A p53 score derived from TP53 CRISPR/Cas9 HMCLs predicts survival and reveals major role of BAX in BH3 mimetics response

To establish a strict p53-dependent gene expression profile, TP53-/- clones were derived from TP53+/+ and TP53-/mut t(4;14) human myeloma cell lines (HMCLs) using CRISPR/Cas9 technology. From the 17 dysregulated genes shared between the TP53-/- clones from TP53+/+ HMCLs, we established a functional p53 score, involving 13 genes specifically downregulated upon p53 silencing. This functional score segregated clones and myeloma cell lines, as well as other cancer cell lines according to their TP53 status. The score was efficient to identify myeloma patient samples with biallelic TP53 inactivation and was predictive of overall survival in MMRF-coMMpass and CASSIOPEA cohorts. At the functional level, we showed that among the 13 genes, p53-regulated BAX expression correlated to, and directly impacted, the MCL1 BH3 mimetic S63845 sensitivity of myeloma cells by decreasing MCL1-BAX complexes. However, resistance to S63845 was overcome by combining MCL1 and BCL2 BH3 mimetics which displayed synergistic efficacy. BH3 mimetics combination was efficient in 97% of patient samples with or without del17p. Nevertheless, scRNAseq analysis showed that myeloma cells surviving to the combination had lower p53 score, showing that myeloma cells with higher p53 score were more sensitive to BH3 mimetics. Taken together, we established a functional p53 score that identifies myeloma cells with biallelic TP53 invalidation, demonstrated that p53-regulated BAX is critical for optimal cell response to BH3 mimetics, and showed that MCL1 and BCL2 BH3 mimetics combination may be of interest for patients with biallelic TP53 invalidation, for whom there is still an unmet medical need.

Added value of molecular karyotype in childhood acute lymphoblastic leukemia

Background

Thanks to an improved therapeutic regimen in childhood B-cell precursor acute lymphoblastic leukemia (BCP-ALL), 5 year-overall survival now exceeds 90%. Unfortunately, the 25% of children who relapse have an initial poor prognosis, potentially driven by pre-existing or emerging molecular anomalies. The latter are initially and essentially identified by cytogenetics. However, some subtle alterations are not visible through karyotyping.

Methods

Single nucleotide polymorphisms (SNP) array is an alternative way of chromosomal analysis allowing for a more in-depth evaluation of chromosomal modifications such as the assessment of copy number alterations (CNA) and loss of heterozygosity (LOH). This method was applied here in retrospective diagnosis/relapse paired samples from seven children with BCP-ALL and in a prospective cohort of 38 newly diagnosed childhood cases.

Results

In the matched study, compared to the initial karyotype, SNP array analysis reclassified two patients as poor prognosis cases. Modulation during relapse was seen for 4 CNA and 0.9 LOH. In the prospective study, SNP reclassified the 10 patients with intermediate karyotype as 7 good prognosis and 3 poor prognosis. Ultimately, in all the children tested, SNP array allowed to identify additional anomalies compared to conventional karyotype, refine its prognostic value and identify some druggable anomalies that could be used for precision medicine. Overall, the anomalies detected could be segregated in four groups respectively involved in B-cell development, cell proliferation, transcription and molecular pathways.

Conclusion

SNP therefore appears to be a method of choice in the integrated diagnosis of BCP ALL, especially for patients initially classified as intermediate prognosis. This complementary method of both cytogenetics and high throughput sequencing allows to obtain further classified information and can be useful in case of failure of these techniques.

Cytogenetics in the management of multiple Myeloma: The guidelines from the Groupe Francophone de Cytogénétique Hématologique (GFCH)

Multiple myeloma (MM) is characterized by the accumulation of malignant plasma cells (PCs) in the bone marrow. Despite considerable advances in the treatment, MM is considered an incurable chronic disease with a very heterogeneous prognosis, mostly depending on genomic alterations whose complexity evolves over time. The cytogenetic analysis of MM is performed on CD138+ sorted PCs, in order to detect the following high risk cytogenetic abnormalities: t(4;14), 17p/TP53 deletion, 1q21 gain/amplification, 1p32 deletion, as well as t(11;14) because of its therapeutic implication. This minimal panel can be enlarged to detect other recurrent abnormalities, according to the prognostic score chosen by the laboratory. Although the knowledge of the genetic landscape of MM is evolving rapidly with improved molecular technologies, risk scores remain to be refined as they require more time for consensual validation. The GFCH present here the overview of genomics alterations identified in MM and related PCs diseases associated with their prognostic factor, when available, and recommendations from an expert group for identification and characterization of those alterations. This work is the update of previous 2016 recommendations.

