Loss of PRP4K drives anoikis resistance in part by dysregulation of epidermal growth factor receptor endosomal trafficking.

Anoikis acts as a critical barrier to metastasis by inducing cell death upon cancer cell detachment from the extracellular matrix (ECM), thereby preventing tumor cell dissemination to secondary sites. The induction of anoikis requires the lysosomal-mediated downregulation of epidermal growth factor receptors (EGFRs) leading to termination of pro-survival signaling. In this study, we demonstrate that depletion of pre-mRNA splicing factor 4 kinase (PRP4K; also known as PRPF4B) causes dysregulation of EGFR trafficking and anoikis resistance. We also report a novel cytoplasmic localization of PRP4K at the late endosome, and demonstrate both nuclear and cytoplasmic localization in breast, lung and ovarian cancer tissue. Mechanistically, depletion of PRP4K leads to reduced EGFR degradation following cell detachment from the ECM and correlates with increased TrkB, vimentin and Zeb1 expression. As a result, PRP4K loss promotes sustained growth factor signaling and increased cellular resistance to anoikis in vitro and in a novel zebrafish xenotransplantation model of anoikis sensitivity, as well as increased metastasis in a mouse model of ovarian cancer. Thus, PRP4K may serve as a potential biomarker of anoikis sensitivity in ovarian and other epithelial cancers.

Epigenetic therapy restores normal hematopoiesis in a zebrafish model of NUP98-HOXA9-induced myeloid disease.

Acute myeloid leukemia (AML) occurs when multiple genetic aberrations alter white blood cell development, leading to hyperproliferation and arrest of cell differentiation. Pertinent animal models link in vitro studies with the use of new agents in clinical trials. We generated a transgenic zebrafish expressing human NUP98-HOXA9 (NHA9), a fusion oncogene found in high-risk AML. Embryos developed a preleukemic state with anemia and myeloid cell expansion, and adult fish developed a myeloproliferative neoplasm (MPN). We leveraged this model to show that NHA9 increases the number of hematopoietic stem cells, and that oncogenic function of NHA9 depends on downstream activation of meis1, the PTGS/COX pathway and genome hypermethylation through the DNA methyltransferase, dnmt1. We restored normal hematopoiesis in NHA9 embryos with knockdown of meis1 or dnmt1, as well as pharmacologic treatment with DNA (cytosine-5)-methyltransferase (DNMT) inhibitors or cyclo-oxygenase (COX) inhibitors. DNMT inhibitors reduced genome methylation to near normal levels. Strikingly, we discovered synergy when we combined sub-monotherapeutic doses of a histone deacetylase inhibitor plus either a DNMT inhibitor or COX inhibitor to block the effects of NHA9 on zebrafish blood development. Our work proposes novel drug targets in NHA9-induced myeloid disease, and suggests rational therapies by combining minimal doses of known bioactive compounds.

Familial essential thrombocythemia with spontaneous megakaryocyte colony formation and acquired JAK2 mutations.

Essential thrombocythemia (ET) is a chronic myeloproliferative disorder, characterized by increased proliferation of megakaryocytes and elevated platelet count that usually occurs sporadically. We report a family with seven affected individuals in three generations, including one individual with a phenotype resembling polycythemia vera, a related disorder. Megakaryocyte (CFU-MK) colony formation occurred in the absence of added cytokines in cultures of peripheral blood from affected family members. Some reports of familial ET have identified mutations in THPO and MPL, the genes for a cytokine (thrombopoietin, TPO) that regulates platelet production and its receptor (c-MPL), respectively. In this family, the MPL gene was excluded by linkage analysis. Although TPO levels were elevated in most affected family members and evidence for linkage was found between the disease and THPO (theta=0.0, Z(max)=3.0), a THPO mutation was not identified by DNA sequencing. The JAK2 V617F mutation that has been associated with 50% of sporadic cases of ET was identified as a somatic mutation, an acquired defect, in peripheral blood of the two most severely affected family members. These patients also had elevated TPO levels. Further study of familial myeloproliferative diseases will help elucidate the initiating genetic events underlying ET.

Herpes zoster infection in the post-hematopoietic stem cell transplant pediatric population may be preceded by transaminitis: an institutional experience.

