Influence of surface morphology of chitosan films modified by chitin nanofibrils on their biological properties.

The paper is devoted to the study of influence of chitin nanofibrils on the structure, surface morphology, mechanical properties, and electrical conductivity of chitosan-based composite films intended for use in biomedical technologies. It was demonstrated that the optimal concentration of chitin nanofibrils in the composite film is 5 wt.%. For the films of this composition, we observed orientation of structural elements on film surface, enhanced mechanical properties as well as an increase in both specific conductivity and proliferative activity of skin fibroblasts on film surface. These results are related to the appearance of oriented structure in nanocomposites and to self-organization of chitosan macromolecules on the surface of chitin nanofibrils. It was revealed that increase in surface energy and surface hydrophilicity did not facilitate effective adhesion, viability and proliferative activity of cells during cultivation on the surface of composite films.

Anticoagulation treatment of cancer patients with deep or superficial leg vein thrombosis - a retrospective observational study of German statutory health insurance claims data (the CERTIFICAT initiative).

Background: Thrombosis is a common complication of cancer with a negative impact on quality of life and overall prognosis. Guidelines recommend low-molecular-weight heparin (LMWH) as initial and prolonged anticoagulation treatment. Little is known about current treatment patterns of these patients in ambulatory care. Patients and methods: The current retrospective observational study interrogates a large German statutory health insurance claims database in order to understand which kind of data can be extracted and analysed. An age- and sex-adjusted sample of about 4.1 million insured people from 2011 to 2016 could be used. Cancer patients with incident deep and superficial leg vein thrombosis were identified. Patients with preexisting cancer were allocated to a normal risk group; those who suffered from simultaneously diagnosed cancer and thrombosis were classified as high-risk group. Results: We identified 322,600 patients with inpatient or outpatient documented cancer diagnosis in at least two different quarters within one year. 87,755 patients were identified with an incident deep or superficial vein thrombosis. 8,201 patients suffered from both cancer and incident thrombosis. 56.9% of the patients received an anticoagulation regimen with predominant LMWH prescription, 24.2% vitamin K antagonists, 17.2% direct oral anticoagulants; in 1.7% of patients, no predominant anticoagulant drug/regime could be identified. On average, patients were prescribed anticoagulants for 4.5 months. An estimate of clinically relevant gastrointestinal bleeding could be derived (1.8% of patients). Conclusions: The dataset allows assigning detailed information of anticoagulant prescriptions in ambulatory care to well-defined groups of cancer patients. A first analysis suggests that in Germany current medical care of patients with cancer-related deep or superficial vein thrombosis does not entirely comply with guideline recommendations regarding type and duration of anticoagulation.

Budesonide + formoterol delivered via Spiromax® for the management of asthma and COPD: The potential impact on unscheduled healthcare costs of improving inhalation technique compared with Turbuhaler®.

BACKGROUND: Fixed-dose combinations of inhaled corticosteroids and long-acting ß2 agonists are commonly used for the treatment of asthma and COPD. However, the most frequently prescribed dry powder inhaler delivering this medicine - Symbicort® (budesonide and formoterol, BF) Turbuhaler® - is associated with poor inhalation technique, which can lead to poor disease control and high disease management costs. A recent study showed that patients make fewer inhaler errors when using the novel DuoResp® (BF) Spiromax® inhaler, compared with BF Turbuhaler®. Therefore switching patients from BF Turbuhaler® to BF Spiromax® could improve inhalation technique, and potentially lead to better disease control and healthcare cost savings. METHODS: A model was developed to estimate the budget impact of reducing poor inhalation technique by switching asthma and COPD patients from BF Turbuhaler® to BF Spiromax® over three years in Germany, Italy, Sweden and the UK. The model estimated changes to the number, and associated cost, of unscheduled healthcare events. The model considered two scenarios: in Scenario 1, all patients were immediately switched from BF Turbuhaler® to BF Spiromax®; in Scenario 2, 4%, 8% and 12% of patients were switched in years 1, 2 and 3 of the model, respectively. RESULTS: In Scenario 1, per patient cost savings amounted to €60.10, €49.67, €94.14 and €38.20 in Germany, Italy, Sweden and the UK, respectively. Total cost savings in each country were €100.86 million, €19.42 million, €36.65 million and €15.44 million over three years, respectively, with an estimated 597,754, 151,480, 228,986 and 122,368 healthcare events avoided. In Scenario 2, cost savings totalled €8.07 million, €1.55 million, €2.93 million and €1.23 million over three years, respectively, with 47,850, 12,118, 18,319, and 9789 healthcare events avoided. Savings per patient were €4.81, €3.97, €7.53 and €3.06. CONCLUSIONS: We demonstrated that reductions in poor inhalation technique by switching patients from BF Turbuhaler® to BF Spiromax® are likely to improve patients' disease control and generate considerable cost savings through healthcare events avoided.