Cytogenetics in the management of myeloproliferative neoplasms, mastocytosis and myelodysplastic/myeloproliferative neoplasms: Guidelines from the Group Francophone de Cytogénétique Hématologique (GFCH)

Myeloproliferative neoplasms, mastocytosis, myeloid/lymphoid neoplasms with hypereosinophilia and tyrosine kinase gene fusions, and myelodysplastic/myeloproliferative neoplasms are clonal hematopoietic cancers that, with the exception of certain entities, have an indolent course. In addition to their increasingly important role in the diagnosis of these entities, as shown by the recent classification of hematolymphoid tumors in the 5th edition of the World Health Organization and the International Consensus Classification of myeloid neoplasms and acute leukemias, identification of the profile of acquired genetic abnormalities is essential for adapting patient management and early detection of patients at high risk of progression. Alongside molecular abnormalities, cytogenetic abnormalities play an important role in the diagnosis, prognosis and follow-up of these diseases. Here, we review the recent literature on the impact of chromosomal abnormalities in these different entities and provide updated cytogenetic recommendations and guidelines for their management.

Diagnosis and prognosis are supported by integrated assessment of next-generation sequencing in chronic myeloid malignancies. A real-life study

Next-generation sequencing (NGS) is used to investigate the presence of somatic mutations. The utility of incorporating routine sequencing to guide diagnosis and therapeutic decisions remains unclear. We report the findings of an observational, multicenter study that aimed to assess the impact of somatic mutation testing by NGS in a reallife setting of chronic myeloid malignancies. A total of 177 patients were enrolled, partitioned into two overlapping groups. In group A (n=94), the indication was to search for clonal hematopoiesis, in a context of suspected myelodysplastic syndrome or myeloproliferative neoplasia. In group B (n=95), the theranostic impact of somatic mutations was studied. A panel of 34 genes was used on DNA extracted from blood or bone marrow samples. Within group A, the detection of clonal hematopoiesis supported the diagnosis of chronic myeloid malignancies for 31 patients while the absence of clonal hematopoiesis ruled out the suspected diagnosis in 47 patients. Within group B, NGS identified prognostically relevant somatic mutations in 32 patients, which had a therapeutic impact in 18 cases. By determining the presence or absence of somatic mutations, the application of NGS in daily practice was found to be useful for an integrated final diagnosis in 83% of the patients. Moreover, the search for somatic mutations had a prognostic impact that led to treatment modification in 19% of the cases. This study outlines the fact that adequate implementation of new investigations may have a significant positive medico-economic impact by enabling appropriate management of patients.

Flow cytometry in the diagnosis of mature B-cell lymphoproliferative disorders

B-lineage lymphoproliferative disorders (LPD) are rather frequent diseases, associated with specific clinical or biological features but also sometimes of fortuitous discovery. Multiparameter flow cytometry plays a major role for a rapid diagnostic indication, on peripheral blood or bone marrow samples in most instances, guiding complementary analyses and allowing for the proper therapeutic management of patients. After describing the important pre-analytical precautions required for an adequate assessment, the immunophenotypic features of small-cell and large-cell lymphomas are described in this review. The ubiquitous expression of CD19 is a first mandatory gating step. A possible clonal proliferation is then suspected by the demonstration of surface immunoglobulin light chain restriction. The aberrant presence of CD5 allows to segregate chronic lymphocytic leukemia and mantle cell lymphoma in most cases. Other LPD exhibit specific immunophenotypic features. A table of useful markers and a decision tree are provided. Of note, immunophenotypic data should as much as possible be interpreted in an integrated manner, involving the patient's clinical and other biological features, and be completed by further chromosomal and/or molecular investigations.

A new cytokine-based dynamic stratification during induction is highly predictive of survivals in acute myeloid leukemia

The aim of this study was to assess the potential impact of the kinetics of serum levels of seven cytokines during induction in acute myeloid leukemia (AML) patients. Indeed, the role of cytokines, in the pathophysiology and response to therapy of AML patients, remains under investigation. Here, we report on the impact of peripheral levels of two cytokines, the Fms‐like tyrosine kinase 3 ligand (FL) and interleukin‐6 (IL‐6), evaluated during first‐line intensive induction. A new risk stratification can be proposed, which supersedes the ELN 2017 classification to predict survivals in AML patients by examining the kinetic profile of these cytokines during the induction phase. It segregates three groups of, respectively, high‐risk, characterized by a stagnation of low FL levels, intermediate risk, with dynamic increasing FL levels and high IL‐6 at day 22, and favorable risk with increasing FL levels but low IL‐6 at day 22.

