lung metastases. Aerosol therapy initiated on the ninth week after i.v. tumor injection and continued for 8 or 10 weeks produced highly significant reductions in the number of animals with both visible and microscopic disease (P < 0.02), the total number of tumor foci in the lungs (P < 0.005), and the size of the individual tumor nodules (P < 0.02). These data suggest that L-9NC aerosol therapy may offer significant advantage over existing methods in the treatment of melanoma and osteosarcoma pulmonary metastases.

Phase II study of recombinant interleukin 1alpha and etoposide in patients with relapsed osteosarcoma.

A Phase II trial using interleukin 1alpha (IL-1alpha) and etoposide for patients with relapsed osteosarcoma (OS) was undertaken to assess the feasibility and tolerability of combination therapy with biotherapy and chemotherapy. Nine patients with histologically proven relapsed OS were treated with IL-1alpha immediately followed by etoposide daily for 5 days every 3 weeks. Surgical resection of lung metastasis or peripheral tumor was performed after two or three cycles. We observed three partial responses; disease was stable in another case. One case could not be evaluated. The side effects associated with combination therapy were as predicted from known side effects of the individual agents; however, more profound neutropenia was observed. Four patients exhibited clinical signs of capillary leak syndrome, i.e., hypotension, edema, and weight gain. The etiology of the capillary leak was unclear, because serum IL-1alpha, IL-2, tumor necrosis factor, and nitric oxide levels could not be used to predict which patients would develop capillary leak. Histological analysis of tumor specimens obtained after two or more courses of therapy showed changes consistent with a response to a biological response modifier: peripheral fibrosis surrounded the metastasis with infiltration of chronic and acute inflammatory cells. Because the response of relapsed OS to any type of salvage regimen has been poor, we interpret the clinical response of this therapy as good. However, the significant side effects associated with this therapy must also be taken into consideration before deciding to use this combination therapy. It is unfortunate that the study was stopped early due to halted production of IL-1alpha. If this agent is again manufactured for clinical use, we conclude that additional evaluation in patients with relapsed OS is warranted.

Growth suppression of established human osteosarcoma lung metastases in mice by aerosol gene therapy with PEI-p53 complexes.

Lung metastases are a frequent complication of osteosarcoma and a treatment that would reduce the severity of this complication would be of great benefit to patients. We have used a formulation consisting of polyethyleneimine (PEI) and a p53 gene administered in aerosol to treat established lung micrometastases as a model of human osteosarcoma in nude mice. The SAOS-LM6 cell line, a metastatic derivative of the p53 null SAOS-2 line, expresses high levels of p53 protein after in vitro transfection with PEI-p53 complexes as determined by ELISA, and transfection with both p53wt and the p53 variant, p53-CD(1-366) in vitro, results in a marked inhibition of SAOS-LM6 cell proliferation. Aerosol delivery of plasmid DNA containing either the p53 gene or a p53-CD(1-366) variant gene formulated with PEI to mice resulted in highly significant reductions in the numbers and size of tumors (P<.001), the total number of tumor foci in the lungs (P<.001) and the size of individual tumor nodules in treated animals compared to untreated, PEI only-treated and PEI-CAT-treated control animals. The different tissues examined did not reveal any signs of toxicity or inflammation after repeated exposure to PEI-DNA. The aerosol delivery of PEI-based formulations of p53 or synthetic p53 variant genes represents a promising new strategy for the treatment of established human osteosarcoma lung metastases. The noninvasive nature of aerosol delivery coupled with low toxicity also make this therapeutic approach potentially appropriate for combination therapy with either radio- or chemotherapy.

A nude mouse model of human osteosarcoma lung metastases for evaluating new therapeutic strategies.

The purpose of these studies was to develop a metastatic osteosarcoma nude mouse model to evaluate the in vivo efficacy of new therapeutic compounds. Human SAOS-2 osteosarcoma cells (10(6) cells) were injected i.v. into nude mice. Cells isolated from a rare pulmonary metastases 6 months later were established (SAOS-LM1) in culture and re-injected. This procedure was repeated 5 additional times to produce the SAOS-LM6 cell line. Visible pulmonary nodules were present 8 weeks following i.v. injection of 10(6) SAOS-LM6 cells as compared to 17 weeks using SAOS-LM2 cells. Microscopic SAOS-LM6 pulmonary metastases were demonstrated at 6 weeks. Administration of adriamycin on week 9 resulted in regression of macroscopic SAOS-LM6 lung tumors. The ability of the model to be used to evaluate the effectiveness of a biologic agent against microscopic disease was also verified. It was concluded that this model can assess therapeutic efficacy and therefore, may have a role in investigating the potential of novel approaches aimed at eliminating pulmonary metastatic osteosarcoma.

A fludarabine-based conditioning regimen for severe aplastic anemia.

