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Treatment of chronic myeloid leukemia (CML) with tyrosine kinase inhibitors has advanced to a stage where many patients achieve very low or undetectable levels of disease. Remarkably, some of these patients remain in sustained remission when treatment is withdrawn, suggesting that they may be at least operationally cured of their disease. Accurate definition of deep molecular responses (MRs) is therefore increasingly important for optimal patient management and comparison of independent data sets. We previously published proposals for broad standardized definitions of MR at different levels of sensitivity. Here we present detailed laboratory recommendations, developed as part of the European Treatment and Outcome Study for CML (EUTOS), to enable testing laboratories to score MR in a reproducible manner for CML patients expressing the most common BCR-ABL1 variants. [ABSTRACT FROM AUTHOR]

Hematopoietic stem cell transplantation is becoming an increasingly important approach to treatment of different malignant and non-malignant disorders. There is thus growing demand for diagnostic assays permitting the surveillance of donor/recipient chimerism posttransplant. Current techniques are heterogeneous, rendering uniform evaluation and comparison of diagnostic results between centers difficult. Leading laboratories from 10 European countries have therefore performed a collaborative study supported by a European grant, the EuroChimerism Concerted Action, with the aim to develop a standardized diagnostic methodology for the detection and monitoring of chimerism in patients undergoing allogeneic stem cell transplantation. Following extensive analysis of a large set of microsatellite/short tandem repeat (STR) loci, the EuroChimerism (EUC) panel comprising 13 STR markers was established with the aim to optimally meet the specific requirements of quantitative chimerism analysis. Based on highly stringent selection criteria, the EUC panel provides multiple informative markers in any transplant setting. The standardized STR-PCR tests permit detection of donor- or recipient-derived cells at a sensitivity ranging between 0.8 and 1.6%. Moreover, the EUC assay facilitates accurate and reproducible quantification of donor and recipient hematopoietic cells. Wide use of the European-harmonized protocol for chimerism analysis presented will provide a basis for optimal diagnostic support and timely treatment decisions. [ABSTRACT FROM AUTHOR]

Timely diagnosis of impending graft rejection is crucial for effective therapeutic intervention after allogeneic hematopoietic stem cell transplantation (SCT). We have investigated the predictive potential of early leukocyte subset-specific chimerism for graft loss in children undergoing SCT. In total, 192 pediatric patients transplanted for the treatment of malignant and non-malignant diseases after reduced-intensity or myeloablative conditioning were investigated. Surveillance of lineage-specific chimerism was initiated upon first appearance of leukocyte counts amenable to cell sorting. Graft rejection occurred in 23 patients between 24 and 492 days post-transplant (median 63 days). The first chimerism analysis of T and NK cells performed at a median of 20 days after SCT identified three different risk groups that were independent from the conditioning regimen: recipient chimerism (RC) levels in T cells below 50% indicated a very low risk of rejection (1.4%), whereas high levels of RC (>90%) both in T and NK cells heralded graft loss in the majority of patients (90%) despite therapeutic interventions. RC >50% in T cells and 90% in NK cells defined an intermediate-risk group in which timely immunotherapy frequently prevented rejection. Early assessment of T- and NK-cell chimerism can therefore be instrumental in the risk assessment and therapeutic management of imminent graft rejection. [ABSTRACT FROM AUTHOR]

Analysis of short tandem repeats (STR) by PCR analysis is routinely used in chimerism diagnostics to monitor donor engraftment and to diagnose relapse. Some applications require chimerism analysis of low cell numbers, but no standardized protocol is available for DNA isolation from 1000 to 30 000 cells. The EU-supported EuroChimerism Consortium (project QLRT-2001-01485) selected four different protocols for 'small-scale' DNA isolation, which were tested by six laboratories for their ability to recover reproducible amounts of good quality DNA, suited for PCR-based STR analysis. The protocols included two direct lysis methods with and without detergents and proteinase K, and two commercial column-based kits. The direct lysis method using detergents and proteinase K showed the highest DNA recovery and the best performance in the multiplex PowerPlex16 STR assay. DNA isolated with this method also showed the highest sensitivity in chimerism analysis using singleplex PCR reactions of EuroChimerism STR markers. Sensitivity was reached ranging from 1 to 20% of recipient cells in a donor background. In conclusion, the direct lysis method using detergents and proteinase K is a standardized DNA isolation method well suited for chimerism studies on low cell numbers. [ABSTRACT FROM AUTHOR]