Epidemiology, clinical picture and long-term outcomes of FIP1L1-PDGFRA-positive myeloid neoplasm with eosinophilia: Data from 151 patients

FIP1L1-PDGFRA-positive myeloid neoplasm with eosinophilia (F/P+ MN-eo) is a rare disease: robust epidemiological data are lacking and reported issues are scarce, of low sample-size and limited follow-up. Imatinib mesylate (IM) is highly efficient but no predictive factor of relapse after discontinuation has yet been identified. One hundred and fifty-one patients with F/P+ MN-eo (143 males; mean age at diagnosis 49 years; mean annual incidence: 0.18 case per million population) were included in this retrospective nationwide study involving all French laboratories who perform the search of F/P fusion gene (study period: 2003-2019). The main organs involved included the spleen (44%), skin (32%), lungs (30%), heart (19%) and central nervous system (9%). Serum vitamin B12 and tryptase levels were elevated in 74/79 (94%) and 45/57 (79%) patients, respectively, and none of the 31 patients initially treated with corticosteroids achieved complete hematologic remission. All 148 (98%) IM-treated patients achieved complete hematologic and molecular (when tested, n = 84) responses. Forty-six patients eventually discontinued IM, among whom 20 (57%) relapsed. In multivariate analysis, time to IM initiation (continuous HR: 1,01 [0.99-1,03]; P = .05) and duration of IM treatment (continuous HR: 0,97 [0,95-0,99]; P = .004) were independent factors of relapse after discontinuation of IM. After a mean follow-up of 80 (56) months, the 1, 5- and 10-year overall survival rates in IM-treated patients were 99%, 95% and 84% respectively. In F/P+ MN-eo, prompt initiation of IM and longer treatment durations may prevent relapses after discontinuation of IM.

FLT3 ligand plasma levels have no impact on outcomes after allotransplant in acute leukemia

OBJECTIVE

This study was designed to assess the impact on outcomes of early soluble Fms-like tyrosine kinase 3 ligand concentrations (sFLc) in patients receiving an allogeneic hematopoietic stem cell transplantation (allo-HSCT) for acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML).

METHODS

This was a prospective monocentric study including all allo-HSCT patients included in the previous FLAM/FLAL study (Peterlin et al., 2019). Blood samples collected before the start of conditioning then post-transplant were frozen, stored and tested by ELISA. The parameters considered were hematopoietic recoveries, Leukemia Free Survival and Overall Survival, acute and chronic GVHD, grade 3 or 4 acute and/or extensive chronic GVHD-free and relapse-free survival (GRFS).

RESULTS

Forty-one patients were included, a total of 179 samples were assayed for sFLc. There was no impact of sFLc levels (<=median vs> median) on acute and chronic GVHD incidences, LFS, OS nor GRFS.

CONCLUSION

At variance with induction results for AML (Peterlin et al., 2019) endogenous sFLc do not appear to be a prognostic marker at the time of or after allo-HSCT. Even though the results are negatives, this is, to the best of our knowledge, the only prospective series specifically addressing the question of sFLc impact after allo-HSCT in acute leukemias.

p53 regulates CD46 expression and measles virus infection in myeloma cells

In this study, we assessed the sensitivity of myeloma cells to the oncolytic measles virus (MV) in relation to p53 using 37 cell lines and 23 primary samples. We showed that infection and cell death were correlated with CD46 expression, which was associated with TP53 status; TP53 abn cell lines highly expressed CD46 and were preferentially infected by MV when compared with the TP53 wt cell lines (P = .046 and P = .045, respectively). Infection of myeloma cells was fully dependent on CD46 expression in both cell lines and primary cells. In the TP53 wt cell lines, but not the TP53 abn cell lines, activation of the p53 pathway with nutlin3a inhibited both CD46 expression and MV infection, while TP53 silencing reciprocally increased CD46 expression and MV infection. We showed using a p53 chromatin immunoprecipitation assay and microRNA assessment that CD46 gene expression was directly and indirectly regulated by p53. Primary myeloma cells overexpressed CD46 as compared with normal cells and were highly infected and killed by MV. CD46 expression and MV infection were inhibited by nutlin3a in primary p53-competent myeloma cells, but not in p53-deficient myeloma cells, and the latter were highly sensitive to MV infection. In summary, myeloma cells were highly sensitive to MV and infection inhibition by the p53 pathway was abrogated in p53-deficient myeloma cells. These results argue for an MV-based clinical trial for patients with p53 deficiency.

A novel complete blood count-based score to screen for myelodysplastic syndrome in cytopenic patients

The diagnosis of myelodysplastic syndromes (MDS) is often challenging, time- and resource-consuming. A thorough analysis of complete blood count (CBC) parameters could, however, help to screen for MDS among other causes of cytopenia. To test this hypothesis, 109 newly-diagnosed MDS patients and 399 cytopenic patients older than 50 years with confirmed absence of MDS were enrolled in a prospective study. Multiparametric analysis highlighted three CBC parameters that were significantly different between the two cohorts: mean corpuscular volume, absolute neutrophil count and median neutrophil complexity and width of dispersion of the events measured (Ne-WX), which were used to define an MDS-CBC score. This score enables the prediction of MDS with 86% sensitivity and 88% specificity. The MDS-CBC score excluded MDS in 89% of cytopenic controls. Moreover, high score values at MDS diagnosis significantly correlated with decreased event-free (P = 0·02) and overall survival (P = 0·01). The power of this score was confirmed in an independent validation cohort (MDS n = 34, cytopenic controls n = 28). The MDS-CBC score is an easy and fast tool to exclude or suspect MDS in unselected patients with cytopenia of unknown reasons at the time of analysis, by prompting blood smear examination. It may thus improve allocation of further MDS-specific work-up in patients with cytopenia at the time of CBC assessment.

