Detection of a Cooper-pair density wave in Bi2Sr2CaCu2O8+x.

The quantum condensate of Cooper pairs forming a superconductor was originally conceived as being translationally invariant. In theory, however, pairs can exist with finite momentum Q, thus generating a state with a spatially modulated Cooper-pair density. Such a state has been created in ultracold (6)Li gas but never observed directly in any superconductor. It is now widely hypothesized that the pseudogap phase of the copper oxide superconductors contains such a 'pair density wave' state. Here we report the use of nanometre-resolution scanned Josephson tunnelling microscopy to image Cooper pair tunnelling from a d-wave superconducting microscope tip to the condensate of the superconductor Bi2Sr2CaCu2O8+x. We demonstrate condensate visualization capabilities directly by using the Cooper-pair density variations surrounding zinc impurity atoms and at the Bi2Sr2CaCu2O8+x crystal supermodulation. Then, by using Fourier analysis of scanned Josephson tunnelling images, we discover the direct signature of a Cooper-pair density modulation at wavevectors QP ≈ (0.25, 0)2π/a0 and (0, 0.25)2π/a0 in Bi2Sr2CaCu2O8+x. The amplitude of these modulations is about five per cent of the background condensate density and their form factor exhibits primarily s or s' symmetry. This phenomenology is consistent with Ginzburg-Landau theory when a charge density wave with d-symmetry form factor and wavevector QC = QP coexists with a d-symmetry superconductor; it is also predicted by several contemporary microscopic theories for the pseudogap phase.

Towards a global cancer knowledge network: dissecting the current international cancer genomic sequencing landscape.

BACKGROUND: While next generation sequencing has enhanced our understanding of the biological basis of malignancy, current knowledge on global practices for sequencing cancer samples is limited. To address this deficiency, we developed a survey to provide a snapshot of current sequencing activities globally, identify barriers to data sharing and use this information to develop sustainable solutions for the cancer research community. METHODS: A multi-item survey was conducted assessing demographics, clinical data collection, genomic platforms, privacy/ethics concerns, funding sources and data sharing barriers for sequencing initiatives globally. Additionally, respondents were asked as to provide the primary intent of their initiative (clinical diagnostic, research or combination). RESULTS: Of 107 initiatives invited to participate, 59 responded (response rate = 55%). Whole exome sequencing (P = 0.03) and whole genome sequencing (P = 0.01) were utilized less frequently in clinical diagnostic than in research initiatives. Procedures to identify cancer-specific variants were heterogeneous, with bioinformatics pipelines employing different mutation calling/variant annotation algorithms. Measurement of treatment efficacy varied amongst initiatives, with time on treatment (57%) and RECIST (53%) being the most common; however, other parameters were also employed. Whilst 72% of initiatives indicated data sharing, its scope varied, with a number of restrictions in place (e.g. transfer of raw data). The largest perceived barriers to data harmonization were the lack of financial support (P < 0.01) and bioinformatics concerns (e.g. lack of interoperability) (P = 0.02). Capturing clinical data was more likely to be perceived as a barrier to data sharing by larger initiatives than by smaller initiatives (P = 0.01). CONCLUSIONS: These results identify the main barriers, as perceived by the cancer sequencing community, to effective sharing of cancer genomic and clinical data. They highlight the need for greater harmonization of technical, ethical and data capture processes in cancer sample sequencing worldwide, in order to support effective and responsible data sharing for the benefit of patients.

Human papillomavirus (HPV): making the case for 'Immunisation for All'.

Human papillomavirus (HPV) contributes to the most common sexually transmitted infections, with repeated and persistent infection with particular types causing disease in both men and women. Infection with low-risk HPV types can lead to genital warts and benign lesions of the oral cavity, while high-risk types can cause various HPV-related malignancies. The incidence of head and neck cancers has been rising in the past number of decades mostly due to oropharyngeal cancer linked to HPV infection. HPV vaccination has been shown to be effective for cervical and other anogenital HPV-related cancers, and there is significant potential for HPV vaccination to prevent oropharyngeal cancers, given that the HPV types implicated in this disease can be protected against by the HPV vaccine. Few countries have implemented a universal HPV vaccination programme for males and females, with many countries arguing that female-only vaccination programmes protect males via herd immunity and that men who have sex with men will be protected via targeted vaccination programmes. We argue these may be limited in their effectiveness. We propose that the most effective, practical, ethical and potentially cost-effective solution is universal HPV vaccination that might lead to control of HPV-related diseases in men and women alike.