Invasive fungal disease (IFD) is a life-threatening event in immunocompromised patients, and there is an urgent need for reliable screening methods facilitating rapid and broad detection of pathogenic fungi. We have established a two-reaction real-time PCR assay permitting highly sensitive detection of more than 80 fungal pathogens, covering a large spectrum of moulds, yeasts and Zygomycetes. To assess the clinical potential of the assay, more than 600 consecutive specimens from 125 pediatric patients carrying a high risk of IFD were analyzed. An excellent correlation between PCR positivity and the presence of proven, probable or possible fungal infection according to the European Organization for Research and Treatment of Cancer criteria was demonstrated, as revealed by the sensitivity of the assay of 96% (95% CI: 82-99%). The negative predictive value of the panfungal PCR assay presented was 98% (95% CI: 90-100%), while the specificity and the positive predictive value were 77% (95% CI: 66-85%) and 62% (95% CI: 47-75%), respectively. The results indicate that molecular screening of patients during febrile neutropenic episodes by the assay presented could help prevent unnecessary toxicity resulting from empirical antifungal treatment in individuals who may not be at risk of imminent fungal disease. Our observations raise the possibility that rapid species identification may be required to increase the positive predictive value for impending fungus-related disease. [ABSTRACT FROM AUTHOR]

Invasive adenovirus (AdV) infections are associated with high morbidity and mortality in allogeneic stem cell transplant recipients. We observed that molecular detection of the virus in stool specimens commonly precedes AdV viremia, suggesting that intestinal infections may represent a common source of virus dissemination. To address this notion, we have investigated 153 consecutive allogeneic transplantations in 138 pediatric patients by quantitative monitoring of AdV in stool specimens and peripheral blood by a pan-adenovirus real-time (RQ)-PCR approach. AdV was detectable in serial stool specimens in all cases of AdV viremia during the post-transplant course (P<0.0001). The incidence of AdV viremia in individuals with peak virus levels in stool specimens above 1 × 10E6 copies per gram (n=22) was 73% vs 0% in patients with AdV levels in stool specimens below this threshold (n=29; P<0.0001). Serial measurement of AdV levels in stool specimens by RQ-PCR permitted early diagnosis of impending invasive infection with a sensitivity and specificity of 100% (95% confidence interval (CI) 96–100%) and 83% (95% CI 67–92%), respectively. The median time span between detection of AdV loads in stool specimens above 1 × 10E6 copies per gram and first observation of viremia was 11 days (range 0–192). Quantitative monitoring of the AdV load in stool specimens therefore provides a rationale for early initiation of antiviral treatment with the aim of preventing progression to life-threatening invasive infection. [ABSTRACT FROM AUTHOR]

The rapid identification of fungal pathogens in clinical specimens is a prerequisite for timely onset of the most appropriate treatment. The aim of the present study was to develop a sensitive and rapid method for the species-specific identification of clinically relevant fungi. We employed fluorescent polymerase chain reaction (PCR)-fragment length analysis of the highly variable internally transcribed spacer 2 (ITS2) region to identify individual fungal species by their specific amplicon sizes. The specificity of the technique was ascertained by the detailed analysis of 96 strains derived from 60 different human-pathogenic fungal species. To achieve adequate sensitivity for species identification in patients with invasive fungal infection, who often display very low pathogen loads in peripheral blood, the ITS2 region was amplified by semi-nested PCR prior to amplicon-length analysis. Serial specimens from 26 patients with documented fungal infections were investigated. The fungal pathogens identified included different Aspergillus and Candida species, Rhizopus oryzae and Fusarium oxysporum. Fragment length analysis of the ITS2 region upon amplification by semi-nested PCR permits the sensitive identification of fungal species. The technique can be readily implemented in routine diagnostics. [ABSTRACT FROM AUTHOR]

The article discusses the role of tyrosine kinase (TK) inhibitors as the standard treatment for patients with chronic myeloid leukemia (CML). It says that the level of resistance to individual TK inhibitors may vary from slightly reduced sensitivity to total insensitivity. Further, patients treated with imatinib, mutations conferring only moderately impaired sensitivity may be approached by increasing the dose.