"Double-hit" chronic lymphocytic leukemia: An aggressive subgroup with 17p deletion and 8q24 gain

Chronic lymphocytic leukemia (CLL) with 17p deletion (17p-) is associated with a lack of response to standard treatment and thus the worst possible clinical outcome. Various chromosomal abnormalities (including unbalanced translocations, deletions, ring chromosomes and isochromosomes) result in the loss of 17p and one copy of the TP53 gene. The objective of the present study was to determine whether the type of chromosomal abnormality leading to 17p- and the additional aberrations influenced the prognosis in a series of 195 patients with 17p-CLL. Loss of 17p resulted primarily from an unbalanced translocation (70%) with several chromosome partners (the most frequent being chromosome 18q), followed by deletion 17p (23%), monosomy 17 (8%), isochromosome 17q [i(17q)] (5%) and a ring chromosome 17 (2%). In a univariate analysis, monosomy 17, a highly complex karyotype (≥5 abnormalities), and 8q24 gain were associated with poor treatment-free survival, and i(17q) (P = .04), unbalanced translocations (P = .03) and 8q24 gain (P = .001) were significantly associated with poor overall survival. In a multivariate analysis, 8q24 gain remained a significant predictor of poor overall survival. We conclude that 17p deletion and 8q24 gain have a synergistic impact on outcome, and so patients with this "double-hit" CLL have a particularly poor prognosis. Systematic, targeting screening for 8q24 gain should therefore be considered in cases of 17p- CLL.

The doubling potential of T lymphocytes allows clinical-grade production of a bank of genetically modified monoclonal T-cell populations

BACKGROUND AIMS

To produce an anti-leukemic effect after hematopoietic stem cell transplantation we have long considered the theoretical possibility of using banks of HLA-DP specific T-cell clones transduced with a suicide gene. For that application as for any others, a clonal strategy is constrained by the population doubling (PD) potential of T cells, which has been rarely explored or exploited.

METHODS

We used clinical-grade conditions and two donors who were homozygous and identical for all HLA-alleles except HLA-DP. After mixed lymphocyte culture and transduction, we obtained 14 HLA-DP-specific T-cell clones transduced with the HSV-TK suicide gene. Clones were then selected on the basis of their specificity and functional characteristics and evaluated for their doubling potential.

RESULTS

After these steps of selection the clone NAT-DP4^(TK), specific for HLA-DPB1*04:01/04:02, which produced high levels of interferon-γ (IFNγ), tumor necrosis factor (TNF), interleukin-2 (IL-2) and granulocyte-macrophage colony-stimulating factor (GM-CSF), was fully sequenced. It has two copies of the HSV-TK suicide transgene whose localizations were determined. Four billion NAT-DP4^(TK) cells were frozen after 50 PDs. Thawed NAT-DP4^(TK) cells retain the potential to undergo 50 additional PDs, a potential very far beyond that required to produce a biological effect. This PD potential was confirmed on 6/16 additional different T-cell clones. This type of well-defined clone can also support a second genetic modification with CAR constructs.

CONCLUSION

The possibility of choosing rare donors and exploiting the natural proliferative potential of T lymphocytes may dramatically reduce the clinical and immunologic complexity of adoptive transfer protocols that rely on the use of third-party T-cell populations.

Curcumin induces cell death of the main molecular myeloma subtypes, particularly the poor prognosis subgroups

Multiple myeloma (MM), a plasma cell malignancy, remains incurable despite the development of new therapies. Curcumin anti-tumor effects were previously characterized in multiple myeloma, however only few MM cell lines were included in these studies. Since myeloma is a heterogeneous disease it is important to address the impact of myeloma molecular heterogeneity in curcumin cell death induction. In the present study, a large panel of human myeloma cell lines (HMCLs) (n = 29), representing the main molecular MM subgroups, was screened for curcumin sensitivity. We observed that curcumin cell death induction was heterogeneous, of note 16 HMCLs were highly sensitive to curcumin (LD₅₀ < 20.5 μM), 6 HMCLs exhibited intermediate LD₅₀ values (20.5 μM ≤ LD₅₀ < 32.2 μM) and only 7 HMCLs were weakly sensitive (35 < LD₅₀ < 56 μM). Cell lines harboring the t(11;14) translocation were less sensitive (median LD50 32.9 μM) than non-t(11;14) (median LD50 17.9 μM), which included poor prognosis t(4;14) and t(14;16) cells. Interestingly, curcumin sensitivity was not dependent on TP53 status. For the first time we showed that primary myeloma cells were also sensitive, even those displaying del(17p), another poor prognosis factor. We also unravel the contribution of anti-apoptotic Bcl-2 family molecules in curcumin response. We found that down-regulation of Mcl-1, an essential MM survival factor, was associated with curcumin-induced cell death and its knockdown sensitized myeloma cells to curcumin, highlighting Mcl-1 as an important target for curcumin-induced apoptosis. Altogether, these results support clinical trials including curcumin in association with standard therapy.

