Conserved residues in yeast initiator tRNA calibrate initiation accuracy by regulating preinitiation complex stability at the start codon

Eukaryotic initiator tRNA (tRNA_i) contains several highly conserved unique sequence features, but their importance in accurate start codon selection was unknown. Here we show that conserved bases throughout tRNA_i, from the anticodon stem to acceptor stem, play key roles in ensuring the fidelity of start codon recognition in yeast cells. Substituting the conserved G31:C39 base pair in the anticodon stem with different pairs reduces accuracy (the Sui⁻ [suppressor of initiation codon] phenotype), whereas eliminating base pairing increases accuracy (the Ssu⁻ [suppressor of Sui⁻] phenotype). The latter defect is fully suppressed by a Sui⁻ substitution of T-loop residue A54. These genetic data are paralleled by opposing effects of Sui⁻ and Ssu⁻ substitutions on the stability of methionylated tRNA_i (Met-tRNA_i) binding (in the ternary complex [TC] with eIF2-GTP) to reconstituted preinitiation complexes (PICs). Disrupting the C3:G70 base pair in the acceptor stem produces a Sui⁻ phenotype and also reduces the rate of TC binding to 40S subunits in vitro and in vivo. Both defects are suppressed by an Ssu⁻ substitution in eIF1A that stabilizes the open/P_OUT conformation of the PIC that exists prior to start codon recognition. Our data indicate that these signature sequences of tRNA_i regulate accuracy by distinct mechanisms, promoting the open/P_OUT conformation of the PIC (for C3:G70) or destabilizing the closed/P_IN state (for G31:C39 and A54) that is critical for start codon recognition.     

Cytocompatibility of novel extracellular matrix protein analogs of biodegradable polyester polymers derived from α-hydroxy amino acids

One of the challenges in regenerative medicine is the development of novel biodegradable materials to build scaffolds that will support multiple cell types for tissue engineering. Here we describe the preparation, characterization, and cytocompatibility of homo- and hetero-polyesters of α-hydroxy amino acid derivatives with or without lactic acid conjugation. The polymers were prepared by a direct condensation method and characterized using gel permeation chromatography, ¹H-nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, optical activity, and solubility. The surface charge of the polymers was evaluated using zeta potential measurements. The polymers were coated onto glass cover slips followed by characterization using nano-surface profiler, thin film reflectometry, and atomic force microscopy (AFM). Their interaction with endothelial and neuronal cells was assessed using adhesion, proliferation, and differentiation assays. Of the characterized polymers, Poly-HOVal-LA, but not Poly-(D)HOPhe, significantly augmented nerve growth factor (NGF)-induced neuronal differentiation of the PC12 pheochromcytoma cells. In contrast, Poly-HOLeu increased by 20% the adhesion of endothelial cells, but did not affect PC12 cell differentiation. NGF-induced Erk1/2 phosphorylation in PC12 cells grown on the different polymers was similar to the effect observed for cells cultured on collagen type I. While no significant association could be established between charge and the differentiative/proliferative properties of the polymers, AFM analysis indicated augmentation of NGF-induced neuronal differentiation on smooth polymer surfaces. We conclude that overall selective cytocompatibility and bioactivity might render α-hydroxy amino acid polymers useful as extracellular matrix-mimicking materials for tissue engineering.     

Th17 and non-Th17 interleukin-17-expressing cells in chronic lymphocytic leukemia: delineation, distribution, and clinical relevance

Background

The levels and clinical relevance of Th17 cells and other interleukin-17-producing cells have not been analyzed in chronic lymphocytic leukemia. The objective of this study was to quantify blood and tissue levels of Th17 and other interleukin-17-producing cells in patients with this disease and correlate blood levels with clinical outcome.

Design and Methods

Intracellular interleukin-17A was assessed in blood and splenic mononuclear cells from patients with chronic lymphocytic leukemia and healthy subjects using flow cytometry. Interleukin-17A-producing cells were analyzed in formalin-fixed, paraffin-embedded spleen and lymph node sections using immunohistochemistry and immunofluorescence.

Results

The absolute numbers of Th17 cells in peripheral blood mononuclear cells and the percentages of Th17 cells in spleen cell suspensions were higher in patients with chronic lymphocytic leukemia than in healthy subjects; in six out of eight paired chronic lymphocytic leukemia blood and spleen sample comparisons, Th17 cells were enriched in spleen suspensions. Circulating Th17 levels correlated with better prognostic markers and longer overall survival of the patients. Two “non-Th17” interleukin-17-expressing cells were identified in chronic lymphocytic leukemia spleens: proliferating cells of the granulocytic lineage and mature mast cells. Granulocytes and mast cells in normal spleens did not express interleukin-17. Conversely, both chronic lymphocytic leukemia and healthy lymph nodes contained similar numbers of interleukin-17+ mast cells as well as Th17 cells.