Donor CD4 T cells convert mixed to full donor T-cell chimerism and replenish the CD52-positive T-cell pool after alemtuzumab-based T-cell-depleted allo-transplantation.

Donor lymphocyte infusions (DLI) are used to resolve mixed T-cell chimerism (TCC) after allo-SCT despite a substantial risk of GVHD. We analyzed the impact of prophylactic CD8-depleted (CD8(depl)) DLI in 20 recipients of anti-CD52 alemtuzumab in vivo T-cell-depleted allografts with declining donor TCC after day +60. A total of 13 patients received CD8(depl) DLI and 7 patients did not. All but one of the DLI patients converted to complete donor T-cell chimeras, whereas only one non-DLI patient converted spontaneously. DLI induced transient acute GVHD in five and extensive chronic GVHD in two patients. These data suggest the use of CD8(depl) DLI as an effective treatment for mixed TCC, particularly in patients at high risk for GVHD. We also observed that the majority of reconstituting donor-derived T cells after alemtuzumab conditioning were CD52-negative. CD8(depl) DLI significantly increased the proportion of CD52-positive CD4 T cells, whereby their beneficial effect on reconstituting the post-transplant T-cell repertoire was shown.

Antithymocyte globulin for the prevention of graft-versus-host disease after unrelated hematopoietic stem cell transplantation for acute myeloid leukemia: results from the multicenter German cooperative study group.

A total of 155 patients with acute myeloid leukemia (AML) received hematopoietic stem cell transplants from unrelated donors after standard conditioning. Clinical outcome after the use of two different antithymocyte globulins for the prevention of graft-versus-host disease (GvHD) was analyzed in a retrospective study as follows: rabbit ATG (Thymoglobulin Sangstat/Genzyme, n=49, median age 42 years, 53% in CR, further ATG-S); rabbit ATG (ATG-Fresenius, n=38, median age 42 years, 58% in CR, further ATG-F) or no ATG (n=68, median age 36 years, 55% in CR). The groups were comparable regarding disease status at transplant, age, CMV status and cytogenetics. Grade III-IV acute GvHD was found in 15% in the ATG and 27% in the no ATG group (P=0.44). The most important independent risk factors for chronic GvHD (cGvHD) were the use of ATG, disease status at transplant and conditioning. cGvHD developed significantly more frequently in no ATG group. With the median follow-up of 34 months, the 5-year survival is 42% for those transplanted in CR. To conclude, these data demonstrate that the transplants performed in CR, with ATG, are associated with a good outcome, low incidence of cGvHD and no increase of relapse.

First-line high-dose chemotherapy for patients with poor prognosis extragonadal germ cell tumors: the experience of the European Bone Marrow Transplantation (EBMT) Solid Tumors Working Party.