Intra-unit-cell electronic nematicity of the high-T(c) copper-oxide pseudogap states.

In the high-transition-temperature (high-T(c)) superconductors the pseudogap phase becomes predominant when the density of doped holes is reduced. Within this phase it has been unclear which electronic symmetries (if any) are broken, what the identity of any associated order parameter might be, and which microscopic electronic degrees of freedom are active. Here we report the determination of a quantitative order parameter representing intra-unit-cell nematicity: the breaking of rotational symmetry by the electronic structure within each CuO(2) unit cell. We analyse spectroscopic-imaging scanning tunnelling microscope images of the intra-unit-cell states in underdoped Bi(2)Sr(2)CaCu(2)O(8 +) (delta) and, using two independent evaluation techniques, find evidence for electronic nematicity of the states close to the pseudogap energy. Moreover, we demonstrate directly that these phenomena arise from electronic differences at the two oxygen sites within each unit cell. If the characteristics of the pseudogap seen here and by other techniques all have the same microscopic origin, this phase involves weak magnetic states at the O sites that break 90 degrees -rotational symmetry within every CuO(2) unit cell.

ESMO expert consensus statements on the screening and management of financial toxicity in patients with cancer.

BACKGROUND: Financial toxicity, defined as both the objective financial burden and subjective financial distress from a cancer diagnosis and its treatment, is a topic of interest in the assessment of the quality of life of patients with cancer and their families. Current evidence implicates financial toxicity in psychosocial, economic and other harms, leading to suboptimal cancer outcomes along the entire trajectory of diagnosis, treatment, supportive care, survivorship and palliation. This paper presents the results of a virtual consensus, based on the evidence base to date, on the screening and management of financial toxicity in patients with and beyond cancer organized by the European Society for Medical Oncology (ESMO) in 2022. METHODS: A Delphi panel of 19 experts from 11 countries was convened taking into account multidisciplinarity, diversity in health system contexts and research relevance. The international panel of experts was divided into four working groups (WGs) to address questions relating to distinct thematic areas: patients with cancer at risk of financial toxicity; management of financial toxicity during the initial phase of treatment at the hospital/ambulatory settings; financial toxicity during the continuing phase and at end of life; and financial risk protection for survivors of cancer, and in cancer recurrence. After comprehensively reviewing the literature, statements were developed by the WGs and then presented to the entire panel for further discussion and amendment, and voting. RESULTS AND DISCUSSION: A total of 25 evidence-informed consensus statements were developed, which answer 13 questions on financial toxicity. They cover evidence summaries, practice recommendations/guiding statements and policy recommendations relevant across health systems. These consensus statements aim to provide a more comprehensive understanding of financial toxicity and guide clinicians globally in mitigating its impact, emphasizing the importance of further research, best practices and guidelines.

Cancer care for Ukrainian refugees: Strategic impact assessments in the early days of the conflict.

BACKGROUND: The invasion of Ukraine by Russia in February 2022 has resulted in destruction of healthcare infrastructure and triggered the largest wave of internally displaced populations and refugees since World War Two. Conflicts in transitioned countries such as Ukraine create new non-communicable disease (NCD) challenges, especially for cancer care for refugees and humanitarian assistance in host countries. In the early days, rapid attempts were made to model possible impacts. METHODS: By evaluating open source intelligence used in the first three months of the conflict through snowball search methods, we aimed to address: (i) burden of cancer in Ukrainian population, specifically considering translating to the refugees population, and its cancer care capacity; ii) baseline capacity/strengths of cancer systems in initial host countries. Moreover, using a baseline scenario based on crude cancer incidence in Ukraine, and considering data from UNHCR, we estimated how cancer cases would be distributed across host countries. Finally, a surveillance assessment instrument was created, intersecting health system's capacity and influx of internally displaced populations and refugees. FINDINGS AND CONCLUSIONS: The total new cancer patients per month in pre-conflict Ukraine was estimated as 13,106, of which < 1 % are paediatric cases. The estimated cancer cases in the refugee population (combining prevalent and incident), assuming 7.5 million refugees by July 2022 and a female:male ratio of 9:1, was 33,121 individuals (Poland: 19284; Hungary: 3484; Moldova: 2651; Slovakia: 2421; Romania: 5281). According to our assessments, Poland is the only neighbouring country classified as green/yellow for cancer capacity, i.e. sufficient ablility to absorb additional burden into national health system; Slovakia we graded as yellow, Hungary and Romania as yellow/red and Moldova as red.

