Activation of the p53 pathway in adipose tissue contributes to insulin resistance associated with obesity. However, the mechanisms of p53 activation and the effect on adipocyte functions are still elusive. Here we found a higher level of DNA oxidation and a reduction in telomere length in adipose tissue of mice fed a high-fat diet and an increase in DNA damage and activation of the p53 pathway in adipocytes. Interestingly, hallmarks of chronic DNA damage are visible at the onset of obesity. Furthermore, injection of lean mice with doxorubicin, a DNA damage-inducing drug, increased the expression of chemokines in adipose tissue and promoted its infiltration by proinflammatory macrophages and neutrophils together with adipocyte insulin resistance. In vitro, DNA damage in adipocytes increased the expression of chemokines and triggered the production of chemotactic factors for macrophages and neutrophils. Insulin signaling and effect on glucose uptake and Glut4 translocation were decreased, and lipolysis was increased. These events were prevented by p53 inhibition, whereas its activation by nutlin-3 reproduced the DNA damage-induced adverse effects. This study reveals that DNA damage in obese adipocytes could trigger p53-dependent signals involved in alteration of adipocyte metabolism and secretory function leading to adipose tissue inflammation, adipocyte dysfunction, and insulin resistance.

Low-dose vemurafenib induces complete remission in a case of hairy-cell leukemia with a V600E mutationHairy-cell leukemia (HCL) is a lymphoproliferative disorder characterized by the presence of CD103-positive circulating B cells, pancytopenia and splenomegaly.1 HCL cases were recently shown to harbor a mutation at codon 600 of BRAF (V600E), suggesting that this genetic event represents a key driver of the disease.2 Recently, Dietrich et al. reported a case of refractory HCL treated with escalating doses of vemurafenib. Vemurafenib exhibited remarkable activity, with rapidly decreased splenomegaly, increased platelets, and normalization of hemoglobin and granulocyte counts.3 In consideration of these data, we used vemurafenib to treat a 72-year old patient who presented with a relapse of HCL and the BRAF V600E mutation. In 1989, our then 49-year old male patient was diagnosed with HCL, treated with a splenectomy and follow-up interferon, and demonstrated a complete hematologic response. However, in 2003 and 2009, the patient presented with relapses and was treated with cladribine. Tolerance was very poor with grade IV infectious toxicities after both treatments. In June 2012, the patient presented with a new progression, as revealed by the presence of dyspnea and bicytopenia (platelet count 24x10 9 /L, hemoglobin 6.9 g/dl), a normal neutrophil count, and a circulating HCL level of 4x10 9 /L (morphological examination). A bone marrow aspiration was performed but was not conclusive. The V600E mutation was detected in blood leukemic cells. Considering the patient's medical history, and after obtaining informed consent, we initiated vemurafenib at a dose of 240 mg twice daily (Day 0). The kinetics of the hemogram and hairy-cell leukemia are detailed in (Table 1) + cell fraction had decreased from 86% to 5%, and the patient remained cytopenic (Figure 1) and required one final red blood cell transfusion. Due to the satisfactory treatment efficiency and the persistent cytopenia, we maintained the treatment with vemurafenib at a constant dose (240 mg x 2), which is in contrast to the management of previously published case of HCL.3 The percentage of cells harboring the V600E mutation was monitored using a pyrosequencing assay, and this method has recently been described as rapid, sensitive and quantitative.4 At Day 56, the immunophenotyping and percentage of mutated cells were comparable to those of a healthy volunteer donor (Figure 2). The blood cell counts at Day 56 had improved, with a hemoglobin level of 9.2 g/dL without transfusion, leukocytes 3. + cell frequency of 5%. At this point, the vemurafenib was stopped. One month after completion of the treatment (Day 90), the patient showed complete remission, as defined by Grever (hematologic blood count was normal and blood morphological examination showed no evidence of HCL cells).5 However, close follow up was maintained. Our observations suggest that the inhibition of mutated BRAF by vemurafenib may represent an important therapeutic advancement for the treatment of...

The advent of tyrosine kinase inhibitor (TKI) therapy has considerably improved the survival of patients suffering chronic myelogenous leukemia (CML). Indeed, inhibition of BCR-ABL by imatinib, dasatinib or nilotinib triggers durable responses in most patients suffering from this disease. Moreover, resistance to imatinib due to kinase domain mutations can be generally circumvented using dasatinib or nilotinib, but the multi-resistant T315I mutation that is insensitive to these TKIs, remains to date a major clinical problem. In this line, ponatinib (AP24534) has emerged as a promising therapeutic option in patients with all kinds of BCR-ABL mutations, especially the T315I one. However and surprisingly, the effect of ponatinib has not been extensively studied on imatinib-resistant CML cell lines. Therefore, in the present study, we used several CML cell lines with different mechanisms of resistance to TKI to evaluate the effect of ponatinib on cell viability, apoptosis and signaling. Our results show that ponatinib is highly effective on both sensitive and resistant CML cell lines, whatever the mode of resistance and also on BaF3 murine B cells carrying native BCR-ABL or T315I mutation. We conclude that ponatinib could be effectively used for all types of TKI-resistant patients.