Extragonadal germ cell tumors are classified according to the staging system of the International Germ Cell Cancer Collaborative Group (IGCCCG). The 5-year overall and disease-free survival rates for poor prognosis patients are 41 and 48%, respectively after standard-dose chemotherapy. We report the experience of the EBMT Solid Tumours Working Party (STWP) with first-line HDCT with hematopoietic progenitor cell support (HPCS) in patients with poor prognosis extragonadal nonseminomatous germ cell tumor (NSGCT). Between 1990 and 2001, 22 extragonadal NSGCT patients (21 M, 1 F), median age 30 years (range 17-52) were treated with first-line HDCT with HPCS. Primary site was mediastinum in 11 patients, retroperitoneum in 10, and unknown in one. The Carbopec regimen, consisting of high doses of carboplatin, etoposide, and cyclophosphamide, was used in most cases (12 patients). No treatment-related deaths occurred. No patient developed myelodysplasia or a secondary leukemia. In total, 17 of 22 patients (77%) achieved complete remission. At a median follow-up of 50 months (range 26-132), 15 patients (68%) are alive disease-free. The survival rates of patients with poor prognosis extragonadal NSGCT treated with first-line HDCT in the EBMT STWP experience appear higher than that expected according to the IGCCCG classification.

Intensive chemotherapy with idarubicin, cytarabine, etoposide, and G-CSF priming in patients with advanced myelodysplastic syndrome and high-risk acute myeloid leukemia.

In an attempt to improve the complete remission (CR) rates and to prolong the remission duration especially in elderly patients > 50 years of age, we have used a combination chemotherapy of idarubicin (10 mg/m2 IV x 3 days), cytarabine (AraC, 100 mg/m2 CIVI x 7d), and etoposide (100 mg/m2 x 5 days) in combination with granulocyte colony-stimulating factor (G-CSF) priming [5 mg/kg SQ day 1 until absolute neutrophil count (ANC) recovery] for remission induction. Responding patients received two consolidation courses of idarubicin, AraC, and etoposide, followed by a late consolidation course of intermediate-dose AraC (600 mg/m2 IV every 12 h x 5 days) and amsacrine (60 mg/m2 IV x 5 days). A total of 112 patients (57 male/55 female) with a median age of 58 years (range: 22-75) have been entered and are evaluable for response: 19 refractory anemia with excess of blast cells in transformation (RAEB-T), 84 acute myeloid leukemia (AML) evolving from myelodysplastic syndrome (MDS), and 9 secondary AML after chemotherapy/radiotherapy. The overall CR rate was 62%, partial remission (PR) rate 10%, treatment failure 16%, and early death rate 12%. The CR rate was higher in patients < or = 60 years (68 vs 55%), mainly due to a lower early death rate (5 vs 21%, p<0.001). After a median follow-up of 58 months, the median overall survival is 14.5% and median duration of relapse-free survival 8 months. After 60 months, the probability of CR patients to still be in CR and alive is 16% (20% in patients < or = 60 years and 13% in patients >60 years), while the probability of overall survival is 12% (15% in patients < or = 60 years and 9% in patients > 60 years). Compared to our previous trial (AML-MDS Study 01-92) which was done with identical chemotherapy but no G-CSF priming in 110 patients with RAEB-T, AML after MDS, or secondary AML (identical median age, age range, and distribution of subtypes), the CR rate in all patients, as well as CR rate, overall survival, and relapse-free survival in patients > 60 years have significantly been improved. Thus, intensive chemotherapy with G-CSF priming is both well tolerated and highly effective for remission induction in these high-risk patients.

Safety and feasibility of CHOP/rituximab induction treatment followed by high-dose chemo/radiotherapy and autologous PBSC-transplantation in patients with previously untreated mantle cell or indolent B-cell-non-Hodgkin's lymphoma.