RITA (Reactivating p53 and Inducing Tumor Apoptosis) is efficient against TP53abnormal myeloma cells independently of the p53 pathway

Background

The aim of this study was to evaluate the efficacy of the p53-reactivating drugs RITA and nutlin3a in killing myeloma cells.

Methods

A large cohort of myeloma cell lines (n = 32) and primary cells (n = 21) was used for this study. This cohort contained cell lines with various TP53 statuses and primary cells with various incidences of deletion of chromosome 17. Apoptosis was evaluated using flow cytometry with Apo2.7 staining of the cell lines or via the loss of the myeloma-specific marker CD138 in primary cells. Apoptosis was further confirmed by the appearance of a subG1 peak and the activation of caspases 3 and 9. Activation of the p53 pathway was monitored using immunoblotting via the expression of the p53 target genes p21, Noxa, Bax and DR5. The involvement of p53 was further studied in 4 different p53-silenced cell lines.

Results

Both drugs induced the apoptosis of myeloma cells. The apoptosis that was induced by RITA was not related to the TP53 status of the cell lines or the del17p status of the primary samples (p = 0.52 and p = 0.80, respectively), and RITA did not commonly increase the expression level of p53 or p53 targets (Noxa, p21, Bax or DR5) in sensitive cells. Moreover, silencing of p53 in two TP53^mutated cell lines failed to inhibit apoptosis that was induced by RITA, which confirmed that RITA-induced apoptosis in myeloma cells was p53 independent. In contrast, apoptosis induced by nutlin3a was directly linked to the TP53 status of the cell lines and primary samples (p < 0.001 and p = 0.034, respectively) and nutlin3a increased the level of p53 and p53 targets in a p53-dependent manner. Finally, we showed that a nutlin3a-induced DR5 increase (≥1.2-fold increase) was a specific and sensitive marker (p < 0.001) for a weak incidence of 17p deletion within the samples (≤19%).

Conclusion

These data show that RITA, in contrast to nutlin3a, effectively induced apoptosis in a subset of MM cells independently of p53. The findings and could be of interest for patients with a 17p deletion, who are resistant to current therapies.

Oriented carbon nanostructures containing nitrogen obtained by ion beam assisted deposition

In this paper, we report the deposition of graphite multilayer containing nitrogen covering nanometric nickel particles. In-situ photoelectron emission spectroscopy (XPS) reveals the presence of nitrogen in the carbon layer covering the nickel particles. The field emission properties of the structures are reported. Atomic force microscopy displays regular domelike structures. Raman spectroscopy shows the characteristic frequencies associated with graphite and disordered structures. High-resolution transmission electron microscopy confirms the presence of multiwall well-organized graphite layers covering the nickel particles. Disorder increases on increasing nitrogen content. The samples were prepared in-situ by depositing first a few atomic layers of nickel and subsequent islands formation by thermal annealing. Then, an argon ion beam bombards an ultrapure carbon target and simultaneously the growing film is assisted with a second low-energy nitrogen ion beam (ion beam assisted deposition).

Large deletions 5' to the ETO breakpoint are recurrent events in patients with t(8;21) acute myeloid leukemia

Recurrent chromosomal rearrangements are observed in many leukemia subtypes. Recently, it has been shown that several of these translocations/inversions were associated with the loss of sequences located in the vicinity of the chromosomal breakpoints. So far, such deletions have not been described for the t(8;21) translocation. We have analyzed a series of 65 patients with t(8;21) using several probes specific for the ETO and AML1 regions. We have found six patients (9%) with deletion of the region 5' to ETO. In all six patients, the deletion encompassed at least 260 kb, and was even larger in two patients (up to 2 Mb). A similar analysis of the 21q22 region did not reveal any deletion of the 3'AML1 region. In conclusion, cytogenetically undetectable small deletions located immediately 5' to the ETO breakpoint were found to accompany the t(8;21) translocation in a significant percentage of cases. The clinical significance, if any, of these deletions remains to be determined.

