Thomas Prebet

Protein tyrosine kinase 7 has a conserved role in Wnt/β-catenin canonical signalling

The receptor protein tyrosine kinase 7 (PTK7) was recently shown to participate in noncanonical Wnt/planar cell polarity signalling during mouse and frog embryonic development. In this study, we report that PTK7 interacts with β‐catenin in a yeast two‐hybrid assay and mammalian cells. PTK7‐deficient cells exhibit weakened β‐catenin/T‐cell factor transcriptional activity on Wnt3a stimulation. Furthermore, Xenopus PTK7 is required for the formation of Spemanns organizer and for Siamois promoter activation, events that require β‐catenin transcriptional activity. Using epistatic assays, we demonstrate that PTK7 functions upstream from glycogen synthase kinase 3. Taken together, our data reveal a new and conserved role for PTK7 in the Wnt canonical signalling pathway.

The cell polarity PTK7 receptor acts as a modulator of the chemotherapeutic response in acute myeloid leukemia and impairs clinical outcome

The pseudo tyrosine kinase receptor 7 (PTK7) is an orphan tyrosine kinase receptor assigned to the planar cell polarity pathway. It plays a major role during embryogenesis and epithelial tissue organization. Here we found that PTK7 is also expressed in normal myeloid progenitors and CD34(+) CD38(-) bone marrow cells in humans. We performed an immunophenotyping screen on more than 300 patients treated for hematologic malignancies. We demonstrated that PTK7 is expressed in acute myeloid leukemia (AML) and is mostly assigned to granulocytic lineage differentiation. Patients with PTK7-positive AML are more resistant to anthracycline-based frontline therapy with a significantly reduced leukemia-free survival in a multivariate analysis model. In vitro, expression of PTK7 in cultured leukemia cells promotes cell migration, cell survival, and resistance to anthracycline-induced apoptosis. The intracellular region of PTK7 is required for these effects. Furthermore, we efficiently sensitized primary AML blasts to anthracycline-mediated cell death using a recombinant soluble PTK7-Fc protein. We conclude that PTK7 is a planar cell polarity component expressed in the myeloid progenitor compartment that conveys promigratory and antiapoptotic signals into the cell and that represents an independent prognosis factor of survival in patients treated with induction chemotherapy.

The increase from 2.5 to 5 mg/kg of rabbit anti-thymocyte-globulin dose in reduced intensity conditioning reduces acute and chronic GVHD for patients with myeloid malignancies undergoing allo-SCT

We previously reported that reduced intensity conditioning (RIC) regimen with fludarabine, BU and 2.5 mg/kg of rabbit anti-thymocyte globulin (r-ATG) was effective but associated with a high rate of acute and chronic GVHD. Therefore, we increased the dose of r-ATG to 5 mg/kg. In this report, we analyzed 87 patients with AML or myelodysplastic syndrome (MDS) undergoing allo-SCT from an HLA-identical sibling donor from 2000 to 2010. RIC consisted of fludarabine, BU and r-ATG 2.5 mg/kg on 1 day (r-ATG1; n=53) or 2.5 mg/kg per day over 2 days (r-ATG2; n=22). Grade 2–4 acute GVHD incidence at day 100 was 30.2% and 8.8% in the r-ATG1 and r-ATG2 groups, respectively (P=0.038). Extensive chronic GVHD incidence was 60.4% and 12% in the r-ATG1 and r-ATG2 groups, respectively (P<0.001). The relapse incidences (RI) at 24 months were 18.9% and 28.5% in r-ATG1 and r-ATG2 groups, respectively (P=0.640). Overall and PFS were not different between the r-ATG1 and r-ATG2 groups. r-ATG dose at 5 mg/kg in the setting of RIC seems a good balance allowing GVHD prevention and antitumor effect with a remarkable reduction of GVHD incidence without an identical level of increased relapse rate.

Reduced-intensity conditioning with Fludarabin, oral Busulfan, and thymoglobulin allows long-term disease control and low transplant-related mortality in patients with hematological malignancies.