Patients with no prior chemotherapy and with advanced and progressive follicular lymphoma (FCL) or mantle cell lymphoma (MCL) were enrolled into a treatment protocol combining CHOP/rituximab-CHOP therapy with subsequent consolidation high-dose therapy (HDT) to evaluate the safety and feasibility of this treatment. Overall, 15 patients were enrolled and 13 patients completed the entire treatment protocol without major toxicities or increased infectious complications. One patient withdrew consent after achieving complete remission (CR) prior to HDT. One patient was taken off study with signs of disease progression after induction treatment. All patients showed stable engraftment after HDT. Response rates appear to be favorable, indicating an additional effect of rituximab and HDT. Overall, 12 of 13 patients achieved CR/CRu and one patient partial remission. Follow-up of immune reconstitution displayed transient severe combined immunodeficiency with slow normalization of the cellular and humoral compartments without a significant increase of infectious complications. Taken together, high-dose chemotherapy can be safely given following treatment with CHOP+rituximab. Efficacy in this small cohort of patients was encouraging with sustained remissions in both FCL and MCL patients. Upfront HDT should be considered as a therapeutic option especially in young and/or high-risk patients.

Filgrastim mobilization and collection of allogeneic blood progenitor cells from adult family donors: first interim report of a prospective German multicenter study.

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) mobilized peripheral blood progenitor cells (PBPCs) from healthy individuals are a rapidly emerging alternative source to bone marrow for allogeneic transplantation. Although widely applied in the meantime, only limited information on feasibility and safety of mobilization and collection of PBPCs is currently available from prospective multicenter studies specifically designed to investigate this donation modality. This ongoing multicenter study on the performance as well as the short- and long-term safety profile of rhG-CSF-induced mobilization and collection of PBPCs was initiated in October 1999. The study is designed to recruit a total of 300 healthy family donors who will be followed regularly for a period of 5 years after donation. The first interim report presented here summarizes results obtained after enrollment of 150 donors from nine German institutions. The study protocol allowed the individual choice between two dose regimens of rh-CSF (10 micro g/kg per day vs 2x8 micro g/kg per day of donor body weight). The primary endpoint was defined as a yield of > or =5x10(6) CD34(+) cells/kg of recipient body weight in a single leukapheresis product. This endpoint was attained by 50% of donors receiving the lower rhG-CSF dose regimen and by 75% of donors with the higher dose regimen ( p<0.0009). A total of 478 acute adverse events attributable to the mobilization procedure were recorded and manifested predominantly as transient bone pain and headaches (80%). No persistent hematologic or nonhematologic adverse events have occurred in this study so far. Thus, the current experience in a prospective multicenter study supports previous single-center and retrospective registry reports in that the collection of PBPCs after rhG-CSF mobilization is feasible and associated with frequent, but generally mild and acceptable side effects.

Nonmyeloablative stem cell transplantation in adults with high-risk ALL may be effective in early but not in advanced disease.

The feasibility of nonmyeloablative stem cell transplantation (NST) was evaluated in 22 adults with high-risk ALL. 16/22 patients had advanced disease and 11/22 had Ph+ ALL. Eleven patients received NST as first stem cell transplantation (SCT). Eleven patients had relapses after allogeneic or autologous SCT and underwent a salvage NST. 18/22 patients (82%) engrafted after NST. 13/16 patients (81%) with active disease reached complete remission (CR). 11 of 13 patients developed GVHD. After first NST 10/11 patients (91%) engrafted. Six of seven patients with active disease reached CR. Three of five relapsing patients reached subsequent CR after donor lymphocyte infusions, termination of immunosuppression or imatinib. Three of 11 patients (27%) are alive in CR 5 to 30 months after NST. Eight of 11 patients have died, 3/8 from leukemia and 5/8 from transplant-related causes. After salvage NST, 8/11 patients (73%) engrafted. Seven of nine patients with active disease reached CR. Only one of 11 patients transplanted, who was in CR before undergoing salvage NST is alive 19 months after NST. Five of 11 have died from leukemia, one of 11 after graft failure and four of 11 from transplant-related causes. Four of 22 patients (18%) are alive in CR 5, 14, 19 and 30 months after NST. NST is feasible in adults with high risk ALL. However, transplant-related mortality remains high and only patients transplanted in CR seem to have long-term disease-free survival.