[Influence of corneal refractive surgery on the lacrymal film]

Functional and clinical signs of ocular surface involvement are observed after corneal refractive surgery (LASIK or PRK) and are evocative of dry eye syndrome. The surgical process induces a total or partial section or abrasion of the corneal-sensitive nerves. This anatomical consequence of surgery is responsible for a lachrymal dysregulation with reduced tear production. Neither technique is currently able to demonstrate its superiority in preserving the lachrymal secretion. These postoperative findings should be clearly explained to patients before surgery and discomfort should be prevented with artificial tears and/or punctual plugs for 1 to 6 months after surgery.

Ionising radiation induces the expression of PARP-1 and PARP-2 genes in Arabidopsis

By screening for Arabidopsis genes activated by ionising radiation (IR)-induced DNA damage, we have isolated a cDNA hybridising with a 3.2-kb mRNA that accumulates rapidly and strongly in irradiated cell suspensions or whole plants. The cDNA codes for a 110-kDa protein that is highly homologous to the 116-kDa vertebrate poly(ADP-ribose) polymerase (PARP-1). It is recognised by a human anti-PARP-1 antibody, binds efficiently to DNA strand interruptions in vitro, and catalyses DNA damage-dependent (ADP-ribose) polymer synthesis. We have named this protein AtPARP-1. We have also extended our observations to the Arabidopsis app (AtPARP-2) gene, demonstrating for the first time that IR-induced DNA strand interruptions induce rapid and massive accumulation of AtPARP-1 and AtPARP-2 transcripts, whereas dehydration and cadmium preferentially induce the accumulation of AtPARP-2 transcripts. The IR-induced PARP gene expression seen in Arabidopsis is in striking contrast to the post-translational activation of the PARP-1 protein that is associated with genotoxic stress in animal cells. AtPARP-1 transcripts accumulate in all plant organs after exposure to ionising radiation, but this is followed by an increase in AtPARP-1 protein levels only in tissues that contain large amounts of actively dividing cells. This cell-type specific accumulation of AtPARP-1 protein in response to DNA damage is compatible with a role for the AtPARP-1 protein in the maintenance of DNA integrity during replication, similar to the role of "guardian of the genome" attributed to its animal counterpart.

Deletion of 5q31 is observed in megakaryocytic cells in patients with myelodysplastic syndromes and a del(5q), including the 5q- syndrome

One of the most common structural rearrangements in myelodysplastic syndrome (MDS) is a deletion of the long arm of chromosome 5, del(5q). The 5q- syndrome is a distinct entity, that presents with specific morphologic abnormalities of the megakaryocytic lineage. Thus, we evaluated the presence or absence of the del(5q) in these cells. We performed fluorescence in situ hybridization analysis using unique sequence probes (one for 5q31, the other for the 5p telomeric band), and tested bone marrow specimens from 10 patients with MDS (including 6 patients with the 5q- syndrome) and a del(5q). Megakaryocytes were identified by nuclear morphology, size, and ploidy index. Our results demonstrate the presence of the del(5q) in the megakaryocytic lineage and, thus, the involvement of these cells in the disease process.

Molecular cloning and developmental expression of AtGR1, a new growth-related Arabidopsis gene strongly induced by ionizing radiation

Screening for mRNAs that accumulate after DNA damage induced by ionizing radiation, we have isolated a 2.0-kb cDNA coding for a new Arabidopsis PEST-box protein named AtGR1 (A. thaliana gamma response 1) with an expression profile similar to that observed for several plant cell cycle-related proteins. Using an anti-AtGR1 antibody, we have shown that the AtGR1 protein is expressed at basal levels in mitotically dividing cells (meristematic tissues and organ primordia) and at a strongly enhanced level in endoreduplicating cells (stipules, trichomes). Using transgenic Arabidopsis plants that express the GUS reporter gene under the control of the AtGR1 promoter, we have demonstrated that the observed AtGR1 protein distribution is due to the promoter activity. Our results suggest that basal AtGR1 levels are associated with progression through mitosis, whereas elevated intracellular levels of AtGR1 seem to induce changes between the S and M phases of the cell cycle that trigger somatic cells to enter the endoreduplication cycle. Ionizing radiation-induced rapid and dose-dependent accumulation of AtGR1 mRNA in cell cultures and plant tissues leads to tissue-specific accumulation of AtGR1 protein, best observed in ovules, which never undergo an endoreduplication cycle. It therefore appears that the radiation-induced transient AtGR1 accumulation reflects DNA damage-dependent transient cell cycle arrest before mitosis, which is necessary to accomplish DNA repair prior to chromosome segregation and cytokinesis.

Arabidopsis SGS2 and SGS3 genes are required for posttranscriptional gene silencing and natural virus resistance

Posttranscriptional gene silencing (PTGS) in plants resuits from the degradation of mRNAs and shows phenomenological similarities with quelling in fungi and RNAi in animals. Here, we report the isolation of sgs2 and sgs3 Arabidopsis mutants impaired in PTGS. We establish a mechanistic link between PTGS, quelling, and RNAi since the Arabidopsis SGS2 protein is similar to an RNA-dependent RNA polymerase like N. crassa QDE-1, controlling quelling, and C. elegans EGO-1, controlling RNAi. In contrast, SGS3 shows no significant similarity with any known or putative protein, thus defining a specific step of PTGS in plants. Both sgs2 and sgs3 mutants show enhanced susceptibility to virus, definitively proving that PTGS is an antiviral defense mechanism that can also target transgene RNA for degradation.