Species of Alternanthera (Family Amaranthaceae) are efficient primary hosts for the obligate root hemi-parasite Santalum album (Family Santalaceae). The first experiment presented in this paper examines whether four closely related Alternanthera taxa differ in their performance as host. S. album seedlings were grown in pots with Alternanthera dentata cv 'Ruby', Alternanthera dentata cv 'Tricolor', Alternanthera amoena cv 'Aurea', and Alternanthera angustifolia respectively. Seedlings were between 5 and 11 weeks old at the beginning of the experiment. Haustorial connections had been formed with the roots of A. dentata cv "Tricolor" and Alternanthera amoena cv "Aurea" after 10 weeks. The variety A. dentata cv "Ruby" formed haustorial connections after 4 weeks. Sandal seedlings did not form any haustorial connections with A. angustifolia during the trial period. Shoot and root growth of S. album seedlings were similar in the presence of the four host taxa and did not change significantly throughout the experimental time period, probably due to the low number of haustorial connections between host and parasite. Of the four taxa tested, A. angustifolium showed the least potential as primary host because of poor root growth, early mortality and a complete lack of haustorial connections between host and parasite. The second experiment (1) examined whether young sandalwood seedlings can utilise essential minerals when administered directly to their own leaves, and (2) compared the growth response to foliar feeding with the growth observed in the presence of A. dentata var. "Ruby", which is likely due to a transfer of nutrients from host to parasite. The absorption of nutrients was determined as an increase in the growth of sandal seedlings after 20 weeks. The data indicate that S. album seedlings are able to utilise foliar nutrients. However, the presence of A. dentata var. "Ruby" leads to a larger increase in growth than the application of foliar nutrients. [ABSTRACT FROM AUTHOR]

Monitoring of BCR-ABL transcripts has become established practice in the management of chronic myeloid leukemia. However, nucleic acid amplification techniques are prone to variations which limit the reliability of real-time quantitative PCR (RQ-PCR) for clinical decision making, highlighting the need for standardization of assays and reporting of minimal residual disease (MRD) data. We evaluated a lyophilized preparation of a leukemic cell line (K562) as a potential quality control reagent. This was found to be relatively stable, yielding comparable respective levels of ABL, GUS and BCR-ABL transcripts as determined by RQ-PCR before and after accelerated degradation experiments as well as following 5 years storage at −20°C. Vials of freeze-dried cells were sent at ambient temperature to 22 laboratories on four continents, with RQ-PCR analyses detecting BCR-ABL transcripts at levels comparable to those observed in primary patient samples. Our results suggest that freeze-dried cells can be used as quality control reagents with a range of analytical instrumentations and could enable the development of urgently needed international standards simulating clinically relevant levels of MRD.Leukemia (2007) 21, 1481–1487; doi:10.1038/sj.leu.2404716; published online 3 May 2007 [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to an article about the principle of Recipient-Shared-Donor code in the monitoring of chimerism.

Real-time quantitative RT-PCR (RQ-PCR) is a sensitive tool to monitor minimal residual disease (MRD) in leukemic patients through the amplification of a fusion gene (FG) transcript. In order to correct variations in RNA quality and quantity and to calculate the sensitivity of each measurement, a control gene (CG) transcript should be amplified in parallel to the FG transcript. To identify suitable CGs, a study group within the Europe Against Cancer (EAC) program initially focused on 14 potential CGs using a standardized RQ-PCR protocol. Based on the absence of pseudogenes and the level and stability of the CG expression, three genes were finally selected: Abelson (ABL), beta-2-microglobulin (B2M), and beta-glucuronidase (GUS). A multicenter prospective study on normal (n=126) and diagnostic leukemic (n=184) samples processed the same day has established reference values for the CG expression. A multicenter retrospective study on over 250 acute and chronic leukemia samples obtained at diagnosis and with an identified FG transcript confirmed that the three CGs had a stable expression in the different types of samples. However, only ABL gene transcript expression did not differ significantly between normal and leukemic samples at diagnosis. We therefore propose to use the ABL gene as CG for RQ-PCR-based diagnosis and MRD detection in leukemic patients. Overall, these data are not only eligible for quantification of fusion gene transcripts, but also for the quantification of aberrantly expressed genes.Leukemia (2003) 17,, 2474-2486. doi:10.1038/sj.leu.2403136 Published online 9 October 2003 [ABSTRACT FROM AUTHOR]