PBOX-15, a novel microtubule targeting agent, induces apoptosis, upregulates death receptors, and potentiates TRAIL-mediated apoptosis in multiple myeloma cells.

BACKGROUND: In recent years, much progress has been made in the treatment of multiple myeloma. However, a major limitation of existing chemotherapeutic drugs is the eventual emergence of resistance; hence, the development of novel agents with new mechanisms of action is pertinent. Here, we describe the activity and mechanism of action of pyrrolo-1,5-benzoxazepine-15 (PBOX-15), a novel microtubule-targeting agent, in multiple myeloma cells. METHODS: The anti-myeloma activity of PBOX-15 was assessed using NCI-H929, KMS11, RPMI8226, and U266 cell lines, and primary myeloma cells. Cell cycle distribution, apoptosis, cytochrome c release, and mitochondrial inner membrane depolarisation were analysed by flow cytometry; gene expression analysis was carried out using TaqMan Low Density Arrays; and expression of caspase-8 and Bcl-2 family of proteins was assessed by western blot analysis. RESULTS: Pyrrolo-1,5-benzoxazepine-15 induced apoptosis in ex vivo myeloma cells and in myeloma cell lines. Death receptor genes were upregulated in both NCI-H929 and U266 cell lines, which displayed the highest and lowest apoptotic responses, respectively, following treatment with PBOX-15. The largest increase was detected for the death receptor 5 (DR5) gene, and cotreatment of both cell lines with tumour necrosis factor-related apoptosis-inducing ligand (TRAIL), the DR5 ligand, potentiated the apoptotic response. In NCI-H929 cells, PBOX-15-induced apoptosis was shown to be caspase-8 dependent, with independent activation of extrinsic and intrinsic apoptotic pathways. A caspase-8-dependent decrease in expression of Bim(EL) preceded downregulation of other Bcl-2 proteins (Bid, Bcl-2, Mcl-1) in PBOX-15-treated NCI-H929 cells. CONCLUSION: PBOX-15 induces apoptosis and potentiates TRAIL-induced cell death in multiple myeloma cells. Thus, PBOX-15 represents a promising agent, with a distinct mechanism of action, for the treatment of this malignancy.

Exposure of coastal environments to river-sourced plastic pollution.

Marine litter is a global problem which poses an increasing threat to ecosystem services, human health, safety and sustainable livelihoods. In order to better plan plastic pollution monitoring and clean-up activities, and to develop policies and programmes to deter and mitigate plastic pollution, information is urgently needed on the different types of coastal ecosystem that are impacted by land-sourced plastic inputs, especially those located in proximity to river mouths where plastic waste is discharged into the ocean. We overlayed the most current existing information on the input of plastic to the sea from land-based sources with maps of coastal environments and ecosystems. We found an inverse relationship exists between coastal geomorphic type, plastic trapping efficiency and the mass of plastic received. River-dominated coasts comprise only 0.87% of the global coast and yet they receive 52% of plastic pollution delivered by fluvial systems. Tide-dominated coasts receive 29.9% of river-borne plastic pollution and this is also where mangrove and salt marsh habitats are most common. Wave-dominated coasts receive 11.6% of river-borne plastic pollution and this is where seagrass habitat is most common. Finally, rocky shores comprise 72.5% of the global coast, containing fjords and coral reefs, while only receiving 6.4% of river-borne plastic pollution. Mangroves are the most proximal to river-borne plastic pollution point sources of the four habitat types studied here; 54.0% of mangrove habitat is within 20 km of a river that discharges more than 1 t/yr of plastic pollution into the ocean. For seagrass, salt marsh and coral reefs the figures are 24.1%, 22.7% and 16.5%, respectively. The findings allow us to better understand the environmental fate of plastic pollution, to advance numerical models and to guide managers and decision-makers on the most appropriate responses and actions needed to monitor and reduce plastic pollution.

Novel pyrrolo-1,5-benzoxazepine compounds display significant activity against resistant chronic myeloid leukaemia cells in vitro, in ex vivo patient samples and in vivo.