Amplification of the 11q23 region in acute myeloid leukemia

Cytogenetic abnormalities involving the 11q23 region are found in both acute lymphoblastic leukemia (ALL) and myeloid leukemia (AML). Molecular consequences of 11q23 translocations are the formation of chimeric genes, all of them involving the MLL (mixed-lineage leukemia) gene. To evaluate the usefulness of fluorescence in situ hybridization (FISH) in detecting MLL rearrangements in AML, we analyzed 181 patients with an MLL-specific probe. Among them, we detected three patients with multiple FISH signals, reflecting genomic amplification of this chromosomal region. Extra copies of MLL have been reported previously in four patients, but did not correspond to a true gene amplification. For the first time, we describe genomic amplification of the 11q23 region (up to more than 50 copies) in AML patients. This genomic amplification could affect MLL, but other genes in the vicinity could also be the primary target. Genes Chromosomes Cancer 26:166-170, 1999.

14q32 translocations and monosomy 13 observed in monoclonal gammopathy of undetermined significance delineate a multistep process for the oncogenesis of multiple myeloma. Intergroupe Francophone du Myélome

Clonal plasma cells in monoclonal gammopathy of undetermined significance (MGUS) have been shown to bear copy number chromosome changes. To extend our knowledge of MGUS to structural chromosomal abnormalities, we have performed fluorescence in situ hybridization experiments with probes directed to the 14q32 and 13q14 chromosomal regions in 100 patients with either MGUS or smoldering multiple myeloma (SMM). 14q32 abnormalities were observed in at least 46% of patients with MGUS/SMM, with these abnormalities being present in the majority of clonal plasma cells. Whereas t(11;14)(q13;q32) occurs in 15% of MGUS/SMM patients, an incidence similar to that of overt multiple myeloma (MM) patients, translocation t(4;14)(p16;q32) is observed in only 2% of these cases [P = 0.002 for difference with t(11;14)], as compared with 12% in MM patients (P = 0.013). Monoallelic deletions of the 13q14 region were found in 21% of patients, with two types of situations. In half of the evaluable patients, and especially in patients with SMM, the deletion is present in the majority of clonal plasma cells, as in MM, whereas in the other half of the evaluable patients (essentially in MGUS patients), it is observed in subclones only. These data enable us to elaborate a plasma cell oncogenesis model from MGUS to MM.

P53 deletion is not a frequent event in multiple myeloma

Recently a high incidence of interstitial deletion of the P53 locus has been reported in multiple myeloma (MM) patients. Considering the importance of such an event, we analysed 79 patients with advanced-stage disease using fluorescence in situ hybridization (FISH). Strikingly, we found only 7/79 patients with a P53 deletion. In order to rule out any differences in probe selection, we reanalysed all the patients with the same probe as that used in a previous study, and confirmed the low incidence of P53 deletion (7/79, 9%). The only explanation is a difference in hybridization efficiency. Since hybridization is far less efficient on malignant plasma cells than on other bone marrow cells we suggest that this poor hybridization efficiency may lead to a false P53 deletion.

Yap1 and Skn7 control two specialized oxidative stress response regulons in yeast

Yap1 and Skn7 are two yeast transcriptional regulators that co-operate to activate thioredoxin (TRX2) and thioredoxin reductase (TRR1) in response to redox stress signals. Although they are both important for resistance to H2O2, only Yap1 is important for cadmium resistance, whereas Skn7 has a negative effect upon this response. The respective roles of Yap1 and Skn7 in the induction of defense genes by H2O2 were analyzed by two-dimensional gel electrophoresis. Yap1 controls a large oxidative stress response regulon of at least 32 proteins. Fifteen of these proteins also require the presence of Skn7 for their induction by H2O2. Although about half of the Yap1 target genes do not contain a consensus Yap1 recognition motif, the control of one such gene, TSA1, involves the binding of Yap1 and Skn7 to its promoter in vitro. The co-operative control of the oxidative stress response by Yap1 and Skn7 delineates two gene subsets. Remarkably, these two gene subsets separate antioxidant scavenging enzymes from the metabolic pathways regenerating the main cellular reducing power, glutathione and NADPH. Such a specialization may explain, at least in part, the dissociated function of Yap1 and Skn7 in H2O2 and cadmium resistance.