Chimaerism of FACS-sorted leucocyte subsets (CD14+, CD15+, CD3-/56+, CD3+/4+, CD3+/8+, CD19+) was monitored prospectively between days +14 and +100 in 39 children undergoing allogeneic stem cell transplantation with reduced intensity-conditioning regimens. Cell subsets exceeding 1% of nucleated cells were subject to cell sorting. Chimaerism was analysed by dual-colour FISH and/or by short tandem repeat-polymerase chain reaction. The chimaerism pattern on day +28 was evaluated with regard to its correlation with graft rejection. Of 39 patients, nine patients had donor chimaerism (DC) in all subsets. Mixed/recipient chimaerism (MC/RC) was detectable within T cells in 62%, within NK cells in 39% and within monocytes and granulocytes in 38% of the patients. The correlation of secondary graft rejection with the chimaerism pattern on day +28 revealed the strongest association between RC in NK-cells (P<0.0001), followed by T cells (P=0.001), and granulocytes and monocytes (P=0.034). Notably, patients with RC in T cells rejected their graft only if MC or RC was also present in the NK-cell subset. By contrast, none of the children with DC in NK cells experienced a graft rejection. These observations suggest that, in the presence of recipient T-cell chimaerism, the chimaerism status in NK-cells on day +28 might be able to identify patients at high risk for late graft rejection.Leukemia (2003) 17, 1934-1942. doi:10.1038/sj.leu.2403087 [ABSTRACT FROM AUTHOR]

Summary:Cytomegalovirus (CMV) DNAemia was detected by PCR in 30/125 (24%) consecutive paediatric patients undergoing allogeneic stem cell transplantation. All patients with CMV DNAemia received pre-emptive ganciclovir until two consecutive negative results were obtained. CMV-IgG-positive patients (R+) had a significantly increased risk of DNAemia as compared to CMV-IgG-negative (R-) patients (62% vs 8%) P<0.0001. The incidence of DNAemia was 71% (10/14) in R+ transplanted from seronegative donors (D-) compared to 54% (13/32) in those transplanted from seropositive donors (D+). Of 30 (40%) children with DNAemia, 12 developed CMV disease despite pre-emptive treatment. The overall incidence of disease was 0% (0/59) for R-/D-, 9% (3/23) for R+/D+, 7% (2/29) for R-/D+ and 57% (8/14) for R+/D-. In patients with DNAemia, 4/20 (20%) patients with D+ and 8/10 (80%) with D- became symptomatic. In the multivariate analysis of both groups, patients at risk (R+ and/or D+) and patients with DNAemia, a negative donor serostatus was the only factor associated with a significantly increased incidence of disease. Seven of 9 patients with lethal CMV disease had received CMV-IgG-negative grafts. The data suggest that in CMV seropositive recipients donor CMV seropositivity is associated with a reduced incidence of CMV disease and a favourable outcome following pre-emptive treatment.Bone Marrow Transplantation (2003) 31, 803-808. doi:10.1038/sj.bmt.1703927 [ABSTRACT FROM AUTHOR]

Leukemia (2003) 17, 224–227. doi:10.1038/sj.leu.2402756 [ABSTRACT FROM AUTHOR]

The choice of adequate controls for reverse transcriptase (RT-) PCR analysis has been the focus of a debate pursued in Leukemia over the past 3 years. Twenty-six authors from 15 different centers contributed to the Debate, and the points presented have been carefully evaluated. This survey reviews the issues discussed, and presents current options for appropriate positive controls in RT-PCR assays which are based on the views shared by the majority of participants in the Debate. It is understood, however, that the recommendations presented cannot be regarded as definitive guidelines. They reflect the present state of knowledge, and certainly need to be revisited. [ABSTRACT FROM AUTHOR]