Herpes zoster (HZ), a varicella-zoster virus reactivation, frequently complicates hematopoietic stem cell transplantation (HSCT). Its incidence, complications, and associated risk factors in 310 children undergoing HSCT were reviewed. In all, 61 of 201(32%) patients who had undergone allogeneic and 10 of 109 (9%) patients who had undergone autologous HSCT developed HZ. Of 90 VZV seropositive allogeneic patients, 50 (53%) developed HZ. Seven (17%) of 41 VZV seropositive autologous patients developed HZ. Although a substantial number of patients develop HZ in the early post-HSCT period, risk for HZ persists and HZ can occur up to 5 years post-HSCT. Risk factors for HZ included age >10 years (P<0.0001), allogeneic HSCT (P<0.001), and total body irradiation (TBI) (P<0.059) in allogeneic recipients. Of 37, 22 (59%) patients experienced an elevated alanine aminotransferase (ALT), unassociated with GVHD, in the month preceding HZ. Of the 48/64 patients (75%) hospitalized for treatment (median stay, 6 days; range, 2-39), length of stay was unaffected by donor type but increased by cutaneous dissemination and visceral involvement (P=0.023 and 0.034, respectively) in allogeneic patients. Consideration of HZ infection particularly in patients >10 years of age with elevated ALT after TBI-conditioned allogeneic HSCT may permit earlier diagnosis and therapeutic intervention.

Dietary substitution of medium-chain triglycerides improves insulin-mediated glucose metabolism in NIDDM subjects.

Dietary medium-chain triglycerides (MCT) may improve insulin-mediated glucose metabolism. To examine this possibility, 10 non-insulin-dependent diabetes mellitus (NIDDM) patients, 4 hypertriglyceridemic, and 6 normotriglyceridemic nondiabetic control subjects were examined with a 5-day cross-over design, in which the short-term metabolic effects of a 40% fat diet containing 77.5% of fat calories as MCT were compared with an isocaloric long-chain triglyceride-containing diet. In diabetic patients, MCT failed to alter fasting serum glucose concentrations but reduced preprandial glycemic excursions by 45% (F = 7.9, P less than 0.01). On MCT, the amount of glucose needed to maintain euglycemia during an intravenous insulin infusion was increased in diabetic subjects by 30%, in hypertriglyceridemic subjects by 30%, and in normotriglyceridemic control subjects by 17%. MCT increased mean +/- SE insulin-mediated glucose disposal (4.52 +/- 0.56 vs. 2.89 +/- 0.21 mg.kg-1.min-1; n = 3, P less than 0.05) but failed to alter basal glucose metabolism or insulin-mediated suppression of hepatic glucose output. Metabolic responses to MCT were observed independent of sulfonylurea therapy or severity of fasting hyperglycemia. No change in fasting serum insulin or triglyceride concentrations were seen with MCT administration. Although MCT increased mean fasting serum beta-hydroxybutyrate levels from 0.10 +/- 0.03 to 0.26 +/- 0.06 mM (P less than 0.05) in normotriglyceridemic nondiabetic subjects, no change was seen in diabetic patients. Thus, MCT-containing diets increased insulin-mediated glucose metabolism in both diabetic patients and nondiabetic subjects. In diabetic subjects, this effect appears to be mediated by increases in insulin-mediated glucose disposal.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoic acid residues in a take-over mechanism for the pyruvate dehydrogenase multienzyme complex of Escherichia coli.

The pyruvate dehydrogenase complex of Escherichia coli contains two lipoic acid residues per dihydrolipoamide acetyltransferase chain, and these are known to engage in the part-reactions of the enzyme. The enzyme complex was treated with trypsin at pH 7.0, and a partly proteolysed complex was obtained that had lost almost 60% of its lipoic acid residues although it retained 80% of its pyruvate dehydrogenase-complex activity. When this complex was treated with N-ethylmaleimide in the presence of pyruvate and the absence of CoASH, the rate of modification of the remaining S-acetyldihydrolipoic acid residues was approximately equal to the accompanying rate of loss of enzymic activity. This is in contrast with the native pyruvate dehydrogenase complex, where under the same conditions modification proceeds appreciably faster than the loss of enzymic activity. The native pyruvate dehydrogenase complex was also treated with lipoamidase prepared from Streptococcus faecalis. The release of lipoic acid from the complex followed zero-order kinetics for most of the reaction, whereas the accompanying loss of pyruvate dehydrogenase-complex activity lagged substantially behind. These results eliminate a model for the enzyme mechanism in which specifically one of the two lipoic acid residues on each dihydrolipoamide acetyltransferase chain is essential for the reaction. They are consistent with a model in which the dihydrolipoamide acetyltransferase component contains more lipoic acid residues than are required to serve the pyruvate decarboxylase subunits under conditions of saturating substrates, enabling the function of an excised or inactivated lipoic acid residue to be taken over by another one. Unusual structural properties of the enzyme complex might permit this novel feature of the enzyme mechanism.