Graft rejection is a common problem after alternative donor transplantation for patients with refractory severe aplastic anemia (SAA). Intensification of the conditioning regimen, with the inclusion of irradiation, has often been advocated to combat this problem. With this approach engraftment rate improved, but the incidence of transplant-related complications is also increased, resulting in little change in the overall outcome. We investigated the use of the combination of fludarabine, cyclophosphamide and anti-thymocyte globulin as the conditioning regimen in five multiply-transfused SAA patients. Three patients received an HLA one-antigen disparate related donor transplant, while two patients were given marrow from matched, unrelated donors. The regimen was well tolerated, with only grade I toxicity encountered. With a median follow-up of 9 months, all patients are alive with complete donor chimerism. We conclude that fludarabine may be used in place of irradiation to augment the conditioning regimen of cyclophosphamide and anti-thymocyte globulin for alternative donor transplantation in children with SAA.

Lorazepam for seizure prophylaxis during high-dose busulfan administration.

Seizure is a recognized complication of high-dose busulfan (BU) therapy and phenytoin (DPH) is widely used as prophylaxis. A number of adverse effects have been associated with DPH and it may also interfere with BU metabolism. We used lorazepam (median dose 0.022 mg/kg) i.v. or p.o. before each dose and for 24 h after the last dose of BU as seizure prophylaxis to 29 children undergoing hematopoietic stem cell transplantation. The regimen was well tolerated and drowsiness was the only significant side-effect. Twelve patients were able to receive the entire prophylaxis by mouth. No seizure developed during and within 48 h of BU. Concomitant pharmacokinetic studies showed no alternation of the absorption and clearance of BU during lorazepam administration. Lorazepam can be used as an alternative for seizure prophylaxis during high-dose BU treatment.

Individualizing high-dose oral busulfan: prospective dose adjustment in a pediatric population undergoing allogeneic stem cell transplantation for advanced hematologic malignancies.

We investigated whether adjusting the oral busulfan (BU) dosage on the basis of early pharmacokinetic data to achieve a targeted drug exposure could reduce transplant-related complications in children with advanced hematologic malignancies. Twenty-five children received a preparative regimen consisting of thiotepa (250 mg/m2 i.v. daily for 3 days), BU (40 mg/m2 per dose p.o. every 6 h for 12 doses), and cyclophosphamide (60 mg/kg i.v. daily for 2 days) and then underwent allogeneic stem cell transplantation. Busulfan clearance and area under concentration time-curve (AUC) were determined after the first dose using a one-compartment pharmacokinetic (PK) model with first-order absorption. The initial PK analysis was successfully completed after the first BU dose in 21 patients (84%). A final AUC of 1000-1500 microM x min/dose was targeted and subsequent doses were modified as necessary to achieve this value. Fourteen of the 25 patients (56%) required dose adjustment. Follow-up PK analysis was completed in 21 patients and 16 of these achieved the targeted BU exposure for the course of therapy. Interpatient variability in BU clearance was high (up to five-fold). The most frequent regimen-related toxicities were cutaneous and gastrointestinal (stomatitis and diarrhea). Only one patient developed hepatic veno-occlusive disease. Our study demonstrates the feasibility of adjusting the oral BU dose in individual pediatric patients. Although toxicity associated with BU seemed to be reduced, this conclusion is tempered by the fact that the overall regimen-related toxicity (RRT) remains substantial and reflected the effects of all agents used in the preparative regimen.

Biologic response modifiers in pediatric cancer.

Biologic response modifiers are becoming an important addition to surgery, chemotherapy, and radiotherapy in the management of cancer. As this field of research grows and expands, more biologic response modifiers will be incorporated into therapeutic regimens. By stimulating the immune system to eradicate minimal residual disease, these agents may improve the disease-free and long-term survival rates of patients with a variety of malignancies. The challenge is to incorporate biologic response modifiers into the treatment armamentarium in ways that will maximize their tumorigenicity.

Human bone marrow transplant rejection is associated with telomere cleavage.

Telomeres that guard chromosomes are shortened with each cell division because of replication-dependent sequence loss at both termini. The gradual erosion of telomeric length has been directly related to the process of aging in vivo. Recently we have reported, in murine and human cancer cells treated with different apoptogens, cleavage and extrusion of telomeric DNA prior to cell death on one hand and an amplification of telomeric DNA in metastatic epithelial malignancies of different histopathologic origin on the other. This study tested our hypothesis that telomere cleavage is linked to transplant rejection in cancer patients receiving stem cells either from bone marrow (BM) or umbilical cord blood transfusion. Telomere integrity and mitotic catastrophe were studied by cytogenetic and molecular fluorescence in situ hybridization (FISH) techniques in two BM samples taken from a male stem cell transplant recipient diagnosed with aplastic anemia. The first BM sample, which was aspirated 27 days after transplant, was mitotically active. Only one of 50 metaphases showed a chromatid break. Every cell karyotyped was of male origin with 46, XY chromosome constitution. The second BM sample aspirated 52 days after transplant gave no metaphases and most interphase cells appeared dead. FISH preparations of the second BM sample showed cleavage and drastic reduction of telomeric DNA at the time the patient was rejecting the transplant. In contrast, the first BM sample had shown no indication of cleavage of the telomeric DNA, although the percentage of telomeric area was smaller than in the control. The replicative stress imposed on the stem cells engrafted may result in an accelerated aging effect, possibly due to the erosion of telomeric DNA. We, therefore, conclude that BM rejection could be directly associated with the cleavage, clustering, and extrusion of telomeric DNA in the donor cells.