Conclusions

Th17 cells are elevated in chronic lymphocytic leukemia patients with better prognostic markers and correlate with longer survival. Furthermore, non-Th17 interleukin-17A-expressing cells exist in chronic lymphocytic leukemia spleens as maturing granulocytes and mature mast cells, suggesting that the microenvironmental milieu in leukemic spleens promotes the recruitment and/or expansion of Th17 and other IL-17-expressing cells. The pathophysiology of Th17 and non-Th17-interleukin-producing cells in chronic lymphocytic leukemia and their distributions and roles in this disease merit further study.     

Interleukin 2: a review

Interleukin 2 (IL 2) is a central mediator of the growth and functional activity of B- and T-cells, and cytotoxic cells, including Natural Killer and Lymphokine Activated Killer cells. Significant defects in the production of, and response to, IL 2 have been described in a variety of congenital and acquired immunodeficiency states. IL 2 has demonstrated major anti-tumor activity in animal models. The biochemistry and molecular biology of IL 2 and its gene are reviewed, along with data regarding the IL 2 receptor, normal T-cell activation, abnormalities in IL 2 production and response in immunodeficiency states and leukemia, and initial explorations of IL 2 in the treatment of human cancer.     

Absence of the wild-type allele predicts poor prognosis in adult de novo acute myeloid leukemia with normal cytogenetics and the internal tandem duplication of FLT3: a cancer and leukemia group B study

The FLT3 gene is mutated by an internal tandem duplication (ITD) in 20-25% of adults with acute myeloid leukemia (AML). We studied 82 adults <60 years of age with primary AML and normal cytogenetics, who received uniform high-dose therapy and found FLT3 ITD in 23 (28%) patients. When the 23 FLT3 ITD+ cases were compared with the 59 cases with wild-type (WT) FLT3, disease-free survival (DFS) was inferior (P = 0.03), yet overall survival (OS) was not different (P = 0.14). However, 8 (35%) of 23 FLT3 ITD/+ cases also lacked a FLT3 WT allele (FLT3(ITD-R)) as determined by PCR and loss of heterozygosity. Thus, three genotypic groups were identified: normal FLT3(WT/WT), heterozygous FLT3(ITD/WT), and hemizygous FLT3(ITD/-). DFS and OS were significantly inferior for patients with FLT3(ITD/-) (P = 0.0017 and P = 0.0014, respectively). Although DFS and OS for FLT3(WT/WT) and FLT3(ITD/WT) groups did not differ (P = 0.32 and P = 0.98, respectively), OS of the FLT3(ITD/-) group was worse than the FLT3(WT/WT) (P = 0.0005) and FLT3(ITD/WT) (P = 0.008) groups. We propose a model in which FLT3(ITD/-) represents a dominant positive, gain-of-function mutation providing AML cells with a greater growth advantage compared with cells having the FLT3(WT/WT) or FLT3(ITD/WT) genotypes. In conclusion, we have identified the FLT3(ITD/-) genotype as an adverse prognostic factor in de novo AML with normal cytogenetics. A poor prognosis of the relatively young FLT3(ITD/-) adults (median age, 37 years), despite treatment with current dose-intensive regimens, suggests that new treatment modalities, such as therapy with a FLT3 tyrosine kinase inhibitor, are clearly needed for this group of patients.     

Liposomal daunorubicin in the treatment of relapsed or refractory non-Hodgkin''s lymphoma.

Purpose:To assess the efficacy and toxicity of liposomal daunorubicin administered as a two-hour intravenous infusion to patients with relapsed or refractory non-Hodgkins lymphoma (NHL). Patients and methods:Eligible patients had relapsed or refractory NHL with measurable or evaluable disease, and low grade, select intermediate grade, or mantle cell pathologic types. Prior exposure to an anthracycline or anthracenedione was allowed. Liposomal daunorubicin at a dose of 100 mg/m² was given intravenously over a minimum of 120 minutes every 3 weeks, as a single agent. Results:Thirty-three patients were accrued: twenty-three (70%) had low-grade histologies; six (18%) had intermediate-grade histologies (follicular large-cell and diffuse small cleaved); and four (12%) patients had mantle-cell lymphoma. Eighteen (55%) had received two or more prior regimens; fourteen (42%) received a prior anthracycline. A median of six cycles of liposomal daunorubicin were administered (range 1–15). Of 31 patients evaluable for response, 2 complete and 10 partial remissions were documented for a major response rate of 39% (95% confidence interval (CI): 22%–58%). The median duration of response was 19.5 months (range 4.3–41.1+). Six responders (50%) had received a prior anthracycline; one responder had mantle-cell histology. The major toxicities were grade 3 or 4 neutropenia in 26 patients (79%), mild to moderate nausea in 22 (67%), and fatigue in 16 (48%). Conclusions:Liposomal daunorubicin at 100 mg/m² every three weeks has activity in patients with relapsed or refractory NHL, including patients with prior exposure to an anthracycline. Further studies of liposomal daunorubicin in combination with other agents are warranted.     