Sequential analysis of chimerism after allogeneic blood stem cell transplantation (BSCT) has been shown to be predictive for graft failure and relapse. We have explored the impact of a novel approach for the quantitative determination of chimerism using a commercial PCR assay with multiplex amplification of nine STR-loci and fluorescence detection. The feasibility was studied in 121 patients transplanted from related or unrelated donors. Follow-up investigation was performed in 88 patients. Twenty-eight of these patients had received a transplantation after dose-reduced conditioning therapy. Results were compared to data obtained by FISH analysis in a subgroup of patients receiving grafts from sex-mismatched donors. The analysis was possible in all patients, the median number of informative alleles was 4 (range 1-8) compared to 7 (range 1-9) in the related and unrelated situation, respectively. A good correlation was seen in 84 samples from 14 patients analyzed in parallel with STR-PCR and FISH. Decreasing values of donor chimerism were detected prior to or concomitantly with the occurrence of graft failure and relapse of disease in all patients investigated prospectively. Using FACS-sorted material, eg peripheral blood CD34+ cells, the assay permitted the detection of residual recipient cells with high sensitivity (down to one CD34+ Kasumi cell in 40,000 normal WBC). Evaluation of the inter-laboratory reproducibility revealed that in 20 samples analyzed in three different centers, the median coefficient of variation was 2.1% (range 0.7-9.6%). Taken together, the results support the use of the test as a valuable tool in the follow-up of patients undergoing allogeneic BSCT. In cases lacking PCR-detectable disease-specific gene products, this assay may represent an alternative to recently established real-time PCR methods. [ABSTRACT FROM AUTHOR]

Presents an analysis of chimerism within specific leukemia subsets for detection of residual or recurrent leukemia in pediatric patients after allogenic stem cell transplantation. Approaches to treat residual leukemia; assessment of the kinetics of chimerism; Nomenclature used for results of chimerism analysis.

Juvenile myelomonocytic leukaemia (JMML) is a rare paediatric disease and allogeneic stem cell transplantation is the only curative approach. The roles of pretransplant treatment, conditioning regimen and graft-versus-host disease (GVHD) are still unclear. Eleven children with JMML underwent allogeneic BMT in our institution. Donors were matched unrelated (n = 6) matched siblings (n = 4) and one mismatch family donor. Transplant-related mortality (TRM) was 36%. Three patients relapsed after transplantation. Two of three patients with relapse are in continuous remission after donor lymphocyte infusion or second BMT, respectively. To evaluate the role of pretransplant treatment, conditioning regimen and GVHD, we have summarised our series with other published single centre reports and give an overview on a total of 65 patients with JMML who underwent allogeneic BMT. No significant correlation between pretransplant treatment, conditioning regimen and TRM could be observed. Overall relapse rate is high (47%). TBI is associated with a significantly higher relapse rate (P = 0.012). Other conditioning modalities, intensive chemotherapy and splenectomy prior to stem cell transplantation do not seem to have a significant impact on relapse rate. Patients with or without GVHD showed no significant difference in relapse rate (58% vs 45%). In the event of relapse after transplantation withdrawal of immunosuppression, donor lymphocyte infusion or second transplant was successful in 6/11 patients. Graft-versus-leukaemia effect seems to play an essential role in bone marrow transplantation for JMML. Bone Marrow Transplantation (2000) 26, 377–382. [ABSTRACT FROM AUTHOR]