BACKGROUND: Imatinib is a direct and potent inhibitor of the constitutively active tyrosine kinase, breakpoint cluster region-Abelson (Bcr-Abl), which is central to the pathogenesis of chronic myeloid leukaemia (CML) patients. As such, imatinib has become the front-line treatment for CML patients. However, the recent emergence of imatinib resistance, commonly associated with point mutations within the kinase domain, has led to the search for alternative drug treatments and combination therapies for CML. METHODS: In this report, we analyse the effects of representative members of the novel pro-apoptotic microtubule depolymerising pyrrolo-1,5-benzoxazepines or PBOX compounds on chemotherapy-refractory CML cells using a series of Bcr-Abl mutant cell lines, clinical ex vivo patient samples and an in vivo mouse model. RESULTS: The PBOX compounds potently reduce cell viability in cells expressing the E225K and H396P mutants as well as the highly resistant T315I mutant. The PBOX compounds also induce apoptosis in primary CML samples including those resistant to imatinib. We also show for the first time, the in vivo efficacy of the pro-apoptotic PBOX compound, PBOX-6, in a CML mouse model of the T315I Bcr-Abl mutant. CONCLUSION: Results from this study highlight the potential of these novel series of PBOX compounds as an effective therapy against CML.

Two-dimensional magnetic monopole gas in an oxide heterostructure.

Magnetic monopoles have been proposed as emergent quasiparticles in pyrochlore spin ice compounds. However, unlike semiconductors and two-dimensional electron gases where the charge degree of freedom can be actively controlled by chemical doping, interface modulation, and electrostatic gating, there is as of yet no analogue of these effects for emergent magnetic monopoles. To date, all experimental investigations have been limited to large ensembles comprised of equal numbers of monopoles and antimonopoles in bulk crystals. To address these issues, we propose the formation of a two-dimensional magnetic monopole gas (2DMG) with a net magnetic charge, confined at the interface between a spin ice and an isostructural antiferromagnetic pyrochlore iridate and whose monopole density can be controlled by an external field. Our proposal is based on Monte Carlo simulations of the thermodynamic and transport properties. This proposed 2DMG should enable experiments and devices which can be performed on magnetic monopoles, akin to two-dimensional electron gases in semiconductor heterostructures.

Size-dependent influence of NOx on the growth rates of organic aerosol particles.

Atmospheric new-particle formation (NPF) affects climate by contributing to a large fraction of the cloud condensation nuclei (CCN). Highly oxygenated organic molecules (HOMs) drive the early particle growth and therefore substantially influence the survival of newly formed particles to CCN. Nitrogen oxide (NOx) is known to suppress the NPF driven by HOMs, but the underlying mechanism remains largely unclear. Here, we examine the response of particle growth to the changes of HOM formation caused by NOx. We show that NOx suppresses particle growth in general, but the suppression is rather nonuniform and size dependent, which can be quantitatively explained by the shifted HOM volatility after adding NOx. By illustrating how NOx affects the early growth of new particles, a critical step of CCN formation, our results help provide a refined assessment of the potential climatic effects caused by the diverse changes of NOx level in forest regions around the globe.

The emergence of DNA methylation as a key modulator of aberrant cell death in prostate cancer.

It is now well established that cancer cells exhibit a number of genetic defects in the machinery that governs programmed cell death and that sabotage of apoptosis is one of the principal factors aiding in the evolution of the carcinogenic phenotype. A number of studies have implicated aberrant DNA methylation as a key survival mechanism in cancer, whereby promoter hypermethylation silences genes essential for many processes including apoptosis. To date, studies on the methylation profile of apoptotic genes have largely focused on cancers of the breast, colon and stomach, with only limited data available on prostate cancer. Here we discuss the major developments in the field of DNA methylation and its role in the regulation of aberrant apoptosis in prostate cancer. The most significant advances have involved the discovery of apoptotic gene targets of methylation, including XAF1, (fragile histidine triad (FHIT ), cellular retinol binding protein 1 (CRBP1), decoy receptor 1(DCR1), decoy receptor 2 (DCR2 ), target of methylation-induced silenceing 1 (TMS1), TNF receptor superfamily, member 6 (FAS), Reprimo (RPRM) and GLI pathogenesis-related 1 (GLIPR1). These genes are reported to be hypermethylated in prostate cancer and some offer potential as diagnostic and prognostic markers. We also introduce the concept of an 'apoptotic methylation signature' for prostate cancer and evaluate its potential in a diagnostic, prognostic and therapeutic setting.

Hypoxia in prostate cancer: a powerful shield against tumour destruction?