Treatment of aggressive non-Hodgkin's lymphoma in elderly patients with thiotepa, Novantrone (mitoxantrone), vincristine, prednisone (TNOP)

The aging of the population and the increased incidence of non-Hodgkin's lymphoma will result in a large number of elderly patients with this disorder. Newer therapies will be required for this group of patients. This article reports a new therapy for elderly patients with diffuse aggressive non-Hodgkin's lymphoma. Patients were treated with TNOP (thiotepa 20 mg/m(2), mitoxantrone (Novantrone) 10 mg/m(2), vincristine (Oncovin) 1 mg/m(2) all on day 1 and prednisone 60 mg/m(2) on days 1 through 5 of a 21-day course. Twenty-six patients were enrolled on study. The patients' ages ranged from 66 years to 87 years, with a mean age of 75.5 years. Eleven patients had a partial response (42%) and 4 patients had a complete response (15%) for a total response of 57%. Eighty-one percent of patients survived 1 year and 54% survived for 2 years. The median survival was 26 months. Hematologic and nonhematologic toxicity was tolerable. We believe that TNOP is an excellent therapeutic option in this group of elderly patients, particularly in the palliative setting.     

Pharmacokinetics of recombinant interleukin 2 in humans

This report summarizes the pharmacokinetics in humans of recombinant interleukin 2 (IL-2) given as an i.v. bolus, i.v. or i.p. infusion, and i.m. or s.c. injection. Immediately after an i.v. bolus the serum IL-2 level equals the dose divided by the plasma volume, in a typical human 650 units/ml for a dose of 10(6) units/m2. The level initially decreases with a half-life of 12.9 min, followed by a slower phase with a half-life of 85 min out to 4 h after the bolus. The median steady state level during an i.v. infusion of 10(6) units/m2 over 6 h is 41 units/ml. A clearance rate of approximately 120 ml/min is obtained from either the i.v. bolus or infusion data and is consistent with the renal filtration being the major route of clearance. Serum levels remain fairly constant for about 8 h after s.c. or i.m. injection but are approximately 2% of the level seen immediately after an i.v. bolus. The area under the time-concentration curve suggests that about 30% of the IL-2 activity is transported from the site of an i.m. injection to the blood. After i.p. infusion IL-2 is only slowly transported to the blood. The median serum IL-2 levels are 430-fold lower than levels in the i.p. fluid and decrease with a median half-life of 6.3 h.     

Treatment of Philadelphia Chromosome Positive (Ph +) Chronic Myelogenous Leukemia in Blast Crisis and Ph + Acute Leukemia with High Dose Cytosine Arabinoside (HDARAC)

High dose cytosine arabinoside (HDARAC) was administered to eleven patients in the blastic phase of Philadelphia (Ph) chromosome positive chronic myelogenous leukemia (CML). Four patients presented in blastic phase and in seven patients blastic transformation had evolved from a previous chronic phase. All patients had been heavily pretreated with chronic phase drugs (hydroxyurea, myleran) or a protocol designed to treat the chronic phase (L-5 protocol) and with blastic phase regimens (anthracycline/araC combination or vincristine/prednisone). One of 11 patients achieved a complete remission (365 + days) and two patients achieved a partial response. No cytogenetic remissions were observed. The other patients were considered treatment failures with 3/8 surviving less than one month after therapy. Blasts were, at least temporarily, eliminated in all patients receiving at least 7 doses of HDARAC, although repopulation was rapid. HDARAC may be satisfactory therapy for accelerated phase CML but is minimally active in blastic phase CML.     

Remarkably similar antigen receptors among a subset of patients with chronic lymphocytic leukemia

Studies of B cell antigen receptors (BCRs) expressed by leukemic lymphocytes from patients with B cell chronic lymphocytic leukemia (B-CLL) suggest that B lymphocytes with some level of BCR structural restriction become transformed. While analyzing rearranged V(H)DJ(H) and V(L)J(L) genes of 25 non-IgM-producing B-CLL cases, we found five IgG(+) cases that display strikingly similar BCRs (use of the same H- and L-chain V gene segments with unique, shared heavy chain third complementarity-determining region [HCDR3] and light chain third complementarity-determining region [LCDR3] motifs). These H- and L-chain characteristics were not identified in other B-CLL cases or in normal B lymphocytes whose sequences are available in the public databases. Three-dimensional modeling studies suggest that these BCRs could bind the same antigenic epitope. The structural features of the B-CLL BCRs resemble those of mAb's reactive with carbohydrate determinants of bacterial capsules or viral coats and with certain autoantigens. These findings suggest that the B lymphocytes that gave rise to these IgG(+) B-CLL cells were selected for this unique BCR structure. This selection could have occurred because the precursors of the B-CLL cells were chosen for their antigen-binding capabilities by antigen(s) of restricted nature and structure, or because the precursors derived from a B cell subpopulation with limited BCR heterogeneity, or both.