HLA-mismatched family members may represent an important cell source for patients that require stem cell transplantation but lack both a matched sibling donor and a closely matched unrelated donor. We report the outcome of 19 transplantations from HLA two- or three- loci mismatched parental donors in which 14 pediatric patients with hematological malignancies or other disorders, received a median of 21.5 x 106 (range, 5.4-58) highly purified CD34+peripheral blood stem cells (PBSC), as well as 4.7 x 104 (range, 0.4-12) donor T cells per kg body weight. T cell depletion was performed using a two-step CD34-positive selection on two different magnetic beads devices. Ten of 14 patients presented with rapid myeloid engraftment. The four patients who presented with graft failure (two non-engraftments, two rejections) received a second stem cell graft and one a third. Graft rejection was detected early by polymerase chain reaction (PCR) analysis of FACS-sorted T cells. Eight of the 14 patients are still alive after a median observation period of 15. 6 months (range, 3-31.3) with full donor chimerism in all hematopoietic cell lineages. No acute organ graft-versus-host disease (GVHD) and no chronic GVHD have occurred. One patient experienced relapse of leukemia. We conclude that transplantation of allogeneic PBSC from haploidentical donors will open new perspectives for pediatric patients for whom an HLA-matched stem cell graft is not available. Close monitoring of recipient and donor hematopoiesis might be of clinical value, to recognize early engraftment or rejection. [ABSTRACT FROM AUTHOR]

The monitoring of chimerism by PCR has become a routine diagnostic approach in patients after allogeneic bone marrow or peripheral blood stem cell transplantation. Nevertheless, a temporal correlation between molecular and hematologic assessment of engraftment has not been clearly established. To address this issue, and to determine the potential clinical implications of early kinetics of mixed chimerism, we have investigated 66 allogeneic stem cell transplantations (SCTs) in 58 pediatric patients suffering from different types of leukemia (n = 44) or non-malignant hematologic disorders (n = 14) by close molecular monitoring during the first days and weeks after transplantation. Patient- and donor-derived hematopo-iesis were assessed at 1- to 3-day intervals in peripheral blood samples by PCR analysis of highly polymorphic microsatellite loci (STR-PCR). Detection of an increasing, and ultimately dominant donor-specific allelic pattern, which we defined as molecular engraftment, preceded hematologic engraftment by a median of 7 days (range 1-17 days) in all patients investigated. PCR analyses during the first days after transplantation facilitated detection of molecular engraftment according to the above definition by day +14 (range day +2 to day +14), thus permitting prediction of successful engraftment (upper limit of (the two-sided confidence interval p[SUB0] = 6%) while the peripheral leukocyte counts were mostly below 200/μl. In three cases, however, the criteria for molecular engraftment were not fulfilled by day +14. These patients also failed to show hemato-logic engraftment, and required a second transplantation. Close monitoring by STR-PCR showed that graft rejection and autologous recovery can occur early and with very rapid dynamics. Molecular analysis of specific leukocyte subsets isolated by flow-sorting enabled sensitive assessment of changes in the pattern of chimerism which had escaped detection in assays using whole white blood cell (WBC)... [ABSTRACT FROM AUTHOR]

Background We report a routine flow cytometric (FACS) approach to quantify circulating leukocytes (NC) in myeloablated patients before and during regeneration after allogeneic transplantation of either whole bone marrow (BM) or of highly purified (> 99%) blood-derived CD34 + cells (PBSC). Methods Blood samples were analyzed daily between infusion of the transplant and hematopoietic reconstitution. Significant differences in the composition of NC types and CD34 + cells were observed between the two CD34 sources. The detection threshold for NC was roughly 1 cell per μL blood. Results The cell nadir of < 100 NC/μL was reached on Day +4 (BM) and on day 0 (PBSC), when unusual CD34 + cells of recipient genotype were detected in all patients. They were not clonogenic, showed high CD34 expression, but were negative for CD45, CD38, CD33, CD50, HLA-DR and Stro-1. Between Days +5 and +16, the onset of hematopoietic reconstitution was clearly detectable in multi-parameter evaluation of the FACS data. This was a median of 3.5 days before NC increased above 200/μL blood and 4-10 days before granulocyte counts were > 500/μL. It was marked by the appearance of monocytes, immature (CD38 + ) granulocytes, and clonogenic donor CD34 + cells exhibited normal size and phenotype. Discussion We conclude that dynamic FACS analyses can reliably detect hematopoietic reconstitution, but also graft rejection, before a visible increase NC numbers. This may have considerable impact on clinical management strategies. [ABSTRACT FROM AUTHOR]

Focuses on multiplex polymerase chain reaction (PCR) for quality control of template RNA/complementary DNA in reverse transcription-PCR assays. Exclusion of genes known to have processed pseudogenes from the assay; Evaluation of the reliability of the method.