Tumour hypoxia is progressively emerging as a common feature of prostate tumours associated with poor prognosis. While the molecular basis of disease progression is increasingly well documented, the potential role of hypoxia in these processes remains poorly evaluated. By dissecting the impact of hypoxia-inducible factor 1 alpha on molecular responses, this review provides evidence for a powerful protecting role of oxygen deprivation against oxidative stress injury, androgen deprivation, chemotherapeutic and radiation cytotoxicity. We propose hypoxia as a potent tumour-induced shield against destruction and suggest its targeting may need to be routinely addressed in the management of prostate cancer.

The tissue plasminogen activator gene promoter: a novel tool for radiogenic gene therapy of the prostate?

BACKGROUND: Radiation therapy is a treatment modality routinely used in cancer management so it is not unexpected that radiation-inducible promoters have emerged as an attractive tool for controlled gene therapy. The human tissue plasminogen activator gene promoter (t-PA) has been proposed as a candidate for radiogenic gene therapy, but has not been exploited to date. The purpose of this study was to evaluate the potential of this promoter to drive the expression of a reporter gene, the green fluorescent protein (GFP), in response to radiation exposure. METHODS: To investigate whether the promoter could be used for prostate cancer gene therapy, we initially transfected normal and malignant prostate cells. We then transfected HMEC-1 endothelial cells and ex vivo rat tail artery and monitored GFP levels using Western blotting following the delivery of single doses of ionizing radiation (2, 4, 6 Gy) to test whether the promoter could be used for vascular targeted gene therapy. RESULTS: The t-PA promoter induced GFP expression up to 6-fold in all cell types tested in response to radiation doses within the clinical range. CONCLUSIONS: These results suggest that the t-PA promoter may be incorporated into gene therapy strategies driving therapeutic transgenes in conjunction with radiation therapy.

Characterization of a reference material for BCR-ABL (M-BCR) mRNA quantitation by real-time amplification assays: towards new standards for gene expression measurements.

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 degrees 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.

Transcriptional subtyping and CD8 immunohistochemistry identifies poor prognosis stage II/III colorectal cancer patients who benefit from adjuvant chemotherapy.

PURPOSE: Transcriptomic profiling of colorectal cancer (CRC) has led to identification of four consensus molecular subtypes (CMS1-4), which have prognostic value in stage II/III disease. More recently, the Colorectal Cancer Intrinsic Subtypes (CRIS) classification system has helped to define the biology specific to the epithelial component of colorectal tumors. However, the clinical value of these classifications in predicting response to standard-of-care adjuvant chemotherapy remains unknown. PATIENTS AND METHODS: Using samples from 4 European sites, we assembled a novel stage II/III CRC patient cohort and performed transcriptomic profiling on 156 samples, targeted sequencing and generated a tissue microarray to enable integrated "multi-omics" analyses. We also accessed data from 2 published stage II/III CRC patient cohorts: GSE39582 and GSE14333 (479 and 185 samples respectively). RESULTS: The epithelial-rich CMS2 subtype of CRC benefitted significantly from adjuvant chemotherapy treatment in both stage II and III disease (p=0.02 and p<0.0001 respectively), while the CMS3 subtype significantly benefitted in stage III only (p=0.00073). Following CRIS sub-stratification of CMS2, we observed that only the CRIS-C subtype significantly benefitted from adjuvant chemotherapy in stage II and III disease (p=0.0081 and p<0.0001 respectively), while CRIS-D significantly benefitted in stage III only (p=0.0034). We also observed that CRIS-C patients with low levels of CD8+ tumor-infiltrating lymphocytes were most at risk of relapse in both stage II and III disease (p=0.0031). CONCLUSION: Patient stratification using a combination of transcriptional subtyping and CD8 immunohistochemistry analyses is capable of identifying poor prognostic stage II/III patients who benefit from adjuvant standard-of-care chemotherapy. These findings are particularly relevant for stage II disease, where the overall benefit of adjuvant chemotherapy is marginal.

Radiation to control transgene expression in tumors.