OBJECTIVE The development of reduced-intensity conditioning regimens rather than myeloablative regimens for allogeneic stem cell transplantation has led to decreased treatment-related mortality and increased use of this treatment modality, especially in older patients with hematological malignancies. No randomized controlled trials have been performed resulting in determining effectiveness on phase II studies, which rarely report on long-term survival. MATERIALS AND METHODS In an attempt to address this limitation, we analyzed a single-center cohort of 100 consecutive patients with hematological malignancies undergoing allogeneic stem cell transplantation from a human leukocyte antigen-matched related donor with median follow-up of 60 months. The reduced-intensity conditioning regimen consisted of oral Busulfan, rabbit anti-thymocyte globulin, and Fludarabin. RESULTS Median age was 50 years (range, 18-64 years). The incidences of acute and chronic graft-vs.-host disease were 43% and 81%, respectively. The probability of nonrelapse mortality at 1 and 5 years was 15% and 25%, respectively. Nonrelapse mortality was adversely associated with acute graft-vs.-host disease (hazard ratio = 6; p = 0.0002). Of the 52 patients with measurable disease, 37 (71%) achieved a response. Relapse/progression occurred at a median of 11 months (range 1-52 months) in 21 patients, for a cumulative incidence of 22%. The probability of overall survival and progression-free survival at 5 years were 60% and 54%, respectively. Overall survival and progression-free survival were favorably influenced by having had previous autologous stem cell transplantation and a low CD34(+) cell dose. Overall survival, progression-free survival, and nonrelapse mortality improved over time in this cohort of patients. CONCLUSIONS These results are encouraging for populations different in term of age, diagnosis, and disease status.

Histone méthyltransférases - Une nouvelle classe de cibles thérapeutiques dans le traitement du cancer ?

Epigenetic gene regulation contributes, together with genetic alterations, to cancer development and progression. In contrast to genetic disorders, the possibility of reversing epigenetic alterations has provided original targets for therapeutic application. In the last years, work has been focused on the pharmacological restoration of epigenetic regulation balance using epidrugs which yield hopes for novel strategy in cancer therapy. Histone acetylation and DNA methylation are epigenetic modifications which have been closely linked to the pathology of human cancers, and inhibitors of both enzyme classes for clinical use are at hands. Novel findings accumulated during the last years both in chemistry and biomedical applications give rise to new targeted treatments against cancer. Since their links with pathogenesis and progression of cancer were recognized, histone methyltransferases emerge as promising therapeutic targets in cancer treatment.

Platelet recovery and transfusion needs after reduced intensity conditioning allogeneic peripheral blood stem cell transplantation.

OBJECTIVE The aim of this retrospective study was to assess platelet transfusion needs and the kinetics and predictive factors for platelet recovery after reduced-intensity conditioning (RIC) allogeneic hematopoietic stem cell transplantation (HSCT). MATERIALS AND METHODS The profile of platelet recovery and transfusion needs in the first 100 days after RIC allo-SCT from a human leukocyte antigen-identical sibling donor was analyzed in a single-center series of 166 consecutive patients. RESULTS Platelet recovery (>20g/L) was observed at a median of 9 days (range, 0-99 days) after allo-SCT. One-hundred forty-five patients could be assessed for platelet recovery at day +100, of which 99 (68%) had a platelet count >99g/L. In the multivariate analysis, a lower platelet counts before the start of conditioning, and occurrence of grade III to IV acute graft-vs-host disease significantly influenced day-100 platelet recovery >100 x 10(9)/L (odds ratio [OR] = 2.51; 95% confidence interval [CI], 1.13-5.61; p = 0.025; and OR = 7.6; 95% CI, 3.0-19.29; p = 0.00002, respectively). Eighty-three patients (50%) did not require any platelet transfusion during follow-up. Multivariate analysis found the following parameters to be significantly associated with platelet transfusion needs: conditioning regimen type (use of antithymoglobulin: OR = 3.96; 95% CI, 1.77-8.89; p = 0.008), platelet count prior to RIC administration (>144g/L; OR = 0.18; 95% CI, 0.08-0.39; p = 0.00001) and occurrence of grade III to IV acute GVHD (OR = 11.62; 95% CI, 4.01-33.66; p = 0.000006). CONCLUSIONS Overall, these observations show a lower rate of platelet transfusion and faster platelet recovery kinetics after RIC HSCT, but also highlight the negative effect of severe acute GVHD as a risk factor for increased need for platelet transfusions.

A simplified, 96-well–adapted, ATP luminescence–based motility assay

Directional motility assays make use of Boyden chambers or Transwell culture inserts with porous membranes that separate cells seeded in the upper chamber from a chemoattractant supplied in a lower chamber. These assays are often time-consuming and are associated with several limitations due to manual counting and inconsistent results; low signal-to-noise ratio and fluorescence interference; and high cost and the need for specific equipment. Here, we describe a simple, direct, and easy ATP luminescence-based motility assay (ALMA), which can be used for 96-well plate quantification.

The PTK7 Receptor Family

PTK7 represents the only member of its family. It has a classical RTK structure with an extracellular domain, a transmembrane domain, and an intracellular domain. However, this domain lacks catalytic activity and therefore PTK7 also belongs to the pseudokinase group. PTK7 is processed by metalloproteinases MT1-MPP and ADAMs and sequentially by γ-secretase. No ligand has been identified to date.