VLX1570 induces apoptosis through the generation of ROS and induction of ER stress on leukemia cell lines.

A novel proteasome deubiquitinase inhibitor, VLX1570, has been highlighted as a promising therapeutic agent mainly for lymphoid neoplasms and solid tumors. We examined in vitro effects of VLX1570 on eight myeloid and three lymphoid leukemia cell lines. From cell culture studies, 10 out of 11 cell lines except K562 were found to be susceptible to VLX1570 treatment and it inhibited cell growth mainly by apoptosis. Next, to identify the signaling pathways associated with apoptosis, we performed gene expression profiling using HL-60 with or without 50 nmol/L of VLX1570 for 3 hours and demonstrated that VLX1570 induced the genetic pathway involved in "heat shock transcription factor 1 (HSF1) activation", "HSF1 dependent transactivation", and "Regulation of HSF1 mediated heat shock response". VLX1570 increased the amount of high molecular weight polyubiquitinated proteins and the expression of HSP70 as the result of the suppression of ubiquitin proteasome system, the expression of heme oxygenase-1, and the amount of phosphorylation in JNK and p38 associated with the generation of reactive oxygen species (ROS) induced apoptosis and the amount of phosphorylation in eIF2α, inducing the expression of ATF4 and endoplasmic reticulum (ER) stress dependent apoptosis protein, CHOP, and the amount of phosphorylation slightly in IRE1α, leading to increased expression of XBP-1s in leukemia cell lines. In the present study, we demonstrate that VLX1570 induces apoptosis and exerts a potential anti-leukemic effect through the generation of ROS and induction of ER stress in leukemia cell lines.

Japanese family with congenital factor VII deficiency.

Congenital factor VII (FVII) deficiency is a rare bleeding disorder with autosomal recessive inheritance. The present female patient was diagnosed with congenital FVII deficiency because of low hepaplastin test (HPT), although vitamin K was given. Heterozygous p.A191T mutation was detected in the peripheral blood, and the same mutation was also found in the mother and sister. To the best of our knowledge, this is the fourth reported case of p.A191T mutation of FVII in the literature and the first to be reported in Japan. FVII coagulation activity (FVII:C) in asymptomatic heterozygous carriers is mildly reduced. Therefore, some patients may not be accurately diagnosed with congenital FVII deficiency. In infants with low HPT without vitamin K deficiency, congenital FVII deficiency should be considered.

Detection of RBM15-MKL1 fusion was useful for diagnosis and monitoring of minimal residual disease in infant acute megakaryoblastic leukemia.

Acute megakaryocytic leukemia (AMKL) with t(1;22)(p13;q13) is a distinct category of myeloid leukemia by WHO classification and mainly reported in infants and young children. Accurate diagnosis of this type of AMKL can be difficult, because a subset of patients have a bone marrow (BM) blast percentage of less than 20% due to BM fibrosis. Therefore, it is possible that past studies have underestimated this type of AMKL. We present here the case of a 4-month-old female AMKL patient who was diagnosed by presence of the RBM15-MKL1 (OTT-MAL) fusion transcript by RT-PCR. In addition, we monitored RBM15-MKL1 fusion at several time points as a marker of minimal residual disease (MRD), and found that it was continuously negative after the first induction chemotherapy even by nested RT-PCR. Detection of the RBM15-MKL1 fusion transcript thus seems to be useful for accurate diagnosis of AMKL with t(1;22)(p13;q13). We recommend that the RBM15-MKL1 fusion transcript be analyzed for all suspected AMKL in infants and young children. Furthermore, monitoring of MRD using this fusion transcript would be useful in treatment of AMKL with t(1;22)(p13;q13).

Binimetinib, a novel MEK1/2 inhibitor, exerts anti-leukemic effects under inactive status of PI3Kinase/Akt pathway.

A MEK1/2 inhibitor, binimetinib is promising as a therapeutic agent for malignant melanoma with N-RAS mutation. We examined in vitro effects of binimetinib on 10 human myeloid/lymphoid leukemia cell lines, and found that three of five cell lines with N-RAS mutation and one of five without N-RAS mutation were responsive to treatment with binimetinib. Binimetinib inhibited cell growth mainly by inducing G1 arrest and this action mechanism was assisted by gene set enrichment analysis. To identify signaling pathways associated with binimetinib response, we examined the status of MAP kinase/ERK and PI3Kinase/Akt pathways. The basal levels of phosphorylated ERK and Akt varied between the cell lines, and the amounts of phosphorylated ERK and Akt appeared to be reciprocal of each other. Interestingly, most of the binimetinib-resistant cell lines revealed strong Akt phosphorylation compared with binimetinib-sensitive ones. The effect of binimetinib may not be predicted by the presence/absence of N-RAS mutation, but rather by Akt phosphorylation status. Moreover, combination of binimetinib with a PI3K/Akt inhibitor showed additive growth-suppressive effects. These results suggest that binimetinib shows potential anti-leukemic effects and the basal level of phosphorylated Akt might serve as a biomarker predictive of therapeutic effect.