Significant evidence has accumulated indicating that certain genes are induced by ionising radiation. An implication of this observation is that their promoter regions include radiation-responsive sequences. These sequences have been isolated in the promoter of several genes including Erg-1, p21/WAF-1, GADD45alpha and t-PA. The mechanism by which radiation induces gene expression remains unclear but involves putative binding sites for selected transcription factors and/or p53. Consensus CC(A/T)6GG sequences have been localized in the Erg-1 promoter and are referred to as serum response elements or CArG elements. The tandem combination of CArG elements has been shown to improve gene expression levels, with a 9-copy motif conferring maximum inducibility. The response of these genes to ionising radiation appears to follow a sigmoid relationship with time and dose. Therapeutic induction of suicide genes and significant cytotoxicity can be achieved at clinically relevant x-rays doses both in vitro and in vivo but was found to be cell-type dependent. Radiation-inducible gene therapy can be potentially enhanced by exploiting hypoxia through the inclusion of hypoxia-response element motifs in the expression cassette, the use of the anaerobic bacteria or the use of neutron irradiation. These results are encouraging and provide significant evidence that gene therapy targeted to the radiation field is a reasonably attractive therapeutic option and could help overcome hypoxic radioresistant tumors.

The influence of cyclosporin alone, or cyclosporin and methotrexate, on the incidence of mixed haematopoietic chimaerism following allogeneic sibling bone marrow transplantation for severe aplastic anaemia.

We previously reported a randomized trial comparing Cyclosporin-A (CsA) and short-term methotrexate versus CsA alone for graft-versus-host disease (GvHD) prophylaxis in 71 patients undergoing allogeneic haematopoietic stem cell transplantation (HSCT) from a human leucocyte antigen-identical sibling for severe aplastic anaemia (SAA). We found a better survival in the group receiving the two-drug prophylaxis regimen with no significant difference in the probability of developing GvHD between the two groups. The present study details chimaeric analysis and its influence on survival and GvHD occurrence in 45 of the original 71 patients in whom serial samples were available. Analysis was carried out in a blinded prospective manner. Seventy-two per cent achieved complete donor chimaerism (DC), 11% stable mixed chimaerism (SMC) and 17% progressive mixed chimaerism (PMC). The overall 5-year survival probability was 82% (+/-11%) with a significant survival advantage (P = 0.0009) in DC or SMC compared to those with PMC. Chronic GvHD was more frequent in DC patients, whereas no patient with SMC developed chronic GvHD. Graft failure occurred in 50% of the PMC group. This study demonstrates the relevance of chimaerism analysis in patients receiving HSCT for SAA and confirms the occurrence of mixed chimaerism in a significant proportion of recipients.

Wilms' tumor gene 1 (WT1) expression in childhood acute lymphoblastic leukemia: a wide range of WT1 expression levels, its impact on prognosis and minimal residual disease monitoring.

Wilms' tumor gene 1 (WT1) is overexpressed in the majority (70-90%) of acute leukemias and has been identified as an independent adverse prognostic factor, a convenient minimal residual disease (MRD) marker and potential therapeutic target in acute leukemia. We examined WT1 expression patterns in childhood acute lymphoblastic leukemia (ALL), where its clinical implication remains unclear. Using a real-time quantitative PCR designed according to Europe Against Cancer Program recommendations, we evaluated WT1 expression in 125 consecutively enrolled patients with childhood ALL (106 BCP-ALL, 19 T-ALL) and compared it with physiologic WT1 expression in normal and regenerating bone marrow (BM). In childhood B-cell precursor (BCP)-ALL, we detected a wide range of WT1 levels (5 logs) with a median WT1 expression close to that of normal BM. WT1 expression in childhood T-ALL was significantly higher than in BCP-ALL (P<0.001). Patients with MLL-AF4 translocation showed high WT1 overexpression (P<0.01) compared to patients with other or no chromosomal aberrations. Older children (> or =10 years) expressed higher WT1 levels than children under 10 years of age (P<0.001), while there was no difference in WT1 expression in patients with peripheral blood leukocyte count (WBC) > or =50 x 10(9)/l and lower. Analysis of relapsed cases (14/125) indicated that an abnormal increase or decrease in WT1 expression was associated with a significantly increased risk of relapse (P=0.0006), and this prognostic impact of WT1 was independent of other main risk factors (P=0.0012). In summary, our study suggests that WT1 expression in childhood ALL is very variable and much lower than in AML or adult ALL. WT1, thus, will not be a useful marker for MRD detection in childhood ALL, however, it does represent a potential independent risk factor in childhood ALL. Interestingly, a proportion of childhood ALL patients express WT1 at levels below the normal physiological BM WT1 expression, and this reduced WT1 expression appears to be associated with a higher risk of relapse.