A new antioxidant with alkyl hydroperoxide defense properties in yeast

To isolate new antioxidant genes, we have searched for activities that would rescue the tert-butyl hydroperoxide (t-BOOH)-hypersensitive phenotype of a Saccharomyces cerevisiae strain deleted for the gene encoding the oxidative stress response regulator Skn7. We report the characterization of AHP1, which encodes a 19-kDa protein similar to the AhpC/TSA protein family within a small region encompassing Cys-62 of Ahp1p and the highly conserved N-terminal catalytic AhpC/TSA cysteine. Ahp1p contains a peroxisomal sorting signal, suggesting a peroxisomal localization. AHP1 exerts strong antioxidant protective functions, as demonstrated both by gene overexpression and deletion analyses, and is inducible by peroxides in an Yap1- and Skn7-dependent manner. Similar to yeast Tsa1p, Ahp1p forms a disulfide-linked homodimer upon oxidation and in vivo requires the presence of the thioredoxin system but not of glutathione to perform its antioxidant protective function. Furthermore, in contrast to Tsa1p, which is specific for H2O2, Ahp1p is specific for organic peroxides. Therefore, with respect to substrate specificity, Ahp1p differs from Tsa1p and is similar to prokaryotic alkyl hydroperoxide reductase AhpC. These data suggest that Ahp1p is a yeast orthologue of prokaryotic AhpC and justifies its name of yeast alkyl hydroperoxide reductase.

The H2O2 stimulon in Saccharomyces cerevisiae

The changes in gene expression underlying the yeast adaptive stress response to H2O2 were analyzed by comparative two-dimensional gel electrophoresis of total cell proteins. The synthesis of at least 115 proteins is stimulated by H2O2, whereas 52 other proteins are repressed by this treatment. We have identified 71 of the stimulated and 44 of the repressed targets. The kinetics and dose-response parameters of the H2O2 genomic response were also analyzed. Identification of these proteins and their mapping into specific cellular processes give a distinct picture of the way in which yeast cells adapt to oxidative stress. As expected, H2O2-responsive targets include an important number of heat shock proteins and proteins with reactive oxygen intermediate scavenging activities. Exposure to H2O2 also results in a slowdown of protein biosynthetic processes and a stimulation of protein degradation pathways. Finally, the most remarkable result inferred from this study is the resetting of carbohydrate metabolism minutes after the exposure to H2O2. Carbohydrate fluxes are redirected to the regeneration of NADPH at the expense of glycolysis. This study represents the first genome-wide characterization of a H2O2-inducible stimulon in a eukaryote.

Methylammonium-resistant mutants of Nicotiana plumbaginifolia are affected in nitrate transport

This work reports the isolation and preliminary characterization of Nicotiana plumbaginifolia mutants resistant to methylammonium. Nicotiana plumbaginifolia plants cannot grow on low levels of nitrate in the presence of methylammonium. Methylammonium is not used as a nitrogen source, although it can be efficiently taken up by Nicotiana plumbaginifolia cells and converted into methylglutamine, an analog of glutamine. Glutamine is known to repress the expression of the enzymes that mediate the first two steps in the nitrate assimilatory pathway, nitrate reductase (NR) and nitrite reductase (NiR). Methylammonium has therefore been used, in combination with low concentrations of nitrate, as a selective agent in order to screen for mutants in which the nitrate pathway is de-repressed. Eleven semi-dominant mutants, all belonging to the same complementation group, were identified. The mutant showing the highest resistance to methylammonium was not affected either in the utilization of ammonium, accumulation of methylammonium or in glutamine synthase activity. A series of experiments showed that utilization of nitrite by the wild-type and the mutant was comparable, in the presence or the absence of methylammonium, thus suggesting that the mutation specifically affected nitrate transport or reduction. Although NR mRNA levels were less repressed by methylammonium treatment of the wild-type than the mutant, NR activities of the mutant remained comparable with or without methylammonium, leading to the hypothesis that modified expression of NR is probably not responsible for resistance to methylammonium. Methylammonium inhibited nitrate uptake in the wild-type but had only a limited effect in the mutant. The implications of these results are discussed.

Assessment of family history of alcoholism in sons of alcoholic fathers

Results of studies of sons of alcoholics (SOAs) may vary depending on the density of the family history of alcoholism of the SOA subjects selected. To assess how reliably SOA subjects report a history of alcoholism in first- and second-degree relatives, we compared family histories obtained from 20 SOAs with those provided by their fathers. In all 20 cases, SOAs and their fathers agreed that the father met criteria for alcohol dependence but for no other primary Axis I psychiatric disorder. However, agreement was not as good for whether other paternal relatives in addition to the father were affected (kappa = 0.36) or for whether the family history was unigenerational or multigenerational for alcoholism (kappa = 0.44). Whether this discrepancy was due to under-reporting by the son or over-reporting by the father is unclear. These results suggest that 18-25 year old SOAs are reliable sources regarding alcohol dependence in their fathers, but that for determination of density of the family history of alcoholism, other relatives should also be interviewed directly.