Rituximab in vivo purging is safe and effective in combination with CD34-positive selected autologous stem cell transplantation for salvage therapy in B-NHL.

The purpose of this study was to evaluate feasibility and efficacy of Rituximab included into a sequential salvage protocol for CD20(+) B-NHL in relapse or induction failure. Twenty-seven patients with CD20(+) B-NHL in relapse or induction failure received Rituximab combined with DexaBEAM (R-DexaBEAM) for stem cell mobilization. Additional ex vivo selection of CD34-positive cells was performed using the CliniMacs device. Two doses of Rituximab were included in the high-dose therapy regimen (HDT). R-DexaBEAM was well tolerated and 26 of 27 patients mobilized sufficient numbers of CD34(+) blood stem cells. Application of R-DexaBEAM resulted in significant depletion of peripheral B cells. No treatment-related deaths occurred after HDT and all patients showed stable engraftment of hematopoesis. Combined immunodeficiency was observed post HDT and eight patients developed CMV antigenemia. Remission rate post HDT was 96% (CR, 24/26; PR, 1/26). Overall and progression-free survival (PFS) at 16 months post HDT (range 6-27) is 95% and 77%, respectively. With regard to histology, PFS was 71% in aggressive lymphoma (n = 11), 74% in indolent FCL (n = 10) and 100% in MCL (n = 5). The treatment protocol has proven feasible, with high purging efficiency and encouraging remission rates.

Failure of sustained engraftment after non-myeloablative conditioning with low-dose TBI and T cell-reduced allogeneic peripheral stem cell transplantation.

We investigated whether a T cell-reduced allogeneic stem cell transplant (SCT) with minimal conditioning and subsequent donor lymphocyte infusions (DLI) could reduce the incidence and severity of GVHD while retaining stable engraftment. Five patients with hematological malignancies (three MM, one CLL, one Chediak-Higashi syndrome) were conditioned with TBI (200 cGy). One patient additionally received fludarabine (120 mg/m(2)). CsA and mofetyl-mycophenolate (MMF) were administered to prevent GVHD. All patients were grafted with >3 x 10(6)/kg highly purified CD34(+) cells together with 2 x 10(6)/kg CD3(+) cells (three patients) or 1 x 10(5)/kg CD3(+) cells (two patients). Quick hematopoietic recovery and initial mixed donor chimerism was observed. Treatment-related toxicity was minimal in all but one patient who died of treatment-refractory GVHD on day 112. The four other patients only achieved partial donor T cell chimerism. BM and PBMC donor chimerism was lost between day 40 and 209 despite DLI. Three patients are alive with disease and one is in CR. We conclude that T cell-reduced SCT using 200 cGy as the conditioning regimen does not result in stable hematopoietic engraftment. Predominant donor T cell chimerism is not a prerequisite for initial allogeneic hematopoietic proliferation. However for sustained long-term engraftment it is of major importance.

Second German consensus on immunogenetic donor search for allotransplantation of hematopoietic stem cells.

The present paper summarizes the results of the second German consensus meeting on immunogenetic donor search for allotransplantation of hematopoietic stem cells held in Essen in November 1999 under the auspices of the German Society for Immunogenetics (DGI) and the German Working Party for Blood and Marrow Transplantation (DAG-KBT). Immunogeneticists and transplant physicians from all over the country agreed to update the national standards for: (1) search strategy including the role of unrelated and extended family donor search after unsuccessful core family donor search, (2) histocompatibility loci to be typed, (3) histocompatibility typing techniques to be used (HLA serology vs DNA-based HLA typing, cellular tests, serum cross-match), and (4) acceptable HLA mismatches in the context of a defined underlying disease, donor type, and conditioning regimen.

Short Report: Engraftment of T-cell-depleted allogeneic haematopoietic stem cells using a reduced intensity conditioning regimen.