Outcomes of second allogeneic hematopoietic stem cell transplantation for patients with acute lymphoblastic leukemia.

For patients with ALL who relapse following allo-SCT, only a second SCT provides a realistic chance for long-term disease remission. We retrospectively analyzed the outcomes of 31 patients with relapsed ALL after a prior allo-SCT, who received a second SCT (SCT2) at our center. With a median follow-up of 3 years, 1- and 3-year PFS was 23 and 11% and 1- and 3 year OS rates were 23 and 11%. Twelve patients (39%) were transplanted with active disease, of whom 75% attained a CR. We found a significant relationship between the time to treatment failure following first allograft (SCT1) and PFS following SCT2 (P=0.02, hazard ratio=0.93/month). In summary, a second transplant remains a potential treatment option for achieving response in a highly refractory patient population. While long-term survival is limited, a significant proportion of patients remains disease-free for up to 1 year following SCT2, providing a window of time to administer preventive interventions. Notably, our four long-term survivors received novel therapies with their second transplant underscoring the need for a fundamental change in the methods for SCT2 to improve outcome.

Reduced-intensity conditioning using fludarabine, melphalan and thiotepa for adult patients undergoing haploidentical SCT.

Haploidentical SCT (HaploSCT) has been most commonly performed using a myeloablative, TBI-based preparative regimen; however, the toxicity with this approach remains very high. We studied the feasibility of a reduced-intensity conditioning regimen in a phase II clinical trial using fludarabine, melphalan and thiotepa and antithymocyte globulin (ATG) for patients with advanced hematological malignancies undergoing T-cell depleted HaploSCT. Twenty-eight patients were entered in the study. Engraftment with donor-derived hematopoiesis was achieved in 78% of patients after a median of 13 days. Six patients experienced primary graft failure, three out of four tested patients had donor-specific anti-HLA antibodies (DSA) (P=0.001). Toxicity included mostly infections. A total of 21 out of 22 patients with AML/myelodysplastic syndrome (MDS) achieved remission after transplant (16 with relapsed/refractory AML). Five out of the 12 patients (42%) with AML/MDS with <15% BM blasts survived long term as compared with none with more advanced disease (P=0.03). HaploSCT with this fludarabine, melphalan and thiotepa and ATG RIC is an effective, well-tolerated conditioning regimen for patients with AML/MDS with low disease burden at the time of transplant and allowed a high rate of engraftment in patients without DSA. Patients with overt relapse fared poorly and require novel treatment strategies.

Development of a subdural vein thrombosis following aggressive factor VII replacement for postnatal intracranial haemorrhage in a homozygous factor VII-deficient infant.

Congenital factor VII deficiency is a rare (1:500,000) autosomally recessive coagulopathy with variable expression and high penetration. In infants the most devastating presentation is that of intracranial haemorrhage. An infant is described with severe factor VII deficiency who developed postnatal intracranial haemorrhage. The baby was treated with factor VII concentrate (ImmunoA.G., Vienna, Austria). Three weeks after the haemorrhage he developed a dural venous sinus thrombosis. Although factor VII-deficient patients may need treatment with factor VII concentrate, this needs to be carefully monitored because of the thrombotic risk.

Transient leukemia with extreme basophilia in a phenotypically normal infant with blast cells containing a pseudodiploid clone, 46,XY i(21)(q10).

PURPOSE: Transient leukemia and extreme basophilia occurred in a phenotypically normal newborn with expression of isochromosome (21)(q10) in the blast population. PATIENTS AND METHODS: A newborn boy was found to have an elevated white blood cell count of 120,800 with 33% blasts. The peripheral blood also contained elevated numbers of basophils and neutrophils with unusual staining properties. The blasts, evaluated by flow cytometry and light and electron microscopy, had the properties of megakaryoblasts. Cytogenetic studies revealed 46,XY karyotype in peripheral blood lymphocytes; however, analysis of the blast cells from the bone marrow showed an abnormal chromosome 21. RESULTS: The blast cells in the peripheral blood disappeared by day 42 without chemotherapy. The red blood cell count and platelet count normalized by 2 months. Chromosomal analysis of skin fibroblasts and bone marrow after the disappearance of the blast cells in the peripheral blood showed a 46,XY phenotype. CONCLUSIONS: The leukemic cell of transient leukemia has the potential of forming cells of basophil and megakaryocyte lineages. Trisomy of the q arm of chromosome 21 contains sufficient genetic information for the development of transient leukemia in a phenotypically normal newborn.