No abstract [ABSTRACT FROM AUTHOR]

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We have determined the canine and feline N-, K-, and H-ras gene sequences from position +23 to +270 covering exons I and II which contain the mutational hot spot codons 12, 13, and 61. The results were used to assess the degree of similarity between ras gene DNA regions containing the critical domains affected in neoplastic disorders in different mammalian species. The comparative analyses performed included human, canine, feline, murine, rattine, and, whenever possible, bovine, leporine (rabbit), porcelline (guinea pig), and mesocricetine (hamster) ras gene sequences within the region of interest. Comparison of feline and canine nucleotide sequences with the corresponding regions in human DNA revealed a sequence similarity greater than 85% to the human sequence. Contemporaneous analysis of previously published ras DNA sequences from other mammalian species showed a similar degree of homology to human DNA. Most nucleotide differences observed represented synonymous changes without effect on the amino acid sequence of the respective proteins. For assessment of the phylogenetic evolution of ras gene family, a maximum parsimony dendrogram based on multiple sequence alignment of the common region of exons I and II in the N-, K-, and H-ras genes was constructed. Interestingly, a higher substitution rate among the H-ras genes became apparent, indicating accelerated sequence evolution within this particular clade. The most parsimonious tree clearly shows that the duplications giving rise to the three ras genes must have occurred before the mammalian radiation. [ABSTRACT FROM AUTHOR]

The article cites an opinion about the latest achievements in the field of chimerism and transplant-related diagnostics. Surveillance of chimerism within total peripheral blood leukocytes or specific cell lineages is an indispensable tool for the clinical management of transplant recipients. The journal "Leukemia," has addressed the challenges of clinical diagnostics in the allogeneic stem cell transplantation.

During the last decade, several studies have shown that quantification of minimal residual disease (MRD) provides prognostic information that can be used for treatment decisions in individual patients. In acute lymphoblastic leukemia, MRD information obtained at early time points during therapy allows the recognition of high-risk and low-risk patients, who may benefit from treatment intensification or treatment reduction, respectively. In acute promyelocytic leukemia and chronic myeloid leukemia, MRD information at specific time-points enables effective early treatment intervention.

Leukemia (2003) 17, 252–254. doi:10.1038/sj.leu.2402753 [ABSTRACT FROM AUTHOR]

Leukemia (2003) 17, 221–223. doi:10.1038/sj.leu.2402755 [ABSTRACT FROM AUTHOR]

Different bacteria and fungi live as commensal organisms as part of the human microbiota, but shifts to a pathogenic state potentially leading to septic infections commonly occur in immunocompromised individuals. Several studies have reported synergistic or antagonistic interactions between individual bacteria and fungi which might be of clinical relevance. Here, we present first evidence for the interaction between Klebsiella pneumoniae and several Aspergillus species including A. fumigatus, A. terreus, A. niger and A. flavus which cohabit in the lungs and the intestines. Microbiological and molecular methods were employed to investigate the interaction in vitro, and the results indicate that Klebsiella pneumoniae is able to prevent Aspergillus spp. spore germination and hyphal development. The inhibitory effect is reversible, as demonstrated by growth recovery of Aspergillus spp. upon inhibition or elimination of the bacteria, and is apparently dependent on the physical interaction with metabolically active bacteria. Molecular analysis of Klebsiella-Aspergillus interaction has shown upregulation of Aspergillus cell wall-related genes and downregulation of hyphae-related genes, suggesting that Klebsiella induces cell wall stress response mechanisms and suppresses filamentous growth. Characterization of polymicrobial interactions may provide the basis for improved clinical management of mixed infections by setting the stage for appropriate diagnostics and ultimately for optimized treatment strategies. [ABSTRACT FROM AUTHOR]

Leukemia (2003) 17, 612. doi:10.1038/sj.leu.2402855 [ABSTRACT FROM AUTHOR]

Introduces articles on medical care published in the December 1999 issue of the periodical 'Leukemia.' Article on Chimerism in the periodical; Debate on standardization of technical approaches of molecular technology.