Graft-versus-host disease (GVHD) remains a significant complication in patients undergoing allogeneic stem cell transplantation (SCT) using a reduced intensity conditioning regimen. Although T-cell depletion (TCD) reduces the risk of GVHD after a myeloablative conditioning regimen, it is associated with an increased risk of graft failure. We have therefore examined whether TCD compromises engraftment using a fludarabine-based conditioning regimen. Fifteen patients have been transplanted using such a regimen of whom 13 underwent ex vivo TCD. All but one patient demonstrated durable engraftment and no patient receiving a TCD product developed severe GVHD. Thus, TCD may play a role in GvHD prophylaxis using such regimens.

Research for corresponding dental therapy for patients undergoing bone marrow and peripheral blood stem-cell transplantation.

In an interdisciplinary co-operation between the Haematology Department of the III. Medical Clinic, University of Mainz, and the Polyclinic for Restorative Dentistry Mainz, Germany, a total of 61 patients (33 men, 28 women, average age 43.2 +/- 11.5 years) received dental examination just before undergoing bone marrow transplantation (BMT) (n = 17) and peripheral blood stem-cell transplantation (PBSCT) (n = 44) respectively. The aim of this study was to determine the frequency of dentogenic complications during the aplasia phase. - Patients, who were scheduled for either bone marrow or blood stem-cell transplantation, have been examined in view of their serious susceptibility to infections during the aplasia phase, even though the probability of an exacerbation is said to be quite low, as it has been shown in the present study.

Intensive chemotherapy with idarubicin, ara-C, etoposide, and m-AMSA followed by immunotherapy with interleukin-2 for myelodysplastic syndromes and high-risk Acute Myeloid Leukemia (AML).

Intensive chemotherapy followed by treatment with interleukin-2 (IL-2) was evaluated in a prospective, randomized, multicenter trial including 18 patients with refractory anemia with excess of blasts in transformation (RAEB-T), 86 patients with acute myeloid leukemia (AML) evolving from myelodysplastic syndromes, and six patients with secondary AML after previous chemotherapy. Median age was 58 years (range: 18-76 years). Forty-nine patients (45%) achieved a complete remission (CR) after two induction cycles with idarubicin, ara-C, and etoposide, 52% of them aged 60 years (p=0.06). After two consolidation courses, patients were randomized to four cycles of either high- or low-dose IL-2. Patients aged up to 55 years with an HLA-identical sibling donor were eligible for allogeneic bone marrow transplantation. The median relapse-free survival was 12.5 months, with a probability of ongoing CR at 6.5 years of 19%. Overall survival of all patients was 8 months, and 21 months for the CR patients. Median survival was significantly longer among patients aged

Infectious complications during neutropenia subsequent to peripheral blood stem cell transplantation.

Type, severity and incidence of infection during the neutropenic period after peripheral blood stem cell transplantation (PBSCT) for treatment of malignant disease were studied in 66 patients treated at a single institution. Data of 34 female and 32 male patients with a median age of 43 years suffering from leukemia (12), lymphoma (35), multiple myeloma (six) or solid tumors (13) were retrospectively analyzed. All patients had received at least 2.5 x 10(6) CD34-positive cells for stem cell rescue after high-dose chemotherapy. Ninety-four percent of the patients experienced at least one febrile episode during their post-transplant course. The patients recovered quickly and defervesced after a median of 4 days. The incidence of bacteremia was 39% and gram-positive cocci were the predominant pathogens. In contrast, severe organ infections were rare. Only 5% of the patients suffered from lung infiltrates. No invasive fungal infections were observed. No transplant-related deaths occurred in the 66 patients studied. We conclude that the severe, but shortlasting neutropenia after peripheral blood stem cell transplantation is associated with a high incidence of bacterial infection. The severity of the majority of these infections is moderate. With appropriate anti-infective therapies these infections can be managed and life-threatening infectious complications, in particular fungal infections, are rare. Empirical anti-infective regimens specifically designed for this clinical situation should be explored.

Peripheral blood stem cell (PBSC) mobilization with chemotherapy followed by sequential IL-3 and G-CSF administration in extensively pretreated patients.

Extensive pretreatment has been identified as a significant risk factor for failure of sufficient PBSC mobilization. From published data and our own experience we defined pretreatment variables which render patients at risk for not collecting at least 2.5 x 10(6) CD34-positive cells per kg bodyweight (BW). These variables were previous unsuccessful PBSC mobilization trial, previous large field radiotherapy, four or more cycles of myelosuppressive chemotherapy regimens, and combinations of extended field radiotherapy plus chemotherapy. Based on these inclusion criteria we treated 19 patients with disease-specific conventional-dose chemotherapy followed by sequential subcutaneous administration of IL-3 (5 microg/kg BW) for 5 consecutive days and G-CSF (10 microg/kg) until PBSC collection or neutrophil recovery. Patients were 10 males and nine females with a median age of 43 years. Diagnoses were non-Hodgkin's lymphoma n = 5, Hodgkin's disease n = 2, multiple myeloma n = 2, CML n = 4, AML n = 4 and testicular cancer n = 2. Twelve patients had prior unsuccessful trial of PBSC mobilization with chemotherapy followed by G-CSF. Except for mobilization chemotherapy-related neutropenic fever, no major toxicities (WHO grade > or = 2) were observed. Growth factors were well tolerated. Collection of at least 2.5 x 10(6) CD34-positive cells per kg BW was possible in 11 out of 19 patients (58%). In five out of 12 patients with a previous unsuccessful trial of PBSC mobilization, the study regimen mobilized sufficient CD34-positive cells. Nine patients went on to high-dose chemotherapy followed by autologous PBSC transplantation. Prompt hematologic recovery was seen in all of them. In conclusion, the sequential administration of IL-3 followed by G-CSF after conventional-dose chemotherapy allows successful PBSC collection in the majority of extensively pretreated patients.

Analysis of the p53 and MDM-2 gene in acute myeloid leukemia.

The MDM-2 (murine double minute 2) gene codes for a cellular protein that can bind to the p53 tumor suppressor gene product, thereby functioning as a negative regulator of p53. In order to define the role of the MDM-2 gene in the pathogenesis of human acute myeloid leukemia, the expression and the sequence of the MDM-2 gene were examined in samples of bone marrow and/or peripheral mononuclear cells of 38 patients by using immunostaining, polymerase chain reaction (PCR), single strand conformation polymorphism, and sequencing. Immunohistochemical staining detected a weak accumulation of the MDM-2 protein in AML patients of FAB classification M4 and M5. RT-PCR analysis revealed a heterogeneous expression pattern of MDM-2 mRNA in AML samples of different FAB classification. An increased level of MDM-2 mRNA expression was observed in 17 of 38 AML patients when compared to normal controls. No structural changes in a 488 bp region extending from nucleotide 890 to 1378 of the MDM-2 cDNA were detected using RT-SSCP and sequence analysis. In addition, heterogeneous expression of p53 transcripts was found with the highest p53 mRNA levels in AML M4 and M5. Interestingly, there seems to be a correlation between the relative ratios of p53 and MDM-2 mRNA levels in AML M4 and M5: in 15 of 23 cases high p53 mRNA expression was directly associated with high levels of MDM-2 transcripts. An exclusively intranuclear p53 immunostaining pattern was found in 10 of 16 (58%) AML FAB M4 and M5, whereas the remaining AML samples tested were negative for p53 (0/10). Using RT-SSCP analysis and direct sequencing of the RT-PCR amplification products of p53 exon 5-8, we observed that only 1 of 38 AML patients showed a point mutation in the p53 gene. This missense mutation occurred in the evolutionary highly conserved region of p53 at codon 255 (Ile to Phe). These data indicated that structural alterations of the p53 gene do not play an important role in the initiation and progression of AML. However, abrogation of p53 tumor suppressor function due to MDM-2 overexpression may be an alternative molecular mechanism by which a subset of AMLs may escape from p53-regulated growth control.